Little Known Warbler of the Northeast

Two years ago the 200^th anniversary of the scientific discovery of the Connecticut Warbler passed, as far as I know, uncelebrated, even unmarked by anyone in the birding community. During the autumn of 1812 one of the fathers of American ornithology, Alexander Wilson, the immigrant sometime-school teacher from Scotland determined to describe all of the birds of his new homeland, the United States, collected a specimen of a large, furtive warbler and named it for the state he had shot it in. Since that day, remarkably little knowledge has been uncovered about the Connecticut Warbler's biology. In spite of an army of birders carrying an array of technically advanced optics and communications devices, despite eBird, HBW Alive, and BNA Online, Oporonis agilis, the "agile autumn bird" (Gruson 1972), remains an obscure, little known forest species. 

We have learned that the Connecticut has a loud, rollicking song, sung in a voice somewhat reminiscent of the voice of an Ovenbird or a waterthrush. The authors of the recently published The Warbler Guide present sonograms of three song variations  and summarise the species’ song as “1 section of 3- or 4- Element Phrases repeated 3 or 4 times (only shared with Common Yellowthroat); irregular, jerky, percussive rhythm… [with a] staccato, emphatic quality.” I like to transcribe the typical song as a fast, loud ringing “chippy chuppy, chippy chuppy, chippy chuppy” which is unlike the song of any other North American warbler.

Philadelphia Vireo - one of the species added to B.C.'s bird list by Cowan and Martin in 1938. Photo by Chris Siddle. 

We have also determined that the Connecticut Warbler is a long distance migrant that crosses the Gulf of Mexico via the West Indies on its way to and from its wintering grounds somewhere in South America. Exactly where its wintering range occurs is poorly known. There's an odd 2000 km gap between known wintering sites in northern South America and wintering sites in Amazonian Brazil. It could be that the birds collected in the northern part of the southern continent were mostly late autumn migrants, and the Connecticut Warbler spends the winter in a region of Amazonia where oddly enough it is the only North American migrant in the neighbourhood. All of the other birds are resident tropical species.  

The Connecticut Warbler has revealed to us only the most basic information about its breeding biology.  Over 70 years passed between the collecting of the first specimen known to science and the discovery of the first nest. In 1883 Ernest Thompson Seton, later to gain fame as a popular writer of animal stories and one of the founders of the America Boy Scouts movement, happened to see a small brown bird flush from a mossy mound in a tamarack swamp near Carberry, Manitoba. Like several other New World Warblers the Connecticut nests on the ground, often in a hummock. Seton's discovery, though pleasing to Seton,  did not open the flood gates of scientific enquiry concerning the Connecticut Warbler. Safe from spying ornithologists in its mosquito-loud northern forests, the Connecticut Warbler remained obscure.  Forty years later in the 1920s 2 or 3 more nests were found, this time near Belvedere, Alberta, but the discoveries didn't clarify a thing. From the discovery of a few more nests over the years to the present, even the most basic information remains to be discovered about this warbler. A single 1961 study conducted by Lawrence Walkinshaw and William Dyer, based on a single nest in Michigan, has remained the source of most information regarding the bird's reproduction but it makes for pretty thin reading. The Birds of North America Online account, which sums up most of what science knows about the species is still full of words like “unknown”, and phrases such as“further study is required”.

Is it little wonder that American birders often “need” Connecticut Warbler on their life lists? The bird migrates very late in spring, often well after almost all other warblers have already started nesting. As Pete Donne writes in Pete Dunne’s Essential Field Guide Companion (2006) “Running from one to two weeks behind the flood of most warblers, Connecticut Warblers arrive in Florida from early to late May and reach breeding grounds in late May to mid-June.” This inconvenient schedule conflicts with the mid-May field trips at places like Point Pelee and other migration spots. Many Americans see or hear their first Connecticut Warblers on special June excursions to northern Minnesota, Michigan or Wisconsin, the only states where the bird breeds within the contiguous United States. With the remaining 90% of its breeding range sprawling in an arc from southwest Quebec northwestwards across Ontario, through the central parts of the Prairies Provinces and northeastern B.C., the Connecticut Warbler still requires birders living across southern Canada to make special excursions into the southern boreal forest to find it. In British Columbia, the majority of birders live around Vancouver and Victoria. For them to add the Connecticut Warbler to their provincial lists, they must travel to terra incognito, the Peace River area.

