126 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8^ 



immune to the poison of the venomous serpents and kill them when- 

 ever they run across them. Among mammals, skunks, raccoons, and 

 l)ears dig up and devour the eggs of turtles ; skunks, foxes, and wild- 

 cats eat snakes and lizards ; the hadger is known to feed upon tortoises 

 and snakes, the coyotes on horned-toads and garter snakes, the opos- 

 sum on horned-toads, and ground squirrels and grasshopper mice upon 

 lizards. 



Discussion.— The reptiles are not a A'ery numerous group in our 

 fauna and it would appear that they have natural enemies in due 

 proportion. While some of the turtles are monarchs of the waters 

 they inhabit when adult, yet their young must run the gauntlet of 

 numerous enemies which cut the number down so that there are no 

 indications whatever of an increase in the number of these species. 

 So it is apparently with all the forms that when adult seem too large 

 to have many enemies to fear ; they are small and relatively helpless 

 in the earlier stages of their life, and it is then that predators do 

 great execution. In the class of reptiles, fratricide in almost every 

 direction seems to be one of the most important elements of natural 

 control. That such control is effectively exercised, the relatively 

 stationary character of the reptile population sufficiently attests. 



AvES (Birds) 



Protective adaptations. — Much has been written about ])rotective 

 coloration in the bird world, including the nests, the eggs, the sitting 

 bird upon the nest, and later the nestlings, the fledglings with their 

 special plumages, and extending to the adults of hundreds of species, 

 some of which (Anatidae) have a special protective dress, the eclipse 

 plumage, during the season when the flight feathers are moulted. The 

 ringed plovers of numerous species are said to have ruptive color 

 patterns tending to break up the outline of the birds and render them 

 inconspicuous. (The phylogenetic significance of this group character 

 apparently is ignored.) 



Crests of birds in some cases are said to be used to frighten their 

 enemies, as are various sudden displays of contrastingly colored 

 feathers elsewhere. Boldly marked birds of colors held to be warning 

 in other classes of animals are numerous and the unusual often in- 

 tense and striking coloration of the lining of the mouth of certain 

 nestlings is held to be warning in effect. It has even been claimed that 

 the color of some bird eggs advertises their low digestibility and that 

 they are therefore avoided by all but ravenously hungry predators. 



Bird enemies. — Birds, not content with preying upon animals of 

 every class from protozoans to niamnials, also draw^ upon their own 



