Rare Breeders: Orchard Orioles

Everyone loves the sight of orioles. Their flame-orange stomach is in stark contrast to our green forests. Orioles are also famed for their fine woven nests that hang from tree limbs. In Vermont, Baltimore Orioles are common, but there is a second, lesser-known oriole that is slowly expanding into Vermont.

Orchard Orioles are smaller than their brighter cousins. Their dark chestnut stomach makes it easy to distinguish it from Baltimores. Indeed, they can look all dark without the aid of binoculars. Females are mostly yellow as opposed to the light orange female Baltimore. Both species have a similar-sounding voice, but Orchards tend to include more guttural sounds between clear whistled notes in their song, reminiscent of a blackbird.

Most birdwatchers in Vermont aren’t likely to confuse the two species simply because Orchard Orioles are uncommon. They are currently only found in the Champlain Valley, but their presence is increasing. The 2003-2007 Vermont Breeding Bird Atlas found Orchard Orioles in 19 blocks, up from only one block in the first atlas completed 25 years ago. By comparison, 386 blocks were found to support Baltimore Orioles in the recent atlas.

Like their cousins, Orchard Orioles prefer large trees near open areas for nesting, including orchards. However, they maintain a significantly shorter nesting period than Baltimores. Orchards arrive from their tropical wintering grounds in early May and are among the first migratory birds to head south, some having returned as early as mid-July.

We don’t often think of birds other than hummingbirds as being significant pollinators, but Orchard Orioles are known to be important pollinators for some tropical tree species. They consume mostly spiders on the breeding grounds, but they shift to mostly nectar and pollen in the tropics. While going after nectar, they collect pollen on their head and carry it to other plants.

A number of birdwatchers have been reporting on the progress of a pair of Orchard Orioles at the Farrell Creek access for Dead Creek in Addison. On Sunday June 22, a pair was observed feeding nestlings that may be ready to fledge by this weekend.

Other Sightings

Notable bird sightings this time of year are of uncommon breeding species in the state. In the past week, a Least Bittern was observed in West Rutland Marsh along with 17 Virginia Rails, a high count. An American Wigeon was spotted in Addison June 22 with five ducklings trailing behind. A Long-eared Owl was found in Grand Isle on June 21, the same day that several Grasshopper Sparrows were observed in Addison.

Although outside of the usual scope of this column, Mississippi Kites are nesting in a residential area in Newmarket, New Hampshire. As its name implies, this is a southern species, making this an exciting, but rare discovery. Many Vermont birdwatchers are traveling east to view these spectacular birds.

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

-Julie Hart

A Sky Blue, Sky High Songster

A high-pitched buzzy song and brilliant flashes of blue in the treetops have recently greeted a few lucky, persistent Champlain Valley birders. At least one, and possibly two, Cerulean Warblers have been discovered on Snake Mountain in Addison/Bridport, while a third report issued from Bristol. This species is arguably the most rare breeding wood-warbler in Vermont, which lies at the northeastern-most periphery of its range. Cerulean Warblers were first confirmed nesting in the state in 1977, and no more than a handful of birds have been documented in any year since. In fact, the recently-concluded Vermont Breeding Bird Atlas obtained only four records of the species over its five years of intensive, statewide field work. Only one of these involved confirmed nesting in Essex Center, while the other three reports came from Colchester, North Hero, and Highgate Center.

The rarity of Cerulean Warblers in Vermont is accentuated by the difficulty of both finding and observing them. This small, canopy-foraging insectivore nests very locally in mature deciduous forests, often in riparian or floodplain situations. Breeding sites seem to shift over time, such that the species cannot be predictably located in any given year. Floodplain forests along the Lamoille River in Milton supported a small colony for many years in the 1980s and 1990s, but this population has apparently disappeared. The rapid, buzzy song can be mistaken for that of a Black-throated Blue Warbler or Northern Parula, possibly causing some birds to be missed. Nests are well-concealed, open cups of bark fibers, grass stems, and hair bound together with spider web; they are typically placed on a horizontal tree limb in the middle to upper canopy.

