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Eastern Kingbird; Tyrannus tyrannus
The Eastern Kingbird (Tyrannus tyrannus) is the most common kingbird in North America. The species’ physical attributes, habitat preferences, breeding behaviors and migratory/survival skills all contribute to its prominence and abundance.
The Eastern Kingbird is classified as a songbird, but it is in its own songbird subgroup that innately know their calls at birth (in contrast to most songbirds that learn their calls during growth and development). Like many songbirds, the Eastern Kingbird has two distinct songs. One song is its “dawn song,” and the other is its mating call. Both can be described as a rapid and loud whistling “chatter-zeer” noise, but the mating call is more “high-pitched and explosive”.
Adult Eastern Kingbirds have black heads, a blueish-black mantle and bluish-grey wings with a white outer band, a black tail with a white tip, and their distinct red, yellow, and orange crowns on the front of their heads. These crowns are used as in defense and mating displays (Complete Birds of North America). Its lifespan is around seven years which is quite long for a songbird. Its longevity is one factor in its wide distribution and abundance (Birds of North America: DK Publishing).
Kingbirds nest in open habitats, especially trees such as hawthorns, apples, elms, mulberry, Osage-oranges, and Norway spruces. Nests are mainly made of layers of twigs, leaves and dirt. Open wetland spaces are preferred so that it can have a large field of vision for a potential next meal or a nearby competitor or threat. The Eastern Kingbird is an aerial-hawking insectivore or “flycatcher” that is quite abundant across the Northeastern United States. It is also found west of the Mississippi River and across the Great Plains to the Pacific Ocean. It may also be found in Canada and in the South American tropics during the winter season (The Birds of North America). Its light weight and broad wingspan relative to its small body allow it to be agile while also being aggressive (especially during their May-August mating season). This “aggressive advantage” is a leading factor as to why Eastern Kingbirds are so abundant and dominant in a wide range of habitats.
Kingbirds tend to avoid nesting near heavily forested areas as it provides less open space for hunting and mating. They are also less common in rural and urban populated areas. In Pennsylvania, they are most abundant in the northeast and in the northwestern glaciated-regions. This is due to an abundance of open wetland habitats and resources (The Birds of Pennsylvania).
The birds gravitate toward small bodies of water, orchards, and grassy fields due to the open space and insects. Beetles, wasps, winged ants, flies and bees are their preferred prey in these areas. It isn’t only food resources that are critical for survival, though, it is also the resources for nest success. (Audobon Field Guide and Sibley Field Guide). A recent study found that Eastern Kingbirds are more likely to use the most available nest resource in their surrounding habitat. It also showed that nesting closer to these environmental resources contribute largely to the species’ nest success. Also, when the birds’ nest canopy cover is generally lower and smaller in size, the nest success is higher. This may be due to less exposure to predation from high-flying birds which provides good protection. The tendency for a kingbird to re-nest in the same area as before is dependent on predatory factors from the previous nesting area. Ultimately, it is much more effective to take safety precautions as opposed to fighting for safety, regardless of how fierce the Eastern Kingbird can sometimes be. (Comparative Analysis of Habitat Selection, Nest Site and Nest Success by Cedar Waxings and Eastern Kingbirds).
Breeding behaviors of the Eastern Kingbird also prove to be interesting. Since there are more males than females in a typical kingbird populations, the female kingbirds often have more than one mating partner during their lifetimes. This has allowed them to become slightly dominant and more aggressive than the male. Studies have revealed the kingbirds with a mid-sized wingspan to be more productive than ones with a bigger or smaller wingspan, but things such as clutch size and tarsus length had no contributing factor to the lifetime reproductive success of the birds. The study results showed that the main reason for lifetime reproductive success in Eastern Kingbirds is due to their age longevity and ability to reproduce more often than most other birds in their lifetimes. (Murphy, Michael).
Males display their orange crowned plumage as they fly in a zig zag motion trying to attract potential mates. Kingbirds who start their dawn songs earlier have a better overall morphology than later arriving kingbirds, and the early arriving singing males were more likely to mate with the earlier arriving singing females. Since the Kingbird has two types of songs, this may contribute to its mating success. Song and morphology are just two of the many dominant traits that go into the category of genetic dominance (Dawn Song of the Eastern Kingbird: An Honest Signal of Male Quality?).
