Wetmore — A Whippoorvrill from Porto Rico. 237 



known; bones of this species examined from La Cueva Catedral, near 

 Morovis.) 



Remarks. — This species is most nearly allied to the typical subspecies of 

 the eastern whippoonvill but differs from it markedly in the characters 

 given in the diagnosis. It has less in common with the larger Setochalcis 

 v. macromystax of the southwestern United States and northern Mexico or 

 with the whippoorwill from southern Mexico and Guatemala known as 

 Setochalcis v. chiapensis. The latter is large in size thus resembling ma- 

 cromystax but differs from that subspecies in being very dark above. The 

 Cuban Whippoorwill (S. cubanensis), which must be mentioned by virtue 

 of its geographic proximity, differs from S. noctitherus so strikingly in lack 

 of buffy coloration on the hind neck, where there is no trace of a paler collar, 

 much larger size, and enormously developed rictal bristles that it may be 

 dismissed without further comment. 



The longest rictal bristles of the Porto Rican Whippoorwill measure ap- 

 proximately 33 mm. so that they are similar in development to those of 

 Setochalcis v. vociferus. The seventh, eighth and ninth primaries (counting 

 from the inside of the wing) are narrowly sinuate toward the tips, and the 

 front of the tarsus is feathered down to the toes . The posterior surface of the 

 tarsus is entirely bare. The pecten on the middle claw is similar to that 

 in the Whippoorwill of the eastern United States. 



According to Mr. Ridgway 1 fifteen specimens of Setochalcis vociferus voci- 

 ferus gave the following measurements (in millimeters): wing 147-163 

 (155.3); tail 105-123.5 (116); exposed culmen 10-14 (12.5); tarsus 16-18 

 (16.6); middle toe 16-17.5 (16.5). (Females.) 



It will be noticed that the Porto Rican Whippoorwill agrees closely with 

 Setochalcis vociferus vociferus in length of tail, culmen, tarsus and middle 

 toe. It is therefore a bird of somewhat similar size in body to the eastern 

 Whippoorwill but has a much shorter wing. The latter character is a de- 

 velopment usual in species of insular range, where there is no need for ex- 

 tended migrations with changing seasons. An extended alar surface is of 

 value to a bird performing long journeys as with it less effort is required to 

 maintain position in the air in overcoming the pull of gravity. Where this 

 need is obviated there may easily be a reduction in wing surface, as indi- 

 cated by length of wing. In species like the Whippoorwills that secure 

 their prey by making short sallies in the air in pursuit of flying insects this 

 reduction, while noticeable, would of necessity be less than in forms of less 

 active habit. 



The species described herewith is probably nearly extinct, if indeed it is 

 not actually in that category. During ten months' field work in Porto 

 Rico in 1911 and 1912 the writer saw one goatsucker that may possibly have 

 belonged to the present species, but failed to secure it. Though he was in 

 residence in the country districts during the greater part of this period these 

 birds were not heard calling, nor were they mentioned directly by the natives 

 who were cognizant of most of the birds of the island. As Whippoorwills 

 are terrestrial in habit the decrease of the present form may be attributed 

 to the mongoose, scourge of ground haunting vertebrates, a species that 

 was introduced here about 1872. 



l Birds of North and Middle America, U. S. Nat. Mus., Bull. 50, Vol. VI, 1914, p. 517. 