Cerulean Warbler populations have declined at the steepest rate of any North American wood-warbler, about 3% annually since the mid-1960s. Concern for the species’ conservation is very high, but a formal petition to list cerulean warblers as federally threatened was rejected in 2006. Although its limiting factors are not well understood, multiple habitat threats exist at both ends of the species’ migratory range. Loss and fragmentation of mature forests in the Mississippi and Ohio River Valleys have reduced its core breeding range. Up to 60% of mid-elevation forests in the Andes Mountains, where Cerulean Warblers winter, are estimated to have been lost to production of coffee, coca, tea, hill rice, and livestock grazing. The international Cerulean Warbler Technical Group, formed in 2001, is spearheading focused conservation efforts on behalf of this dazzling, at-risk species.

Other Sightings

With the spring migration now complete and the nesting season in full swing, birding highlights are fewer and further between. The past week featured a Least Bittern on Grand Isle on June 11^th. This small relative of the more common and vocally conspicuous American Bittern is rarely encountered by Vermont birders. Its secretive behavior and occupancy of dense emergent marshlands make it a difficult bird to see, let alone hear. Encounters away from the Champlain valley and West Rutland Marsh are extremely few. Great Egrets continue their expansion into the state, as evidenced by reports of single birds last week in Delta Park, Shelburne, and Winooski. A Bonaparte’s Gull at Herrick’s Cove on the Connecticut River on June 10 was unusual away from Lake Champlain at this time of year.

Among land-based birds, highlights included a rarely-observed Long-eared Owl in Grand Isle on the 9^th. Blue-winged Warblers were reported from five locations statewide, while a hybrid ‘Brewster’s’ Warbler (Blue-winged x Golden-winged Warbler cross) was spotted in Middlebury on the 14th. Four Grasshopper Sparrows, a state-threatened species, were observed at Franklin County State Airport, also on the 14th. Two Orchard Orioles continue to be present at the Farrell Access on Dead Creek

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

-Chris Rimmer
(Cerulean Warbler photo by Matthew Studebaker: flickr or personal website)

Field Study Update: Stratton Mountain

The weather was tough this week, but helped spare us from the black flies. With temperatures as low as 38 and only climbing into the low 50s, black flies were held at bay, but this also quieted the bird life. Most are now on nests or have young and with cold temperatures, attention turns to survival for insectivorous birds.

We now are now monitoring 5 Bicknell's thrush nests on Stratton Mountain. All of them have complete clutches of eggs, some just finished laying, which is a bit late. Thanks to the gift of radio telemetry, we find nests no matter where the thrushes build them. And this year we have found two in odd places. One is in the top of a dead broken tree (see photos). With no Red Squirrels anywhere to be found, songbirds should have a great nesting year.

For a few weeks we have heard a Veery singing on our study plot. In 16 years of montane bird studies, this is a first for us. We occasionally capture them in late summer as they disperse, but we have never had them singing in this habitat during the breeding season. This week we decided to investigate this bird a bit further. I recorded its song with a shotgun microphone. Much to our surprise, this bird sang a slightly odd Veery song and then about every 3rd song it sang a short Veery song that ended abruptly and broke into the ending of a Bicknell's thrush song! We quickly captured it in a mist net playing its own song back to itself. Its plummage suggested that it might be a hybrid between a Bicknell's thrush and a Veery! Interestingly, recent genetic studies suggest that Veery, Gray-cheeked Thrush and Bicknell's thrush are all very closely related species. We will be studying our data on this individual and doing some more behavioral observations to determine just what the origins of this bird might be.

House Wrens

Are your nest boxes filled to overflowing with small sticks and twigs? Have you seen eggs of other cavity nesters such as chickadees, Tree Swallows, or Eastern Bluebirds on the ground or pierced with small holes? These are sure signs that a House Wren has moved in.

