Canada warbler

May is the prime time to see Canada warblers in the Chesapeake region. 

A month later, after several days of rain, the weather in Maryland turned bright, sunny and warm. My wife and I were seized by a powerful case of spring fever. We simply had to get outside.

The little bird had followed its own irresistible urge up through Central America and Mexico and continued through an expanding swath of the eastern United States, including the Chesapeake watershed.

Our paths crossed that May morning along Indian Creek in the Lake Artemesia natural area in Prince George’s County, MD. We saw the bird streamside, actively capturing flying insects, which would power its flight even farther north.

The Canada warbler (Cardellina canadensis) was at eye level, and we could see the bright yellow underside (from chin to belly) with the diagnostic black necklace across its breast. The necklace, composed of black streaks ringing the top of the breast, was the key field mark, and it was unmistakable.

The bird’s face included a broad bill, yellow spectacles, thin white eye-rings, a black forehead and black wedgelike sideburns. Up top, the bird was a solid dark gray with a hint of blue.

There were no wing bars or tail markings. The stark contrast in feather colors indicated this was a male. Females tend to be paler overall.

In the Chesapeake, May is prime time to view wood warblers, that delightful set of birds known for their bubbling songs and flashes of bright colors. We call them neotropical migrants, birds of the “New World” (neo) that come to us from the geographic region we call the Tropics.

Few migrate as far as the Canada warbler. It winters in northeastern South America, residing along the leeward side of the Andean Range.

Summer breeding territory in North America includes the sub-boreal Canadian forests from Alberta to the Maritime Provinces. In the United States, the bird breeds in New England, the Great Lakes region and along the upper elevations of the Appalachian ridge.

Canada warblers are one of the last migrants heading north and one of the first to return south. Although they leave their winter territory in early April, it takes them until May to reach Maryland. They arrive on their breeding grounds in Canada in June and start heading south again in August.

Breeding territory is usually characterized by forested wetlands with dense, mossy understories.

Our spot along Indian Creek was typical of stopover landscapes: cool, damp woods hugging a stream.

Canada warblers use a variety of hunting techniques, from flycatching to hovering, from methodically gleaning low branches to searching leaf litter.

In the fall especially, Canada warblers may expand their diet to include fruits. They are very active feeders, often with tails cocked and wings flicking.

These warblers build nests on the ground, in low branches or even upturned tree roots. Females shape crude cup nests and line them with deer or rabbit fur. They lay one egg a day for five or six days in a row. After the last laid egg, mom settles in to incubate the clutch. Ten or 12 days later, the eggs hatch — more or less all at once.

Although they are born featherless and helpless, they develop rapidly. Chicks take just eight days before they leave the nest.

Banded birds have returned to the same nesting area for several years in a row. Some have even reused their old nest sites. It may be thousands of miles from the warbler’s winter home, but nest site fidelity suggests that Canada warblers are as attached to their summer homes as they are to their winter ones. How they find that natal area is a wonder of avian memory and navigation.

Although the population of these warblers is rather large, there has been a precipitous drop in its abundance over the last several decades. Canada warbler numbers are down 60 percent since

1970, and the trend may be accelerating. This is primarily due to the loss of appropriate habitat. The massive die-off of insects throughout the Western Hemisphere and global climate change may also figure in the decline.

Within a day or so, the warbler we were watching would be gone. With luck, we would see one of his brethren during the fall migration in September.

It seems remarkable, but the long-distant migrant is merely following the best path for its reproductive success. That path might involve huge distances, but somewhere is the perfect combination of food supply, temperature, nesting material and protection from predators, as well as other ecological factors that are the ideal fit for the species. It has taken centuries to develop this formula, and it is both amazing and complex.

Spring is upon us. A universal biological clock ticks. We humans are pushed outdoors.

Millions of birds heed the call of the seasons in their own way. Miraculously, both warbler and birder find themselves inexorably drawn to the woods. When paths cross, it is a joy not to be missed.

Mike Burke, an amateur naturalist, lives in Mitchellville, MD.

The views expressed by columnists are not necessarily those of the Bay Journal.

Mike Burke, a Bay Journal columnist, is an amateur naturalist based in Maryland, having retired from a career that toggled between Capitol Hill and the U.S. Environmental Protection Agency.

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