Ivory-billed Woodcreeper Xiphorhynchus flavigaster Scientific name definitions

The Ivory-billed Woodcreeper is a relatively typical member of the genus Xiphorhynchus, being a mid-sized woodcreeper with a longish, pale bill, rufous wings and tail, heavily white-streaked upperparts, and marginally more sparsely pale-streaked underparts, which are otherwise grayish brown. It is a regular member of roving mixed-species foraging flocks. This species ranges widely over both slopes in Middle America, from northern Mexico south to northwest Costa Rica. Throughout this large range, the Ivory-billed Woodcreeper occupies a considerable array of wooded habitats, especially deciduous areas, and reaches almost 3000 m elevation, although the species is more usually found below 1500 m.

20–26·5 cm; male 40–62 g, female 35–56g. Relatively large woodcreeper with long, moderately heavy and slightly decurved bill. Nominate race has face finely streaked buffy and blackish, indistinct buffy supercilium and eyering contrasting with weak dark postocular stripe; crown and nape deep greyish-brown with conspicuous pale buff spot-like streaks; back and scapulars light greyish-brown to olive-brown, broadly and extensively streaked buff, each streak narrowly edged blackish; tawny-brown rump contrasts little with cinnamon-rufous to rufous-chestnut wings and tail; median and greater coverts like back, lessers more rufescent, lesser and median coverts having fine pale shaft streaks, those on medians edged blackish; remiges lighter than tail, outer primaries paler still, less rufescent, with dusky tips; buffy throat finely streaked dusky, separated from submoustachial region by dusky malar stripe; upper breast slightly paler than throat, with blackish-edged feathers producing scaly appearance; rest of underparts light buffy brown with broad dusky-edged buff streaks that weaken towards lower belly; underwing-coverts ochraceous buff; iris light reddish-brown to dark brown; bill pale horn-white, greyish-ivory or pale flesh, base of upper mandible brownish or bluish; legs and feet yellowish-green to olive-grey or brownish. Distinguished from other woodcreepers in range mainly by combination of large size, heavy and relatively straight bill that is largely pale, boldly streaked upperparts, dark malar stripe. Female is slightly smaller than male (1 Puebla-Olivares, F. and Figueroa-Esquivel, E.M. (2009). Sexual dimorphism in Ivory-billed Woodcreepers (Xiphorhynchus flavigaster) in Mexico. Journal of Ornithology. 150(4): 755–760. Close ). Juvenile resembles adult, but slightly darker, throat more boldly streaked, streaks on breast and back duller and with broader black edges, bill brownish. Race mentalis is very like nominate, but smaller, with conspicuously shorter bill; tardus is much smaller, and paler and greyer both above and below; yucatanensis is similar in coloration to mentalis but slightly smaller, throat pale buff and unmarked; eburneirostris is like nominate but has throat markings limited to a few fine streaks at lower edge, overall coloration darker and browner (less greyish), crown and nape sooty black, back deeper brown, streaking above and below richer buff; ultimus is like eburneirostris but larger, with bill longer and heavier, upperparts slightly darker, underparts richer buff, streaks below with blacker edges; saltuarius is also similar to eburneirostris but paler, especially on belly, with streaks above much larger and more prominent, those below less sharply defined; an aberrant individual had throat heavily streaked black, breast streaks with wavy black edges, back streaks broader, wing-covert streaks more broadly edged black and underwing-coverts mottled (“X. striatigularis”); ascensor is darkest of all, upperparts richer and darker brown, wings and tail deep chestnut, crown streaked rather than spotted, streaks both above and below broader and more boldly margined with black, those below extending farther down belly.

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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.

Occupies a variety of wooded habitats from lowlands to middle elevations of foothills. Apparently most common in deciduous woodland, but occurs also in lowland and montane evergreen forests, gallery forest, thorn-scrub, lower reaches of cloudforest, pine-oak (Pinus-Quercus) or pine woodland, and both mangroves and freshwater swamps. Found not only in mature forest, but also in second growth, forest edge and plantations; not nearly so dependent on true forest as are most woodcreepers. Unlike most members of family, probably more common in drier situations than in humid forest. Occurs over a wide elevational range, mainly tropical lowlands and foothills from sea-level to c. 1500 m, but at least occasionally into subtropical zone to 2800 m; possibly more common at lower elevations in N, but in foothills in S.

