Vermont Weekly Bird Notes: Prepare Yourself for an Irruption

Signs are beginning to suggest that an irruption is underway. There’s no need to be concerned about molten lava or ash fallout however, this is an irruption of boreal birds. Every fall, birders across North America anxiously await the possible influx of northern birds that don’t winter in their areas every year. These periodic bird irruptions add a dramatic level of excitement to winter birding, and liven up our bird feeding stations as well.

There are 2 basic groups of irruptive migrants – boreal finches and other songbirds that depend on fluctuating tree-fruit crops, and owls and other predatory birds that depend on cyclically fluctuating rodent populations. Both groups specialize on food supplies which may fluctuate more than 100-fold from year to year. However, seedcrops in widely separated regions may fluctuate independently of one another, as may rodent populations, so that poor food supplies in one region may coincide with good supplies in another. If these species are to have access to rich food supplies every year, they must often move hundreds or thousands of miles. In years of widespread food shortage (or high populations relative to food supplies) extending over many thousands or millions of square miles, large numbers of individuals migrate to lower latitudes as an irruptive migration.

Compared to regular migrants, these nomadic populations rarely return to the same breeding areas in successive years. Moreover, band recoveries and radio-tracking confirm that the same individuals can breed in different years in areas separated by hundreds or even thousands of miles. Similarly, irruptive species typically winter in widely separated localities in different years, sometimes on opposite sides of a continent. A few extreme examples include a Pine Siskin that was banded in Quebec in one winter and recaptured 2,455 miles away in California during a subsequent winter, and a Common Redpoll banded in Michigan and recovered in East Siberia 6,350 miles distant!

This year, there are indications that some of the boreal seed-eaters are irrupting south in good numbers. Birders and bird banding stations across the Northeast are reporting higher than normal numbers of Purple Finches, Pine Siskins, Evening Grosbeaks, and both nuthatch species. But, since the arrival time and movement patterns of irruptive species are highly variable, it is nearly impossible to predict with certainty whether irruptions will occur and/or for how long. Data from the online birding checklist, eBird, revealed that reports of Pine Siskins were high during the fall of 2004, but then dropped suddenly in mid-December to more typical levels. The following year however, the opposite pattern emerged, with very few siskins reported until mid-December when sightings increased dramatically and remained stable throughout the winter.

Locally this week, a flock of 2 to 3 dozen Pine Siskins were reported in Etna, NH, while at Dead Creek Wildlife Management Area in Addison, VT, a Clay-colored Sparrow and a Nelson’s Sharp-tailed Sparrow were sighted. Finally, a Long-tailed Jaeger was observed on Grand Isle. You can explore all the birds reported last week in Vermont and add your own sightings at Vermont eBird.

Vermont Weekly Bird Notes: Sister Sparrows

Nelson’s Sharp-tailed Sparrow ©Ted Eubanks

What do you get when you plug a non-descript brown sparrow into an electrical outlet (do not try at home)? With brilliant yellowish-orange hues on their head and chest, Sharp-tailed Sparrows could win beauty contests in the sparrow family. How appropriate that this is the time of year they pass through Vermont, resembling the colors of the autumn sugar maples.

Once its own species, the sharp-tailed sparrow was “split” into two species in 1995 based on physical characteristics and DNA evidence. The Saltmarsh Sharp-tailed Sparrow is named for its preferred habitat, and breeds along the eastern coast as far south as Virginia. Their limited distribution makes their population particularly vulnerable to development pressures along the east coast. The Nelson’s Sharp-tailed Sparrow breeds further north into New Brunswick and Nova Scotia, in freshwater marshes in Central Canada to the Midwest, and around the James and Hudson Bays. The two species overlap in coastal northern New England.

Sightings of Sharp-tailed Sparrows are rare in Vermont, with only a few individuals reported each year. This week a Nelson’s was seen on two different dates at the Brattleboro Retreat Meadows. In recent years they have been spotted in marshes along Lake Champlain. Because they cling to the coast, Saltmarsh sparrows are extremely rare in Vermont (the last sighting was in 1986). Moreover, both species “skulk” around in grasses on the ground, and their secretive nature poses a challenge even for the most diligent and observant birder.

Eastern Sharp-tailed Sparrows spend almost their entire life cycle in saltwater marshes, making them potential candidates as “signals” of marsh health. Dr. Greg Shriver at the University of Deleware found that sharp-taileds are useful indicators of mercury contamination in Maine marshes. Interestingly, Saltmarsh sparrows have consistently higher mercury levels than Nelson’s sparrows within the same marsh. Shriver speculates that the larger saltmarsh sparrow may feed higher on the food chain where mercury accumulates.

This week’s bird reports were liberally spattered with other sparrows, including White-crowned, White-throated, Field, Savannah, Song, Fox and Lincoln’s sparrows. Migrants included flocks of Yellow-rumped warblers, Palm warblers, and Ruby-crowned Kinglets. An Orange-crowned Warbler was reported from Mt. Holly and from Whitney Creek. Pine siskins, Purple Finches, Juncos, and Evening Grosbeaks have been reported in flocks, often at feeders. A Red-bellied Woodpecker was seen at Whitney Creek and also at a feeder in Sunderland. Waterbirds continue to flow down Lake Champlain; Tuesday’s report included 123 Bonaparte’s Gulls, 93 Common Mergansers, 44 White-winged Scoters, and 50 Black Scoters. A Long-tailed Duck was seen from the Charlotte Town Beach, and Ross’s Geese have been sighted among the approximate 2000 Snow Geese at Dead Creek.