Shortly before and just after its breeding season, kingbirds are aggressive and territorial as they assert their levels of dominance. One study looked further into the effect that the bird’s behavior has on its breeding success. When the results were analyzed, the study found that the birds did indeed exhibit a pattern of delayed breeding. This delayed breeding that was observed is due to the aggressive nature of the birds, which results in the birds taking a longer time to find nesting space as well as a partner with which to reproduce. The study also showed a pattern of non-territorial birds having to migrate in order to reproduce (Cooper, N.W. “Density-Dependent Age at First Reproduction in the Eastern Kingbird).
Eastern Kingbirds are monogamous and because of this, brood-parasitism is generally uncommon but quasi-parasitism is more common. Brood parasitism is essentially when another species uses the Eastern Kingbird’s nest as a host-nest for its own young while quasi-parasitism refers to individuals of the same species laying eggs in the host nest. So, it is more likely for kingbird nests to be parasitized by a member of its own of species rather than another. Due to the fact that it is difficult to introduce breeding alternations for reproductive strategies in monogamous avian organisms, it is difficult to measure the frequency of quasi-parasitism and brood parasitism in the species. (McKitrick, M.C.) Cowbird are the most well known brood parasite of the kingbird. One experiment attempted to measure the interactions of Cowbirds with the Eastern Kingbirds. It found that the Kingbird will typically dispose of any added cowbird eggs within twenty-four hours. Kingbird eggs introduced to the nests were also quickly ejected and or abandoned, but at a slightly smaller rate than the brood parasite eggs. Results showed that the evolutionary response to a parasitic nest-threat wasn’t discriminatory towards any one type of invading species, but rather a response to the recognition of the parasitism of the nest in general. Although the study helped to show how the kingbirds often respond to parasitism, it is difficult to currently detect the rate of nest parasitism in the species. (Sealy, Spencer).
Eastern Kingbirds eat a variety of insects, aquatic animals, rodents and small amphibians such as frogs. During the fall and winter migration seasons, the birds become more social and switch their diet from insects and small rodents to tropical berries and nuts. They attack predators like hawks, crows, blue jays and squirrels, sometimes knocking them out of their nests. The Eastern Kingbird has an attack or defense strategy that is rather brutal. The kingbird swoops in on its prey and picks it up with its tiny, yet strong hinging beak and smashes it into a nearby perch until it eventually kills it and swallows it down. This aggressive nature is due to the fact that it relies heavily on insects, other prey, and fruits (during wintering seasons) for retaining a hydration level necessary for survival (All About Birds).
A fruit that is commonly consumed for both its nutritional and moisture levels is the wild fruit of the Yagrumo Macho tree (found along disturbed sites and forest edges). A high concentration of this tree is found in central Brazil, and the Eastern Kingbird migrates in large numbers to the center of the tropical South American Country. It returns to North America when the fruit’s availability drops with the changing of seasons. During spring migration, the kingbird follows the Mexican east coast northward back to America for mating season. When migrating, Eastern Kingbirds flock in groups that range up to several dozens. Due to the timing and rate of migration directly relating to the availability of the Yagrumo fruit as well as other fruits in Central America, it is safe to say this birds’ migration patterns are directly caused by their dietary resource availability.
There have also been numerous studies regarding the Eastern Kingbirds’ survival capabilities. One experiment was conducted to show which characteristics of the bird contributed to migratory success. Among a few sets of variables measured were wing span, body size, arrival times, and breeding tendencies. There was a clear genetic and behavioral advantage correlation between female and male kingbirds. The ones who arrived earliest during the spring time also seemed to have the best physical attributes for survival such as a large wingspan and a narrow body. These same birds also proved to be more than likely to mate with each other and at a faster rate than the other birds.
