The collapse of the Rusty Blackbird population has gone on for decades. An alarm was sounded in the scientific community in 1999 by Russell Greenberg and his coauthor Sam Droege using data collected from different sources including the Christmas Bird Counts contributed by citizen science members.

This blog post is a synopsis of the article
"Rusty Blackbirds are Rising from Obscurity but Falling in Number" by David W. Shaw.
Hopefully, this synopsis will encourage you to read the full article.

The Rusty Blackbird

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During the breeding season the Rusty Blackbirds change color.

Female	Male
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The range map for the Rusty Blackbirds is shown below.

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The Rusty Blackbird feeds mostly on plant matter and insects. The Rusty Blackbird has been documented feeding on other birds like sparrows, robins, and snipe.

Rapidly Declining Population

The Rusty Blackbird species is one of North America's most rapidly declining bird species. The population of Rusty Blackbirds has declined an estimated 85% to 99% over the past forty years. The cause for this population decline has completely puzzled scientists.

Using a model generated from eBird data researchers are able to map the concentration of Rusty Blackbirds over their range.

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From detailed data like this researchers noted that the breeding range of Rusty Blackbirds has moved from the wetlands in the southern parts of the boreal forest into the far north.

Breeding Range

Since the mid-1900's 30% of North America's boreal wetlands have dried up. And during the last few decades the wetlands in the southern boreal forests have been hit by industrial development. This is believed to have contributed to the decline of the population of Rusty Blackbirds and several other bird species like Horned Grebes, Lesser Yellowlegs, and Solitary Sandpipers.

Horned Grebe	Lesser Yellowlegs	Solitary Sandpiper
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Winter Range

Researchers tracked three Alaskan bred Rusty Blackbirds during their migration south to their primary wintering grounds in the lower Mississippi Valley. The Rusty Blackbirds paused their migration for a few weeks in the prairie wetlands of the eastern Great Plains. This highlighted the importance of the prairie wetlands to the migration of Rusty Blackbirds.

However once the Rusty Blackbirds reached their wintering grounds in the lower Mississippi Valley it was discovered that the birds were not wetland dependent. The main food sources for the Rusty Blackbirds in South Carolina were pecans and earthworms.

Big flocks of Rusty Blackbirds were associated with pecan trees in commercial pecan groves and suburban areas. This was puzzling because Rusty Blackbird bills are not strong to crack open the tough pecan shells. But the Rusty Blackbirds were very selective about which pecan trees the congregated in. Their strategy is to congregate in trees near driveways and roadways. The pecans fall onto the road surfaces and are crushed by passing vehicles. After the pecans are crushed the clever Rusty Blackbirds descend to forage on the broken pecan pieces.

Rusty Blackbirds were found to thrive in suburban areas with good habitat. The three components making a good suburban habitat for Rusty Blackbirds are pecan trees, grassy areas with a source of earthworms, and a nearby wetland of some type.

Many Factors Leading to Population Decline

For decades the Rusty Blackbirds went unnoticed by scientists as their population rapidly declined. However, knowledge is power in conservation science. Scientists now know there is not just one cause contributing to the decline of the Rusty Blackbird population. Factors such as a changing climate, disappearing wetlands, methyl-mercury pollution contribute to the population decline. Scientists are optimistic about the Rusty Blackbird's ability to persist into the future.

Sources and More Information

Rusty Blackbird, The Cornell Lab of Ornithology's All About Birds website

Rusty Blackbirds are Rising from Obscurity but Falling in Number, All About Birds, 2 April 2018

eBird, Cornell Lab of Ornithology

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