Golden-wings

The last time I saw a golden-winged warbler on our property was May 29, 2008, when I heard him singing his “bee, bzz, bzz” song and tracked him to his usual nesting spot at the top edge of First Field.

A golden-winged warbler singing his “bee, bzz, bzz” song in Ontario

A golden-winged warbler singing his “bee, bzz, bzz” song in Ontario (Photo by Mark Peck on Flickr, Creative Commons license)

Of course, that wasn’t the only place I saw golden-winged warblers on our property. But it’s the only place that has remained the same with clusters of black locust saplings, a 37-acre field of goldenrod in front, and upslope a mature mixed hardwood forest. This is ideal golden-wing nesting habitat according to the speakers at a Golden-winged Warbler Weekend I attended last April at Penn State Altoona, which was partially sponsored by Pennsylvania Audubon as well as our own Juniata Valley Audubon Society (JVAS).

Yet so-called ideal golden-wing habitat on both their nesting and wintering grounds has been increasingly empty of these handsome warblers with their black eye patches and throats and yellow foreheads and wing patches. Once they bred throughout the northeastern and north-central United States and southern Ontario, but since the 1960s, there has been a 66% decline throughout their range.

A golden-winged warbler from the sub-population in Minnesota/Wisconsin

A golden-winged warbler from the sub-population in Minnesota/Wisconsin (Photo by Tom Benson on Flickr, Creative Commons license)

Back in the 1990s, the Cornell Laboratory of Ornithology and several partners convened the Golden-winged Warbler Working Group and, with the help of 300 citizen-scientists throughout the birds’ breeding range, conducted a golden-wing survey from 1999 to 2006. They found that the golden-wing population had receded to two isolated sub-populations, one in Minnesota/Wisconsin and the other along the Appalachian Mountains. But the Appalachian Mountains’ regional population was down a whopping 98%, in part because the golden-wing habitat had decreased 43% since the 1960s.

Here in Pennsylvania, the Game Commission is one of the partners with the Cornell Lab in trying to recover golden-wing habitat. According to Jeffrey Larkin, a wildlife biology professor at the Indiana University of Pennsylvania, who is the regional coordinator for the GWWA (golden-winged warbler) Working Group, writing with Maria Bakermans in the Second Breeding Bird Atlas Project, golden-winged warblers nest “in ephemeral early successional habitat resulting from abandoned farmland, fire disturbance, timber harvest, utility rights-of-way, and managed shrublands.” They have a patchy distribution in the commonwealth, mainly through the southern Allegheny Mountains and through the Ridge and Valley Province with hotspots in Bedford and Huntingdon counties and much lesser numbers in the northeastern Pocono Plateau—in total about 6,300 singing males.

Fertile hybrids of the golden-wings, the Lawrence’s warbler, upper image, and Brewster’s warbler, lower

Fertile hybrids of the golden-wings, the Lawrence’s warbler, upper image, and Brewster’s warbler, lower (Photos of Lawrence’s warbler by Dominic Sherony, link to https://www.flickr.com/photos/9765210@N03/3513160337 and of Brewster’s warbler by Mark Peck, link to https://www.flickr.com/photos/76929746@N04/8231455202, both on Flickr with Creative Commons licenses)

Since then, according to Doug Gross, Endangered and Non-game Bird Section Supervisor, the golden-wing range continues to contract, with no populations in the southeastern or northwestern parts of Pennsylvania and very few in the northern tier counties outside of Sproul State Forest and the Poconos. What populations are left are found mostly “off-road, requiring a walk into a cutting, a wetland, or a scrub barren to find these birds,” Gross writes in the October 2015 PSO Pileated, the newsletter of the Pennsylvania Society for Ornithology.

Habitat loss is only one of their problems. Nest parasitism by brown-headed cowbirds is another. The third problem, hybridization with blue-winged warblers, has produced fertile hybrids called “Lawrence’s” and “Brewster’s” warblers. Subsequently the GWWA Working Group discovered through pioneering genetic work on golden-wing blood samples by Rachel Vallender, that even birds that looked like golden-wings Vermivora chrysoptera had genetic evidence of post hybridization with their close congeners blue-winged warblers V. pinus.

The only solution to that problem seems to be targeting “landscapes with expansive forest cover at higher elevations” for golden-wings, which will keep them away from the lower-elevation breeding blue-wings, or so the researchers hope. They have already been managing such lands on both private and public land in Pennsylvania and having some success, for instance, at Bald Eagle State Park when Larkin, in 2009, thinned shrubs and trees from an overgrown old field and golden-wings returned.

