Subspecific Appraisal of Red-Breasted Sapsuckers

Abstract

the moment. There is little merit in the idea that impalings serve to attract other animals or that they become more tasty by hanging. That a shrike's inability to eat is caused by a pellet that is ready for ejection, may be, as I have learned from caged birds, a reason for impaling without immediate feeding. Shrikes prefer to pull small bites from impaled prey. The same thorns to which they have become accustomed are used repeatedly, but, in the course of handling a large object, the position of the prey may be changed and different thorns used. Prey is impaled through various parts of the body, but heads of birds and mammals often are removed and impaled separately; commonly they are eaten first. Schreurs found that collurio will impale insects so that they remain alive on the thorn. Ludovicianus may do this, but he claims that senator always kills an insect. Interesting is the attempted defense of impalings by collurio when a human approaches. Little of this is noted in ludovicianus and senator, but in captive Loggerheads it is pronounced. Probably in the wild the shyness of these two species overcomes the urge to defend. Schreurs' statement that the impaling instinct is in operation throughout the year is fully borne out by observations upon permanently resident shrikes both in America and in the Old World. The instinct may be an important element of the breeding cycle, but it must be remembered that it develops independently of this and makes its appearance in young captive birds that have been separated from their parents at an early age. It is vital to the existence of the shrike at all seasons. The significance of similarities in behavior pattern in distinct species of the same genus lies in the strong evidence they afford for common descent and for adaptation to similar modes of life. The characteristics of shrike behavior are as constant and as obvious as many structural features that relate the three species of Lanius under consideration. The inherited behavior is no less conservative in evolulution than the structure. The differences between the species consist of relatively small modifications of the behavior pattern. Tolerance of dense floral habitat, degree of aggressiveness, and concealment of impalings are item? typical of specific differentiation; they might all be termed quantitative differences. Probably there is more dissimilarity in voice, in temperament and in details of movements than has thus far been brought out. In final analysis, the more prominent features of behavior ascertained through a study of natural history prove to be generic or even of family significance.