On a Flock of Tubinares. 317 



outside competition, with Alcidas, shore-birds, land-birds, etc. 

 It is difficult to believe that a Gull of the size of an 

 Albatross would find a place inland, or shore-wise, available 

 food being preempted by vultures, mammals, etc., and there 

 being few available safe nesting-places for birds even as 

 large and clumsy as a Pelican. The only chance such a 

 form would have to pick up a living, would be over wide 

 stretches of sea. As one would expect, the Tubinares, not 

 the Longipennes, have filled this sea gap, the sea being 

 their especial field. 



At the other end of the line, inland Terns, if of much 

 smaller size, would meet an increasingly strong competition 

 for food with the host of smaller land-birds. For instance, 

 a minute species with habits similar to those of the Black 

 Tern, would come in direct competition with Swallows and 

 other insectivores. Small pelagic species would have 

 difficulty in finding proper nesting sites, partly from the 

 abundance of the Alcidse in the north. It is interesting that 

 the small, abundant Wilson^s Petrel, nesting in the southern 

 hemisphere in summer, crosses to the nortiiern hemisphere 

 and helps fill the hiatus left over the north Atlantic by Gulls, 

 Phalaropes and Alcidse when these are necessarily ashore, 

 breedinor in the northern summer. 



The presupposed case would be a comparative unity in 

 the size of the Longipennes, wdiich the facts seem to show^ 



In conclusion, great variation in size and predominance 

 of certain periodic sizes is a definite character of the order 

 Tid)inares, which may be explained by intra-ordinal com- 

 petition. 



XVI. — A Flock of Fubinares. By Robert Cushman 

 MuKPHY, Ph.B., Brooklyn Museum, New York City. 



(Text-figure 5.) 



The accompanying photograph of a flock of Tubinares was 

 taken by the writer on the I'th ofc' November, 1912, in latitude 

 32° 28' S., longitude 45° 42 W., in thQ south Atlantic 



