Signs of Fall 2: Cavity Nesting Team!

Photo by D. Sillman

Photo by D. Sillman

Over the past two years I have written three blogs about our Cavity Nesting Team study up at Harrison Hills Park in northern Allegheny County. We followed up our very satisfying 2015 season with a second round of spring and summer-long monitoring of our 28 cavity nesting boxes, and we have just begun to organize and explore our 2016 data.

In 2015, thirteen of our boxes had bluebird nests with a total of 65 eggs and 48 fledges (a 74% survival rate). We also had nine boxes that had tree swallow nests with a total of 31 eggs and 22 fledges (a 71% survival rate). Nine of our nest boxes, though, did not have any nesting activity, and, so, using the placement of the utilized boxes as a guide, we relocated seven of these inactive boxes to try to make them more attractive to cavity nesting bird species. Our overall criteria for nest box relocation were quite straightforward: boxes too close together tended not have nests (so we spread out the clumped boxes) and boxes right on the edges of field (i.e. very close to surrounding woodlands) were not used (so we moved the boxes away from the extreme edges of our fields).

This year’s Cavity Nesting Team consisted of eight volunteers: Deborah and I and Sharon Svitek took turns monitoring the boxes in and around the “High Meadow.” Patrick and Mardelle Kopnicky checked the boxes around the “Bat House Meadow.” Chris Urik and Odessa Garlitz took turns monitoring the boxes at the park entrance and up in the field near the Environmental Learning Center, and Paul Dudek checked the boxes around the pond and soccer fields in the southern end of the park. Every box was checked each week, and then each observer uploaded their data to an on-line Google spreadsheet. Each week, Deborah compiled and distributed the growing data tables to each member of the team. Chris Urik also made GPS maps of the park showing the precise location of each nesting box.

Photo by D. Sillman

Photo by D. Sillman

As I have talked about before, native cavity nesting bird species (eastern bluebirds, tree swallows, house wrens, Carolina wrens, titmice, chickadees, nuthatches, etc.) naturally use tree holes for their nesting sites. These holes are most often found in older, often dead trees and are typically abandoned cavities that have been chiseled out by woodpeckers. Any site management plan that favors woodpeckers (allowing dead trees to remain in the forest and not managing the forest or manipulating it into an even aged stand) will favor cavity nesting bird species.

Nest boxes, of course, are artificial substitutes for these natural tree holes.

So what did we see in our 2016 study?

First of all our nest box relocation project was very successful! The seven relocated, unused nest boxes from 2015 were all used by cavity nesting birds in 2016! Four of these boxes had bluebird nests, two had tree swallow nests, and one had a chickadee nest.

Photo by D. Sillman

Photo by D. Sillman

Bluebird nesting was more robust this year than last (in 2016, 17 boxes had bluebird nests, 83 eggs were counted and 63 fledges observed (a 76% success rate!)). Like last year, nesting activity in bluebirds had two seasonal peaks: one in late spring (May) and another in late summer (July).

Tree swallow nesting was less active in 2016 than it had been in 2015. Only seven boxes had tree swallow nests this year and only sixteen eggs were observed with just five confirmed fledges (a 31% success rate (compared to a 71% success rate in 2015)). It is possible that the hot, dry summer of 2016 reduced the food supply typically utilized by tree swallows to feed their young (primarily adult forms of insects that have aquatic larvae), or possibly the increased activity of house wrens in the park (described below) interfered with tree swallow nesting and may have even led to the active destruction of both tree swallow eggs and nestlings.

In 2016, three of our nest boxes had chickadee nests (in 2015 only one box had a chickadee nest). We observed a total of fifteen chickadee eggs and four confirmed fledges (a 27% success rate). All chickadee nesting was in May and early June. Two of this year’s chickadee nests were raided by nest predators (accounting for the eleven failed eggs).

Photo by dfaulder, Wikimedia Commons

Photo by dfaulder, Wikimedia Commons

In 2016, nine of our nesting boxes had house wren nests (no boxes from 2015 had house wren nests). Thirty-four eggs leading to twenty-three fledges were observed in these nests (a 68% success rate). Six of the nine house wren nesting boxes had been previously utilized (and nested in) by bluebirds (4 boxes) and chickadees (2 boxes).

House wrens and bluebirds have many similar nesting characteristics: they tend to nest in two seasonal cohorts (early spring (May) and late summer (July/August) and they tend to select nesting sites no more than 50 to 100 feet from a wooded edge. Possibly our box relocation project moved a significant number of our boxes into nesting sites also preferred by house wrens.

House wrens are one of the most common causes of nest failure in bluebirds, tree swallows and chickadees. They destroy eggs, kill nestlings, and even kill adult birds (typically then throwing the broken eggs or dead birds from the invaded nest so that they can start their own nesting cycle). Also, male house wrens attempt to attract females by building numerous “dummy nests” (piles of sticks sometimes stacked up on the active nests of other birds!). These dummy nests are an important sign of house wren activity and can be used to thwart house wren nest invasion. Since these dummy nests contain no eggs, they can be removed from the nest boxes without violating the Migratory Bird Treaty’s protections of native bird species. Prompt removal of these stick piles may keep a male house wren occupied in re-building the displays rather than getting down to actual reproduction.

Also, the literature on “wren guards” (various nest box modifications that are designed to repel house wren nest box invaders) stresses that it is the visual cues of the nesting birds entering and leaving a nest box that are the critical stimulations that then trigger the house wrens to attack the active nest.  Possibly, turning all house wren utilized nest boxes to point their openings away from the surrounding woods (where the house wrens spend much of their time foraging for food and hiding in the covering vegetation) would make the visualization of the nesting birds entering and leaving the nest box less apparent and decrease the rate of house wren infestation.

Photo by D. Sillman

Photo by D. Sillman

So, we had a successful season! We fledged out lots of bluebirds but fewer tree swallows, but we have also, possibly, set up a potential plague of nest-preying house wrens! Next year, we’ll try to reduce the house wren activity and keep our bluebird numbers high! I will let you know how 2017 plays out!

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Signs of Fall 1: Changing Leaves

(parts of this week’s post were first presented in a September 14, 2014 blog!)

Photo by D. Sillman

Photo by D. Sillman

During the last week of July the red maples and the yellow poplars along the Roaring Run Trail began to shed their leaves. On a few of my early morning bike rides breezes would sweep across the tree canopy and send down clouds of yellow and red leaves. A few spots on the trail were well covered with leaves and took on the appearance of autumn.

The trees that usually shed their leaves during a summer drought are the cherries and the locusts. The two, tall, skinny black locusts out on the back edge of my field often lose half of their leaves in a typical July. Sudden breezes send swirling clouds of yellow leaflets down onto the lush, green grass, and the black locusts, which are typically one of the last trees to leaf out in the spring, stand mostly denuded but increasingly watertight against the summer drought. My cherry trees (black and sweet cherries) have the same response to drought but don’t shed their leaves quite as extensively as the locusts. This year both species retained their leaves in spite of the hot, dry summer weather! Soil moisture from our spring rains must have been sufficient for their summer water needs.

Leaf loss is a purely “economic” decision for a tree. Leaves are the organs for photosynthesis and energy acquisition, but they also lose incredible quantities of water via transpiration. In the summer many trees balance their needs for energy (for growth, reproduction, repair etc.) with the necessity of maintaining an acceptable water balance in their tissues and cells. In wet summers these trees can keep all of their leaves, fix abundant energy, and transpire water without damage. In dry summers, the limiting factor of water availability makes the tree give up some of its photosynthetic potential in order to maintain its water balance.

