Fall Migration by Ear

Despite the recent stretch of long-awaited, fine summer weather, fall migration is definitely underway. One of the most vivid ways to witness and appreciate this phenomenon is to venture outside on a clear, cool night and simply listen. Find a quiet spot with minimal noise interference from traffic or other sources. Pick a calm night, or one with light northerly winds, and wait an hour or so after nightfall. High pressure systems from the northwest in autumn tend to stimulate southward migration, so a chilly night with a sky full of stars is a good bet. A full moon is even better.

From now through October, anywhere in Vermont or the Northeast, streams of migrant birds will pass overhead on any given night. Invisible to our eyes, they announce their passage with an astonishing array of nocturnal flight calls. Ranging from chip to tsweet to vheer to clink, these fleeting calls provide an auditory window into one of nature’s great annual spectacles. Nocturnal flights are the rule among long-distance migrants, including most songbirds. The evolution of this behavior is thought to have been driven by the advantages of improved celestial navigation, reduced likelihood of predation, and increased daylight hours for feeding to replenish energy stores.

As migrants wing overhead through the night skies, from hundreds to thousands of feet above us, they maintain contact through their species-specific flight calls. Some of these, like the spring peeper-like notes of the Swainson’s Thrush or the metallic clink of the Bobolink, are distinctive and relatively easy to recognize. Many are so similar, however, that they defy clear-cut identification. Recently, a small band of dedicated and sleep-deprived ornithologists have painstakingly recorded and acoustically identified most nocturnal migrant birds in eastern North America. Their result is a remarkable library of 211 species, available to anyone in CD-ROM form Old Bird, Inc.

Advances in identification of nocturnal flight calls have given rise to a new and promising field of study–automated, computer-based acoustic monitoring of nighttime migration. Many doors are now opening to better understand migratory patterns for cryptic or otherwise little-understood species. This technique may also prove instrumental in guiding sound decisions about siting of communications towers and wind farms. Technology aside, however, there is no substitute for the thrilling experience of witnessing nocturnal migration through simple, unadulterated listening. So, go out there and put your ears to use!

For those among us who still like to see migrant birds, the past week offered several highlights statewide. Standouts among migrant shorebirds were two Red-necked Phalaropes in Addison, a Whimbrel in a St. Albans field along I-89, 4 Pectoral Sandpipers in Grand Isle, and 8 Short-billed Dowitchers in Brandon. As many as two Black-legged Kittiwakes continued to provide rare viewing off Grand Isle, as did a single Little Gull on August 22nd. A soaring ‘kettle’ of 42 Turkey Vultures near Middlebury on the 16th was unusually early, and Common Nighthawks were reported from several locations, with a high count of 24 in Norwich on the 24th.

You can explore all the birds reported last week in Vermont and add your own sightings at Vermont eBird.

-by Chris Rimmer
(Bobolink photo from USFWS)

Ocean-dwelling bird takes right turn, ends up on Lake Champlain

Zugunruhe, a powerful urge to migrate that can send overzealous or inexperienced birds outside of their typical ranges, is a boon to birdwatchers on Lake Champlain. Lake Champlain is a catch basin for ocean-going birds that fly south along the St. Lawrence River instead of following the coast and heading out to sea where they spend the winter.

Almost yearly, Black-legged Kittiwakes are reported on Lake Champlain, and most of them are juveniles, birds hatched this summer. October and November are the best months for spotting them, but keen-eyed birdwatchers have reported several juvenile and an adult Black-legged Kittiwake in the last two weeks. The first sighting was at Charlotte Town Beach on the 5^th of August with additional sightings from Grande Isle.

Kittiwakes are a type of gull so-named for their nasally sounds. The Black-legged Kittiwake breeds in the arctic regions of North America, with the nearest colonies on the northeastern tip of the Gaspé Peninsula. Unlike other gulls, kittiwakes do not feed at dumps. Rather, they forage during the day and prey on small fish near the ocean’s surface. Adults tend to forage close to the breeding colonies, but in years of low food supply, they will travel farther in search of food. Predation of the exposed nestlings increases during these longer trips. Food shortages cause fluctuations in the kittiwake population. Colonies breeding in the high latitudes face more years of nesting failure, possibly due to late ice-out and the resulting lack of food.

Unlike other gulls, kittiwakes nest on cliffs. Cliff ledges large enough to build a nest come at a premium so kittiwakes have developed some unique adaptations to these space constraints. Colonies can be in the hundreds of thousands with some nests actually touching each other. Nests are built in such tight places that the adults must sit facing the cliff face with their tail hanging over the edge. Unfortunately, hatching is a dangerous stage for chicks as some inevitably fall off the edge of the cliff into the ocean.