The slight blush of yellow on the chest, and the bird singing a blue-winged song, provided good evidence of a golden-winged hybrid with a blue-winged warbler to the photographer

The slight blush of yellow on the chest, and the bird singing a blue-winged song, provided good evidence of a golden-winged hybrid with a blue-winged warbler to the photographer (Photo by Kent McFarland on Flickr, Creative Commons license)

Several game lands are also being managed, not only for golden-wings but for the large number of species dependent on similar habitat—American woodcock, ruffed grouse, willow and alder flycatchers, yellow, prairie, black-and-white, Canada, chestnut-sided and hooded warblers, yellow-breasted chats, gray catbirds, eastern towhees, common yellowthroats, indigo buntings and field and song sparrows. Of those species, our First Field hosts at least eight.

But when our JVAS visited State Game Lands No. 322 in mid-May along a large powerline right-of-way managed for golden-wings, the habitat seemed perfect with numerous scrub oaks and bush blueberries. We heard and saw 26 bird species, including three singing prairie warblers, a yellow-breasted chat, five chestnut-sided warblers, two gray catbirds, five eastern towhees, and numerous indigo buntings, field sparrows, and common yellowthroats but not one golden-winged warbler after a couple hours of walking slowly and listening.

JVAS outing to State Game Lands 322 to search for golden-winged warblers with the author at center and JVAS President Laura Jackson to her left in blue jacket

JVAS outing to State Game Lands 322 to search for golden-winged warblers with the author at center and JVAS President Laura Jackson to her left in blue jacket (Photo copyright Mike and Laura Jackson)

Then we visited a JVAS member’s country property where she said they had golden-wings every spring. As soon as we exited our cars next to an unmanaged wet area, we heard a singing golden-wing. We never saw the elusive bird or any others on this property, much to our disappointment. Still, at least one golden-wing was there.

In Pennsylvania, breeding male golden-wings arrive in the first week of May two to seven days before the females, and they sing their primary song. They quickly pair up after the females arrive, and she chooses the nest site, which is usually at the base of leafy material such as wild berries or goldenrod. Sometimes they include a taller, thicker stem that supports the leafy material and allows the adults to grip when they arrive at a nest.

Mayapples blanket the Far Field thicket

Mayapples blanket the Far Field thicket (Photo by Dave Bonta on Flickr)

I remember stumbling on a nest at the Far Field thicket back on June 1, 1996. Mayapples blanketed this relatively open, wet area. A pair of loudly singing golden-wings flew close, and down low in the thicket a pair of Kentucky warblers distraction-displayed and called. As I retraced my steps back through the mayapple area, a golden-wing flew up from the ground. Almost immediately I saw her nest made of dead oak leaves on the outside and lined with grapevines and grasses. The nest held one brown-headed cowbird egg, which I removed, and one porcelain-white golden-wing egg, spotted with orange at the rounder end. Not wishing to attract predators, I never revisited the site.

Later, I read that females build their nests in one to three days and will often abandon incomplete clutches of eggs if they are disturbed. On the other hand, they will re-nest and lay a fresh batch of eggs if the first one is destroyed.

Most complete clutches contain four or five eggs and are incubated solely by the females for 11 days. Both parents feed their young while they remain in their nests for nine days, but after they fledge, the parents may divide them up, a process known as brood-splitting, and feed them as long as 31 days off their nesting territory, since golden-wings don’t have second clutches. They feed their young what they eat themselves—moths and their larvae, other flying insects, ants and spiders.

The Rio Negro cloud forest of Honduras, with large trees, epiphytes, and thick vegetation about 4800 feet elevation

The Rio Negro cloud forest of Honduras, with large trees, epiphytes, and thick vegetation about 4800 feet elevation (Photo by Joe Townsend on Flickr, Creative Commons license)

By late August or early September golden-wings are heading to their southern homes in Central and northern South America. At the Golden-winged Warbler Weekend, Ruth Bennett, a Cornell University PhD student, working under Dr. Amanda Rodewald, explained that she is studying them on their wintering grounds in Honduras, where they are most abundant, along with Costa Rica, Nicaragua and Panama and in lesser numbers in Colombia and Venezuela. Because golden-wings inhabit thick vegetation in mountaintop cloud forests, they are difficult to find so Bennett and other researchers use recorded golden-wing calls to attract males.

From 2009 to 2013, researchers captured, banded, and collected feathers from 1500 separate points. Altogether, they found 581 males and only 80 females, because it seems as if females spend their winters at lower elevations. But there is no doubt that male golden-wings prefer the high elevation humid broadleaf pine and oak forests of Nicaragua and Honduras, especially larger trees with hanging epiphytes at approximately 3,280 feet or more and females a low canopy at 1,640 feet.

Such habitat is rapidly disappearing because of clearing for cattle-farming, and poor agriculture practices in general as well as for open, sunny coffee plantations. Coffee drinkers in North America can help to change such plantations by purchasing only coffee grown in the shade amidst a mixture of plants and trees, so-called shade-grown coffee.