Photo by D. Sillman

Photo by D. Sillman

With the approaching winter the leaves for all deciduous trees are shed primarily to help the trees withstand the dry conditions of winter (also, the freezing of the water in the leaves would destroy their cellular structures and render the leaves useless as photosynthetic organs!). The types of trees that keep their leaves (the coniferous, or “evergreen” trees) do so by making tougher, more water tight “leaves” (often tightly pored needles that are wrapped in layers of waxes) and by some elegant physiological adaptations that go on inside the cells of the needles. This winter acclimation adaptation includes altering the chemical nature of the lipid molecules inside the cells (making the lipids more “unsaturated” and, therefore, more twisted and bent and thus less able to join together in a solid form (this significantly reduces the freezing temperature of the cells!). The cells also increase the cytoplasmic concentrations of these freeze-resistant lipids to amplify this antifreeze effect. The cells also add other solutes to their cytoplasm and break up some of their intracellular proteins into many smaller pieces. Both of these responses act to further decrease their freezing points.

Photo by D. Sillman

Photo by D. Sillman

The cells in these conifer needles also alter their plasma membranes to allow water to move across the membrane more freely. Then, as ice begins to form in the spaces around the cells, the water of cytoplasm is drawn out into the surrounding ice crystals and away from triggering possible freeze events inside the cell itself! An interesting side note here is that the freezing of this surrounding liquid water to form ice releases a small amount of heat energy (the “heat of fusion”) and the cells of the leaf take advantage of this added heat to help maintain their internal liquidity!

When the deciduous trees get ready to shed their leaves in the fall, they undergo several well defined stages of change. First, in response to the duration of the dark period of the day reaching a critical length, the leaves begin to generate large numbers of cells right at the junction of the leaf’s stem and its branch. These cells greatly increase in number but not, at first, in their individual sizes. This layer of cells (the “abscission layer”) slowly starts to interfere with the flow of sugars out of the leaf and nutrients into the leaf. The lack of nutrients entering the leaf stops the synthesis of the new chlorophyll molecules that are needed to replace the ones that wear out in the ongoing process of photosynthesis. Chlorophylls are, of course, the pigments that give plants their characteristic green colors. Initial cessation of chlorophyll production makes the leaves appear a bit paler and less intensely green than they were during the height of summer. Continued breakdown of the chlorophylls then starts to unmask the other pigments (the “accessory” pigments of photosynthesis: the carotinoids and xanthophylls) that had been present in the leaves all summer long). As these pigments are “revealed” the leaves then “turn” orange (from the carotinoids) or yellow (from the xanthophylls) before they finally fall from the tree. The accumulation of the sugars in the leaves also has an effect on eventual leaf color. These sugars stimulate the synthesis of anthocyanin pigments in the leaf. These pigments generate purple or bright red colors in the leaf and are thought (by W. D. Hamilton, the famous “Bill Hamilton” of biology!) to protect the leaf (and particularly next year’s delicate leaf buds) from insect damage.

Photo by D. Sillman

Photo by D. Sillman

The deciduous trees in our area will be turning their autumnal colors over the next month or so. The breakdown of the chlorophyll and the revealing of the accessory pigments is inevitable in our climate zone. In some years, though, the intensity of the reveled colors is much more extreme than in other years. The weather patterns of the fall and of the preceding spring and summer all contribute to the magnitude of the final color response.

Good, healthy abundant leaves are favored if the previous spring had adequate rainfall. A normal to wet summer will then insure that these leaves persisted intact through their active photosynthetic seasons. Warm, sunny autumn days combined with cool but not freezing autumn nights will maximize sugar production and anthocyanin synthesis in the leaves. These accumulating anthocyanins then give the leaves their brilliant red and crimson colors that seem to define a “good” color year in the forest!

The way this year is working out, we should have some very spectacular colors around us, and that is almost everyone’s favorite Sign of Fall!

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Signs of Summer 15: Monarchs (and summer’s end!)

Photo by D. Sillman

Photo by D. Sillman

I saw my first monarch butterfly (Danaus plexippus) three weeks ago. I was driving along on one of my favorite back roads between my house and campus, and I spotted it fluttering out over a diverse old field that was full of butterfly weed and milkweed. By early August I usually see a few monarchs around our house, too, but this year Deborah and didn’t see our first “local” monarch until almost the last day of the month! Monarch Watch (an organization that monitors the yearly surge and retreat of monarchs across North America) reports very low numbers of monarchs in the northern edges of their range this year. They blame storms that killed large numbers of the butterflies even before they could start out from Mexico on their northward trek and also the hot, dry summer weather. They also worry that temperature and day length cues that start the monarchs out on their migration in the early spring may no longer be precisely timed to the developmental cycles of the milkweed and the nectar producing plants growing along the migration route. The monarchs arrive in a habitat where there is no nectar for the adults and where the milkweed is not ready for the monarch eggs and larvae. The elegant efficiency of the monarch migration and its timing with their sustaining plants is beginning to crumble.

Pennsylvania is just one of stops on the seasonal North American northward migration of monarchs. Some of the adult monarchs that hatch here in mid-summer might, in a typical year, continue on north to lay more eggs on the later growing milkweed in New York and New England. I remember in the early 1980’s seeing clouds of monarchs along the New York Interstate just west of Syracuse! These butterflies may have had a part of their life cycle tied to the fields of Western Pennsylvania.

Other monarchs that mature here especially in late summer, though, will turn around and begin the long journey back south. They will lay their eggs on some late season, southern milkweed and then the next batch of adults (or maybe the cohort that comes after that) will head to the coniferous forests in the mountains of the Mexican states of Michoacán and Mexico where they will overwinter.

Photo by T. Hall, Flickr

Photo by T. Hall, Flickr

Two years ago the census of the monarchs in these overwintering forest was alarming low! There were only 35 million individual monarchs in a shrunken forest range of just 3 acres. Twenty years ago the overwintering forest covered 45 acres with an estimated population of over a billion individuals! There is good news and bad news for this past year. The monarch population has recovered from its dangerously low numbers (this  past winter there were 140 million individuals spreading over 10 acres of forest), but the population has still not returned to safe, sustaining levels (in 2002, for example, a single storm killed 500 million monarchs! The population must be large and robust enough to withstand that kind of natural stress!).

Photo by D. Sillman

Photo by D. Sillman

At each milkweed stop the monarchs carry out the same basic cycle: Each female after mating lays three to four hundred eggs on the milkweed (spreading her eggs out over a large number of plants). Then the adult monarchs die. The eggs hatch in three to five days depending on the temperature, and the emerging larvae (the “caterpillars”) feed first on the egg capsule and then begin to eat the milkweed leaves. They molt five times during their larval life stage and increase their body mass more than two thousand times.

