Introduction

Adult female Canada Warbler; Ohio, May.

Adult male Canada Warbler; Ontario, May.

Figure 1. Breeding distribution of the Canada Warbler.

This little-studied wood-warbler breeds in the northeastern U.S., boreal Canada, and through the central ridge of the Allegheny Mountains to Tennessee and Georgia. It undertakes a long annual migration for a wood-warbler, wintering in northern South America. It is often referred to as the “Necklaced Warbler” because of the pattern of black spots across its bright yellow breast.

During the breeding season Canada Warblers inhabit many sorts of forest growth, but the species is most abundant in cool, moist forests with a mix of coniferous and deciduous trees, a dense understory, and complex ground cover, often with standing water and trees that emerge from the subcanopy. It frequents rhododendron thickets in montane areas in the south, steep aspen/poplar forests in the north, and forested wetlands/swamps in the central part of its range. It is often associated with areas having abundant moss cover, nesting on or near the ground in recessed pockets within moss hummocks, upturned tree-root masses or small hillocks with deep litter and dense saplings. This warbler spends relatively little time on its breeding grounds, usually one of the last warblers to arrive and one of the first to depart local nesting areas. Canada Warblers often continue to sing late into the nesting cycle and even during fall migration and on the wintering grounds.

This warbler eats a variety of insects and spiders and uses varied foraging techniques: foliage gleaning, ground foraging, and flycatching. It is an active species, its tail often cocked and wings flicking. In some areas, it feeds largely on the wing, which explains the names used historically for this species: Canadian Flycatcher and Canadian Flycatching Warbler. It is socially monogamous and territorial during the breeding season and often joins mixed-species foraging flocks during winter.

Recent studies on nesting populations have opened new doors on the breeding biology of this species. Nest site (and often mate) fidelity is high, and individuals have been known to persist in local breeding populations up to six years. Females lay one egg per day, with a short incubation period -- ten days after the penultimate egg is laid. The nestling period ranges from 7-9 days.

Populations of this warbler have declined steadily over the past 30 years, likely in response to forest succession and loss of forested wetlands, making this species a high priority for management and monitoring. Its wintering grounds along the east slope of the Andes are also under pressure, but the species apparently can use disturbed forests if sufficient stands of trees remain. Still, trends in many parts of its breeding range exceed 2% loss annually, prompting the need for vigilant study and management.