Canada warbler: ‘Butterfly of the bird world’

By Joan Collins

Northern New York is a birding mecca for many reasons. In winter, sought-after species to our north head south into our region. Year-round boreal species can be viewed in the Adirondacks without traveling to Canada. In the spring and summer, northern New York fills with breeding birds returning from the tropics and other southern wintering locations. Bicknell’s thrush, the only endemic species in the northeastern U.S., attracts birders from around the world to the Adirondacks.

Twenty-eight nesting warbler species is another reason that birders flock to northern New York. Hosting such a large variety of breeding warblers is unique within North America and the result of a wide diversity of habitats spanning the grasslands/wetlands/shrublands in the St. Lawrence Valley to the high elevation boreal habitat in the Adirondack Mountains. Researchers, audio recorders and photographers, with a focus on warblers, spend a great deal of time in northern New York.

Known as the “butterflies of the bird world,” warblers have brilliant colors and charming songs. Migrants begin arriving in the second week of April and continue through May. One of the latest to arrive and first to leave is the beautiful Canada warbler.

The male Canada warbler is dark bluish gray above and bright yellow below with a bold, black, broken necklace and a distinct white- to lemon-yellow-colored eye ring. The wings are completely gray with no wing bars. (Noticing if a warbler has wing bars or not is a quick way to narrow down identification.) The female is similar, but with a duller, fainter necklace and facial pattern. As with many other species, the female is less flashy.

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Their song is a loud, snappy, mixed-up group of notes for which I have no helpful mnemonic aid.

Canada warblers breed across southern Canada and the northeastern United States south to northern Pennsylvania and a few locations farther south in the Appalachian Mountains. They winter in South America, mainly in Colombia and Peru.

Nesting is in a range of deciduous and coniferous forests with a shrubby understory in wet habitats where they feed on insects and spiders. On mountains they are often found by streamside vegetation. I also find them on the edges of bogs and in swampy, wet areas with tangled thickets and tall trees. The trees provide singing perches for males, but most of their time is spent in the understory, making them difficult to view. Females build a nest on or near the ground often in the recessed hole of an upturned tree root mass, rotting tree stump or sphagnum moss hummock.

The Breeding Bird Survey data indicate that over the 45-year period from 1970 to 2014, the range-wide population of Canada warblers decreased by an estimated 62%. Most of its breeding range is within Canada, where it has been listed as threatened since 2008. In New York, it is listed as a “high priority species of greatest conservation need.”

A variety of threats are having a negative impact on the population of Canada warblers. On the wintering grounds in the northern Andes, where the species spends most of the year, habitat loss from deforestation for agriculture and cattle pasturing has been rapid. Over 90% of these mountain forests have been cleared since 1970, making this the most critical threat. They face problems along their migration routes where wet forests have been drained for development, agriculture, industrial expansion and roads, and where they are vulnerable to collisions with power lines, towers, chimneys and turbines. On the breeding grounds, they encounter tree clearing and loss of understory to deer browsing. Acid rain and mercury, climate change and severe weather events are additional menaces.

Hopefully, the reforms to the state Freshwater Wetlands Act passed in the 2022-23 budget will help protect declining species that require wet habitats.

Keep an eye and ear out for the lovely Canada warbler this spring.