The eggs and the larvae are under intense predation and parasite pressures. More than ninety percent of the eggs and caterpillars will fail to survive. Eggs are eaten by ants, earwigs and snails, and larvae are eaten by beetles and other insects (like paper wasps) or killed by parasitoid wasps, bacteria, or fungi. Since the larvae feed exclusively on milkweed leaves they accumulate the milkweed’s cardenolides (a cardiac glycoside that can cause the heart of a vertebrate to stop its contractions!) in their body tissues. These cardenolides make the larvae (and, eventually, the adults) poisonous to most vertebrates. Relatively few monarch caterpillars or adult butterflies, then, will be consumed by vertebrate predators. Research from scientists at Cornell University (published this past winter in the Proceedings of the Royal Society B (November 2015)) showed that monarchs have evolved enzymes that are themselves unaffected by the cardenolide toxins and are thus able to freely accumulate the milkweed toxins in their bodies.

The end stage caterpillar then forms a cocoon (“chrysalis”) within which the tissues and organs of the larvae dissolve and are reformed into the structures of the butterfly. This metamorphosis takes between nine and fifteen days. The adult butterfly then emerges, mates, and continues on its migration and cycle.

Photo by D. Sillman

Photo by D. Sillman

Doc and Linda Mueller have once again shared some of their carefully hatched and tended monarch caterpillars with Deborah and I. On the Sunday before classes started, we put nine of the caterpillars out on my dense cluster of milkweed plants on the west side of my house. The milkweed had had very little evidence of insect activity (most leaves were intact, etc.) before our adding the caterpillars, but even just two days after caterpillar introduction the leaves were showing high levels of shredding and skeletonizing! After five days I spotted one of the caterpillars now at least four times larger, working his way across a thick stem to get to some untouched leaves. My hope is that we get some chrysalises and some adults this year!

The Center for Biological Diversity has requested that the U. S. Fish and Wildlife Service classify the monarch as a “threatened” species. This would allow a better funded effort to be organized to try to re-establish the vital milkweed and nectar plant “stops” along the monarch’s traditional migration routes. It would also allow better coordination with Mexican authorities to try to control the illegal logging in the critical forests of Michoacán and Mexico. It could also help to fund research into the documentation of the ongoing effects of climate change on this once abundant but now increasingly rare butterfly species.

 

 

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Signs of Summer 14: Words

landmarksA good friend sent me a link to a Wall Street Journal article the other day. The article (“Why You Can’t Say Where You Are” by Tom Shippey) reviewed Robert MacFarlane’s new book, Landmarks.   In this book Macfarlane explores the idea that lacking the words to describe the things around you causes you to be less able to see those things clearly, and this growing lack of clarity and focus then causes you to relegate these phenomena to irrelevant trivialities that not worth the effort to save or preserve.

Macfarlane’s starting point is a discussion of some of the words being deleted from the new edition of the Oxford Junior Dictionary. These extirpated words include many basic nouns of the natural world including “acorn,” “buttercup,” “heather” and “wallow.” The editors of the Oxford Junior Dictionary justified their actions by stating  that since modern children do not encounter such objects in their daily lives, the words have become irrelevant. Words like “celebrity,” “attachment,” “blog” and “voice-mail,” though, were added to or maintained their presence in the new edition because of their great relevance to experiential world of youth.

Macfarlane ponders a world in which children increasingly are kept locked away (and safe?) within their homes and other controlled spaces. They are allowed to roam freely about in the “antiseptic” world of the Internet (and that’s a topic for intense discussion later!) but are prevented from encountering or exploring the components of their natural landscapes. The words they need to describe their experiences are not the vocabulary of natural places! Will these children, then, ponders Macfarlane, ever know that the natural world exists? Will they ever see any value in an uncut forest or uncultivated field or wetland? Or will these places be regarded simply as “empty” and “useless?”

supermanWords! When I was in grade school I was an avid reader of DC Comics. I remember a cascade of odd vocabulary words that I slowly assimilated because of their use in these silly (and wonderful!) publications. In fifth grade I explained to my Reading group the meaning of the word “irony” (of course, I had to use Clark Kent and Lois Lane in my explanation!). In high school I remember cramming vocabulary words from the paperback book we simply called the “green book” (because of the color of its cover) in preparation for taking the SAT’s. My friends and I would pepper our lunch time conversations with “pejorative” and “salubrious” and “fecund.” Our absolute favorite new word, though, was “jejune.” It was so useful in describing our high school experience!

There is, though, no vocabulary “green book” for the increasingly lost words that describe the forests and fields around us. Writing about hiking through the rolling hills and the continually re-sculpted forests here in Pennsylvania have forced me to recognize and use words like “hollow” (a small valley or basin) and “copse” (a group of small trees growing closely together) and “swale” (a low lying, often wet stretch of land).  There is some discussion about whether the words “copse” and “coppice” are synonyms, or if coppice implies a stand of shrubs instead of trees, or if coppice is best used as a verb (the action of regularly cutting trees and shrubs (which then regrow in a uniform manner)).

Copse at Mossend Farm, R. Griffith, Wikimedia Commons

Copse at Mossend Farm, R. Griffith, Wikimedia Commons

A copse in which game animals are found is a “spinny” which is quite similar to a “covert” (a dense group of trees and shrubs that shelter game animals). A number of extremely localized words have been derived to describe the hiding places for hunted animals! It is important for hunters to recognize optimum game microhabitats!

In grade school we all sang the “Caisson Song” and the line “over hill over dale we will hit the dusty trail.” In third grade one of my braver fellow students asked our music teacher what a “dale” was. She said, quite confidently, “the opposite of a hill.” True! A dale is a valley, and a small dale can be called a “dell” (with the farmer there in!), and a dell might be justifiably referred to as a “hollow” (although “the farmer in the hollow” has a very sinister ring to it!).

Lothlorien, N. Kenrick, Flickr

Lothlorien, N. Kenrick, Flickr

J.R. R. Tolkien loved both nature and words! Reading his Lord of the Rings takes you through “dingles” (deep wooded valleys) and over “tors” (rocky hills) past “bights” (curved recesses at the edge of a forest) and through “chines” (deep, narrow ravines). Along the way you encounter “cobs” (spiders), “lobs” (also spiders!), and “conies” (rabbits) along with the incredible array of elves, orcs, dwarfs, goblins, dragons and balrogs! The richness of Tolkien’s descriptions of the forests and swamps and wastelands that Frodo and his companions wander through make these books of fantasy feel intensely real!

EarthseaAnother wonderful set of books book that emphasized the power and importance of words is Ursula LeGuin’s 1968 Earthsea Triliogy. Wizards living on the scattered islands of Earthsea labor to learn the “true names” of the inhabitants and all of the other biotic and physical components of their world so that they could use these names to shape and control not only Nature but also the future. Decades before Harry Potter and the Hogwarts School of Witchcraft and Wizardry youthful wizards were being taught far away in Earthsea the secrets of their world!

So far, I have listed fifteen “nature words” in this essay,  and I hope that everyone can see how useful and rich they are!  I wanted to finish with a short vocabulary quiz to help advance the use of complex words in descriptions of nature. There are seven questions and twenty-eight possible answers! Correct answers are listed at the end of the essay! None of these words are jejune (of course!)! Good luck!

