Olivaceous woodcreeper

The olivaceous woodcreeper (Sittasomus griseicapillus) is a passerine bird in subfamily Dendrocolaptinae of the ovenbird family Furnariidae. It is found from central Mexico south through every Central American country, on the island of Tobago, and in every mainland South American country except Chile, French Guiana, and Suriname.

Taxonomy and systematics

The olivaceous woodcreeper is the only member of genus Sittasomus. However, taxonomic systems vary in their treatment of the taxon, with some splitting it into two species. The International Ornithological Committee and the Clements taxonomy assign these 15 subspecies to the olivaceous woodcreeper; Clements distributes them among five groups.

"Grayish" group

S. g. jaliscensis Nelson, 1900
S. g. gracileus Bangs & Peters, J.L., 1928
S. g. sylvioides Lafresnaye, 1850
S. g. perijanus Phelps, W.H. & Gilliard, 1940
S. g. tachirensis Phelps, W.H. & Phelps, W.H. Jr., 1956
S. g. griseus Jardine, 1847

"Pacific"

S. g. aequatorialis Ridgway, 1891

"Amazonian" group

S. g. amazonus Lafresnaye, 1850
S. g. axillaris Zimmer, J.T., 1934
S. g. viridis Carriker, 1935
S. g. transitivus Pinto & Camargo, 1948
S. g. griseicapillus (Vieillot, 1818)

"Reiser's"

S. g. reiseri Hellmayr, 1917

"Olivaceous" group

S. g. olivaceus Wied-Neuwied, M., 1831
S. g. sylviellus (Temminck, 1821)

BirdLife International's Handbook of the Birds of the World (HBW) splits the olivaceous woodcreeper into two species. It retains the eight "Amazonian", "Reiser's", and "Olivaceous" subspecies as S. griseicapillus but with the English name "eastern olivaceous woodcreeper". It places the seven "grayish" and "Pacific" subspecies in S. griseus with the English name "western olivaceous woodcreeper".

The North American and South American Classification Committees of the American Ornithological Society treat the olivaceous woodcreeper as one species but note that it probably consists of several species, perhaps as many as five corresponding to the Clements groups.

Description

The olivaceous woodcreeper is one of the smallest members of its subfamily. It has a slim body and a short straight bill, and unlike most other woodcreepers has no streaks or spots. The sexes' plumages are alike but females average smaller than males. Adults are long. Males weigh and females . Length and weight vary geographically. All subspecies have a dark iris, a dark gray to black maxilla, a black to light gray mandible with a darker tip, and gray, bluish gray, or black legs and feet.

The nominate subspecies S. g. griseicapillus is mostly olivaceous, with an olive-brown hindcrown and rufous rump, tail, and flight feathers. Its vent area is grayish and its flanks buff. In flight the wing shows a tawny band. The other members of the "Amazonian" subspecies group are similar but differ from it thus:

The olivaceous woodcreeper inhabits a range of elevations. In northern Central America it occurs from sea level to . In Colombia it occurs below

Breeding

The olivaceous woodcreeper's breeding season varies geographically, from mid-March to June in Middle America and northern South America to between August and October in southern Amazonia. The species nests in cavities, either natural or those previously used by woodpeckers, but it is not known to excavate its own. Few nests have been studied; one in Costa Rica was lined with dead leaves. The clutch size is two or three eggs. Limited data suggest that most incubation and care of nestlings is by the female, though at least one instance of feeding by both parents has been noted. The incubation period and time to fledging are not known.