- Rosalind Renfrew

Scores of volunteers are eyes and ears of science

VCE citizen science projects featured by the Burlington Free Press Sunday Edition front page. Read the article....

Climate scientist says Nobel Prize will draw attention to cause

The Union of Concerned Scientists, with the help of VCE biologists, recently released a new report on how climate change is affecting New England states. Listen to a short interview with the project chair, Peter Frumhoff, that aired on Vermont Public Radio today.

Weekly Bird Notes: Juncos are a Sign of Winter

The autumn sparrow influx continues this week, with people all over the state reporting Dark-eyed Juncos. These plump sparrows with a gray hood and chest, white belly, and white outer tail feathers are easily recognized cleaning up the spilled seeds below feeders. Many people consider them to be a sign of winter, with their numbers peaking in mid-late October and remaining until spring.

In many places Dark-eyed Juncos are the most abundant feeder birds in the winter months, according to Project Feederwatch, a citizen science project at the Cornell Lab of Ornithology. But casual feederwatchers may not be aware that juncos occur year-round in Vermont. Juncos prefer to nest in coniferous and mixed woods throughout the state, but are most abundant on mountain tops and in the Northeast Kingdom. In fact, volunteers with Mountain Birdwatch, a citizen-science program coordinated by VCE and designed to monitor high-elevation songbirds, often have to wade through the abundant bell-like trills of juncos to identify other birds. Interestingly, residents at higher elevations in the Appalachians have evolved shorter wings than the longer-distance migrants that join them each fall, longer wings making it easier to fly longer distances.

Not all juncos are made the same. If you have ever traveled to other parts of the country, you may have noticed birds that look similar to juncos, but have different patterns of brown, red, and gray. In fact, there are five forms of Dark-eyed Junco: slate-colored (the form found in Vermont), Oregon junco, gray-headed, white-winged, and pink-sided. Each form was once considered its own species, but have since been grouped together as Dark-eyed Junco, as opposed to the Yellow-eyed Junco of southeastern Arizona and Mexico.

If you wish to attract juncos to your yard, juncos favor platform feeders filled with sunflower seed, corn, or millet.

Other Sightings

Two sparrows that breed further north in Canada, the Fox Sparrow and American Tree Sparrow, recently showed up for the first time this fall. The first Fox Sparrow showed up in Grande Isle on the 4th and the first Tree Sparrow showed up on the 6th at Dead Creek. Other fall regulars include a juvenile Sabine’s Gull and five Surf Scoters seen on Lake Champlain from the Charlotte Town Beach on the 5th. A large flock of 115 White-winged Scoters were noted the following day in Grande Isle.

The Sandhill Cranes in Bristol still have not left for warmer weather and were last observed on the 10th. Other birds late to migrate south include a Bobolink and a Sora in Addison on the 6th and a Prairie Warbler at Townsend Lake on the 7th.

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

Vermont Weekly Bird Notes: The Reign of Sparrows

With most warblers and shorebirds now well to our south, many birders in autumn take up pursuit of an avian group that provides numerous identification challenges – the sparrows. Of the 15 species that can be considered to occur regularly in Vermont, only two breed exclusively north of the U.S. One of these, the white-crowned sparrow, is a common transient during its fall and spring migrations. Unmistakably patterned on the head with bold stripes of black and white (adults) or brown and tan (immatures), this large, slender sparrow inhabits brushy and weedy habitats, often in flocks of a dozen or more birds. Arriving in mid- to late September, white-crowned sparrows peak in number during early to mid-October. Birds often frequent feeders, and the earliest reports began coming in last week.

The white-crowned sparrow is considered one of North America’s best-studied songbirds. Seemingly every aspect of the species’ life cycle has been examined – physiology, vocal development, geographic variation in song, migration ecology, breeding biology, to name a few. Of the five recognized subspecies, the easternmost form that migrates through New England is, surprisingly, the least well known. These subspecies differ substantially in behavior, with some populations being year-round residents, others short-distance migrants, and still others migrating thousands of kilometers from their subarctic breeding grounds in Canada and Alaska. The song, occasionally heard during fall migration, begins with a clear whistle and ends with series of buzzes or trills on different pitches.

In addition to white-crowned sparrows, the past week’s birding highlights featured 3 individual jaegers observed moving southward on Lake Champlain. This group is comprised of three closely-related and difficult-to-identify species that breed on the high Arctic tundra. The advent of high-quality optics and a corps of dedicated Vermont lakewatchers have produced a regular of reliable jaeger sightings in recent autumns. Two of the 3 jaegers seen last week were positively identified– a parasitic jaeger off Grand Isle on September 26^th and a long-tailed jaeger off Charlotte on the 27^th . Shorebirds continue to linger at the Dead Creek area, with Brilyea Access yielding the most reliable viewing. The following uncommon species were observed: a single golden plover, 2 long-billed dowitchers, 1 red-necked phalarope, and 2 ruddy turnstones.

Also at Brilyea on the 29^th (with a second sighting at the Brattleboro Retreat Meadows on October 1) was a Nelson’s sharp-tailed sparrow. This furtive inhabitant of weedy, often wet vegetation may be more common than realized in Vermont. Birders wishing to test their identification skills should be on the lookout for this and other uncommon sparrows during the next month.

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

Chris Rimmer