Columns, The Outside Story

Blackpolls Return from South American Wintering Grounds

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Blackpoll Warbler (Setophaga striata)

WHITE RIVER JUNCTION – Hold two nickels and a dime in your hand: that’s the summer weight of a Blackpoll Warbler. This black-capped songbird returns in early May from its wintering grounds in northern South America to its breeding grounds that range from New England’s mountain forests to Alaska’s boreal forest.

Blackpolls are insectivorous, large warblers (weighing 12–13 g). Their body size likely benefits them during long migratory flights and freezing nights on their breeding grounds.

When breeding season begins in June, the male (marked with a black cap or “poll”) sings his high-pitched song from treetops throughout his territory. Meanwhile, female Blackpoll Warblers are busy building their bulky, well-concealed nests low in conifers. They then lay three to five creamy buff or greenish eggs, which they alone incubate. All this stationary incubating means the females must stay well hidden from predators. Their cryptically patterned plumage may help them avoid the gaze of Sharp-shinned Hawks (Accipiter striatus), which are known to prey on both nestlings and, occasionally, attending adults.

Blackpolls are one of ten northeastern montane bird species monitored by VCE’s Mountain Birdwatch program. Thanks to years of data collection, we can identify population trends, such as those published in the 2023 State of the Mountain Birds Report. This report indicates an alarming decline of Blackpoll Warblers in the areas surveyed: approximately 4.5% per year, which corresponds with a 45% overall decline between 2010 and 2023. Under most climate change scenarios, the data indicate that Blackpoll Warbler ranges will move steadily northward and completely disappear from New England and New York by this century’s end.

Rachel McKimmy is a staff member of the Vermont Center for Ecostudies.

Rachel McKimmy

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