Nests are defended from neighbors, as well as the adjacent ledge (used for roosting) and the airspace above the nest. However, since there is so little room to aggressively defend their territory from encroaching neighbors, they clasp each others bills and swing their heads from side-to-side. Sometimes both adults will fall over the cliff and remain clasped until they reach the sea below.

Black-legged Kittiwakes are often observed on Lake Champlain associated with Bonaparte’s Gulls, another small gull that we don’t see much of during the breeding season but passes through in large numbers in the fall. Juvenile kittiwakes have a black band across the nape of the neck which distinguishes them from juvenile Bonaparte’s. Adult kittiwakes at this time of year have a darker gray back and wings tipped with black as opposed to adult Bonaparte’s, which have a narrow line of black edging on the back edge. Tail shape can also be a clue, with kittiwakes possessing a slightly forked tail and Bonaparte’s a rounded tail.

Whether you head to the shores of Lake Champlain in search of this wayward ocean-faring bird or simply to enjoy a late summer afternoon at the beach, you are likely to observe a few other southbound migrants from the far north. Shorebirds are moving through in numbers, with Black-bellied and Semipalmated Plovers, Greater Yellowlegs, Whimbrel, Sanderling, and Solitary, Least, and Semipalmated Sandpipers observed in the last week.

You can explore all the birds reported last week in Vermont and add your own sightings at Vermont eBird.

-by Julie Hart
(photos courtesy of USFWS)

VT Weekly Bird Notes: Zugunruhe!

Black-legged Kittiwake by David Cahlander

Zugunruhe!

Hold the “gesundheits” and tissues. Zugunruhe (pronounced “zoog-un-roo-huh”) literally means “restlessness to move.” It is the German word that ornithologists use to describe the urge to migrate.

Right now zugunruhe is happening all around us. An innate, physiological phenomenon, zugunruhe causes birds to become more active. In captive-held birds, species that migrate farther exhibit restlessness for more days than a short-distance migrant. Put simply, zugunruhe lasts longer for a bird that migrates to South America than a bird that has a quick flight to New Jersey.

Studies on zugunruhe conventionally focus on migratory birds. But Barbara Helm and Eberhard Gwinner (of Germany, appropriately) stepped outside the box and looked for zugunruhe in the African stonechat, a non-migratory songbird. They kept the birds in a controlled environment free of migratory cues like photoperiod (amount of daylight). Surprisingly, the stonechats experienced increased restlessness during a period that coincided with the migration season of a related European species.

Helm and Gwinner suggested that migration may not be an all-or-nothing trait, and could be lying dormant in the genes of non-migratory species, to be called on when needed. The African stonechat would have retained zugunruhe from a one-million year-old ancestor. If other non-migratory bird species have this trait, it may be come in handy in the face of environmental instability brought on by climate change.

Zugunruhe aside, for birders migration is the exclamation point at the end of the breeding season. Each weather front brings new species and flock assemblages may not be seen any other time of the year. Like foliage season, migration is the big show before the relative quiet of winter, and the birds are terrifically accommodating.

In a remarkable display of endurance, migrant birds hail from lands hundreds to thousands of miles away and pass right through our neighborhood. It’s a free parade put on every year for anyone wishing to pay attention. No need to travel far and incur the rising cost of gas; migration comes to us, thanks to zugunruhe.

Other Bird Sightings

One of the best places to observe migration is Lake Champlain. Recent highlights are sightings of adult, juvenile, and 1st-year black-legged kittiwakes. Departing from their breeding grounds as far north as the arctic and subarctic coasts, a few Kittiwakes occasionally pass through Vermont on their way to winter in the ocean as far south as Florida. Also seen were Bonaparte’s gulls (up to 125 in one day), a little gull, Caspian and common terns, and great egrets.

Least sandpipers were observed at Charlotte Town Beach and short-billed dowitchers were seen at Dead Creek. All three members of the falcon family that breed in Vermont were at the Hartland State Airport: American kestrel, merlin, and peregrine falcon.


You can explore all the birds reported last week in Vermont and add your own sightings at www.ebird.org/vins.


Rosalind Renfrew

VT Weekly Bird Notes: Molt Migration

Dare I say it? The southward migration of songbirds has begun. A few Tennessee warblers always begin to show up in July. They were first described by the famous ornithologists Alexander Wilson in 1811 from a migrant specimen on the banks of Tennessee’s Cumberland River, its common name belies the fact that its breeding range is restricted almost entirely to the boreal forest zone of Canada, extending into southeastern Alaska and the extreme northern fringe of the United States.

The bulk of Tennessee warbler migration in the northern U.S. begins in late August and peaks in late September, but a few early birds sneak southward in July. According to the online bird records database eBird, there were already Tennessee warblers as far south as the New York City area in July. In Massachusetts they have been found as early as the 4th of July.