1. A valley or basin on the foot of a hill is called a
a. Fell        b. Grove       c. Combe       d. Daddock

2. A wild, uncultivated, usually upland area is called a
a. Pinery        b. Covert      c. Cag         d. Weald

3. A watecourse running through peat, often dry in the summer

a. Bugha    b.ammil     c. feith     d. dag

4. Rough or marshy ground usually overgrown with one kind of plant is called
a. A brake             b. Mast-land             c. Chaparral              d. A forb

5. The rough sod of moorland (with the heather growing on it)

a. brug     b. bruach     c. def      d. beat

6. A place of deep mud or mire is called
a. A heath         b. A slough             c. A ghyll       d. Spronky

7. A grassy, open space in a forest is called a
a. Fen         b. Slive              c. Glade           d. Steppe

Let me know how you did! Use each word five times and it will be yours forever (or so my high school English teacher claimed!).    The words that make up the wrong answers are worth looking up, too! I especially like “spronky!” (Questions 3 and 5, by the way, are terms from MacFarlane’s Glossary I in Landmarks. These Glossaries are the closest things we have to a Natural Green Book!

(Answers:       1 b,     2 d,   3 c   4 a,     4 b,    5  d,     6. b     7.  c  )

 

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Signs of Summer 13: A Fox in Our Field!

Photo by D. Sillman

Photo by D. Sillman

A few weeks ago Deborah and I stepped out on the deck around 8 pm to give Izzy a chance to “do her business” (such a sweet way to phrase it!). The sun had dropped below the tops of the trees, but there was still good light and clear visibility. The deer were scattered across the field, both of this year’s fawns were over by the apple tree chewing freshly fallen green apples and paying us little attention, and Izzy was sniffing around in her fenced in yard.

But then, Deborah saw some movement along the north edge of the field in the brushy thicket on the tree line. An animal was moving quickly to the west, away from us, but he was very distinctive: reddish brown in color, pointed ears, long muzzle, low slung carriage, and a long bushy tail with a white tip. It was a red fox (Vulpes vulpes).

We watched the fox vanish and then re-appear several times as it moved in and out of the tangles of raspberry and blackberry along the field edge. Then he entered the woods at the bottom of the field and was gone.

Photo by K. Laubenstein, USFWS, Public Domain

Photo by K. Laubenstein, USFWS, Public Domain

How did I know that this was a red fox and not a coyote? The animal’s size, color, and tail were all distinctive, but it was the reaction of the deer that confirmed it all. They paid no attention at all to the fox! To them, he must have been a very familiar component of our field and woods ecosystem (even though neither Deborah nor I have ever seen him before!). They knew that a fox posed no threat to them or their well grown fawns. A coyote, though, would be a great cause for alarm (especially for the fawns)!

The red fox is the ultimate generalist. It can eat almost any type of food (from fruits and earthworms, to garbage and carrion, to chickens and garden vegetables) and is even able to actively hunt rabbits and mice. It can thrive in both wild and human-dominated habitats and is found all across the Northern Hemisphere (North America, Europe, and Asia).

The red fox is called the “cat-like” canine. Although it is quite obviously a member of the dog and wolf family with overwhelming anatomical and behavior similarities to other canids, the red fox’s long, very thin canine teeth and its ventrally slit pupils with their pronounced tapeta lucida are obvious cat-like features. These anatomical “cat-like” characteristics are accentuated by the fox’s slinking and pouncing, “mousing” hunting behaviors, and also by its use of its sensitive front paws to capture and pin prey. Also, the red fox’s sustained, piercing bite to effect a prey kill (as compared to the bite and shake killing method of most other canids) are remarkably cat-like in nature.

The eye features unquestionably have evolved because of the nocturnal hunting behaviors of the fox. The teeth, use of paws to catch and pin prey and specific stalking behaviors are evolutionary strategies that are most efficient for the capture of small prey items like mice and voles. The “cat-like’ nature of the red fox, then, is logically due to the similarity of prey items and activity times that many cats and the red foxes share. One other cat-like behavior, though, that is not so easily explained is the lateral threat stance used by foxes in aggressive displays (standing sideways, back arched, fur erect etc.).  This very classic “cat pose” seems out of place in the behavioral display of a canine!

There are four possible canids that any of us might see running through our yards and fields: dogs, red foxes, gray foxes, and coyotes (there are, sadly, no wolves in Western Pennsylvania!). Let’s think first about distinguishing our very familiar domesticated species from the cluster of these three wild animals.

Photo by D. Sillman

Photo by D. Sillman

Dogs even on a quick glance look quite different from foxes and coyotes. Dogs have an immense range of sizes (from 5 to 150 pounds!) and a great variation in coat colors and hair lengths. Most dog breeds have floppy ears, short muzzles, and steep foreheads (to make room for their large, domesticated brains!). They also typically hold their tails in an upward curve when they are running. Dogs also look less leggy and usually less lean than their wild counterparts: they have deeper chests and slightly shorter upper leg bones than their wild relatives (as you can see in the picture to the left of my old friend Kozmo!).

We can discuss red foxes and gray foxes together even though they are quite different animals. In fact, they are in completely different genera (the red fox is Vulpes vulpes, and the gray fox is Urocyon cinereoargenteus). They are, however, both small (8 to 15 pounds), pointy muzzled, flat foreheaded, pointy eared canids with long, bushy tails. Red foxes are usually, as their name implies, a reddish-brown color but individuals may be found in a wide range of browns and even grays. Most red foxes, though, will have black legs (their “stockings”) and a white tip on the end of their tails.

Photo by J. M. Phelps, Wikimedia Commons

Photo by J. M. Phelps, Wikimedia Commons

Gray foxes, as their name implies, are usually gray in color (especially on their backs), but they may have a great deal of reddish-brown hair on their sides. Their back coats usually have a dabbled pattern of gray and black (this color pattern makes the gray foxes I have seen in the wild seem to shimmer as they move along!). Gray foxes also have a black stripe down the middle of their backs that extends on down to the tip of their tails. They lack the black leg stockings and the white tail tip of the red fox. You might also see a gray fox up in a tree! Although red foxes and coyotes are known to climb trees at need, the gray fox with its curved claws is very well adapted to and very accomplished at tree climbing! Finally, red foxes, as I mentioned above, are much more likely to be found around people. The gray fox is a more specialized species of forest habitats.

Photo by D. Moss, Wikimedia Commons

Photo by D. Moss, Wikimedia Commons

The coyote (Canis latrans (or here in the East, C. latrans x C. lycaon (eastern coyotes are hybrids of the western coyote and the eastern (gray) wolf)) is much larger than either of the foxes but right in the middle of the size range of domesticated dogs (eastern coyotes weigh between 30 and 45 pounds). The eastern coyote is larger than the western sub-species due to the genetic influence of the eastern wolf. Coyotes have pointed ears, a long, pointy muzzle, a flattened forehead, and a shorter, though often bushy (usually black-tipped) tail that it carries below its back when it runs. Coyotes have a lean, leggy look due their shallower chest and longer upper leg bones (as compared to those of a domesticated dog). As I have written in previous blogs, the eastern coyote is a seldom seen but nearly ubiquitous species in almost any wild, rural, suburban or urban habitat throughout the eastern United States. My neighbors just across the street have seen coyotes running in the shadows across their open yards, and I have seen film of coyotes in suburban Chicago quietly watching people moving from their cars to their front doors totally oblivious of their presence.

So, there are dog-like animals out there running around in the night! They are alert and watchful and mostly want to be left alone! Sounds like a good deal to me!

