Nashville Warbler

Leiothypis ruficapilla

Introduction

This small spritely warbler of second growth forests is relatively unspectacular in appearance. It breeds in north central North America and isolated portion of the mountainous Pacific Northwest. It winters in Mexico and Central America.

Identification

Adult Male (spring/summer)

Head is blue-gray with white eye-ring. Deep chestnut patch on crown is often difficult to see. The nape and mantle are gray. Back, wings and tail are olive green. Throat and breast are pale yellow. Undertail coverts are bright yellow.

Adult Female (spring/summer)

Head is dull gray and under parts duller than adult male. Chestnut patch on the crown is smaller.

Juvenile

Similar but with brownish wash to back and whitish throat patch.

General Information

General:

Small short-tailed warbler with a sharply pointed bill.
Length: 12cm. Length: 11.5cm. Wing: 19cm. Weight: 8.7grams.

Behaviour:

A rather active warbler, often feeding at the tips of twigs or weed stalks. The western birds often bob their tails. Spring migrants often feed high up in budding trees, but fall birds are often lower, frequently feeding on low weed stems.
Feeds primarily on insects but will take berries and nectar in nonbreeding season.

Habitat:

Found in brushy areas and low woods, often in deciduous trees, open second-growth woods, thickets and woodland edges.

Information:

It was discovered in 1808 near Nashville, Tennessee by Alexander Wilson, who saw it in migration there and named it for the city. The deep chestnut cap is partly concealed by other feathers but can be exposed when the bird raises its crest, such as when it is alarmed or displaying to another bird. A flight song is sometimes given, with slow, fluttering wing beats. The nest is cuplike of conifer needles, mosses, fur, and hair, placed on the ground often at base of shrubs. Four to five eggs are laid, white speckled with brown.

Similar species:

Connecticut Warbler.

Conservation Status:

Populations appear to be stable. Listen as Least Concern.

Maps & Statistics

Capture Rates:

As suggested by the capture rate of a few individuals during migration in April, May and September, the Nashville Warbler is a vagrant to Colony Farm. It is typically found in dry conditions at moderate to high altitude in the southern interior of British Columbia and winters in southern Mexico.

Ageing and Sexing (Band Size: 0A, 0)

Molt Summary:

PF: HY partial (June – Sept); PB: AHY complete (June – Sept). Molts occur on the summer grounds.
Preformative usually includes all med and gr covs. Some retain 1-3 juv outer gr covs. Occasionally (10%) 1-2 terts, and (~15%) 1-2 central rects (r1). 20-50% replace the greater alula.
PA: Limited-partial (Jan – May) and limited to the head and may be more extensive in HY/SYs than in AHY/ASYs.

Juvenile

MAY - August

Juveniles have grayish body plumage and relatively distinct buffy yellow wing bars; Juv M=F.

HY/SY

AUGUST - JUly

Ageing wood warblers in late summer/early fall requires close scrutiny as molt limits can be difficult to see when hatch year (HY) birds still have very fresh retained juvenal feathers.

The wings of these two HY females in September are good examples of this. Under magnification the contrast between replaced lesser, median, greater coverts and carpal covert and retained primary coverts and main alula feathers (A2/A3) can be seen the molt limits indicated with red arrows between the outer greater covert and inner primary covert and alula covert (A1) and main lower alula feather (A2). Molt limits like this can be quite subtle with birds in the hand and for this reason, especially after adults of these same species begin to show signs of approaching the end of their complete prebasic molt age should always be confirmed by additional criteria such as skull ossification.

AHY / ASY

AUGUST - July

Nashville Warblers can be sexed by the amount of concealed rufous crown patch. Adult (AHY/ASY) males like this one show an extensive crown patch measuring up to 16mm with the amount of rufous on individual feathers measuring more than 5mm from the base.

The wing of the above ASY male in April is a good example of what definitive adult plumage, with no discernible molt limits among the coverts or alula, looks like in spring. Notice the uniformly adult wing coverts and broad, truncate outer primary coverts with relatively distinct and broad, yellow-green edging.