Rusty Blackbird at Otter View Park - Photo by Ron Payne

In the Fall, Blackbirds form together in very large flocks sometimes containing thousands of birds for their migration. These flocks are largely made up of Red-Winged Blackbird and Common Grackle, and Brown-headed Cowbird, sometimes mixed together and sometimes in very species-specific flocks. At the same time, also coming through with them in smaller numbers are the Rusty Blackbird. Seen only as a migrant in Addison County, Rusty Blackbirds nest in bogs in the Northeast Kingdom and northern Green Mountains of Vermont. This species has seen a rapid decline in numbers from an estimated sixteen million in 1965 to just two million currently. The suspected reasons behind this drop are the effects of acid rain, mercury accumulation and the effects of global climate change on their boreal wetland nesting grounds.

In the past month, Otter View Park in Middlebury had provided a good opportunity to see these birds with flocks from a handful to a dozen present there. They have been making use of the drainage stream that runs by the start of the boardwalk to forage for food and are also feeding on the abundant dogwood berries around the park.

They can be a bit of a tricky bird to ID however being similar to the other more common blackbird species found in the area. Rusties are very similar in size and shape to male Red-Winged Blackbird but lack that species colorful  wing patch and have a distinctive pale eye. Confusing things though, Common Grackle also have a pale eye, and have iridescent head feathers, a feature male Rusties also share in their breeding plumage. They can be separated by the Grackle’s overall larger size and distinctive long “boat-tail.” And finally, in their non-breeding plumage, Rusties take on their namesake rust colored head feathers which can lead to confusion with the male Brown-headed Cowbird. The Cowbird however has a black eye, a thicker bill and is  smaller overall in comparison to Rusties.

If you happen to see Rusty Blackbirds anywhere, I urge you to report your sightings to eBird. Researchers are particularly interested in gathering information on them on their wintering grounds to the south of us, but I’m sure that any data they can collect on this declining species would be valuable to them.

– Ron Payne