Northern Rough-winged Swallow

The Northern Rough-winged Swallow is common throughout its breeding range but is generally overlooked or missed due to its low population numbers compared to other swallows. It breeds in southern Canada, the US and parts of northern Mexico. It is a year round resident in parts of the southern US, Mexico and Central America and winters in Mexico, Central America and the southern tip of Florida.

Adult Male (spring/summer)

Head is dull brown. All upperparts are uniform dull brown: no contrasting markings. Drab buffy throat, light gray brown breast and belly. Broad white undertail coverts are often visible from above.

Adult Female (spring/summer)

Similar to adult male.

Juvenile

Similar to adults with buffy throat and bright cinnamon wingbars.

General:

Medium size drab brownish swallow. Length: 12-15cm. Wing: 27-30cm. Weight: 10-18grams.

Behaviour:

The Northern Rough-winged Swallow is an aerial forager adept at low-elevation flight over fields and along narrow gullies and other irregular terrain. It feeds over water more than most species of swallows and occasionally picks floating insects from the water surface.

Habitat:

Prefers open habitats with openings in various vertical surfaces including banks, gorges and human structures.

Information:

Usually solitary, occasionally loosely colonial. Often nest in Bank Swallow colony, where they perch on roots protruding from bank, something Bank Swallows never do. Nests in burrows, cavities probably made by other species but may dig its own. Clutch is 4-8 white eggs.
The Northern Rough-winged Swallow’s most distinguishing characteristic is its “rough” primary feather, from which its common name has been derived. In adults the stiffened barbs of the leading web of the outer primary feather lack terminal barbules. In males the barbs are recurved into minute hooklets, and in the female they are prolonged into a definite, naked point that is little or not at all recurved. In males this produces “a file-like roughness when the finger is drawn along the edge of the quill from base toward tip” (Ridgway 1904). Early taxonomists were so taken with this characteristic that they referred to it in both the genus and species portions of this bird’s scientific name. The Greek appellation for the genus, Stelgidopteryx, is a combination of two words meaning “scraper wing,” and the species name of serripennis, assigned by Audubon, is a combination of two Latin words meaning “saw feather.” The possible adaptive significance of this feature remains a mystery.

Similar species:

Bank Swallow, Tree Swallow.

Conservation Status:

Listed as Least Concern.

Capture Rates:

Small numbers of this usually solitary aerial insectivore arrive at Colony Farms in late May. This, as well as being difficult to capture, is reflected by low capture rates of Northern Rough-winged Swallows during June and July.

Molt Summary:

PF: HY/SY complete (Aug-Jan); PB: AHY complete (Jul-Dec); PA absent-limited
Preformative molt begins on the summer grounds (including some flight feathers) and complete, during migration, at a stopover site or on the winter grounds.

Sexing:

There is variation in the barbs on the outer edge of the outer primary (P9) by age and sex.

In HY birds the barbs are lacking or very short; some Juv/HY males can be separated from females by weakly hooked tips to the barbs which are lacking in Juv/HY females.

in AHY females the barbs are weakly hooked and in AHY males the barbs are long and strongly hooked.

The photos below show the barbs on the outer primary P9 of an AHY female (breeding) in July with 2x magnification (top photo) and 5x magnification (bottom photo).

Juveniles have feathers of the upperparts edged cinnamon and the barbs on the outer primary (p9) reduced by sex. Juvenile M=F by plumage although some may be distinguished by the barbs on p9.

HY in August showing the cinnamon edged coverts and tertials diagnostic of juvenile birds.