Wandering Warblers
By: U.S.Fish Wildlife Alaska
Tags: Arctic, Migration, Birds, Science, Alaska

Alaska’s Songbirds

Wandering Warblers

Tiny Migrant Songbirds with Arctic Aspirations

Townsend’s Warbler (Setophaga townsendi) is arguably the most striking warbler species that breeds in Alaska. 📷 Intermountain Bird Observatory/Zak Pohlen

Of fifty warbler species regularly found throughout the U.S. and Canada, 11 make their way to Alaska each summer to breed. Like many other migratory birds, warblers take advantage of abundant insects and prime nesting habitat to raise young in the U.S. and Canada, before traveling to warmer areas like Mexico, Central and South America, and the Caribbean to spend the winter.

Several species of warbler breed in Arctic National Wildlife Refuge in the summer, all using the treed or shrubby habitats found in the southern portion as well as the Brooks Range and its foothills. Here, Arctic Refuge’s Porcupine River cuts through the surrounding boreal forest creating picturesque cliffs and canyons. 📷 USFWS/Callie Gesmundo

Migration is no easy task for any bird, let alone warblers, which average less than the weight of one AAA battery! Prior to our understanding of bird migration, people had many interesting ideas about where migratory birds went during the colder winter months. Centuries ago, people thought birds hibernated underground or underwater, while others proposed they transformed into new species (as people noticed seeing different birds at different times of the year). Some even thought birds flew to the moon and spent the winter there. The truth is that these minute creatures (made mostly of feathers and hollow bones) traverse the globe, some doubling their body weight to survive non-stop flights across oceans.

In the 17tth century an English educator named Charles Morton wrote the first extensive work on bird migration, in which he wrongly suggested birds migrate to the moon. 📷 Michele Lamberti via Flickr

As birds go, Alaska is unique among North American states and provinces. Numerous species travel several flyways (migration routes) to meet in Alaska during the summer months. These migratory birds come from wintering grounds in the Americas, eastern Asia, Oceana, and Africa before arriving on their breeding grounds here in Alaska. And Alaska’s warblers are no exception to the incredible journeys and diversity of migratory routes and wintering locations.

Blackpoll Warblers

Blackpoll Warbler (Setophaga striata). 📷 USFWS/Zak Pohlen

Blackpoll Warblers are a summer breeder in the northern coniferous forests throughout Alaska and Canada. Males sport a striking black cap during summer (superficially similar to the Black-capped Chickadee) and sing an insect-like high pitch trill to attract a mate. Though not as flamboyant as other warbler species, it makes up for it with its fascinating migratory feats.

This map shows animated weekly abundances of Blackpoll Warblers throughout the calendar year. The data used to create this animation was collected by citizen scientists who submitted sightings of Blackpoll Warblers to eBird.

Attaching small devices known as geolocators, scientists tracked Blackpoll Warblers from their breeding grounds to their wintering grounds, uncovering one of the most impressive migrations among birds. Blackpoll Warblers that breed in Alaska travel up to 12,400 miles roundtrip each year, crossing the entire North American continent before making a non-stop 3–4 day transoceanic flight to northern South America.

Scientists use geolocators to collect light level data (i.e. daylight) to estimate an individual’s location. In order to collect the location data, the geolocator must be retrieved from the tagged individual, downloaded, and analyzed. 📷 USFWS/Zak Pohlen

Before they complete this amazing leap across the ocean, they spend a month fattening up along the eastern seaboard, doubling their body weight with fat reserves in order to survive the arduous oceanic crossing.

Birds do not grow feathers on every part of their body, but rather in uniformed sections called feather tracts or pterylae. Scientists check a bird’s condition by lightly blowing along the featherless spaces (called apteria) to check the amount of muscle and fat present. 📷 Intermountain Bird Observatory/Callie Gesmundo

Blackpoll Warblers have lost over 90% of their population since the 1970s. Understanding where these birds go is critical to our understanding of what’s driving this population loss.

Wilson’s Warbler

Wilson’s Warblers can be spotted in nearly all parts of the United States at some point during the calendar year.