Cave Swallows

(Petrochelidon fulva)

Chatham, Massachusetts: 25 November, 2010

Blair Nikula

The following images are of some of 40+ Cave Swallows seen in Chatham, MA, on 25 November 2010.  These birds were part of the largest incursion of this species yet recorded in Massachusetts. All images were taken with a Canon 7D and Canon 100-400 IS lens.

In this image 10 Cave Swallows (8 on the gutter, 2 on the singles) are roosting on a house just north of Chatham Light.

The above image cropped to provide a closer look at 7 of the birds.

Here is a mass of swallows roosting on a sheltered portion of a roof on the southeast corner of Morris Island.  How many birds are there?!

The above image cropped, but it's still virtually impossible to determine how many birds there are.  I think there are at least 20, and possible as many as 25.  Believe it or not, all of these birds were alive - they all scattered on a couple of occasions, once when a Cooper's Hawk made a pass at them (unsuccessfully, I think)!


Two birds roosting on the side of a house a couple hundred yards north of Chatham Light.

All of the birds - at least all I have photos of - were in the midst of flight feather molt.  Note on the left hand bird the outermost three primaries and innermost secondaries are faded and brownish in contrast to the dark, fresh 6 inner primaries and outer 4 secondaries.  According to Pyle's "Identification Guide to North American Birds, Part I" (1997), adults complete their prebasic molt by the end of September. Thus, any bird still in molt in late November should be a hatch-year bird. (Unlike most birds, most juvenile swallows apparently undergo a complete prebasic molt.)

The following images of individual birds in flight at Chatham Light and Morris Island.  Note that all of them have from 1-4 old outer primaries and, where the tail can be seen well, 1-5 old outer tail feathers.

On this bird the outermost 2 primaries are old.

Outermost 4 primaries are old; outermost 5 rectrices are old.

Outermost 2 primaries and outermost 3 rectrices are old (and some anomalous wear on the inner primaries of the left - but not right - wing?)

Outer 2 primaries and outer 2(?) rectrices old.

Outer 4 primaries old

Outer 4 (or 3?) primaries old

Postscript: Unfortunately, in the two days after these photos were taken, more than two dozen dead Cave Swallows were found in Chatham. Some were freshly dead, while others had been dead for a few(?) days. So, what was initially an exciting event quickly took a morbid turn. The silver lining to this sad event is that the specimens may provide useful information on the ages, sexes, and origins of these birds.