 

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Signs of Summer 12: This Year’s Deer

Photo by D. Sillman

Photo by D. Sillman

White-tailed deer are both a charismatic species of our eastern forests and a major problem. The sight of a deer emerging from a stand of trees or brush is breathtakingly beautiful, but the damage they do to tree seedlings and forest understory plants (not to mention gardens, shrubs and ornamentals) is devastating. Some foresters, in fact, refer to white-tailed deer as “tree locusts,” and forest ecologists worry that the consequences of deer browsing on tree seedlings might include the disruption of forest succession and renewal throughout the northeast! Fern-lands and moor-lands could possibly replace our diverse hardwood forests if deer consume the next successional generation of trees!

Photo by N. Tonelll, Flickr

Photo by N. Tonelll, Flickr

In many of our state parks and game lands there are enclosures designed to prevent white-tail deer from browsing on tree seedlings and other understory plants. These “deer exclosures” have fences 8 or 10 feet tall, and the areas that they protect are typically filled with densely growing understory plants and large numbers of tree seedlings and saplings. The forest outside the fence barrier, though, often has a cleaned out, park-like appearance that is referred to as a “deer savannah” (see picture to the left). The impact of the deer is terribly clear! The deer are consuming tree seedlings and also many of the other ecologically important plants of the forest understory.

In 1900 it was estimated that there were only 500,000 white-tailed deer left in North America. Intense hunting pressures and massive deforestation through the Nineteenth Century had decimated their numbers and made them a species only rarely seen in our forests. The sighting of a deer, in fact, could make front page news in some of the rural newspapers of northwestern Pennsylvania! Today, however, there are estimated to be over 15,000,000 white-tailed deer in North America! Forest regeneration, elimination of natural predators, and strict hunting laws have allowed this species to reach population numbers and densities that far exceed those even of the pre-European settlement forest ecosystems!

Photo by Penn State

Photo by Penn State

A three year study conducted at the Penn State Deer Research Center (State College, PA) was recently published in the journal Biological Invasions. This paper examined the interactions between native and invasive plants and deer. In particular, the study was designed to determine which types of seven native and eight exotic plants were eaten by white-tailed deer.    The plants were grown in containers that were then placed into a deer enclosure containing eight mature does. Cameras equipped with motion detectors monitored and recorded deer feeding behaviors, and at the end of the study period the amount of each plant that was consumed was determined.

Four plants were avoided by the deer. Three of these were exotic invasives (garlic mustard (Alliaria petiolata), Japanese barberry (Berberis thunbergii) and Japanese stiltgrass (Microstegium vimineum)), and one was a native (but frequently invasive) species (hay-scented fern (Dennstaedtia punctilobula)). All four of these plants are common invasives in our deer infested forests! This study clearly showed that their abundance in these ecosystems is due to their not being consumed by deer. Selective browsing by deer is contributing to the persistence and spread of these invasive plants!

Deborah and I noticed on our Baker Trail hikes six years ago that many native plants were avoided by deer in favor of introduced ornamental and garden species. We planted a native perennial garden in our field in an attempt to have some deer resistant flowering plants around our house. We especially planted bee balm (Monarda spp) and enjoyed its bright blossoms and the wonderful array of bees and hummingbirds it attracted! The “deer resistance” worked for about a year, but then the deer decimated all of the previously resistant species (especially the bee balm!). Deer are adaptable (and voracious!). We now hide the bee balm in our fenced-in yard!

Photo by B. Lammers, Wikimedia Commons

Photo by B. Lammers, Wikimedia Commons

A recent article in the New York Times (by James Gorman, July 18, 20166) discussed another aspect of the large, eastern U.S. white-tailed deer population: collisions with cars. Each year there are more the one million deer/car encounters, and two hundred people a year die as a result!  Gorman’s article highlights some serious discussions among wildlife biologists (in the journal Conservation Letters) about a way to reduce deer populations and the subsequent number and staggering costs of deer/vehicle accidents. These wildlife biologists estimate that over thirty years the change that they have proposed could prevent 155 human deaths and 21,400 human injuries, and save $2.3 billion! The change is quite simple: re-introduce the eastern cougar to its original range throughout the East! These researchers estimate that a cougar would kill 259 deer over its six year life span, and that allowing cougars to return to their historical population densities would help to bring the exploding deer populations under control!

Of course there are a few downsides to having a large, active predator among us. Livestock would be attacked and eaten (estimated losses 2.35 million dollars a year), people would be attacked and even killed (estimated only one person per year would die of cougar inflicted injuries), and house pets would also be consumed by the cougars (the researchers, though, could not come up with a realistic estimate of the numbers of dogs and cats that would be eaten by the cougars). The researchers also acknowledged that the fear of being in a car crash doesn’t generate the same level of anxiety in most people as the possibility of being leaped upon by a lurking cougar.  They recognize that their plan has a steep uphill climb to reach any level of public acceptance!

There is also the distinct possibility that adding cougars to the eastern U.S. fauna might not affect deer populations at all! The wildlife biologists acknowledge that 75% of the deer killed by cougars would probably have died due to some other fatal event, and that more fawns would be expected to be born if the number of adults were reduced. So, total deer population numbers might stay the same!

I don’t expect cougars to be widely re-introduced into our eastern forests. We do need, though, to be aware of the seriousness of our current deer problem! We can’t fence in a whole forest to prevent the browser hijacking of its natural regrowth and succession, but we need to find a way to find a new, functional balance to maintain our forest biomes!

Photo by D. Sillman

Photo by D. Sillman

Just a short note about the deer in my yard and field: we have, as I have written about many times before, a herd of deer that numbers 7 or 8 individuals. This year there are two older and three younger does (probably last year’s fawns) and two fawns. For the first time in six years, there are no twin fawns. The two older does have each had a single offspring. There is also a young buck that tries to join this loose group out. He is sporting short, simple looking antlers and may be the male sibling of one of the younger, yearling does. The fawns are very interested in the buck (see photo above!), and we have watched them approach him to sniff and even touch noses. Usually, though, the does chase the young buck away if he tries to get too close or too familiar.

Photo by D. Sillman

Photo by D. Sillman

The big attraction, right now, for the deer are the green apples that are falling from the trees in our orchard! The fawns especially like the sour, hard apples and are out under the old trees at almost any time during the day. There must be something incredibly addictive in the taste of these apples! Twisted up faces and violent head shaking while chewing them doesn’t seem to deter any of them from taking a second (and third, and fourth!) bite!

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Signs of Summer 11: Trees, Mastodons and Giant Ground Sloths

Photo by D. Sillman

Photo by D. Sillman

I was trimming low branches under my Norway spruce a few days ago, making room for some leftover stones from my driveway wall re-construction, when I found a white oak seedling growing along with some struggling Virginia creeper and poison ivy. The seedling looked quite healthy in the cool, moist, but almost sunless space under the spruce, and since, at least until very recently,  there have been no white oaks growing on my property, I assumed that this seedling’s acorn was flown in a few years ago and accidentally dropped by a blue jay or crow.

Reproducing oak trees invest a substantial amount of their metabolic energy into their acorns. They make their acorn “packages” as appealing as possible to a wide range of birds and mammals and count on some acorn consumers being clumsy with these nutritious morsels. A few of the acorns will, hopefully, be dropped in places where germination is possible and where seedling browsers aren’t abundant. I was looking at the winner of an intense reproduction gauntlet: an oak seedling growing far from the parental tree.

In a nutshell (sorry, very bad pun!) that’s why plants have evolved fruit and nuts! Inside these tempting pieces of food are the embryos of the plants’ next generation, and those plants that can use animals to fly or walk at least some of these embryos to more distant habitats will disperse, thrive and then go on to produce more and then even more individuals. They will be more likely to “win” the great biological contest of survival and replication!

