_Stelgidopteryx_, BAIRD, Birds N. Am. 1858, 312. (Type, _Hirundo
serripennis_, AUD.)
[Line drawing: _Cotyle serripennis._
32269]
GEN. CHAR. Bill rather small; nostrils oval, superior, margined
behind, but scarcely laterally by membrane, but not at all overhung;
the axes of the outline converging. Frontal feathers soft, and, like
chin, without bristles. Tarsi equal to middle toe without claw; the
upper end covered with feathers all round, none at lower end. Basal
joint of middle toe adherent externally nearly to end; internally,
scarcely half. Lateral toes about equal, their claws not reaching
beyond base of middle claw. Tail slightly emarginate; the feathers
broad, and obliquely rounded at end. Edge of the wing rough to the
touch; the shafts of the fibrillæ of outer web of outer primary
prolonged and bent at right angles into a short stiff hook. Nest (of
_S. serripennis_) in holes in banks; eggs pure white, unspotted.
Color dull brown above.
The great peculiarity of this genus consists in the remarkable
roughness of the edge of the wing, said to occur also in
_Psalidoprocne_, CAB. The object is uncertain, but is probably to
enable the bird to secure a foothold on vertical or inclined rocks,
among or on which it makes its nest. A favorite breeding-place of _S.
serripennis_ is in the piers and abutments of bridges, and these hooks
might render essential aid in entering into their holes.
The birds of this genus have usually been referred to _Cotyle_, which,
however, they resemble only in color. The nostrils are exposed,
instead of being overhung; the tarsus is bare below, not feathered,
and the lateral claws are considerably curved, and not reaching beyond
the base of the lateral, as in _Cotyle_. The structure of the wing is
very different.
There are at least five species or races of this genus in America,
although only one belongs with certainty to the United States. A
second, however, (_S. fulvipennis_), Mexican and Guatemalan, is not
unlikely to occur in Arizona or New Mexico. This differs in having the
chin and throat reddish-fulvous, not mouse-gray; the belly tinged with
yellow.
Stelgidopteryx serripennis, BAIRD.