112 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



relative abundance would seem to warrant, for the reason that, as a 

 group, they are relatively inaccessible to birds, many of the deeper- 

 water forms being entirely so. 



Pisces (Fishes) 



Protective adaptations. — It has been held that the great group of 

 spiny-rayed fishes is protected from enemies to a greater degree than 

 the soft-finned families, and in general harsh scales and spines are 

 deemed protective. Some fishes have poison glands connected with 

 certain specialized spines. Some of the species with disagreeable 

 qualities have colors that are said to be warning, while the great 

 majority of fishes exhibit varying degrees of cryptic coloration, many 

 of them having more or less ability to change in color in response to 

 that of their environment. Such in brief are some of the more or 

 less theoretical defenses of fishes ; as to actual physical protection, it 

 may be said that fishes are shielded from most birds by their aquatic 

 habits and many of them even from water birds by their living at 

 considerable depths. 



Bird enemies. — It is well known that whole families of the so-called 

 lower orders of birds are specialized to prey upon fishes, for example 

 the loons, terns, cormorants, anhingas, pelicans, mergansers, herons, 

 and kingfishers. There are special fish eaters in other groups, and 

 many birds not at all specialized to prey upon fishes nevertheless con- 

 sume them to some extent more or less habitually. Nearctic birds 

 which subsist almost exclusively upon fishes include : the western 

 grebe, Caspian, royal and Cabot terns, black skimmer, anhinga. double- 

 crested cormorant, brown and white pelicans, man-o'-war bird, and 

 osprey. Others making fishes from 50 to 90 per cent of their diet are : 

 the common loon, Holboell's grebe, black. Mandt's and pigeon guille- 

 mots, common and Brunnich's murre, kittiwake, glaucous-winged, 

 herring, and ring-billed gulls, gannet, violet-green cormorant, Ameri- 

 can and red-breasted mergansers, bald eagle, and belted kingfisher. 



Nearly 5.000 records of fishes being eaten are contained in our 

 tabulations of the food of nearctic birds, and of these nearly half were 

 identified no further than the class. The remaining determinations 

 grouped by families are listed herewith : 