Photo by fir0002, Wikimedia Commons

Photo by fir0002, Wikimedia Commons

There are examples of this process all over my yard and field: there are chestnut seedlings growing in several corners of my two acres where squirrels, carrying the nuts dropped them (or buried them) and then went off to do something else. I have watched gray squirrels carrying chestnuts that are still encased in their spiky burrs suddenly stop, shake their heads and fling the nut away. My sense is that one of the burr spikes jabbed itself into the flesh of the squirrel and triggered the reflexive shudder and toss! Could the sharp spikes of these burrs be more than just protective barriers against non-dexterous nut predators? Maybe they are dispersal triggers, too? The latter might even be more important in an evolutionary scheme!

Fruit is designed to attract consumers at just the right time so that the mature plant seeds can go for a ride often inside of the fruit consumer’s intestines. The seeds then leave the consumer along with a dollop of fertilizer (feces has many uses!), and, if all of the environmental variables line up, the seeds germinate, grow, survive and then also reproduce. I look around my yard and see raspberry thickets, mulberry trees, grape vines, cherry seedlings, and poison ivy growing in perfusion all thanks to the bird dispersal of each species edible and enticing fruit!

So, fruits are made to be eaten (seed and all) and the payoff for the plant, as I have said before, is the sudden acquisition of wings and legs!

There are a few apparent glitches in this scheme, though. There are quite a few plants (especially some trees) that have fruits that either can’t be eaten or seeds within their fruit that would, quite literally choke a horse. A seed that can’t be swallowed will be very hard to disperse! The plant’s investment into that fruit and seed, then, does not result in the big dispersal payoff (it more closely resembles the investments that I have in my retirement portfolio!).

Photo by Haplonn, Wikimedia Commons

Photo by Haplonn, Wikimedia Commons

Dan Janzen (University of Pennsylvania) is a renowned tropical ecologist (and the author of the 1983 book Costa Rica Natural History which I have enjoyed and relied on as an authoritative reference for the past thirty years).  Many years ago Janzen noticed that a middle canopy tree of the rain forest of Costa Rica called the “pink shower tree” (or Cassia grandis) had long, woody seed pods that were not eaten by any of the native animals of Costa Rica. These seed pods, though, were avidly consumed by cattle and horses (both of which were alien exotic species in these ecosystems!). He eventually described about forty other tree species of these forests that produced fruits that were not eaten by any of the native animals! Unconsumed fruit meant non-dispersed seeds! The evolutionary “fruit and seed dispersal contract” was not being honored in today’s ecosystems!

Giant ground sloth, Photo by Ballista, Wikimedia Commons

Giant ground sloth, Photo by Ballista, Wikimedia Commons

Janzen in collaboration with Paul Martin of the University of Arizona developed the idea of “ecological anachronisms.” The Costa Rican trees must have developed their fruits in co-evolutionary relationships with large animals that had since gone extinct!  These trees without their giant ground sloths or massive, elephant-like gomphotheres now were investing their precious metabolic energy into a seed disposal system that no longer existed! They had become “ecological anachronisms.”

A tree that grows closer to home that also reflects a hidden evolutionary history is the Osage orange (Maclura pomifera). The fruit of the Osage orange is a large, seed-filled, softball sized sphere that contains a white, sticky fluid. No animal eats these fruit and, not surprisingly, the Osage orange has a very restricted natural range (in east-central Texas,

Osage orange fruit, B. Martin, Wikimedia Commons

Osage orange fruit, B. Martin, Wikimedia Commons

southeastern Oklahoma, and northwestern Arkansas) even though it is very well adapted to grow throughout the continental United States and southern Canada (it has been planted, often as a living fence, in 39 of the lower 48 states!). This natural range restriction is undoubtedly due to the absence of natural seed disperses (probably mammoths or giant ground sloths, two species that went extinct in the later Pleistocene when, coincidentally or not, humans first came to the North American continent).

Kentucky coffee bean fruit, Hardyplants, Public Domain

Kentucky coffee bean fruit, Hardyplants, Public Domain

There are many other temperate and tropical trees that have fruit and seeds that are anachronistic: the large seed pods of the Kentucky coffee bean tree and the honey locust (two trees that my students and I have planted in conjunction with the Pennsylvania “Tree Vitalize” program) are not eaten by native animals (and both tree species have very constricted natural ranges in spite of their robust ability  to grow under a wide variety of conditions (as demonstrated by their survival along the streets of New Kensington and many other towns in Western Pennsylvania!)). Avocados, as Lee Drake pointed out last March in Albuquerque, look like giant ground sloth or mastodon food to me! So do papayas, pawpaws, persimmons, and even wild squash! Big fruit and seeds require big mouths and big intestines to be ecologically and evolutionarily functional!

Photo by Dantheman, Wikimedia Commons

Photo by Dantheman, Wikimedia Commons

There are many features of our trees and forests that reflect other ecological anachronisms and relationships with departed species. Whit Brounaugh wrote a wonderful article entitled “The Trees That Miss the Mammoths” in the Winter 2010 issue of American Forests, and George Monbiot wrote “Thinking Like an Elephant” in the June 2015 issue of BBC Wildlife. Growth patterns of trees, the strength of their trunks and branches, the patterns and sizes of their protective thorns, etc. all suggest a long, adaptive evolutionary interaction between the trees and large browsers and seed dispersers that no longer exist.

Many of our trees have been sculpted by evolutionary and ecological ghosts, and the momentum of these evolutionary changes has continued even long after these “prime movers” were gone!

 

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Signs of Summer 10: Eastern Towhee

Photo by D. Sillman

Photo by D. Sillman

Eastern towhees (Pipilo erythrophthalmus ) are one of Deborah’s and my favorite birds of summer. We met our first towhee in 1984 out on the old farm we rented in northern Allegheny County. A pair of them set up their nesting territory in the woody thickets that bordered the long, rutted, gravel path that was our only way in and out of the hollow where our farm house and barn were situated. We frequently walked down the path to get to the hiking trails and pipeline cuts that ran up into the wooded ridges to our south and whenever we did we were chirped and chittered at by the flashing male towhee. Initially we had to go to our Peterson Field Guide to figure out that he was, as they were called then, a rufous-sided towhee. They were on the same page as the rose-breasted grosbeak which was just after the page with the blue grosbeaks and the indigo buntings, three birds that we also had the great pleasure of seeing on the farm that summer. It was a wonderful place for birds!

At first I thought the towhee, in spite of its obvious field guide location among the sparrows, was some sort of robin or related thrush. It was smaller than a robin but so much larger than a sparrow that it really took some intellectual discipline to accept the kind of bird that they were! Their beaks, once you got a good look at them, were obviously cone-shaped and very non-thrush-like, but it made me glad to see later on as I read about them that they are frequently called “ground robins” (which, if you think about it, is a very strange name! I mean what should you then call regular robins that are mostly found on the ground?).

Photo by D. Sillman

Photo by D. Sillman

Towhees are birds of thickets and edges. They build their cup-shaped nests on the ground under the protective cover of dense branches and vines and frequently dig the nest down into the covering leaf litter for better concealment. They typically feed in the surrounding leaf litter, too, using a two footed scratching technique to fling the dry leaves about to uncover a wide variety of insects and other invertebrates. In fact, one of the best ways to find a towhee out in the field is to listen for loud, energetic scratching under the bushes!