Modeled by JVAS President Laura Jackson, the golden-winged warbler T-shirt is part of a fund-raising effort to help preserve the habitat of the birds in Pennsylvania and Honduras

Modeled by JVAS President Laura Jackson, the golden-winged warbler T-shirt is part of a fund-raising effort to help preserve the habitat of the birds in Pennsylvania and Honduras (Photo copyright Mike and Laura Jackson)

In addition to creating more nesting habitat for golden-wings here, both on public and private land, with the aim of creating an additional one million acres of golden-wing habitat by 2050 and increasing the global population by 50%, a winter range conservation plan is also imperative.

Much work and research is necessary both here and there because there is still more to learn about the life history of these birds, but with so many researchers and citizens fired up to save this species, I felt optimistic, after our Golden-winged Warbler Weekend, that soon I will once again hear and see this beautiful warbler on our golden-wing habitat at the edge of First Field.

 

Carolina Chickadees

For years I thought I could tell the difference between black-capped and Carolina chickadees by their songs and calls. After all, I had heard them one winter on the mall in Washington, D.C. and they certainly sounded different from the black-cappeds I was used to. So last winter, when I heard a calling chickadee that sounded different, I wondered if it could be a Carolina chickadee.

black-capped chickadee

Photo of a black-capped chickadee taken near our house by Dave Bonta, February 15, 2006

I located the bird perched in a cedar tree outside my window. While I studied the bird, I looked at my four field guides and learned that black-capped chickadees are larger than Carolina chickadees by a quarter to half an inch with longer tails and bigger heads. In addition, black-cappeds have more white on their wing edges and their white cheek patches are entirely white while those of Carolinas blend to pale gray at the rear.

But most of my guides agreed that their songs and calls should be my guide. Carolinas’ “chick-a-dee” calls are higher pitched and more rapid than black-cappeds and their whistled “fee-bee, fee-bay” is distinct from the single “fee-bee-ee” or “fee-bee” of black-cappeds.

As I examined my singer, I noticed its white wing edges and decided it was only a black-capped. Studying the most recent Carolina chickadee range maps in the Second Atlas of Breeding Birds in Pennsylvania, it was clear that none had been reported in Blair County where I live even though if I drew a straight line from east to west across the commonwealth, our home would be at the northern edge of Carolina chickadee territory.

A Carolina chickadee in Codorus State Park

A Carolina chickadee in Codorus State Park, southwestern York County, February 9, 2013 (Image by Henry T. McLin on Flickr, Creative Commons license)

But that’s not how it works in Pennsylvania. Since 1975, Carolinas have been expanding northward at about seven-tenths of a mile per year in southeastern and south western Pennsylvania, and they now live as far north as Lehigh and Schuylkill counties in the east and Beaver County in the west. However, they are mostly absent at higher elevations in the Allegheny Mountains and southern Appalachian physiographic sections of Pennsylvania according to Robert L. Curry’s account in the atlas.

Curry, who teaches biology at Villanova University, has been conducting field studies of the population ecology and behavior in hybridizing Carolina and black-capped chickadees in southeastern Pennsylvania since 1997. That’s when his students built 450 fake nests of short lengths of sewer pipe and made them look like trees with a cavity and top entrances in an attempt to attract cavity-nesting chickadees.

They erected their fake nests in Chester County to study Carolina chickadees, Nolde Forest near Reading in southern Berks County to study both Carolina chickadees and hybrid Carolina/black-cappeds, and Hawk Mountain Sanctuary on the easternmost ridge in the Valley and Ridge province of Pennsylvania to study black-capped chickadees. (Our ridge is the westernmost in the province, incidentally.)

Even though Carolina and black-capped chickadees have been distinct species for between one and 2.5 million years, from Kansas to New Jersey these two species meet, mate and give birth to hybrid species. But Curry and students have learned that male Carolinas, which are more aggressive than male black-cappeds, mate with female black-cappeds, but female Carolinas rarely mate with male black-cappeds. Furthermore, these hybrid birds lay a large number of infertile eggs, in contrast to a 92% hatching success of an average of five eggs laid by Carolinas in 55 nests in southeastern Pennsylvania with similar fertility rates in black-capped chickadees.

Curry and other researchers don’t agree that anyone can identify Carolina and black-cappeds by their unique calls and songs in hybrid areas because hybrids can sing Carolina, black-capped and intermediate songs. Carolinas can also learn and sing black-capped songs and black-cappeds can learn Carolinas’ songs. So researchers use “diagnostic protein, nuclear DNA, and mitochondrial DNA markers” to identify species according to the life history of Carolina chickadees in The Birds of North America.