Rain and colder environments are bad for food because there are few insects to eat in harsh, cold, and/or wet conditions during the migrating time for the kingbirds. The obvious physical advantages and other traits in the most dominant kingbirds allowed them to push through such tough conditions much better than the more average birds (Cooper, N.W. “Reproductive Correlates of Spring Arrival Date in the Eastern Kingbird (Tyrannus tyrannus).
Sometimes physical advantages aren’t enough to ward off predators. Kingbirds can sometimes fall prey to other larger birds such as hawks, crows, and even arboreal snakes and tree squirrels. Regardless, it is known for using its aggressiveness to quickly turn the predator into a prey (Guide to Boreal Birds). A study was performed to test different populations of Eastern Kingbirds on their response to nest predation in one controlled environment and whether or not they protected their young. It was found that when an adult kingbird is approached by something that it perceives as a threat, it will flee the nest. It was concluded that when introduced to the crow model predator, only a percentage of the birds recognized the crow as a threat. This was probably due to certain birds having grown up in environments where crows were not common. After repeated exposure trials, the majority of the birds began to flee their nests. Of the two different types of nest “variables” being measured in the experiment, (one being a nest full of a mother’s unhatched eggs and the other being full of a mother’s young), there were no distinct results showing if an adult kingbird was more likely to defend their unhatched young as opposed to hatched young. Although the unhatched young did seem to be defended at a slightly higher rate as the already hatched young, this is not enough evidence to support that the kingbird will care for and protect its young less and less as they grow. The experiment helped to prove that parents are more caring and nurturing of their young and seem to care less as the young mature (Siderius, Joanne).
The Eastern Kingbird can survive in stressful environments. A study conducted from 1981-1983 to determine the influence of wetlands acidification and lake water chemistry on the growth and reproduction of the Eastern Kingbird. The kingbird exhibited an unorthodox pattern of population growth and eating habits that were unaffected by the fact that the lakes became more acidic. The birds adapted to the food limitations caused by lower pH levels. (Blancher, P.).
Another study measured different two populations of kingbirds: one on a floodplain and the other more human-populated rural upland. Clutch size, overall egg mass, and nest success did not vary across different locations and environments. The survival rate of the kingbirds in the floodplains in this study was the only factor measured that was much higher than the other populations’ survival rates. This shows that many environmental factors have barely any limiting effect at all on the Eastern Kingbird; the only real evident limiting factor that showed up in the experiment results were the reduced survival rates (2.5%) of the birds in the rural upland environment. It was concluded that this is mostly due to an increased rate of humans moving into rural areas and new buildings being constructed. The birds in the rural areas lose more habitat space in those areas (Habitat-Specific Demography of a Long Distance, Neotropical Migrant Bird, The Eastern Kingbird).
Kingbirds populations have slowly declined in North America over the course of the past half century. Because they are so widespread, it would be very hard for them to significantly decline in overall population. This means that they are listed under the category of least concern by environmental analysts (BirdLife International).
General Information Bibliography
Dewey, Tanya. “Tyrannus Tyrannus – Eastern Kingbird.” Animal Diversity Web, www.borealbirds.org/bird/eastern-kingbird.
“Eastern Kingbird – Topic Overview.” All About Birds, www.allaboutbirds.org/guide/Eastern_kingbird/id.
“Eastern Kingbird.” Audubon, www.audubon.org/field-guide/bird/eastern-kingbird.
“Guide to Boreal Birds: Eastern Kingbird.” Boreal Songbird Initiative, 2015, www.borealbirds.org/bird/eastern-kingbird.
Murphy, Michael T. “Eastern Kingbird: Tyrannus tyrannus.” The Birds of North America, 1 Jan. 1996, birdsna.org/species-account/bna/species/easkin.
McWilliams, Gerald. The Birds of Pennsylvania, Comstock Publishing Associates of Cornell University Press, 2000. Sibley, David. The Sibley Field Guide to Birds in Eastern North America. Knopf, Alfred, 2003.
“Tyrannus Tyrannus – Species Factsheet.” BirdLife International, 2016, www.birdlife.org/datazone/species /factsheet/227000506.
Vuilleumier, Francois. Birds of North America, DK Publishing, 2009.
Wood, Christopher. Complete Birds of North America, National Geographic Society, 2006.
