Content for this page researched and created by Mariah Briggs

The Rusty Blackbird (Euphagus carolinus) is one of the most rapidly decreasing species in North America (The Cornell Lab). The population has declined 85-99% over the past forty years. This decline stretches back to the late 18^th and 19^th centuries (Decline of the Rusty Blackbird) and is considered the “most dramatic population declines ever documented in a once common North American land bird” (Scarl). Although the precise reasons for this decline are not known, research has revealed some potential causal factors. For example, farmers are allowed to control the blackbirds on their farm lands using lethal means (Woodford), and there has been an dramatic loss of wooded wetlands along with the bird’s other preferred breeding habitats (Strickland). There is an International Rusty Blackbird Working Group that monitors the bird between March and April. Scientists use this data to target what they should be doing to ensure a future for these birds. 

The Rusty Blackbird is a medium-sized bird that has a medium length tall. Their bills are slender and slightly decurved (The Cornell Lab). The males can be easily identified by their rusty feathered edges, pale yellow eyes, and buffy eyebrows. During breeding season the males are a dark glossy black. Females are a gray-brown color with the rusty feather edges and pale yellow eyes with an array of darker feathers around them. These birds have a very energetic call, “kurlulr-teEE” which ends with a high-pitched note. They are 8.3 to 9.8 inches long with a 14.6 inches’ wingspan. They weigh 1.7-2.8 ounces. 

Rusty blackbirds most commonly live in wooded swamps and use boreal forests as their breeding sites (The Cornell Lab). They can be found in wet areas, flooded woods, swamps, marshes, and pond edges. These damp habitats are great spots for foraging especially in winters. During the winter, they are most commonly found in the Eastern United States. Theses central and eastern part of the boreal forests have shown the most decline of all the areas (Decline of the Rusty Blackbird).

Habitats have been lost not only because of human activities but also through competition between a variety of other, more aggressive species. Female rusty blackbirds are especially sensitive to competition and habitat exclusion.

Additionally, breeding grounds have been lost due to local climate effects of global warming and changes in rain patterns that have led to drought.  Acid rain has also negatively impacted trees in the boreal forest and has negatively affected the rusty blackbird. Loss of this important winter habitat is a significant factor in the observed decline in this species(Special Section).

Rusty blackbirds start their winter seasonal migration in mid-September (Species Information). They spend around a month (from mid-October to mid-November  resting and eating at random places along their migratory path before arriving at their final destination. The entire winter migration takes  10 to 12-weeks. However, when return to the north in the spring, they go at a faster pace. Beginning in late March or early April they arrive at their northern breeding ranges in about two weeks. There are two or three different paths for these migrations: the Atlantic flyway, the Mississippi flyway, and maybe even the Central flyway. In their migrations, they do pass through Pennsylvania, however, they do not nest here (Unlock the Mystery). Pennsylvania has a great abundance of riparian forests and many acres of wetlands within which the migrating rusty blackbirds can find shelter and food.

These birds are very difficult to locate because of their very small numbers. During their migration, they fly through 39 eastern, central, and Midwestern states (Strickland). Scientists believe that these migratory paths create a separation between populations that winter in Mississippi Alluvial Valley and Atlantic coastal plain (Hobson). Their migratory paths increase the species vulnerability to predators.  

The Rusty Blackbirds breed along the northern boundaries of their ranges (Kennard). They usually lay between three and six pale blue-green with brown and gray spotted eggs (Audubon). The female will usually incubate the eggs to keep them incubated for 14 days. Both parents help to feed the nestlings. The nestlings fledge in 11 to 14 days.

Nests are usually located in a secluded areas typically in dense shrubs along a waterway. Nests are built of sticks, grasses, mosses, and lichens (Boreal Songbird). Most rusty blackbirds ( 70% of the population) breeds in the boreal forests of Canada.

When males are ready to mate, they fan out their tails, open their bills and make squeaking noises. In an experiment, forty-three birds’ nests were observed and evaluated, and it was noted that these birds may be overexposing their nests to predators (Powell). Nest observation studies may help in understanding why some eggs do not hatch and why the population is in such rapid decline (Matsuoka).

Rusty blackbirds typically feed on the ground and flip over leaves in order to find insects. They also eat a large number of snails and other mollusks (On the Decline). These birds are manly known for their intake of invertebrates (Newell) and these include both land and aquatic invertebrates.     However, they are also known to attack and eat other birds such as sparrows, robins, snipes, and many others (The Cornell Lab). Their diet may play a huge role in their decline because they have to ensure that they are eating things that do not carry diseases (Woodford). Since rusty blackbirds often eat aquatic organisms they are often exposed to high levels of toxins. Mercury has been discovered in these birds and may be one of the causes of their reproductive declines (Decline of the Rusty Blackbird).

Rusty blackbirds regularly for mixed flocks with Common Grackles, Red-Winged Blackbirds, and European Starlings (The Cornell Lab). They often remain in separate groups based on their age and their sex (Mettke-Hofmann).  In an experiment, 207 of these birds were caught and tagged (a total of 136 Adults And 71 young). The majority of these birds were adult females; this could mean that there may be an abundance of adult female Rusty Blackbirds. 