Apparently resident throughout range; possibly some upslope movement in non-breeding season.

Diet mostly arthropods, but small vertebrates (principally lizards) also taken. Prey taken over army-ants included a large green orthopteran, also a significant number of lizards (20% of all prey observed taken in one study). Stomachs contained a high diversity of prey; in a study in S Mexico primarily snails (taken in significantly greater quantities than by other woodcreepers at site), beetles, spiders, various orthopterans, ants and caterpillars, but also scorpions and pseudoscorpions, bugs (Hemiptera), planthoppers and cicadas (Homoptera), flies, wasps, and a few lizards. Most prey less than 10 mm in length, but spiders, orthopterans and some beetles on average larger, and caterpillars on average c. 35 mm. Usually alone, but sometimes in pairs, and often as attendant of mixed-species flocks. Considered a core follower, with high propensity for flocking; present in 5–25% of flocks studied at one site in E Mexico, and in 16% of flocks at site in W Mexico (where 82% of observations involved birds with flocks); one study demonstrated significant preference for larger flocks over smaller ones. Also regular attendant of army-ant swarms (Eciton burchelli, rarely Labidus praedator); single birds present at nearly 30% of swarms studied at site in S Mexico. Forages while hitching in spiral motion up trunks and, especially, branches, mainly from mid-levels to subcanopy, but regularly to canopy, and occasionally down to fallen logs or ground; sometimes reverses downwards or creeps along undersides of branches, like smaller Lepidocolaptes. Forages mainly by probing bark crevices, bromeliads and other epiphytes, and, at least on occasion, clusters of dead leaves; at times observed to pry off loose bark to expose hidden prey, tapping lightly on dead branches, or dropping to ground to rummage among dead leaves. An ecologically plastic species that has even been seen to forage for insects on coastal mudflats among stumps left after mangroves were cleared. Over ants, alights low on trunks, dropping to ground to take prey.

Song in W Mexico c. 2·5 seconds long, 15–20 piercing whistles in loud cascade that first ascends slightly and increases in volume before descending and slowing, “t-t-t-ttttttttt-t-tewtewtew-tew-tew”; in rest of range a “laughing” whinny 4–7 seconds long, 25–45 clear whistles reaching peak pitch, fastest tempo and greatest volume in first second, then steady for a short period, and eventually fading, slowing and falling, slower than in W Mexico and often likened to song of Canyon Wren (Catherpes mexicanus), but sometimes ending in upward-inflected “whee whee-wheep” or “weet, weet”. Calls include sharp, almost explosive “tchee-oo”, “skweeú” or “squirp”, which in W Mexico can be softer “chehr”; also explosive, descending series of 4–12 notes, “tyew-tyew-tyew” or “s-keé, kee, kee, kee, kee, kee, kur”, similar to calls of X. susurrans; also a dry rattle like that of woodpecker (Picidae).

Specimens in breeding condition in late Mar to mid-Aug in N & C of range (Mexico to Honduras); in Mexico, nests with eggs in late Apr to early Jun in NW & E, nestlings in Jun in S, and fledglings being fed in mid-Jun to late Jul in W & S. Nests described have been low, 1–1·7 m up, in cavity amid snag or in gap between fig (Ficus) roots and tree, lined with fibres, wood chips or bark flakes, in one case c. 7·5 cm across. Clutch 2–3 white eggs, average 29 × 21 mm. Annual moult in Aug–Sept overlaps with later nesting attempts.

Not globally threatened (Least Concern). Fairly common to common over most of range (primarily lowlands in Mexico, Belize, Guatemala and Honduras, but in foothills in NW Costa Rica); uncommon and local at upper end of elevational range, and in lowlands of NW & N Costa Rica; now very rare at N limit of range in W Mexico (S Sonora), where previously not uncommon. Estimated density at site in NE Mexico 17·5 pairs/100 ha; home range at site in S Mexico estimated at 4 ha. A generalist species, frequenting both open and closed environments; far less dependent on true forest than are most woodcreepers, possibly an adaptation that allows it to survive at N limit of dendrocolaptid distribution. Consequently, appears only moderately sensitive to human disturbance, provided that patches of forest remain; numbers captured during study on Yucatán Peninsula increased after area was hit by a hurricane (at least where not subsequently burned).