These little suburban-loving wrens are fond of shrubby, edge habitats around backyards, gardens, and parks all across the country. The male’s habit of filling every available cavity in his territory with sticks and twigs, even if another species has already begun nesting, may lead you to think the bird has an obsessive-compulsive disorder. Most believe this is simply an attempt to prepare all available nest sites for nesting and subsequent “inspection” by a female.

Once the male has paired with a female, she selects the nest cavity and takes over nest-building duties, leaving any “dummy” nests, consisting of hundreds of sticks but no lining material, unusable by other birds. Within her selected cavity, the female often removes some of the sticks, forming a small platform at the bottom and building a nest cup of grasses, inner bark, hair and feathers on top. She also adds egg sacs of predatory jumping spiders, whose spiderlings consume nest-dwelling mites that parasitize wrens.

The habit of piercing or removing other birds’ eggs often leads to frustrations with House Wrens, especially among those who are trying to attract bluebirds or other bird species. Research has shown that House Wrens avoid using nest sites greater than about 100 feet from any significant woody vegetation. So if Eastern Bluebirds are your desired house guests, place your boxes in open fields at least 100 feet from forest edges and brushy areas.

Bird Sightings

Great Egrets were observed this week at the Retreat Meadows in Brattleboro, and at the Dead Creek Wildlife Management Area in Addison. Cerulean Warblers have been observed at 2 different locations at the southern end of Snake Mountain in Addison and Bridport. A Dunlin was observed at Kent Pond in Killington, and 2 Whippoorwills were heard in Brandon. You can explore all the birds reported last week in Vermont and add your own sightings at Vermont eBird.

Sampling Bobolink feathers across the U.S.

The Bobolink wintering ecology project is happening on the breeding grounds this year! With the help of some fellow researchers and field technicians, Bobolink feathers are being collected across the breeding range, from Vermont to Oregon.

You've always heard "you are what you eat". It's true for Bobolinks too. The feathers were grown on the wintering grounds, and carry with them information about the Bobolinks' diet at the time they were grown in South America. We're looking at whether there are differences in diet among Bobolinks that breed in different regions. In Vermont we're also looking at interseasonal associations: whether males that arrive early on the breeding grounds (more fit reproductively) had a different winter diet than late arrivals.

This project depends entirely on the cooperation of several collaborators. Noah Perlut at UVM has collected feathers from 35 males in Vermont. Dan Kim of the Whooping Crane Foundation collected feathers from 30 males in Nebraska, so far. Mike Baird, a teacher who does volunteer bird banding on the side, will collect feathers in Oregon. And with logistical help of the USGS Northern Prairie Wildlife Research Center, we've collected feathers from 17 Bobolinks (and counting) in North Dakota. In the end, we will have sampled feathers from across the Bobolinks' range, and for the first time will be able to assess potential links between wintering and breeding ground activities.

- Rosalind Renfrew

Field Report: Stratton Mountain

Here is a quick field report from the Vermont Center for Ecostudies montane field station on Stratton Mountain. This is our 11th year working intensively on demographics and ecology of Bicknell's Thrush and other songbirds there and the 16th year for Mt. Mansfield. Our crew this year is led by veteran duo Juan Klavins and Sarah Frey..

This week on Stratton Mountain was a good one despite trying weather. We were able to capture about a dozen Bicknell's Thrushes including several females. These females now have miniature radio transmitters on them to enable us to easily find there nests and monitor them with minimal disturbance. Surprisingly, one female had a well developed brood patch with an egg in its oviduct 2 nights ago. Average egg laying date is June 10th.

We have now captured over 25 Bicknell's thrushes already this year. One of the females was a bird that Sarah actually banded on Stratton as a nestling in 2004! We have not captured our oldest male from last year yet. He was 11 years old last year!

This year, as expected, has proven to be a very low year for red squirrels. There are none on our study plots. Since there were no cones grown last year, this was to be expected and it should be a banner year for songbird productivity. Young, green flowers are already appearing on some fir trees, as expected. Next year will be a strong year for red squirrels. This biennial cycle has been well documented by our long-term work on these study plots and figures prominently in Bicknell's Thrush population regulation.