Towhees also eat a wide range of seeds and fruits and have even been known to consume small lizards and snakes! They also have been observed raiding the nests of other birds to eat eggs and nestlings, but, hey, no species is perfect, right?

Towhees are subject to intense nest parasitism by brown headed cow birds (Molothrus ater). In some areas over half of the eastern towhee nests will have cowbird eggs. The towhees, though, do not seem to able to recognize these foreign eggs and spend a great deal of their reproductive energies feeding and rearing these brood parasites.

Eastern towhees in their northern ranges migrate relatively short distances either between sheltered local habitats or milder, southern regions. They have relatively short wings and are not strong fliers. They dart about from ground to low shrub branches in a very characteristic flapping and gliding flying pattern.

Photo by D. Sillman

Photo by D. Sillman

We regularly see eastern towhees up at Harrison Hills Park when we are out doing our bluebird nest box monitoring. The extensive shrubby areas in the park are ideal for this species, and we are frequently hear both the underbrush scrapping and scratching and also the distinctive “cherrit!” (often sounded out in field guides as “drink your teeeeee!”) of the very territorial males.  The males seem especially interested in us as we walk past or through their territories. They keep a close eye on us and shadow us along our way.

Interestingly, eastern towhees mark out much larger territories than they actually require in order to provide adequate food supplies for their nestlings. They are extremely aggressive against any other towhee that might venture into their territories and have a wide range of displays and postures (frequently involving the flashing of the white tips of their wings) by which they express their anger and outrage! Not surprisingly, towhees are very solitary birds and seldom seen in flocks, but there is a marvelous name for these seldom seen aggregations! A group of towhees is called a “tangle” or a “teapot” of towhees.

Photo by J. Mayer, Flickr

Photo by J. Mayer, Flickr

Towhees can nest two or sometimes even three times in a season. A parental pair stays together for a given spring or summer but then the mating pairs re-shuffle for the next season. The female builds the nest with only minimal assistance from the male. It takes her about five days to complete the nest (a complex mix of sticks, rootlets, grass, bark, and leaves, and lined with soft grass and animal hair (paper and other human materials may even be incorporated into the nest materials).

Two to six creamy white, brown spotted eggs are laid in each clutch. As previously mentioned, nest parasitism by brown headed cowbirds is very high and overall nest predation by chipmunks, raccoons, and a variety of snakes is also quite severe. Nest success rates of less than 20% have been regularly reported. The Cornell Laboratory of Ornithology reports that there are approximately 28 million eastern towhees in North America and that their population has declined by 49% between 1966 and 2015. Loss of brushy habitats (due to human development of sites and also to ongoing forest succession) and the impacts of cowbird parasitism are given as the main causes of these population declines.

I am very happy to report that for the second summer in a row Deborah and I have a towhee residing in our yard! We see him regularly at our front yard bird feeder and also under our arbor vitae and spruce trees digging through the leaf litter. For the past three years I have raked my autumn leaves under these shrubs and trees to give shelter to insects and to generate a food source for foraging birds (not to mention possible overwintering habitat for tree frogs!). Maybe these leaves are the key to drawing towhees in close to our house! They are a truly welcome addition to our local fauna!

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Signs of Summer 9: Summer Signs

Photo by D. Sillman

Photo by D. Sillman

Deborah and I have been keeping our eyes on some of the biological and ecological “events” of the summer of 2016. Since we have just slipped past the halfway point of the season, it’s time to think about some of these.

We have had some very successful reproductive efforts by the birds that visit our feeders and leaf piles! The cardinals and the robins have each had two nesting and fledgling cycles so far and seem to be starting up on another (both are out gathering new beaks-full of grasses and stems for their nests!). The chickadees and titmice have also gotten two nesting cycles done but seem to be less inclined than the cardinals or the robins to start into a third. The Carolina wrens also went through their usual mate re-shuffling kerfuffle in late June and have settled into a second nesting period.

Photo by D. Sillman

Photo by D. Sillman

The common grackles arrived at our feeders late in the spring, but they must have nested and fledged their young very quickly because there is now a robust flock coming to the feeders dominated by a large percentage of dark brown, immature birds. They swoop into the feeder areas about 10 am and especially like the scattered shelled corn (which they frequently dunk in the water of the bird bath before eating!).  I am very tolerant of the grackles and put out extra corn for them at mid-day. I remember them voraciously eating gypsy moth caterpillars back in the gypsy moth explosion years of the 1990’s and want to continue to thank them for their efforts!

Photo by D. Sillman

Photo by D. Sillman

The blue jays and crows have completed their single nesting efforts and are now leading their fledglings around our complex habitats drilling them on food finding protocols and safety procedures. The first and second robin fledglings have gone from stumbling klutzes tripping through the leaf piles to confident, elegant hunters and efficient spearers of worms and caterpillars.

The mourning doves seem as though they have been mating all summer! I have lost track of how many nesting cycles they have gone through! The sharp-shinned hawks mated back in the late winter (the female was, as usual, extremely loud calling from the bare branches of our backyard black locust tree). Early in the morning we frequently see a sharp-shin swooping across the top of the front yard bird feeders. We also frequently find small piles of feathers (usually doves or cardinals) around the edges of our field. We have never seen, though, a sharp-shin fledgling! They are said to be secretive birds during reproduction and very wary of larger hawk predators (like goshawks and red-tails).

So, most of the birds seem to be behaving quite normally for a Western Pennsylvania summer, but many of the insects and other arthropods are acting quite oddly this year and they may be having some impacts on a wide variety of other species!

Aedes albopictus Photo by J. Gathany CDC Wikimedia Commons

Aedes albopictus Photo by J. Gathany CDC Wikimedia Commons

For example (and we are not complaining about this at all!), we have fewer mosquitoes around our house this summer. We are regularly sitting out on our deck well into the evening with minimal aggravation from buzzing and biting mosquitoes. These longer deck times, though, possibly go along with seeing fewer chimney swifts and fewer bats soaring over our field gobbling up all sorts of flying insects (but especially great numbers of mosquitoes!). The hummingbirds also came into our yard quite late this summer (they waited until the lure of the flowering bee balm in Deborah’s flower bed was overwhelming!). Hummingbirds are frequently described as “nectar powered insect eaters.” Possibly the lower numbers of mosquitoes reduced the feeding quality of our yard and field for the hummingbirds and caused them to linger elsewhere until the nectar scents were just too compelling!

Photo by JJ Harrison Wikimedia Commons

Photo by JJ Harrison Wikimedia Commons

Also, and we are not complaining about this either, there were no little “sugar ants” in the kitchen this spring! Every other May and June that we have been in this house (and in one week we will celebrate the 27th anniversary of our house closing!) we have had several weeks, at least, of columns of ants streaming in through tiny cracks around the kitchen window and door in search of any available crumbs or sticky residues. This year the ants did not show up! We think that these ants are mostly odorous house ants (Tapinoma sessile), but they may have been joined in bumper ant years, by the European exotic species called the pavement ant (Tetramorium caespitum).  They are both little black ants that may fall into the very broad, common category of “sugar ant,” but one of them (“odorum”) gives off a bad smell when it is crushed.  We seldom crushed any of them, but frequently washed a number of them down the drain.

