Blackpoll warbler: ‘nature’s hearing test’

Learn more about the hard-to-track blackpoll warbler and how to spot it in the Adirondacks

By Joan Collins

One of the Adirondacks’ many breeding warbler species often goes unnoticed. The blackpoll warbler possesses one of the highest pitched bird songs, often outside the range for people with high-frequency hearing loss. In our area, breeding is at higher elevations over 2,900 feet. To find this species, you need to be up on a mountain, where it is often windy, be able to hear a bird singing just a few, quiet, nearly inaudible notes in a high frequency range, and then spot it. It is a challenge.

As its name implies, the male blackpoll warbler has a black cap. It is mostly gray and white with bold black streaks. The female is an olive-gray color and less sharply marked. Both the male and female have dark wings with two white wing-bars and dull orange to yellow legs and feet.

The breeding range is the boreal habitat of Alaska, Canada, and the mountainous areas of New England and New York. Winters are spent in northern South America east of the Andes below 10,000 feet.

Migration patterns

Blackpoll warblers arrive in the Adirondacks during the second half of May and some arrive as late as early June, spending only about three months on their nesting grounds in the mountains, before departing for an astounding journey south.

The half-ounce blackpoll warbler has the longest overwater flight of any songbird. In the fall, they fly non-stop for three to four days over the Atlantic Ocean to reach northern South America, averaging 1,800 miles over open water.

All across the breeding range, birds make their way to the East Coast in August. After passage of a cold front, they head out over the ocean for their epic flight taking advantage of northwest winds. As they near the Tropic of Cancer, northeast trade winds shift them south-southwest toward South America.

Before their journey south, blackpoll warblers double their body mass. They have a much lower rate of mass loss than other migratory birds, a physiological adaptation to sustain them for their long 88-hour flight.

Habitats and habits

Across the vast range to our north, their habitat includes white, black and red spruce, tamarack, balsam fir and the spruce-alder-willow thickets in the transition zone between taiga and tundra. Their habitat in the Adirondack Mountains is primarily balsam fir forest.

Females build the nests on a branch near the trunk in a balsam fir or, less often, in red spruce, about 1 to 9 feet above the ground. Females lay three to five eggs. Males are mostly monogamous, but sometimes breed with more than one female.

Insects are their primary diet during the nesting season, but seeds and fruit are also consumed during fall migration.

The male blackpoll warbler’s song is a series of high-pitched staccato notes on the same pitch that grows louder in the middle and softer near the end. It sounds like “tsit, tsit, tsit, tsit, tsit, tsit.” Five to 12 notes are given in the frequency 8,900 Hz. Males tend to sing from a prominent perch near the top of a conifer, but they will also sing within the canopy. The same preferred perches are used day after day, where they often sing at a rate of 28 songs every five minutes.

‘In steep decline’

It is estimated 88% of the blackpoll warbler population has been lost during the past 40 years. Partners in Flight rank it a “Common Bird in Steep Decline.”

Vermont Center for Ecostudies’ Mountain Birdwatch (MBW) project is the only rigorous monitoring program tracking blackpoll warbler populations in the northeastern United States. During the 15-year period from 2010 to 2024, MBW data shows a steep overall population decline of 48%.

In response to climate warming, many birds are showing uphill shifts in both the upper and lower boundaries of their altitudinal breeding ranges. Jeremy Kirchman, from the New York State Museum, replicated surveys conducted on Whiteface Mountain in 1974 during 2013–2015. The survey found the lower boundary for blackpoll warbler shifted upslope 500 feet during the preceding 40 years, resulting in a smaller altitudinal breeding range (the upper boundary stayed the same at the top of the peak).

Climate change threatens blackpoll warbler habitat, which is expected to disappear from New England and New York by the end of the century. It has increased severe weather events causing mortality for nestlings and fall migrants and increased wildfires.

In the breeding range, 180 million acres of boreal forest have been impacted by extractive industries. Collisions with tall human-made structures such as towers, lighthouses, buildings and wind turbines are also threats during migration.

Take “nature’s hearing test” this spring.