IN THE FIELD: Hermit Warblers and Rusty Blackbirds

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By Saturday, Mar 26 Environment
Nick Bonomo
Right now, the Hermit Warbler should be on its tropical wintering grounds in Mexico or Central America, like nearly all North American warblers. But one little vagrant was seen in Connecticut in February, far from its native habitat in the Pacific Northwest.

When someone asked me once “what’s the rarest bird you’ve ever seen?” I didn’t have a ready answer. Rareness could mean dwindling numbers, a narrow or remote geographic range, or a bird far out of range. There were the puffins and razorbills on boat trips off the Maine coast, and the Masked Duck in south Texas, one of many Mexican specialties that draw birders to the region. Once a Scissor-tailed Flycatcher, a bird of the central plains, showed up on a grassy airport strip in New York, and I went to gawk at this marvel, with its ridiculously long and aptly-named tail.

 A Hermit Warbler, a denizen of the Pacific Northwest, photographed in Connecticut

A Hermit Warbler, a denizen of the Pacific Northwest, photographed in Connecticut.

Last month, a Hermit Warbler turned up in nearby Barkhamsted, Connecticut. Its plumage indicated a first-year bird—just hatched last summer.

The Hermit Warbler is not rare, exactly. Its population is considered stable, though perhaps vulnerable due to its specialized habitat and small breeding range, according to Cornell Lab. But that range consists of tall coniferous forests along the Pacific Northwest Coast.

And right now, it should be on its tropical wintering grounds in Mexico or Central America, like nearly all North American warblers.

Accordingly, it blew up the birding listservs and birders came from far and wide to see this warbler scouring the frozen banks of the Farmington River in February — a rarity on multiple levels. I, unfortunately, was not one of them, having found out about it too late. For a week it cooperated very nicely, foraging near a particular spot, and reportedly showing little fear of people, sometimes coming right up near their feet.

This little vagrant, only the second state record, seemed to be thriving on aquatic insect matter. Observer Greg Hanisek wrote, “It probably also is finding arthropod eggs, larvae and pupae in trees…A surprising amount of animal material is available all winter in bark crevices, needle clusters, evergreen cones, for birds capable of extracting it.”

Below, a video of a Hermit Warbler, with its song:

 

A handful of Hermit Warbler records exist in the Northeast. “These birds can be surprisingly hardy,” wrote Patrick Comins of Audubon Connecticut, who said it wasn’t “all that unusual for western species to show up here,” especially in late fall. Most likely, they get caught up in a rip current going from the Southwest to the Northeast.

People put out suet and mealworms to help the Hermit Warbler along, as the temperature was soon forecast to plummet below zero. It was seen at the start of that weekend, but no one could find it after that. Either it moved elsewhere or the extreme cold snap was too much for it.

That the Hermit, like most warblers, was beautiful — bright yellow head, bold white wing bars, intricate melding of grays— was just a plus. For birders, rarity always trumps beauty.

Which is why I was so excited when I saw the Rusty Blackbirds.

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A male Rusty Blackbird, in winter plumage. Photo: Steve Golladay.

One doesn’t think of blackbirds as being rare, which is partly why scientists didn’t notice that their population was steadily declining — about 90 percent since the 1960s. This species was always somewhat elusive, breeding in the forested boreal wetlands of Canada. But it used to be considered a common migrant in the Northeast, on its way to wintering grounds mostly in the Southeast.

Rusty Blackbird - NYBG 2/26/11

Rusty Blackbird. Photo: Deborah Tracy-Kral.

I’d never knowingly seen one until a few weeks ago. Walking near the Housatonic one morning in late February, I saw several blackbirds making unfamiliar sounds. Without binoculars I couldn’t get a good look, but I suspected they were Rustys, based on their gurgly, squeaky sounds. The next morning, they were there again and I saw the pale, “rusty” feather edges of the male, and the brownish female with a pale contrasting eye stripe. A loose, noisy flock of at least a dozen moved about in small spurts and eventually gathered high in a lone fir tree.

The wet woods and flooded fields of the Housatonic Valley are perfect habitat for Rustys on the move. In fact, their close association with wetlands could be one factor in their decline. They have been found to have relatively high levels of methylmercury in their bodies, which is more present in wetlands. The International Rusty Blackbird Working Group formed in 2005 to study the species and their precipitous, unusual decline. So far, studies mentioned on its Web site (rustyblackbird.org) have pointed to a network of factors rather than one magic answer.

rusty blackbird2_MK

Rusty Blackbird. Photo: Maha Katnani.

Their boreal breeding range has retracted farther north, due somewhat to development, but also to climate change, as wetlands become drier and more aggressive competitors like Redwing Blackbirds and Common Grackles expand northward. Still, their relatively high nesting success rates point to challenges elsewhere in their range. The continual developing and converting of Southeastern wetlands could be the biggest strain on the population.

The Rustys I saw migrating north, if reported to eBird, can actually contribute to scientists’ understanding of their movements. The Spring Migration Blitz, started two years ago, encourages people to look for and report Rusty Blackbirds, helping to identify critical migratory stopover habitats.

Two weeks after seeing these birds, I was taking a walk in the Hudson Valley. I paused beside a stream in a small quiet patch of floodplain forest, in what I liked to think of as a secret spot. From a short distance away came strange musical phrases, quickly rising and falling. Only when they were punctuated by a distinctive, guttural blackbird “chuk” note, did I realize it was a Rusty Blackbird, just one, maybe two. Once I glimpsed a shadowy dark form through the trees, but mostly, I just listened.

To listen to the call of a Rusty Blackbird, click here.

Below, a video of the Rusty Blackbird in the Squamish River estuary is British Columbia:

 

 


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