Page:Condor12(2).djvu/4

 54 THE CONDOR VOL. XII over, that is, entered by a hole at the side, either on the ground, on a horizontal branch, in an upright fork, or pendant fom some support. The first group is the simplest in form, the last most highly specialized. For the sake of illustration we may compare the nests of the birds breeding in one of our more northerly states--Iowa will do as well as any, as presenting about an average set of conditions--with those of British Honduras birds, so far as the latter are known, making the comparison in accordance with the above classifica- tion. Placing it in tabular form, and letting the numbers express the per cent of the total number of species whose nests fall within each group, we have the following: -' . Nests open Nests open Nests in Nests with LOCATION above supported cavities above, pendant side entrance from below Iowa ........................ [ 69 20 6 5 British Honduras .... 54 28 7 11 These per cents, it is true, are not exact, as the nesting habits of a consider- able number of British Honduras birds are totally unknown. It is doubtful, how- ever, if a knowledge of the life history of all would materially affect the proportions given. If now we leave out of account the nests of Raptoffal, Gallinaceous and Anser- inc birds, the Herons and a few other large forms whose size, warlike disposition or nidifugous habit place them largely out of danger of such enemies as smaller and weaker species must provide against, we obtain still more suggestive results: Nests opell Nests ill Nests open Nests with LOCATION above supported cavities above, pendant side entrance from below Iowa ................... 65 21 8 ] 6 British Honduras .............. 43 32 10 15 It is evident that nests of the first type, tho the most numerous, are more ex- posed to danger froin enemies than any of the others; therefore, the much smaller proportion of nests of this form in the tropics than iu temperate regions doubtless indicate that the abundance of these enemies has brought about numerous instances of modification of what is plainly the most primitive type of nest. Protective adaptations in nests of the first class are numerous among British Honduras birds, as they are also among ours, and in many cases there is strong similarity; this class, therefore, calls for little comment. The following may be noted: the nests of many flycatchers and hummingbirds are covered with lichens in imitation of the branches on which they rest; those of certain tanagers are made to resemble masses of green moss; the curious Manikiu Scololho. rus veraepacis builds a nest that closely resembles a small mass of half-decayed leaves lodged in a tussock of sedge; the large Rail, Aramides albivenlris, builds a loose nest of shreds of palmetto leaves and coarse sedges, and places it on a low branch over a stream, so that it can hardly be distinguisht from a quantity of such material left there by a freshet; and many more examples might be given. Several birds that build nests of the ordinary type frequently choose a situation that is inaccessible to reptiles and small mammals. For example, the two tanagers, Phoenicolhraupis salvini and Eucomelis spodocephala, and the grosbeak, Cyanocompsa concrela, favor certain small palms which are densely clothed with long, slender, needle-like spines. Nothing need be said in regard to nests placed in cavities, either natural or