Black-headed Grosbeak

In many areas of western North America, the melodious song of the Black-headed Grosbeak is a familiar harbinger of spring. This species breeds from subalpine forests to desert riparian zones throughout western North America from southwestern Canada to southern Mexico. It winters in Mexico.

Adult Male (spring/summer)

Black head; large pale conical bill; rusty  orange collar, breast, sides and rump; yellow  belly and wing linings. Bold white wing bars  on black wing. In flight, shows white patches  on wings and yellow underwing coverts and  axillaries.

Adult Female (spring/summer)

Brown head with buffy to white crown and supercilium; buffy to white malar stripe and pale chin; dull orange underparts with faint streaks on flanks; dull brown faintly patterned back and wingbars. Lemon yellow of axillaries and underwing coverts are visible in flight.

Juvenile

Generally resemble adult females, but males are brighter on average than females and have faint streaking on flanks.

General:

Stocky grosbeak with a large head and very large bill. Length: 20-21cm. Wing: 31-32cm. Weight 45grams.

Behaviour:

Flight is slightly undulating with rapid wing beats except for flight displays given in spring. Song is delivered from a high perch and occasionally in flight. Forages in the foliage of trees, eating pine and other seeds, wild berries, insects and spiders. Comes to bird feeders for sunflower seed, other types of seed, and fruit.

Habitat:

Common in open woodlands, forest edges, woods along rivers, edges of second-growth mixed forests, mountain forest edges: orchards and gardens. Relatively tolerant of human disturbance, it breeds in yards and gardens if adequate cover for nesting and feeding is available.

Information:

The Black-headed Grosbeak hybridizes with its eastern counterpart, the Rose-breasted Grosbeak, along their mutual boundary. This situation arose when the treeless prairies, which once formed a barrier between the two species, became dotted with towns and homesteads, providing suitable habitats for both species. The Black-headed Grosbeak is a rather still and secretive bird throughout the summer. The nest is made of twigs, rootlets, flower heads, and stems lined with fine vegetation and are placed in the fork of a tree or shrub 4-25ft above the ground. 2-5 blue-white or green-white with brown spotted eggs is laid.

Similar species: Rose-breasted Grosbeak.

Conservation Status:

Listed as Least Concern the population is large and relatively stable. On breeding grounds Black-headed Grosbeaks benefit from some human activity. Irrigation of arid regions, planting of orchards, creation of openings in dense forest improve habitat for grosbeaks. However, much habitat has been lost to urbanization. It is difficult to assess the net affect of human activities on population.

Capture Rates

Black-headed Grosbeaks utilize diverse habitats and are plentiful during the breeding season at Colony Farms. Males arrive shortly before females in late spring and numbers increase, peaking in August corresponding to juvenile dispersal as is reflected by the capture rates from May – September. Grosbeaks are medium distance migrants, moving southward to central Mexico for the winter as seen by our zero capture rate between October – April.

Molt Summary:

PF: HY partial, PB: AHY complete (A presupplemental molt may occur in HY)
PA: HY/SY partial/incomplete, ASY absent-limited. A presupplemental molt may occur in HYs, with the body plumage being replaced once on stopover and/or the winter grounds in Aug-Sep and again (during the preformative) on the winter grounds in Oct-Nov.
The PS includes no to some med covs and 0 – 2 inner gr covs, but no terts or rects
Molt of HY/SYs on the winter grounds (PF and PA combined) includes no to some med covs, usually all gr covs, occasionally 1 – 3 terts, and 0 – 12 rects. The replacement of the gr covs possibly is protracted, form Sep – Apr. Replacement of the terts and rects appears to occur in Jan – Apr, along with the body plumage again (?), as part of the 1st PA
Adult PB – 1 – 4 ss (among s3 – s6) occasionally can be retained until the winter grounds and rarely until the next PB.

This HY female in August is showing an obvious molt limit between replaced lesser coverts and retained median coverts (red arrow). Notice also the narrow, tapered and relatively worn outer primary coverts.

HY females show very limited white at the base of the primaries extending to only a few millimeters beyond the tip of the longest primary covert. Notice also the very feint and limited white tips to the secondaries and compare to the adult birds below.

Members of the Cardinalis family like Grosbeaks and Buntings where males have such contrasting and distinctive plumages are very helpful for learning molt patterns and especially helpful in looking for molt limits in females of the same species.

This SY male in June is showing glossy black replaced coverts, inner tertials (S8/S9) and all 3 alula feathers. Notice also the lightly pigmented and brownish retained primaries, primary coverts, carpal covert and secondaries and the limited extent of the white patch at the base of the primaries again extending to only a few millimeters beyond the tip of the longest primary covert and limited extent of the white tips to the secondaries and compare with the adult birds below.

This SY male in May is showing a similar pattern of replaced coverts, carpal covert, all 3 tertials and all 3 alula feathers and unusually two inner primary coverts. Notice again the lightly pigmented and brownish retained primaries, primary coverts, and secondaries and the limited extent of the white patch at the base of the primaries and the limited extent of white tips to the secondaries.

This worn SY male in May has replaced most lesser coverts, all median and greater coverts, the carpal covert, all 3 alula feathers and the two innermost tertials (S8 & S9). Notice the sprinkling of retained brownish lesser coverts on this bird and again the limited extent of white at the base of the primaries and to the tips of the secondaries.

This SY male tail in May is showing very obvious replaced inner rectrices (R1). Notice the glossy black rachises of the replaced feathers versus brownish on the retained feathers and the tapered shape of the outer rectrices with no white and compare with the adult male tails below.

Feather wear is also a useful additional ageing criteria, juvenal feathers are poorly structured and wear more quickly than those of adults. The photo below shows an extreme example of an SY female in June showing extensive wear to all rectrices and extreme wear to the central rectrices which cover the outer feathers when the tail is folded.

Feather exposure to sun and abrasion is the major cause of feather deterioration and is especially hard on juvenal feathers. Exposure wears down feathers both through structural weakening and break-down as a result of solar irradiation, and through physical abrasion against foliage and the ground. Because juvenal feathers are of poor quality, they tend to wear down and fade more rapidly than subsequently grown feathers.

The wing of this ASY male in June 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 flight feathers  with an extensive white patch at the base of the primaries. Notice the very truncate inner primaries and outer secondaries, the glossy black rachises of the remiges (primaries and secondaries) and how little wear there is to the tips of these feathers. Notice also the extensive white tips to the secondaries and compare with the first year (HY/SY) birds above.

Three similar examples follow of ASY males in May with no discernible molt limits among the coverts or alula. Notice again the uniformly adult wing coverts and flight feathers and very extensive white patch at the base of the primaries extending more than halfway down the vane of the innermost primaries and extensive white tips to the secondaries.

Notice again the very truncate inner primaries and outer secondaries, the glossy black rachises of the remiges (primaries and secondaries) and fresh, glossy black primary coverts .

The tail of this ASY male in June is a good example of what definitive adult retrices look like in spring. Notice the broad, truncate shape of the outer rectrices with a noticeable corner to the inner web and extensive white patch with overall very little wear to the feathers.

The tail of this ASY male in June, although displaying some wear is also showing truncate outer rectrices with a corner to the inner web and the extensive white extends right on to the tips of the inner rectrices (R3 and R2).