Nov., 1920 THE WING CLAW IN SWIFTS 199 
series of nine C. esculenta. The wing claw was much reduced in seven C. 
troglodytes and in one specimen was absent on one wing. In Collocalia mar- 
ginata no trace of a wing claw was found in an examination of both wings of 
nine individuals, and wing claws were absent also in the type of (. dodge (the 
only specimen of this species seen). Wing claws were present in the type spe- 
eimen of C. bartschi. In the other species of Collocalia available (C. innominata, 
ocista, fuciphaga, vestita, origenis, lowi, inopina, thespesia, and francica) wing 
claws were present on both wings, though occasionally they were small and 
often were curled and twisted. In one individual of CU. f. amelis the wing claw 
on the right wing grew from the base of the pollex instead of the tip. The 
wing claw may possibly develop rather late in the growth of the young bird, 
as I found it absent entirely in three nestlings of Collocala |. isonota, but pres- 
ent in both wings in a fully fledged young of Collocalia origems. It is inter- 
esting to note that in the Tree Swifts (Hemiproenidae), a family considered to 
be closely allied to the true swifts (Micropodidae), no wing claw is present. 
The species examined include Hemiprocne longipenms, mystacea, comata, wal- 
lacer and perlonga. 
While it has proved that the wing claw in the Micropodidae is not a char- 
acter of taxonomic value it has been interesting to note its persistence in gen- 
eral and its absence in certain cases. The section of edible nest swiftlets, cover- 
ing the small blue-black species with more or less white in the plumage, seems 
to be on the way to discarding the wing claw, though here the loss is not as 
yet universal and may vary in one species or even in one individual. From the 
present evidence I am inclined to consider the wing claw in swifts as an archaic 
trait that is no longer of value and is on the way to being lost. There is no 
evidence at hand to show that the claw is used by these birds in attaching or 
climbing on the rough surfaces on which they rest. No wear is evident on the 
wing claw itself, nor is there abrasion on the feathers concealing it. 
From a limited amount of material (all in dried skins) it seems that the 
wing claw does not appear until the young bird is well feathered, so that it is 
not of use in. a juvenile stage. This, however, should be carefully verified in 
fresh material for, if this claw be considered an archaic character, it is strange 
if it does not appear very early in the life of the individual. 
Biological Survey, Washington, D. C., May 26, 1920. 
