30 Allen on an Inadequate "Theory of Birds' Nests." 



than counterbalanced by the readiness with which the nest itself 

 is discovered. 



Not to do Mr. "Wallace or his theory injustice, it may be added 

 that he has instanced a considerable number of large families of 

 birds, found outside of North America, in which the species nest in 

 hollow trees, and in which both sexes do have " surprisingly gay 

 and conspicuous colors." Among these are the Trogons, the Barbcts, 

 the Puff-birds, the Toucans, and the great group of Farrots and 

 Paroquets. But Mr. Wallace has himself given an apparently far 

 better reason for this method of nidification in some of these groups 

 than that involved in his above-given theory, namely, that they have 

 not the necessary " tools " for the construction of an elaborate nest. 

 Most of them are weak-footed and sedentary, while in other cases 

 the form of the bill renders the construction of a nest almost im- 

 possible. Another large group, the species of which nest in holes 

 in trees, are the Woodpeckers. Here an obvious and far more 

 rational explanation is apparent than that afforded by the theory of 

 concealment, for here the scores of dull-plumaged, sombre-colored 

 species nest in holes just as do those that are conspicuously at- 

 tired. In this group the species do not seek cavities already at hand, 

 as is the case in some of the groups just cited, but form them them- 

 selves, and use them not only for purposes of nidification, but often 

 more or less habitually as places of shelter. Nothing seems more 

 natural than that they should avail themselves in this way of the 

 advantages afforded them by their powerful chisel-shaped beaks, 

 which they arc constantly using as an abrading or " digging '' organ 

 in their search for food. The same explanation holds equally good 

 for the plainly colored Tits that nidificate in holes that they them- 

 selves have the power of forming. 



The Auks, Puffins, and some of the Guillemots are among the 

 species I have cited as breeding in burrows. As they arc species 

 (occasionally conspicuous markings about the bill or head excepted) 

 of neutral or obscure tints, — - particularly as respects the exposed 

 dorsal area of the Bitting female, — their resorting to burrows is 

 hardly necessary for concealment, since these species have no 

 " strikingly gay " attire of plumage that would render the sitting 

 bird in any case conspicuous. Such resorts, however, prove to be 

 to them a great source of security, and give them an immense ad- 

 vantage over other species of the same family that breed at the 

 same localities with them, hut in a wholly exposed manner. The 



