ZOOI.OCilCAL SOCIF.'JT Bri.I.FriN 



CORMORANT. 



The crow or raven is an excellent example 

 of a modern bird with a remarkably general- 

 ized diet, in striking contrast to those birds 

 whose bills show them to be fitted for feed- 

 ing only on some strictly defined food. With 

 his strong, ample beak the crow can dig up 

 recently planted corn, or crack the hard shells 

 of acorns ; he enjoys stealing the eggs and 

 the young birds of thrushes, orioles, spar- 

 rows, warblers, and quail, and I have seen 

 a crow chase, capture, and carry off a half- 

 dozen wild mallard ducklings in one morning! 

 These birds are. in addition, able to capture 

 insects of all kinds, besides picking berries, 

 and ducking their heads under water in quest 

 of the shrimps which live in tide-pools. In 

 short, their bill serves them well in procuring 

 many kinds of food, from earth, water, or 

 tree ; as well as in carrying great quantities 

 of sticks, which they use in the construction 

 of their nests. These birds are so skilful with 

 their beaks that a new trick is learned in a 

 very short time. In captivity a crow, when 

 i: tliinks no one is watching, will often take a 

 morsel of food, thrust it beneath a piece of 

 sod, and cover it up with grass, almost with 

 one motion of the beak. 



Functional or adaptive radiation is beau- 

 tifully illustrated by the beak of a gannet, 

 cormorant, snakebird. and pelican — birds 

 which are closely related to one another struc- 

 turally, also having in common a fish diet, 

 swallowing their prey whole. The gannet's 

 beak is thick and very strong, and along the 

 inner edge is a series of fine serrations point- 

 ing backward. The bird dives, from a great 

 height, into the water and seizes a fish in a 

 grip of steel. The upper mandible of the 

 cormorant is furnished with a large, sharp 

 hook, with which the bird gafifs its prey, pur- 

 suinsr it under water. The snakebird. or 



darter, has a bill like a needle, with which it 

 spears the fish, impaling it through and 

 through ; while the pelican, because of its 

 great pouch least vicious of all in its methods, 

 sinijjly engfulfs the fish, the water in which 

 't is swimming and all. then, straining out the 

 liiiuid, tosses the unfortunate into the air and 

 swallows him head first. The rami of the un- 

 der mandible of this bird are long and pliable 

 and so arranged that they can bend far apart, 

 thus making of the great bag of skin beneath 

 the bill and throat an admirable fish-trap. 



This is one of the many instances where 

 several closely related species, with needs so 

 similar that there is danger of fatal compe- 

 tition, are able to exist in great numbers and 

 to avoid all undue struggle for existence by 

 having each an individual method — a niche 

 into which it fits perfectly in the great scheme 

 of Earth's hungry creatures. The snakebird's 

 prev is in the water of dense swamps and 

 bavous : cormorants and pelicans amicably 

 share inland lakes and tidal waters ; while the 

 haunt of the gannet is the high seas. 



Even more closely related to each other 

 are terns and black skimmers. Except in 

 their bills these birds are almost identical in 

 structure, but the bill makes a vast difference 

 in the ajipearance of a bird, as is very ap- 

 parent when these two species are seen llying 

 about together on their breeding-grounds — • 

 low. sandv islands along our coast. The 



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