Summer Warblers: Part One

In the Great Lakes Region of North America, wood-warblers, Parulidae, are one of the most diverse groups of birds with over 40 species. There is a warbler for every habitat type, and of almost every colour pattern – although I haven’t seen any purple warblers! Considering the beautiful and striking plumage of many warbler species, it is no surprise the warblers are favorites of many birders. 

Warblers are insectivores, although a few species become frugivorous when food resources become scarce. Many warblers collect aerial insects, though some forage through leaves or bark to collect food. Most species are long-distance nocturnal migrants – traveling from the Great Lakes region to the neotropics (Central American, some species to South America). Warblers are mostly observed by birders during spring and fall, when large numbers of warblers migrate through the Great Lakes region. 

After spring migration, the majority of Canadian warbler species breed in forest or savanna ecosystems. Preferences vary between species, with some species preferring coniferous forests and other species mostly observed in deciduous forests. Location in the canopy or understory of a forest also depends on the species. A few warbler species prefer grasslands, shrublands, or wetlands rather than forests as their primary breeding location. Peak breeding activity is observed between the end of May and middle of July. When nesting activities have been completed, warblers will undergo a complete molt, which usually occurs near the end of July. August is a transitional month between the breeding season and autumn migration. Warblers will begin to travel towards resource-rich areas to feed and forage in preparation for their migration south. Areas near water, such as the Great Lakes coastal zone, and riparian areas are especially favored as foraging areas. Autumn migration begins for most species in the last week of August, and peaks during mid-September.  

More locally within the Couchiching region, there are plenty of good areas for spring and summer birding. During migration season, songbirds are often found along the coasts of the Great Lakes. These include areas adjacent to the Lake Huron coast, such as Awenda Provincial Park, Wye Marsh, and Tiny Marsh – Wildman Forest Complex. In the summer, these same areas are important for southern species of warblers (i.e., Cerulean Warbler), due to their lush deciduous forests. The vast swamps around Minesing are also important for both migratory and breeding warblers. In Kawartha Lakes, the rare shrubland habitats on Carden Alvar provide important breeding grounds for a variety of open-country warblers, in addition to other bird species such as the Bobolink and Loggerhead Shrike. Northward, the Black River Wildlands supports mixed forests typically of the Canadian Shield, making it a good location to observe more northern warbler species. 

Canadian warblers are divided into 11 genera – Setophaga (American Redstart, Yellow Warbler and allies), Cardellina (Canada Warbler), Oporonis (Connecticut Warbler), Geothlypis (Common Yellowthroat, Mourning Warbler and Kentucky Warbler), Leiothlypis (Tennessee Warbler, Orange-crowned Warbler, and Nashville Warbler), Protonotaria (Prothonotary Warbler), Mniotilta (Black-and-White Warbler), Vermivora (Blue-winged Warbler and Golden-winged Warbler), Parkesia (Waterthrushes), Helmitheros (Worm-eating Warbler) and Seirus (Ovenbird).

This article will only discuss warblers in the Setophaga genus, which is by far the most diverse group of warblers. A future article will explore the ecology and behavior of warblers in other genera. 

Yellow Warbler (Setophaga petechia)

Yellow Warblers are the most widely distributed warbler species in North America, with a breeding range stretching contiguously from the mangroves of Yucatan and Central America north to the edge of the Arctic tundra in Alaska, covering an extremely wide range of environments. Males are almost entirely yellow (including the wing), with orange streaking stretching vertically down the belly. Females appear similar to male Yellow Warblers but without orange streaking.  In Ontario, yellow warblers are most often found within their breeding habitat – shrubby thickets, successional forests, and wetland edges. Yellow Warblers that breed in Ontario migrate south to winter in tropical highlands and rainforests of Central America and northern South America.

Myrtle Warbler (Yellow-rumped Warbler, Setophaga coronata)

The Myrtle or Yellow-rumped Warbler is likely the most abundant warbler species in Ontario due to its versatility – like the Yellow Warbler, it breeds in a wide variety of habitats. Adult males in breeding plumage are gorgeous – each bird has two distinctive yellow flanks below each grey wing, a blue-grey head and back, a black mask and a white cheek and eye line. Female Myrtle Warblers are also vibrant in spring plumage, but can be readily distinguished from males by their brown backs and brown heads. They retain their spring plumage from April – early August, afterwards the male warblers will transform their plumage to resemble females in breeding plumage, whilst the females themselves become duller and more washed-out in autumn plumage. Myrtle warblers breed primarily in mixed forests and boreal coniferous forest regions north of the Lake Erie lowland region. The nests are typically placed on the branches of coniferous trees – though hardwoods are occasionally utilized as well. In the autumn, Myrtle Warblers migrate towards their vast wintering grounds, which stretch from the Lake Erie lowland region to Panama, including almost all other regions in-between those two places. Myrtle Warblers can survive the winter in the southern Great Lakes due to their frugivorous (fruit-eating) tendencies when insect food resources are scarce. Myrtle Warblers are most often observed in Ontario from mid-March to late November.

American Redstart (Setophaga ruticilla)

Within their forest habitat, American Redstarts are one of the most common warbler species in Ontario. Male American Redstarts are distinctive in appearance, with a black head, black wings, orange flanks with a distinctive orange wing patch, and a white belly. Female redstarts have a grey head, with a small white eyering, white belly, and peach flanks. Redstarts breed in most of the deciduous and mixed forest regions of North America, although they are also found in shrublands and other woody habitats. They prefer shaded locations for their nests, within the forest understory. American Redstarts are observed in Ontario between early May and early October. These birds winter in the tropics of Central America, the Caribbean Islands, and South America north of the Amazon Basin.

Pine Warbler (Setophaga pinus)

Pine Warblers are among the earliest migrating warblers in Ontario, typically arriving in mid-April and remaining in the province until late October. They are most often observed in oak-pine woodlands and savannas, and within mixed forests with a pine component. Within these forests, the Pine Warbler breeds almost exclusively in the upper canopy of pine trees. Pine Warblers are primarily olive-yellow, with a white rump – similar in appearance to a few other warbler species, such as the Yellow Warbler and Black-throated Green Warbler. The grey wings of Pine Warblers distinguish Pine Warblers species from Yellow Warblers, which have yellow wings. This warbler winters in the southeastern United States, (the Carolinas, Georgia, Alabama, Mississippi, Louisiana, northern Florida, and the Piney Woods region of Arkansas and Texas).

Stay tuned to learn more about the fourteen other warblers in the Setophaga genus! Sign up for our newsletter to be notified when Part Two is released.

Article by Matthew Palarchio

Photos by Matthew Palarchio, unless otherwise indicated with a copyright (©) symbol.