Warblers

Joe Meche is a member of the board of directors of the North Cascades Audubon Society and has been the editor of the chapter newsletter for the past six years. Joe has been photographing birds and landscapes for over thirty years and has been watching birds for more than fifty years.

Of all the spectacular bird migrations, one of the most spectacular is that of the warblers, or wood warblers, as they are properly known. Contrary to popular lore, the true harbingers of spring are the warblers, those brightly-colored bundles of energy that migrate to their breeding grounds in North America in incomprehensible numbers.

Warblers leave their wintering grounds in Mexico and Central and South America and travel at night, driven by the urge to procreate. The fact that they travel at night contributes to a high mortality rate since many of the birds collide with tall buildings and television and radio towers.

One of the most fascinating aspects of warbler migration is the timing. Since insects are their primary food source, warblers begin to arrive when trees start to produce leaves in spring that provide food for insects and their larvae. It’s practically impossible to estimate the number of insects eaten by warblers, as well as by other birds.

As the warblers progress northward in the spring, they are easier to spot since the trees are in earlier stages of leaf development. This is the best time to practice field identification skills on these small, active birds.

I grew up in the southwestern corner of Louisiana, just a short distance as the spoonbill flies from the Gulf of Mexico. This part of the country is renowned for its incredible variety of year-round birds. In April and May, however, the big highlight of the birding year for many people is the fallout of eastern warblers, along with other passerine species. Fallouts occur with some regularity in the spring when the legendary Yucatan Express begins to move northward.

Most birds are said to move in flocks, but warblers in spring migration move in waves. These waves show up on the Louisiana and Texas Gulf Coast and on coastal radar like clouds, covering trees and shrubs and most of the viewing screen, respectively.

After a nonstop crossing of the open waters of the Gulf of Mexico, often against strong north winds, the small, colorful warblers stop to rest on the first perches they encounter. The spectacle that follows is nature’s own version of Christmas. Like so many Christmas ornaments, the birds sit in trees and shrubs to rest before continuing their northward journey.

I’ve witnessed this phenomenon on numerous occasions and was never anything less than fascinated by the variety of birds crowded together. On banding weekends with the university biology department, our mist nets were like living textbooks of field identification. In our nets were the songs that would fill the backyards and woodlots of the eastern states throughout the summer.

Some eastern warblers and all the western species choose to follow the less-precarious overland route to their breeding grounds in the mountain and coastal habitats that closely simulate their wintering grounds to the south. The north-south mountain ranges serve as perfect guides for warbler species such as MacGillivray’s and Townsend’s which nest in the foothills and coniferous forests of Whatcom County. Hike up to Hannegan Pass in June and you’re certain to find both of these warblers.

As with many birds, warblers follow traditional migration routes. It’s not unusual, however, to see vagrants or strays that might have turned right or left when they should have gone straight—not unlike some humans. We were enjoying a quiet afternoon at the Malheur refuge in southeastern Oregon a few years ago when a couple of carloads of serious Oregon birders pulled into the parking lot. They were all excited that someone had reported a hooded warbler at the headquarters.

To make a long story a little shorter, yours truly captured the hooded warbler on videotape to confirm a rare sighting for the state of Oregon. Kudos for our team! This was especially poignant for me since I grew up with hooded warblers in my neighborhood every year.

Warblers are some of our smallest birds. They are fast and vocal, and can provide some of the toughest challenges in field identification. Ludlow Griscom, noted research ornithologist from Harvard University, said in “The Warblers of North America” (1957), that “Warblers are at once the delight and despair of field observers.”

They come in a variety of colors, with yellow being the most common color. The black-throated blue and cerulean warblers are two notable exceptions to the yellow rule. Plumage patterns and underparts of warblers can be streaked, striped, or plain. Warblers are birds of woodlands and swampy areas, and are primarily insectivores. They spend most of their waking hours flitting about in trees and thickets searching for and devouring great numbers of insects.

Warblers can be found all across the continent in summer, from Alaska to the Canadian Maritime Provinces. Fifty-four warbler species nest in North America and, in total number of species, only the finch family is larger.

All warblers are members of the family Parulidae and have thin, pointed bills. Their slender legs and toes are similar to those of other Passeriformes, or perching birds. Most warblers nest in trees and shrubs, while the common yellowthroats nest near the ground and the prothonotary warbler is a cavity nester. Warblers have the unenviable distinction of being the most likely victims of brood parasites like the brown-headed cowbird.

In Whatcom County, sixteen species of warblers have been recorded. The most common warbler in the county is also the most widespread of all the North American species—the common yellowthroat. Some of the larger concentrations of yellowthroats can be found in the areas around Lake Terrell and Tennant Lake. At Tennant Lake, their withcity-withchity-witchity song can be heard along the trail from the observation tower to the lake. Respectable numbers of yellow warblers can also be seen and heard at the lake.

Since warblers are migratory birds, most of the local species are gone by the time winter sets in; however, the Audubon’s form of the yellow-rumped warbler has been recorded on at least 20 Bellingham Christmas Bird Counts, with a high count of 33 individuals in 1991.

Warblers face many threats to their survival, not only during migration but also in the form of habitat destruction and fragmentation on both their wintering and breeding grounds. The hand of man is creating situations that increase the vulnerability of many species to predators and brood parasites.

The widespread impact that humans are having on warbler species is well documented and only a rapid reversal of these trends can stop the decline in some populations. Habitat preservation and restoration are the key elements that need to be addressed to ensure that these birds continue to thrive in our lifetime.

When spring finally comes to North America, many feel that the American robin is the harbinger of the changing seasons. However, since we usually have robins around here throughout the winter, I always wait to see the first swallows and hear those first warblers. I especially enjoy the chorus of the yellow warbler as it tells us, cheerfully and repeatedly, how life is so sweet-sweet-sweet-oh-so-sweet. §