Ruby-crowned Kinglet

Corthylio calendula

Introduction

This “little king” is a tiny but very energetic bird, and hardly seems to sit still for very long. Its song is very loud and long, a bit surprising given its small size. It breeds across the Boreal forest in coniferous forests at high elevations, from Alaska to Newfoundland, and winters along the western US coast, in the southern US, and in Mexico. It is a year-round resident in southwestern and south-central BC and some western states in the US. .

Identification

Adult Male (spring/summer)

Head is olive-green with pale white eye-ring, bright red crest that is usually hidden and small thing straight black bill. Chin, breast, belly and flanks buffy olive; undertail coverts pale white. Back, scapulars, rump and uppertail coverts olive-green. Darker wings and tail with white and yellow edges. White wing bar, which contrasts with an adjacent blackish bar in wing. Overall a tiny, compact songbird.

Adult Female (spring/summer)

Similar to male but lacks ruby crown or crest.

Juvenile

Similar to adults.

General Information

General:

Large headed, tiny songbird. Length: 9-11cm. Wing: 16-18. Weight: 5-10grams.

Behaviour:

This little bird seems to be constantly on the move; its frequent wing flicking is characteristic. The Ruby-crowned Kinglet is not as social as its cousin, the Golden-crowned Kinglet, and occurs more often on its own than in flocks; in winter however it will sometimes forage loosely with Chickadees and Golden-crowned Kinglets. In general, Ruby-crowned Kinglets feed lower in the canopy than do Golden-crowned Kinglets. When looking for food, it will often hover at the ends of twigs and leaves as it gleans for insects and spiders, and sometimes flying out to catch its prey in the air.

Habitat:

Ruby-crowned Kinglets reside in various habitats at different times of the year: in the summer it is coniferous forests, but during the migration and winter season, they can be found in a much wider variety of habitats, such as deciduous woods or brush edges, parks and suburbs.

Information:

When migrating, the male Ruby-crowned Kinglets arrive on the breeding grounds ahead of females, but after the summer, it is the females that depart first. The nest, made from lichen, leaves, twigs, grasses, hairs and spider webs, is a hanging cup dangling hanging from a thin branch. The eggs are a cream-white with brown speckles; clutch size can be up to 12 eggs, the largest of any North American passerine relative to its size! Pairs of Ruby-crowned Kinglets are usually monogamous, have one brood per breeding season, and form new pairs each year.

Similar species:

Golden-crowned Kinglet, Hutton’s Vireo.

Conservation Status:

Listed as Least Concern. Populations are stable.

Maps & Statistics

Capture Rates:

Although the Ruby-crowned Kinglet can be seen year round in the Lower Mainland, large numbers of this species move from their winter grounds to breed farther north. This is reflected in capture rates occurring from February through May that spike in April when the highest volume of kinglets are passing through on their way north. Captures are seen again on the southward movement during fall migration in September and October.

Ageing and Sexing (Band Size: 0A)

Molt Summary:

PF: HY partial; PB: AHY complete; PA absent-limited
Preformative molt includes 0 – 3 inner gr covs, but usually no terts or rects

Molt limits are often very hard to detect.

Many intermediates occur, especially in May-Jul when feathers become worn.
(F) crown without red or orange feathers.

Beware juvenal males lack red feathers

Juvenile

June - August

Juvenile lacks red in the crown and has a brownish cast to the upperparts, buffy-brown wing bars, loosely textured undertail covs, and the roof of the mouth yellowish. Juv M=F.

Sexing Ruby-crowned Kinglets

After the preformative molt sexes can be separated by crown plumage. Females lack red or orange-red crown feathers.

Males have crowns with red or orange-red feathers. The extent of red crown feathers is normally extensive in males. Birds with one or two red feathers may not be reliably sexed and may be HY/SY males or more likely AHY/ASY females.

HY/SY

AUGUST - July

By late spring many intermediates occur which cannot be reliable aged when feathers become worn. Molt limits are then very hard to detect and require close scrutiny to verify.

This SY male in April is a good example showing fairly uniform wing coverts with feint greenish edging but very worn alula. The remiges (primaries and secondaries) look fresh with little wear to the tips but the innermost greater coverts have been replaced (red arrow). Under magnification these feathers have less wear to the tips than the outer greater coverts and black versus brownish rachises.

AHY/ASY

AUGUST - July

This ASY female in April is showing uniformly adult wing coverts with fresh, greenish edging and distinct, white tips.

Notice the broad, truncate outer primary coverts and alula with distinct greenish edging. Notice also the condition of the visible remiges (primaries and secondaries) with very little wear to the tips.

Tail shape is helpful in ageing many species being tapered and more abraded on retained juvenal feathers in first year birds (HY/SY) and broad and truncate with a corner to the inner web and relatively fresh in adults (AHY/ASY). The outer retrices (R4-R6) tend to show the greatest age specific differences.

The very fact that tail feathers are frequently lost and replaced between normal molts is one of the reasons why tail feather shape must be used with great caution by banders, and only with other supporting characters (e.g., molt limits), when determining the ages of birds in hand.

Tail shape is more reliable in kinglets than many other species but should still be used with caution and in conjunction with the overall appearance of the primary coverts.

Adult rectrices are generally broad and truncate but there is variability and not all adult rectrices are as obviously truncate and rounded as this AHY male in October.

This AHY female in May is showing broad rectrices with a noticeable corner to the inner web but these feathers can still appear pointed in adult (AHY/ASY) birds.

This ASY male in April is also showing fairly rounded rectrices with little wear to the tips of the feathers.

This ASY male in April is showing uniformly adult wing coverts with fresh, greenish edging and distinct, white tips.

Notice again the broad, truncate outer primary coverts and alula with distinct greenish edging. Notice also the condition ands truncate shape of the visible remiges (primaries and secondaries) with glossy rachis and very little wear to the tips.

The tail of the above ASY bird is again showing broad, truncate, glossy and fresh rectrices with a small point at the tip of the shaft.