Another insect change this year is a very small number of brown marmorated stink bugs (Halyomorpha halys ) emerging from their winter, in-house hibernations.  Again, we have no problems with the direction of this change! I talked about this earlier this summer (Signs of Summer #3, June 16 2016). The lower numbers may be due to the growing activity of the predators of stink bug adults and eggs. Everything from spiders and chickadees to earwigs and katydids are now eating these exotic pests.

Photo by D. Sillman

Photo by D. Sillman

And finally, another arthropod that is less numerous and less active in our summer of 2016 ecosystems is the deer tick! We have had, along with most of Pennsylvania and much of the northeast, huge numbers of deer ticks in our rural and suburban ecosystems. These ticks are the arthropod vectors that spread the bacterium that causes Lyme disease, and as a consequence of their large numbers, Pennsylvania has had for the past few years the greatest number of Lyme disease cases in the country. Our yard and field have been a rich reservoir of these ticks. Walking out in the yard in sandals almost guaranteed you a tick or two, and our dog, Izzy, and our cat, Mazie, weekly (and sometimes daily!) picked up deer ticks from their forays within the fenced-in yard off of our deck. This spring and summer, though, we have found no deer ticks on either humans or pets! Further, our trampling around at Harrison Hills Park to check our bluebird houses also has not generated any ticks (a big change from last year!).

I am not sure why, and would like to ask everyone reading this post to think about your tick experiences this summer. Have you seen any deer ticks as a consequence of hiking or yard work or dog/cat interactions? Are we seeing some change in our deer tick populations?

Wow! Pennsylvania will surely get crowded with people if we start to have mosquito free and tick free summers! Real estate prices will go up! House sales will increase! Nothing but good things (unless you like chimney swifts and bats, of course).

More on all of this soon! Happy summer, everyone!

 

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Signs of Summer 8: Cavity Nesting Team!

Photo by D. Sillman

Photo by D. Sillman

Last year I wrote two blogs about our Cavity Nesting Team study up at Harrison Hills Park in northern Allegheny County (May 28 and October 29). We had a very good year with our bluebirds and tree swallows. We had 13 boxes that had bluebird nests with a total of 65 eggs and 48 fledglings (a 74% survival rate), and we had 9 boxes that had tree swallow nests and a total of 31 eggs and 22 fledglings (a 71% survival rate). Nine of our thirty nest boxes, though, did not have any nesting activity, so, using our locations of utilized boxes as a guide, we relocated seven of these inactive boxes to try to make them more attractive to cavity nesting bird species. We left two of the inactive boxes in their 2015 locations because they seemed to be in ideal spots for cavity nesting birds (we must acknowledge, however, that we were wrong about their ideal locations! (see discussion below)). Our overall criteria for relocation were quite straightforward: boxes too close together tended not have nests (so spread out the clumped together boxes) and boxes right on the edges of field (i.e. very close to surrounding woodlands) were not used (so move the boxes away from the extreme edges of our fields).

This year’s Cavity Nesting Team consists of eight volunteers: Deborah and I and Sharon Svitek take turns monitoring the boxes in and around the “High Meadow” area of the park. Patrick and Mardelle Kopnicky check the boxes around the “Bat House Meadow.” Chris Urik and Odessa Garlitz take turns monitoring the boxes at the park entrance and up in the field near the Environmental Learning Center, and Paul Dudek checks the boxes around the pond and soccer fields in the southern end of the park. Every box is checked each week, and then each observer enters their data into an on-line Google spreadsheet. Each week, Deborah compiles and distributes the growing data tables to each member of the team. Chris Urik also has made GPS maps of the park showing the precise location of each nesting box.

Photo by D. Sillman

Photo by D. Sillman

As I talked about last year, native cavity nesting bird species (eastern bluebirds, tree swallows, house wrens, Carolina wrens, titmice, chickadees, nuthatches, etc.) naturally use tree holes for their nesting sites. These holes are typically found in older, often dead trees and are frequently abandoned cavities that have been chiseled out by woodpeckers. Any site management plan that favors woodpeckers (allowing dead trees to remain in the forest and not managing the forest or manipulating it into an even aged stand) will favor cavity nesting bird species.

Nest boxes are artificial substitutes for these natural tree holes. Eastern bluebirds, in particular, came under a great deal of stress in the past century. The influx of the alien invasive English sparrows and European starlings along with the habitat spread of the nest parasite, the brown headed cowbird, were major reasons for the bluebird’s numerical and distributional decline throughout the twentieth century. Human destruction of nesting and feeding habitats also contributed to this decline. Human efforts to provide existing bluebird populations with suitable and secure nesting sites (“bluebird boxes”) have, however, been extremely successful in bringing this beautiful species back from the brink of possible extinction. The North American Breeding Bird Survey reports that since 1966 eastern bluebird populations have increased by nearly two percent a year! The Cornell Laboratory of Ornithology estimates the worldwide population of eastern bluebirds (80% of which spend at least some time in the United States) at a very robust 22 million individuals.

K. Thomas, Public Domain

K. Thomas, Public Domain

We are just past the halfway point of the summer, but our nest box data is showing some very interesting trends. First and foremost, our strategy for moving the inactive nest boxes has been very successful. All seven boxes that we moved have had nesting activity this spring and summer! Five of them have had bluebird nests (and have generated 13 bluebird fledglings), one box had a successful chickadee nest (4 fledglings), and one had a tree swallow nest (with eggs, nestlings and fledglings that were too hidden in the nest materials to count). Further, four of these nests were then utilized by house wrens (although it seems these secondary nests did not produce any viable fledglings). The two inactive boxes from 2015 that we did not move (because they just seemed like PERFECTLY located boxes!) still did not have any nesting activity. We need to look at these two locations more closely to try to see why they were not utilized by any of our cavity nesting species! We need to learn to think more like bluebirds and swallows!

So far this summer 17 of our boxes have had bluebird nests (with 61 eggs and 45 fledglings). These numbers are almost equal to the totals from all of last year, and we are just coming into the second wave of the bluebird nesting and reproduction! We expect to significantly surpass last year’s egg and fledgling totals for bluebirds!

K. Thomas, Public Domain

Tree swallow, K. Thomas, Public Domain

Our tree swallow numbers, though, have been less robust than last year. Only six boxes have had tree swallow nests and there have been only 9 confirmed fledglings (although two nests did have nestlings that we expected did fledge, but the nest construction prevented direct observation of the birds. Even so, the 9 fledglings (even plus the 6 or 7 that might have come from the concealed nests) is well below the 22 fledglings we observed in 2015. Tree swallows have been described as “income” breeders that base their timing of reproduction on

Photo by dfaulder, Wikimedia Commons

House wren, Photo by dfaulder, Wikimedia Commons

short-term rates of food intake near the time of breeding. Reduced clutch size in tree swallows is a strategic response to limited resource abundance. Since the primary food of nestlings are adult insects that have aquatic larvae possibly some factors (weather? water quality? something else? ) have reduced the abundance of these insects and the tree swallows have responded by curtailing reproduction. It is also possible that the increased abundance and nesting activity of the house wrens has affected the tree swallow nesting and reproduction efforts. House wrens are known to actively interfere with the nest box selection and nesting activity of tree swallows.

So the cavity nesting cycle continues! We will keep monitoring these boxes on through Labor Day. I will let you know our final counts and observations!

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