The Canada warbler is a social bird, typically living in flocks (3) (4). It usually arrives at its breeding grounds in May (8) (11), although the timing of breeding varies with location. In Pennsylvania, the majority of nests with eggs have been found between late May and mid-June (8), while in British Columbia, the Canada warbler has been recorded breeding from early June through to late July (11). Individuals may return to the same breeding grounds each year (4).
This species nests in forest and shrubby areas, often alongside power lines and roads (11). The well-concealed nest is typically a rather bulky structure built close to the ground, usually among the roots of a fallen tree, in a cavity in the ground, or in moist thickets, moss hummocks, dense ferns, or anywhere with deep litter and dense saplings (4) (8) (11).
The Canada warbler produces a clutch of four or five eggs, with only a single brood per season (3). The eggs are slightly glossy with a buff or creamy-white appearance, and are speckled with dots of varying tints and shades around the larger end (7). The female lays one egg per day during the laying period, with incubation beginning after the final egg is laid and lasting for 10 to 12 days (4) (6). Once hatched, the young chicks will leave the nest after seven to ten days (4) (6), and may live for up to eight years (3).The nests of the Canada warbler are frequently subject to
by the brown-headed cowbird (Molothrus ater) (7). [brood parasitism]
The Canada warbler feeds on a variety of insects and spiders, which are plucked from foliage or from the ground. It will often wait for insects such as a crane fly to fly past, before pursuing it in flight (3) (4). This species has been observed feeding from the branches of trees, up to four metres above the ground (11).