The next two weeks are the loudest and most active periods for Bicknell's thrush. It is a great time to visit your favorite peak, and enter your sightings into Vermont eBird!
http://ebird.org/content/vt/

Kent McFarland

VCE's Hispaniola Bird Conservation Featured on National Geographic

VCE's research on songbirds in the mountains of the Dominican Republic was featured on National Geographic’s Wild Chronicles television show on PBS. Watch it here!

Filmed this past February, the segment highlights VCE's long-term studies of Bicknell's Thrush and other migrant and resident species on Hispaniola. The feature includes vivid footage of several of Hispaniola's 31 endemic species, some of which are among the most rare and threatened of Caribbean birds.

"The tropical environment of the Dominican Republic is a long way from home for National Geographic grantee Chris Rimmer,” according to National Geographic, which has helped to fund VCE’s work on Hispaniola. “Like the birds he studies, Rimmer migrates to this biologically rich island to conduct his research. The goal of Rimmer's pioneering research on the island is to compile a comprehensive database of both migrant and resident bird species that will lead to sound conservation practices."

Do Not Disturb?

Dave Herr

Drought, grazing, and fire - they may not sound desirable, but some birds respond well to a dose of disturbance. Grassland birds evolved with these phenomena in a dynamic mosaic of diverse prairie habitat across the landscape. Each bird species occupied a unique niche with particular vegetation characteristics. Today these ground-nesters rely on perturbations in the form of grazing, late-season mowing, proscribed burns, and…bombs.

Meet the grasshopper sparrow - a small, brown, inconspicuous bird that skulks beneath the canopy of grasses. It prefers to nest in sparse grasslands that provide enough space for searching out insects on the ground.

Exactly how the grass remains sparse is of no consequence to the bird. Years ago I (carefully) surveyed a population of grasshopper sparrows on a military bombing range in Florida. Fires from practice hits prevented the vegetation from growing tall or dense, and the sparrows felt right at home.

The grasshopper sparrow has a hunched appearance, a stubby tail, and a dash of yellow above the eye and on the front edge of the wing. Perhaps more notable is its namesake song. It cocks its head back and blurts out three punctuated introductory notes followed by a long, high trill. In the sweltering Florida heat I conjured up the nickname ’The-Price-Is-Right’-bird; it sounds like the theme song to this long-time game show.

Vermont sits at the eastern edge of the grasshopper sparrow’s breeding range, and here the species is rare. Small populations can be found in the crewcut grass of small state airports, a military facility, and some agricultural lands in the Champlain Valley. The bulk of the grasshopper sparrow population resides further west in the central and northern plains.

Not all disturbances are created equal. The loss of grasslands to row crops and development has resulted in dramatic population declines of the grasshopper sparrow. And those that once sang amidst the bombing range explosives? They have mysteriously diminished despite the prevalence of adequate habitat.

Other Bird Sightings

Most bird species are getting down to business with building nests and laying eggs, and some cavity nesters like the hairy woodpecker are already feeding chicks. A few late migrants are still lingering in Vermont. Common nighthawk (Burlington, Shelburne, Leffert’s Pond near Rutland), yellow-bellied flycatcher, mourning warbler, blackpoll warbler, and wilson's warbler (Charlotte Wildlife Park) have been sighted, and nocturnal flights of swainson's thrush and gray-cheeked/bicknell's thrush were heard in South Burlington.

A white-eyed vireo was spotted in Brandon, a rare visitor to Vermont that breeds in the southeastern U.S. north to Massachusetts. Other birds reported include black-billed cuckoo, yellow-throated vireo, blue-winged and golden-winged warblers, and a cerulean warbler at Snake Mountain. A Louisiana waterthrush nest with eggs was found outside of Rutland. Campbell’s Bay in Swanton had a good show of shorebirds, including red-necked phalarope, dunlin, semi-palmated plovers, and white-rumped, least, and semi-palmated sandpipers.

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

- Rosalind Renfrew