Two of the most energetically demanding events happen together for these individuals – their annual molt and the southward migration. Songbirds slowly drop their old feathers and grow replacements when the breeding season has ended. Just a few flight feathers at a time are lost and regrown so that they can still fly. Most songbirds do this on or near their breeding grounds and remain quiet and hidden. The Tennessee warbler is able to not only fly, but actually migrate while it molts, a very unusual strategy for a songbird.

“The fact that these tiny songbirds can simultaneously molt and migrate is amazing and is an ornithological puzzle that remains to be solved,” says Chris Rimmer, director of the Vermont Center for Ecostudies, who has studied them on the breeding grounds in northern Ontario as well as on migration through Vermont. “What is even more amazing is that they completely change to feeding on nectar when the reach their winter grounds.”

Tennessee warblers arrive on their winter grounds by October. Alexander Skutch, a famous tropical ornithologist, suggested that the species would be more appropriately named coffee warbler, because of the strong affinity of wintering individuals for shade coffee plantations in Central and South America. Recent studies have affirmed the importance of shade coffee plantations for Tennessee Warblers, especially during the winter dry season. When you are enjoying your cup of shade-grown coffee on the porch, keep your eyes open for the coffee warbler working southward.

Other Bird Sightings

Other birds are also on the move. Three little gulls were seen at Charlotte Town Beach on July 30th among hundreds of Bonaparte gulls. And two juvenile black-legged kittiwakes were found on August 5th. Five great egrets were spotted in Rutland on July 28th.

Yellow-billed cuckoos were seen in Woodstock and Grand Isle on July 28th. A blue-winged warbler Wand a Tennessee warbler were observed in Rupert on August 2nd. Twenty-four white-winged crossbills were present in Westmore on July 29th. Pine siskin and 20 evening grosbeaks were seen in South Starksboro on August 3rd.

You can explore all the birds reported last week in Vermont and add your own sightings at Vermont eBird and the Vermont Bird Report.

Kent McFarland

VCE Research Featured in 7 Days

Mike DiBiasio of 7 Days treks up Stratton Mountain to spend some time with the Vermont Center for Ecostudies as they seek out Bicknell Thrushes, an endangered species of bird. Will Mike help the VCE, or will he run out of steam before he even reaches the top of the mountain?

Click here to read Mike's story about the VCE's efforts.

What’s in a Song: Alder or Willow Flycatcher?

When you hear a bird that you just can’t identify, it often helps to track it down visually with binoculars. But with Willow and Alder flycatchers, that technique won’t prove helpful. These two, tiny, drab songbirds are so identical in appearance that they were thought to be the same species – the Traill’s Flycatcher – until the 1970s. Both species are members of the Empidonax genus, a group of flycatchers notoriously difficult to identify. In Vermont we have 4 of the 5 eastern “Empi” species to sort through – the Least, Yellow-bellied, Alder, and Willow (pictured).

The only sure way to distinguish between the Alder and Willow flycatchers is by their songs. Even when bird banders capture one and have the bird in-hand, it cannot be identified to species (unless they are lucky enough to have it sing!). Both have short, wheezy, songs that can be difficult to pick out among a morning chorus. The more widespread, Alder Flycatcher has a buzzy, 3-syllable song – Fee-BEE-o – accented on the second syllable. It can be reminiscent of a Phoebe’s song (especially when the last syllable is not heard), but with a more burry quality. The Willow Flycatcher, a more southern species which tends to be restricted to lowlands in Vermont, has a slurred, two-part song – FITZ-bew – accented on the first syllable and descending on the second.

Unlike most songbirds, flycatcher songs are innate, not learned from their parents. In an interesting experiment, both Alder and Willow flycatcher chicks were reared separately in captivity. During the critical first two months of life when most songbirds learn “their” song, the chicks were “tutored” only with songs from the other species. The following spring, they each sang their species-specific song, even though they had never heard it before.

Both species are found in shrubby wetlands, although the more restricted Willow, which reaches the northern limit of its range in Vermont, tends to be more common in larger, open wetlands in the Champlain Valley. The Alder Flycatcher, which ranges well into Canada and Alaska, can be found throughout the state, from small, alder thickets in the Green Mountains, to willow swamps, to expansive valley wetlands co-existing with Willow Flycatchers. Two well-known locations where both species can be heard include Dead Creek Wildlife Management Area in Addison, and West Rutland Marsh.

Recent Bird Sightings

Well, it’s August, so the shorebird migration has begun with reports of Greater and Lesser yellowlegs in Middlebury, Solitary Sandpipers in Norwich and at Lake Pauline in Ludlow, and Semipalmated and Least sandpipers on Grand Isle. A Caspian Tern was also seen in Grand Isle, while a group of 5 Great Egrets were observed flying over Rutland. Lastly, 2 Common Nighthawks were seen and heard in Castleton.

You can explore all the birds reported last week in Vermont and add your own sightings at Vermont eBird.

--Steve Faccio