Curry and students documented over the years a northward movement of Carolina chickadees, and by 2006 he added Tuscarora State Park in Schuylkill County to his study area for black-cappeds because almost half of Hawk Mountain’s chickadees were then hybrids while Nolde Forest had only Carolinas. Curry hypothesized that Carolinas are moving northward as a result of warming winter temperatures. Hybrids, he says, live in places with an average low winter temperature of between 15 and 19 degrees Fahrenheit, while black-cappeds prefer colder winter temperatures and Carolinas are primarily southern birds and one of only four birds John James Audubon discovered and named while in coastal South Carolina.

Today they range from south-central Kansas to the Atlantic coast and south from north and southeast Texas to the Gulf Coast and central Florida. Black-cappeds persist south along the highest mountains, but even on Mount Mitchell, the highest mountain in North Carolina, Carolinas replaced black-cappeds after logging and repeated burning, but after reforestation black-cappeds did not return.

Carolina chickadee upside down

Carolina chickadee upside down on a tree snag in Georgia, July 2, 2011 (Image by Evangello Ganzalez on Flickr, Creative Commons license)

Like black-cappeds, Carolinas are acrobatic, hanging upside down from branch tips as they search for insects that make up 80 to 90% of their spring, summer, and fall diets and half their winter diet. The other half is seeds and fruit, including bird feeder seeds, which they often cache for later use, especially in the winter.

They prefer to breed at the edges of deciduous forests with a healthy shrub, midstory, and overstory canopy, but they don’t mind a high human population in the area or fragmented forests as long as there are dead trees or nest boxes for nesting. In Pennsylvania, they breed in late April, which is a week sooner than black-cappeds.

Earlier, during flock formation in late summer or in winter flocks or even as late as early spring, they pair up, forming a bond that can last as long as three years. Males feed the females during courtship and guard them during egg-laying. The feisty Carolina males chase other males away from their mates and their breeding territory and may engage in feet-kicking, bill-jabbing and wing-fluttering in the air or on the ground.

By mid-March, the pairs are excavating and building nests in cavities, natural snags, fence posts or nest boxes. While both parents take turns excavating, the females construct nests with a base of moss and a thick lining of hair or plant fiber, especially the fur of eastern cottontails, white-tailed deer, eastern fox squirrels, opossums, raccoons, or even domestic cows or cats. This fur she fashions into a flap and the nest, with the flap down, probably is an attempt to keep house wrens from destroying the eggs. Other cavity nesters, such as eastern bluebirds, tufted titmice, and house sparrows are also known to take over Carolina chickadees’ nests even those with eggs or nestlings.

Carolina females lay three to 10 white eggs spotted with reddish brown. They also incubate the eggs for 12 to 15 days while the males feed them. In one case in southeastern Pennsylvania, a brooding female was killed on her nest, and Curry suspected a southern flying squirrel was the culprit. Other mammalian predators on eggs, nestlings, and young fledglings are raccoons, opossums, domestic cats, and rat snakes. Avian predators, even on adults, are sharp-shinned and Cooper’s hawks.

Carolina chickadee feeding its young

Carolina chickadee feeding its young in the hole of a North Carolina tree, April 13, 2008 (Image by cotinis on Flickr, Creative Commons license)

Once the eggs hatch, females continue to brood their nestlings until they are eight days old. Both parents feed them for 16 to 19 days, and then they fledge, usually in the morning. The parents continue to feed them for two to three weeks, and after that they are on their own.

Parents that remain paired hold the same territory in successive years, and they remain there where they are joined by young Carolinas to form a winter flock. In these flocks and generally males dominate females and larger males dominate smaller males. Although such dominance doesn’t guarantee winter survival, it does guarantee a breeding territory. Not all Carolinas stay in a flock. Instead, they are flock-switchers or winter floaters, either joining another flock or continuing to move from flock to flock.

To survive the winter, they spend their time along stream valleys in sheltered forest interiors when it is cold and the wind is blowing. They also decrease their movements and the distance they fly between foraging sites. They can enter a state of regulated night hypothermia by dropping their body temperatures to 84 degrees Fahrenheit and pairs will roost together in tree cavities, staying there as long as 15 hours during a 24 hour period to conserve heat. They sunbathe early in the morning by perching on branches sheltered from the wind and facing into the sun with their body feathers fluffed and their wings spread. To obtain water, they drink from bird baths and natural sources and eat snow.

From the first (1984-89) to the second atlas period (2004-09), Curry estimates a 90% increase in Carolinas’ population in Pennsylvania. During the second atlasing period researchers estimated there were 105,000 singing Carolina males. However, Curry concludes that atlas results do not support upslope movement into ridgetops in Franklin and Fulton counties, so it looks like I won’t see Carolinas or hybrids here anytime soon.