Scientific Bibliography
Blancher, P. “Association of Wetland Acidity with Reproductive Parameters and Insect Prey of the Eastern Kingbird.” Acidic Precipitation, 1987, pp 553-567. Springer Link, doi: 10.1007/978-94- 009-3385-9_55.
Cooper, N.W. “Density-Dependent Age at First Reproduction in the Eastern Kingbird.” Okios, vol. 118, no. 3, Mar. 2009, pp. 413-419. Wiley, doi: 10.1111/j.1600-0706.2008.16997.
—. “Reproductive Correlates of Spring Arrival Date in the Eastern Kingbird (Tyrannus tyrannus).” Journal of Ornithology, vol. 152, no. 1, Jan. 2011, pp. 143-152. Springer Link, doi: 10.1007/s10336-010-0559-z.
McKitrick, M.C. “Genetic Evidence for Multiple Percentage in Eastern Kingbirds.” Behavioral Ecology and Social Biology, Mar. 1990, vol. 26, no. 3, March 1990, pp. 149–155. Springer Link, doi: 10.1007/BF00172081.
Murphy, Michael. “Comparative Analysis of Habitat Selection, Nest Site and Nest Success by Cedar Waxings and Eastern Kingbirds.” The American Midland Naturalist, vol. 138, no. 2, 1997, pp. 344-356. JSTOR, doi: 10.2307/2426827.
—. “Dawn Song of the Eastern Kingbird: An Honest Signal of Male Quality?” Animal Behaviour, vol. 75, no. 3, Mar. 2008, pp. 1075–1084. ScienceDirect, doi: dx.doi.org/10.1016/j.anbehav.2007.08.020.
—. “Habitat-Specific Demography of a Long-Distance, Neotropical Migrant Bird, The Eastern Kingbird.” Ecology: A Publication of the Ecological Society of America, vol. 82, no. 5, May 2001, pp. 1304- 1318. Wiley, doi: 10.1890/0012-9658(2001)082[1304:HSDOAL]2.0.CO;2.
—. “Lifetime Reproductive Success of Female Eastern Kingbirds (Tyrannus tyrannus): Influence of Lifespan, Nest Predation, and Body Size.” The Auk, vol. 124, no. 3, Jul. 2007, pp. 1010-1022. aucospubs, doi: 10.1642/0004-8038.
Sealy, Spencer. “Low Frequency of Observed Cowbird Parasitism on Eastern Kingbirds: Host Rejection, Effective Nest Defense, or Parasite Avoidance?” Behavioral Ecology, vol. 6, no. 2, 1995, pp. 140- 145. Oxford Journals, doi: 10.1093/beheco/6.2.140.
Siderius, Joanne. “Nest Defense in Relation to Nesting Stage and Response of Parents to Repeated Model Presentations in the Eastern Kingbird (Tyrannus tyrannus).” The Auk, vol. 110, no.4, Oct. 1993, pp. 921-923. JSTOR, doi: 10.2307/4088648.
Image Gallery Bibliography
Used via Creative Commons
Wikimedia
https://upload.wikimedia.org/wikipedia/commons/8/8d/Eastern_Kingbird_BoyerChute.jpg
MONGO. Wikimedia Commons. Eastern Kingbird. Perched on a plant. 21 Jun. 2007. Public Domain. Accessed 21 Sept. 2016.
- Kingbird perches on a plant scoping out insects for food.
https://upload.wikimedia.org/wikipedia/commons/4/45/Eastern_Kingbird_%284769690133%29.jpg
Huczek, Dawn. Wikimedia Commons. Eastern Kingbird. Spreading its wings. 3 Jul. 2010. Public Domain. Accessed 21 Sept. 2016.
- Kingbird in the middle of takeoff, looking directly into the camera.
https://upload.wikimedia.org/wikipedia/commons/1/13/Kingbird_Profile.jpg
Beezhive.Wikimedia Commons. Kingbird Profile. Perched on a tree branch. 9 Jul. 2008. Public Domain. Accessed 21 Sept. 2016.
- Kingbird posting up on a tree branch.