Tennessee Warblers

The ranges of certain migratory birds are impressively wondrous.

Some passerines – the perching birds – are tiny dynamos. The Tennessee warbler, for example, weighs an average of 10 grams (0.35 ounces). While this diminutive stature might make flight easy, the metabolic rates of birds are astronomically high. Somehow, a creature that weighs a third of an ounce harnesses enough energy and possesses enough stamina to fly thousands of miles.

Meet the resplendent Leiothlypis peregrina:

A female Tennesse warbler - photo by Brad Imhoff/Macaulay Library
A male Tennessee warbler - photo by Chris S. Wood/Macaulay Library

The Tennesse warbler is a member of the family Parulidae, known colloquially as the New World warblers. Its scientific nomenclature – peregrina – comes from the Latin word peregrinus, which means “wanderer.”

The maps of this bird’s range are truly staggering.

The warbler breeds during the late spring and early summer across the breadth of Canada and a few spots in the northern portions of the contiguous United States, including Maine, New Hampshire, Vermont, the Upper Peninsula of Michigan, Wisconsin, Minnesota, and Montana. They overwinter in an area that includes southern Mexico, Cuba, Hispaniola, Central America, and the northern reaches of South America. The extremes of the range sit over 5,000 miles apart. The migratory path includes nearly all the land between Canada and South America, so many in North America get two chances per year to see the Tennessee warblers on the move.

Breeding range in orange; migratory paths in yellow; winter range in blue - graphic from All About Birds

After pondering the map above, you might wonder why this bird is named for a state through which it merely passes. The Tennesse warbler doesn’t spend much time in Tennessee at all.

Ornithologist Alexander Wilson, considered by many to be the greatest American birder before Audubon, encountered a migratory individual in the Volunteer State in 1811. Apparently unaware that the warbler was traveling, Wilson applied the moniker and it stuck.

During migration, the birds are particularly vociferous. They produce pleasing, high-pitched songs:

The Tennessee warbler breeds in boreal forests, also known as taigas or snow forests. These areas are ripe with conifers (to catch them during migration, regions that contain pines often have a greater chance of attracting the birds in flight), which produce the favorite food of the warbler: the spruce budworm.

During the winter, the birds live in tropical forests. According to Cornell Lab’s All About Birds, the warblers become “nectar thieves” during their stays near the equator. Most animals drink nectar from flowers via the front entrance, covering their faces in pollen and taking the tiny, gamete-producing substance to spread. Instead, the warbler pierces the flower tube at the base, slurping the nectar without aiding the flower.

Uncool, warblers.

A male warbler - photo by Jerry Oldenettel
A female Tennessee warbler - photo by Brian Plunkett

Despite their proclivity to leave flowers hanging, these birds are a delight to observe in the wild. Not often can those of us in the United States view a critter that frequents both the taiga and the tropical rainforest. If you’re into birding and live in most of the country, you can catch these common passerines heading north in May and returning south during September and early October.

Further Reading and Exploration

Tennessee Warbler – The Cornell Labs/All About Birds

Tennessee Warbler – Audubon Field Guide

Tennessee Warbler – eBird

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