These Northern Rough-winged Swallows
Stelgidopteryx serripennis were found apparently wintering along the Rio Grande below Amistad Reservoir Dam in Val Verde county, Texas on December 28, 2014 and January 03, 2015. On both dates at least a dozen birds were seen, along with a few Cave Swallows.
They seemed slightly unusual to me - but that may better reflect me paying them more attention than I do when they pass through as migrants elsewhere in the state. NOTE: it is quite possible - likely, even - that some of the photos are of the same individual bird; it is hard to determine while trying to photograph birds among a fast-moving group of hirundines.
Keep in mind that most/all of these birds will have recently completed their Prebasic molt and thus all the flight feathers are fresh, which may account for some of the features mentioned below.
Aspects that I found interesting were:
most of the birds in the photos have pale edging to the inner secondaries, forming a narrow pale band on the folded wing, sometimes enhanced by strong pale fringes on the tertials. In one suitable photo the pale outer fringes to the inner secondaries are fairly prominent.
- on all the images that allow assessment, the bases of the retrices are palish, such that on a fully-spread tail there is a banded effect somewhat remeniscent of a muted Wheatear tail pattern.
on two birds (one from each date; it is possible that they are the same bird...) there is a pale ginger tone on the foreface/chin area - but this might be an artifact(?).
- in at least two photos (again it is possible that it is just one individual) there is a fairly distinct pale collar on the side and top of the neck that contrasts with the darker head (somewhat like that of a female/imm. Purple Martin).
NOTE: where more than one photo is known to be of the same individual, the pics are grouped together:
The photos above were all taken on December 28; the ones below were taken on January 03: