Black-capped Gnatcatcher Polioptila nigriceps Scientific name definitions

The Black-capped Gnatcatcher is almost endemic to northwest Mexico, but just creeps into extreme southeast Arizona in the United States. It prefers dry woodlands and thorn scrub habitats, and is usually fairly common in such areas. The sexes differ in that females lack the very extensive and glossy black cap of the males, which reaches well below the eyes and contrasts with the pale eye-ring. Females also have a pale eye-ring. Although generally considered to be resident, it is possible that at least some individuals of the species’ northernmost populations move south in the post-breeding season.

10–12 cm; 5–8 g. Longish bill narrowing to fine, slightly hooked tip. Breeding male  has glossy black cap and lores extending below eye and just reaching nape, contrasting with bluish-grey hindneck and back; white broken eyering mostly restricted to below eye; wings dusky brownish, greater wing-coverts broadly edged grey, remiges narrowly edged paler grey, tertials broadly edged white; tail strongly graduated (outer rectrix 8–12 mm shorter than central rectrices), black, outer two rectrices mostly white, rectrix 4 broadly tipped with white; head side, throat and underparts white; iris brown; upper mandible blackish-grey, lower mandible medium grey with blackish-grey tip; legs blackish-grey, foot pads glaucous. Female  is plain slate-grey with less bluish cast, head slightly darker than back, dusky colour of remiges paler and browner. Juvenile resembles female. Races differ very slightly, primarily in size; <em>restricta</em> is larger than nominate, and has longer tail.

Editor's Note: This article requires further editing work to merge existing content into the appropriate Subspecies sections. Please bear with us while this update takes place.

• Black-tailed x Black-capped Gnatcatcher (hybrid) Polioptila melanura x nigriceps

Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Mesquite (Prosopis) thickets associated with riparian woodland at N end of range; S populations in thorn-scrub and arid deciduous forest. Primary ecoregions occupied include Sonoran-Sinaloan transition subtropical dry forest (race restricta) and Sinaloan and Jalisco dry forests (nominate). Mostly below 500 m.

Resident; possible that populations in far N of range (N of about SC Sonora) move S after breeding.

Little published information; no specific data on food items, assumed to be mostly sessile arthropods. Primarily gleans items from foliage , occasionally making short sallies to capture flushed prey.

Mewing  “meeihr”, “reeihr” or “pseuih”, with rising and descending frequency modulation and evident harmonics; reminiscent of mewing calls given by P. californica, rougher and more drawn out than those of P. caerulea. Also a soft, chattering “chehchehcheh…” when agitated; alarm a rapid “chew-chew” or “cheh-cheh”, almost indistinguishable from comparable call of P. californica. Loudsong apparently a repeated series of 2–3 mewing notes; also a longer, complex, rambling song  consisting of various sharp “chip” notes, high whistles, mewing notes, and trills, these elements sometimes repeated 2–3 times, but no apparent pattern within or among individuals.

Begins in Mar, with last broods fledged by Jul, in Sonora; nests found in Apr in Sinaloa, May in SW Chihuahua and Jun in Jalisco; recently fledged Brown-headed Cowbirds (Molothrus ater) seen to be fed by present species during Jul and Sept in Jalisco. Nest constructed from small twigs and plant down, cemented together with spider webs, lined with down and plant fibres, placed c. 2 m from ground and supported by small branches and twigs in low tree or bush. Clutch 4 eggs, pale blue or greenish-blue with irregular reddish-brown speckling; incubation of eggs and feeding of young by both sexes; no information on incubation and nestling periods. Parasitism by Brown-headed Cowbird observed in Jalisco; parasitized nest more than 3 km from nearest forest opening, three host eggs punctured, cowbird nestling successfully fledged.

Not globally threatened. Fairly common in suitable habitat; sporadic breeder in extreme S USA (extreme SE Arizona  ). Both races restricted to ecoregions considered to be at serious risk due to agriculture and cattle grazing.