Species Profile: Rusty Blackbird
By Steve Phenicie
An organization exists for practically anything you can think of, and Rusty Blackbirds are no exception. Ever hear of the International Rusty Blackbird Working Group? This group of scientists has been around since 2005 and exists for a good reason—in recent decades populations of “Rusties” have declined sharply, and the reason is difficult to pin down.
The North American Breeding Bird Survey estimates that populations have dropped 90 percent since 1966. Loss of wet woodland habitat through drainage, clearcutting, and conversion to agriculture is one possible reason—particularly in the southeastern U.S. where some 80 percent of the population winters. Historically, the hunting of beavers across North America may also have reduced habitat by diminishing the number of beaver ponds, but the resurgence of beaver populations may be having a positive effect. Rusty Blackbirds in northeastern North America have been recorded with high mercury counts, which could be contributing to their decline there.
The bird’s remote breeding grounds in the hard-to-access boreal forests of the far north, from Newfoundland to Alaska and lapping into New York and northern New England, make it hard to study. No other blackbird has such a northerly breeding distribution. In the winter it is found from Iowa and southern New England south to the Gulf of Mexico. There and during migration it usually hangs out in swampy places, wading in shallow water at the edges of wooded streams. Rusties also forage in open fields and cattle feedlots with other blackbirds.
The Working Group tries to get a better handle on this by organizing birders to report on the birds during specific times of the year, particularly during spring migration. Among its activities are outfitting birds with monitoring devices on their breeding grounds and along western Lake Erie in Ohio and Michigan where they stop during migration. Closer to home, Savannah-based Ogeechee Audubon, in cooperation with the Working Group, monitors Rusty Blackbirds on the campus of a private school. (For the full story on that, see this blog post)
The majority of this species’ diet is insects, including aquatic ones such as caddisflies, mayflies, dragonflies, and water beetles, plus land insects such as grasshoppers and others. It also eats snails, crustaceans, small fish, small salamanders, seeds, waste grain, and a few berries.
It sometimes nests in small, loose colonies but more often in isolated pairs. The female typically lays four or five eggs that are pale blue-green, spotted with brown and gray. The nest site is in dense cover, usually in conifers or in shrubs. Typically it is only a few feet above the water or ground, but it can be up to 20 feet high. The nest, built by the female, is a bulky open cup of twigs and grass. Incubation is by the female only. Both parents feed the nestlings, and the young leave the nest about 11-14 days after hatching.
Around Atlanta, some good spots for Rusties are Piedmont Park, Grant Park, Decatur Cemetery, Cochran Shoals, Constitution Lakes, and, in smaller numbers, at Zonolite Park. Anywhere with flooded woodlands or large blackbird flocks has the potential for them. The name "Rusty" applies to the colors of fall birds, but it could also describe the rusty-hinge sound of its creaking song.
Thank you for this interesting article. I remember seeing good size flocks feeding and swirling about fields in the Midwest when I was growing up. The last time I saw rusties was a small flyover flock when working on Fort Benning last March. I hope we are able to find ways to recover this species before their populations are threatened further.
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