Blood and tissue samples were collected from 579 rusty blackbirds (Edmonds). Total mercury concentrations (THg) were measured were found to be higher in birds living in the Scadian forests. Also, mercury levels were higher in birds in their the breeding grounds versus birds in their wintering grounds. These altering mercury levels may be due to the seasonal shift in food selection by the blackbirds.  

During winter, these birds are very susceptible to disease (Decline of the Rusty Blackbird).  These diseases are aggravated by winter weather stresses. Hermatoza viruses can be quite serious in these winter flocks (Barnard).

Many people are trying to protect this species (The Rusty Blackbird Blitz). Studies have documented state by state abundances of this species, and attempts are being made to protect the bird’s preferred habitats. Though the population has not begun to recover there are more sightings of this species all across its continental range.  

General Bibliography 

Conservation Biology Institute. 2007. Web. 25 September 2016.

Greenberg, Russ. The Rusty Blackbird Blitz-Year 3. Smithsonian National Zoological Park

Conservation Biology Institute. 2011. Web. 24 September 2016.

Greenberg, Russ. Decline of the Rusty Blackbird. Smithsonian National Zoological Park

Rusty Blackbird. Audubon. 2016. Web. 23 September 2016.

Rusty Blackbird. Boreal Songbird Initiative. 2015. Web. 24 September 2016.

Rusty Blackbird. The Cornell Lab of Ornithology. 2015. Web. 23 September 2016.

Scarl, Judith. “Getting Rusty” Take Two: Rusty Blackbird Spring Migration Blitz 2015. eBird. 2015.

Web. 23 September 2016.

Species Information. International Rusty Blackbird Working Group. 2013-2015. Web. 25

September 2016.

Strickland, Jennifer. The Rusty Blackbird: You need to know to help them. Wildlife Facts. 2014.

Web. 22 September 2016.

Unlock the Mystery of the Rusty Blackbird Migration through Pennsylvania. Pennsylvania eBird. 

2013. Web. 20 September 2016.

Woodford, Riley. The Disappearance of the Rusty Blackbird. Alaska Department of Fish and

Game. 2014. Web. 23 September 2016.

Scientific Bibliography 

Barnard, William H, Claudia Mettke-Hofmann, and Steven M. Matsuoka. “Prevalence of Hematozoa

Infections Among Breeding and Wintering Rusty Blackbirds”. The Condor: November 2010, Vol. 112, No. 4, pp. 849-853.

Edmonds, Samuel T. and David C. Evers, Daniel A. Cristol, et al. “Geographic and Seasonal Variation in 

Mercury Exposure of the Declining Rusty Blackbird”. The Condor: November 2010, Vol. 112, No. 4, pp. 789-799.

Greenberg, Russell, and Droege Sam. “On the Decline of the Rusty Blackbird and the Use of

Ornithological Literature to Document Long-Term Population Trends”. Conservation Biology 13.3 (1999): 553-59. Web.

Greenberg, Russell and Steven M. Matsuoka. “Special Section: Rangewide Ecology of the

Declining Rusty  Blackbird Rusty Blackbird: Mysteries of a Species in Decline”. The Condor: November 2010, Vol. 112, No. 4, pp. 770-777.

Hobson, Keith, Russell Greenberg, Steven L. Van Wilgenburg, and Claudia Mettke-Hofmann. “Migratory

Connectivity in the Rusty Blackbird: Isotopic Evidence from Feathers of Historical and Contemporary Specimens”. The Condor: November 2010, Vol. 112, No. 4, pp. 778-788.

Kennard, Fred H. “Notes on the breeding habits of the Rusty Blackbird in northern New

England.” The Auk 37.3 (1920): 412-422.

Matsuoka, Steven, David Shaw, Pamela H. Sinclair, et al. “Nesting Ecology of the Rusty Blackbird in Alaska and Canada”. The Condor: November 2010, Vol. 112, No. 4, pp. 810-824.

Mettke-Hofmann, Claudia, et al. “Competition and Habitat Quality Influence Age and Sex

Distribution in Wintering Rusty Blackbirds”. PLoS One, vol. 10, no. 5, 2015

Newell Wohner, Patti, Robert Cooper, Russell Greenberg, Sara Schweitzer. Weather affects diet 

composition of rusty blackbirds wintering in suburban landscapes. Wiley Online Library. 2015. Web. 24 September 2016.

Powell, Luke L, Thomas P. Hodgman, William E. Glanz, et al. “Nest-Site Selection and Nest

Survival of the Rusty Blackbird: Does Timber Management Adjacent to Wetlands Create Ecological Traps?”. The Condor: November 2010, Vol. 112, No. 4, pp. 800-809

Image Bibliography 

Flickr. Google. 2016. Web. 23 September 2016.

(via creative commons)

1. Rusty Blackbird Eating (Andy Reago and Chrissy McClarren)
2. Rusty Blackbird male (Don Faulkner)  Wikipedia. Google. 2012. Web. 24 September 2016

< https://commons.wikimedia.org/wiki/File:Rusty_Blackbird_(8149329083).jpg >(via creative commons)

1. Rusty Blackbird (Andy Reago and Chrissy McClarren)

< https://commons.wikimedia.org/wiki/File:Rusty_Blackbird_(8149355660).jpg  >

1. Rusty Blackbird in tree (Andy Reago and Chrissy McClarren)