Cape May Warbler

The Cape May Warbler is a striking, boldly marked warbler whose numbers are tightly linked to outbreaks of spruce budworm in the northern boreal forest. Breeding males show a rich chestnut cheek patch bordered by a dark crown and a bright yellow neck collar, with heavy black streaking (often called 'tiger stripes') across a yellow breast.

A distinctive thin, sharply pointed bill, slightly downcurved, is an adaptation shared with a few other nectar-feeding warblers, allowing this species to sip nectar and fruit juice on its wintering grounds. Females and immatures are much duller, grayish-olive with faint streaking and reduced or absent cheek patch coloring, making them considerably harder to identify than the vividly patterned males.

Key Field Marks

• Breeding male: chestnut cheek patch, dark crown, bright yellow neck collar
• Heavy black 'tiger stripe' streaking across a yellow breast
• Yellowish-green rump patch
• Thin, sharply pointed, slightly downcurved bill
• Female/immature: dull grayish-olive with faint streaking and little or no cheek patch color

Similar Species

Yellow-rumped Warbler also shows a yellow rump but lacks the chestnut cheek patch and has a bolder white wingbar pattern and different face pattern. Magnolia Warbler shows heavy breast streaking too but has a distinctive white-banded tail and gray crown rather than the Cape May's chestnut cheek. The thin, pointed bill is a useful mark separating Cape May from other streaked yellow warblers.

Habitat

Cape May Warblers breed in boreal spruce forest, with breeding density and success closely tied to outbreaks of spruce budworm, a favored food source. In migration and winter, they use a wider variety of wooded and shrubby habitats, including gardens with flowering or fruiting plants.

Range

This species breeds across the boreal forest of Canada and a small portion of the northeastern United States. It winters mainly in the Caribbean, especially the Greater Antilles, with some birds reaching Central America.

Migration

Cape May Warblers are medium- to long-distance Neotropical migrants; breeding population size can fluctuate dramatically from year to year in response to spruce budworm outbreak cycles in the boreal forest.

Behavior

During the breeding season, Cape May Warblers forage high in spruce canopy, often specializing heavily on spruce budworm caterpillars when outbreaks occur. On its wintering grounds, it becomes notably more flexible, sipping nectar and fruit juice.

Voice

The song is a very high-pitched, thin, repeated series of single-note phrases, 'seet-seet-seet-seet,' similar in pitch to several other high-voiced warblers. The call is a thin, high 'seet.'

Feeding

It feeds heavily on spruce budworm caterpillars during outbreak years on the breeding grounds, and uses its thin, curved bill and unique semi-tubular tongue to sip nectar and fruit juice on wintering grounds in the Caribbean, a rare trait among warblers.

Nesting & Breeding

The female builds a well-hidden cup nest high in a spruce tree, usually near the very top, making nests extremely difficult to locate. She lays 4-9 eggs, with clutch size often larger during spruce budworm outbreak years when food is abundant.