Cliff and Cave Swallows are Commonplace
Ro Wauer, July 25, 2004, The Victoria Advocate, © 2004
These two look-alike swallows are commonplace throughout almost all of South Texas. That has not always been the case. Although cliff swallows have long utilized concrete overpasses and similar structures during their nesting season, cave swallows have become common only is recent years. Cave swallows, as their name implies, utilize shadowy nesting sites only, such as culverts and the underside of dark kiosks and similar small structures.
Besides their use of different nesting sites, the two species possess rather subtle differences in appearance. Although both are "square-tailed" swallows, at least in comparison with the longer, fork-tailed barn swallow, except for the voice, a positive identification may require careful study. Both possess a whitish belly, dark back and wings, and a buff-colored rump. Cliff swallows possess a dark rufous throat and whitish forehead, while cave swallows have a buff throat and rusty forehead. The voice of the two species often provides the easiest method of identification, especially when these birds are in flight. The call of the cliff swallow is usually described as a low "churr" and nasal "nyew." That of the cave swallow is a clear "weet" or pweet" or a soft, low-pitched "prrt."
Another interesting difference between the two species is their nests. Cliff swallows build the typical gourd-like structure from mud balls that they acquire from nearby puddles. Hundreds can often be found on the edge of concrete overpasses. Cave swallows build open mud nests, much like those of barn swallows, that they paste on rough edges.
Cliff swallows can be found throughout North America except for the southeastern corner of Arkansas, Alabama, Georgia, and Florida. They overwinter in South America. Cave swallows occur north of Mexico only in South Texas, southern New Mexico, and in extreme southern Florida, although nesting has been recorded throughout most of the High Country. They once were found only in natural cave-like sites in limestone area, but they learned that culverts and other man-made structures do just as well. Their principal requirement is a shadowy location. From the mid-1960s until about 1990, Carlsbad Caverns in southern New Mexico was the only place in the United States where cave swallows were known to nest. But by the turn of the century they had begun to expand their breeding grounds eastward in Texas.
One reason why cave swallows have been able to enlarge their range is that they have been able to roost in vacant cliff swallow nests during the wintertime when the original inhabitants are off on their winter vacations. Many populations are able to survive all winter in the original and temporary sites. That gives these new explorers a significant advantage each spring. They are able to nest earlier than they might otherwise if they had to migrate northward, and they therefore are able move northwards into new areas as post-nesting wanderers. It apparently has worked very well.