The Peace River country was the last area of the province to be settled by white people. (Though the first fur trading posts within B.C. were established, albeit briefly, along the banks of the Peace  between the Alberta border and Hudson Hope.) Real settlement, mostly agricultural, occurred from the 1930s onwards. The area was so poorly known biologically that the first detailed survey of its birdlife didn’t take place until 1938, decades after the basic avifauna of southwestern British Columbia was known. And it was in the forests of the Peace, of course, that the Connecticut Warbler had been living since at least the last ice age, a fact that wasn’t even hinted at until almost mid century.

In May 1938 the B.C. Provincial Museum sent young biologist Ian McTaggert Cowan and an assistant, Patrick W. Martin, by truck from Victoria to Tupper Creek at the south end of Swan Lake south of Dawson Creek. Their purpose was to survey the vertebrate fauna of the Peace River Block, as it was then known. They had very little to go on: even though fur trading forts had first appeared along the river as early as 1797 little information had been gathered on the non-game creatures.

Cowan and Martin set up camp on the west side of Swan Lake on 5 May 1938. They collected and made observations from this camp until 8 June when they moved about 100 kms northwards to the south end of Charlie Lake near Fort St. John. On 19 June they returned to Tupper Creek where they remained until 30 June when they left for Victoria.

Cowan and Martin’s surveys of the Peace River area, published in the provincial museum’s first occasional paper (1939), added several species of birds previously unrecorded to the British Columbian list including Franklin’s Gull, Philadelphia Vireo, Black-and-white Warbler, Bay-breasted Warbler, Cape May Warbler, Ovenbird, Rose-breasted Grosbeak, Common Grackle, Le Conte’s Sparrow, Nelson’s Sparrow, all now known to occur regularly in the Peace River area. They were also the first biologists to discover the Connecticut Warbler within the political boundaries of the province.

An extreme enlargement of a male Connecticut Warbler  southwest of Dawson Creek, June, 2014. Photo by Chris Siddle. 

On 22 June 1938 Cowan and Patrick shot the first Connecticut Warbler ever recorded in British Columbia. The bird was a male singing every 50-55 seconds in a grove of young aspens “below an open stand of large poplars, aspens and white spruce.” (p.50) On 24 June about half a mile away another male was singing in climax aspens. A gunshot, presumably from a shotgun discharged by either Cowan or Martin, caused an additional four other Connecticuts to sing. The collectors bagged two of the five birds.

For many years this episode was almost all that was known about the Connecticut Warbler within British Columbia. Sight records slowly accumulated from other locations in the northeastern including Fort Nelson. During my fourteen years investigating the birds of the Fort St. John area I saw or heard the species only a few times. It wasn’t until Mark Phinney began systematic forest surveys around Dawson Creek that the Connecticut Warbler was found to be a local summer resident in aspen forests in the South Peace. Finding a nest, however, was another matter altogether.

To give my readers an idea how hard it can be to find a nest, cunningly hidden on the forest floor, I refer them to a fascinating yet not well known book written by the American bird photographer William Burt. From 1984 to 2000 Burt pursued little known birds for his book, Rare and Elusive Birds of North America. The book contains entertaining narratives of his searches as well as sharply focused photographs of birds within their nesting habitats taken with a large format camera. In search of a Connecticut Warbler’s nest, Burt searched a Tamarack bog near Waskish in north-central Minnesota for two summers. The habitat was open park-like woods “full of mounded moss and ferns and scanty grass and horsetails.” At least six males were singing from an area about sixty to eighty acres in size.

In spite of the relative abundance of singing males, Burt found no nests that first year.  In fact, other than the robust singing of the males, he saw no evidence that the birds were reproducing. Only twice in weeks of watching did he see warblers carrying food only to almost immediately lose track of them.

His second summer began on 10 June with the same woodland “ringing with the songs of males”, but this time he decided that a more systematic search was needed so he laid out ropes on the moss to mark grids. He painstakingly searched the resulting corridors mossy mound by mound. Still he was unsuccessful. Finally he began concentrating on birds calling a sharp peet or whik, alarm notes. One morning, brushing away spider webs, ducking under fallen timber, braving the loud clouds of mosquitoes, as he was moving toward another calling bird, a small bird burst from the mossy mound near his feet. He looked down, parted a few fronds of fern and saw a “grass-lined cup with three brown-specked whitish eggs.” He had his nest.

Two days later there was a full clutch of five eggs. Not wanting to risk disturbing the female, he made only short daily checks to ascertain the nest’s progress. He was waiting for the chicks to be 4 days old before moving a blind near the nest. On 4 July 4 of the 5 eggs had hatched. On 7 July there were five chicks. On 9 July he brought his photographic equipment with him only to find that the nest was empty. Something – a weasel, a jay, a predator – had taken the young. Reflecting upon his efforts to find a nest, William Burt states, “I don’t think there’s any bird in North America, including the black rail, whose nest I’d less want to ever have to find again.”

On 19 June, 2000 Mark Phinney of Dawson Creek found the first Connecticut Warbler nests in British Columbia. That day the nest contained 5 eggs. On 8 July it held 5 well-feathered chicks which left the nest by 10 July. The nest, like most of Phinney’s sightings of the warblers, was southwest of Dawson Creek in pole-aged aspen (25-40 years old) with a general southerly aspect. This habitat is obviously quite different than the Tamarack swamps described by Seton and Burt and other observers in Manitoba and Wisconsin. Nor does it particularly match the older mixed forest of aspen and White Spruce where I had found the birds in the Fort St. John area. Clearly the Connecticut Warbler occurs in more than one type of forest; however, that doesn’t mean that the bird is particularly adaptable. It isn’t. Across its breeding range the species seems to be fussy in its habitat choice and in general avoids areas where the forest is grazed by cattle or broken up by clearings, seismic lines, transmission corridors and other human developments. 

If you’re interested in more information about the Connecticut Warbler here are the references I used while writing this piece:

Bent, A.C. 1953. Life Histories of North American Wood Warblers. Smithsonian Institution, Washington, D.C.

Burt, William. 2001. Rare and Elusive Birds of North America. Universe Publishing, 300 Park Ave. South, New York, 10010.

Campbell, R.Wayne, Neil K. Dawe, Ian McTaggart-Cowan, John M. Cooper, Gary W. Kaiser, Andrew C. Stewart, and Michael C.E. McNall. 2001. The Birds of British Columbia, Volume 4, Passerines: Wood-Warblers through Old World Sparrows. University of British Columbia Press, 2029 West Mall, Vancouver, B.C. V6T 1Z2.

Cooper, John M. and Suzanne Beauchesne. 2004. “Connecticut Warbler” pp. 1-10, in Accounts and Measuring for Managing Identified Wildlife – Accounts V. 2004. “www.env.gov.bc.ca/wld/frpa/iwms/documents.Birds/b.connecticutwarbler.pdf”

Cowan, Ian McTaggart. 1939. The vertebrate fauna of the Peace River district of British Columbia. British Columbia Provincial Museum Occasional Paper No. 1, Victoria.

Dunne, Pete. 2006. Pete Dunne’s Essential Field Guide Companion. Houghton Mifflin C., 215 Park Ave. South, New York, 10003.

Gruson, Edward S. 1972. Words for Birds: A Lexicon of North American Birds with Biographical Notes. Quadrangle Books, NY Times, 330 Madison Ave., New York 10017. 

Pitocchelli, J., J. Bouchie, and D. Jones. 1997. Connecticut Warbler (Oporornis agilis). In The Birds of North America, No. 320 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D.C. 

_____, _____, and ____. 2012. Connecticut Warbler. (revised. The Birds of North America Online. 

Stephenson, Tom and Scott Whittle. 2013. The Warbler Guide. Princeton University Press, 41 William St., Princeton, New Jersey 08540.Winnipeg, Manitoba.

Taylor, Peter (editor-in-chief). 2003. The Birds of Manitoba. Manitoba Naturalists Society,