Notes On the Behavior of Some North American Gulls. I. Aerial Hostile Behavior

Abstract

The Ring-billed Gull, the Herring Gull, Franklin's Gull, and Bonaparte's Gull have many hostile aerial behavior patterns, produced by simultaneous activation of the attack and escape drives. Among these patterns are superficially, and probably deceptively, pure attack and escape reactions, and a whole host of more obviously ambivalent reactions, including ritualized patterns or displays. The four species seem to have similar repertories of aerial hostility; i.e. most of their aerial hostile patterns appear to be homologous. Many (at least) of the same patterns are found in the european Black-headed Gull and the Little Gull. It is probable, therefore, that the range of aerial hostile behavior is essentially similar in all gulls. This does not mean, however, that there are no minor differences between the repertories of different species. Some species have peculiar patterns all their own; and even the strictly homologous patterns of different species may differ in details of physical form, orientation, frequency, strength of motivation, degree of ritualization, etc. The Ring-billed Gull, for instance, can be distinguished by the relative rarity and simplicity of its aerial reactions. Its only aerial hostile displays are a few calls. The aerial hostility of the Herring Gull is particularly reminiscent of the Ring-bill; and most of its aerial patterns are almost equally rare. The Herring Gull does, however, have several distinctive. display postures. The hooded gulls, as a group, can be distinguished from both the Ring-bill and the Herring Gull by the fact that their aerial reactions are performed much more frequently. They all have numerous aerial hostile displays (including many ritualized movements and postures as well as calls), most of which are apparently threat. Some of these displays are of considerable comparative interest. Some of the aerial hostile displays of Franklin's Gull are peculiar in physical form, and many of them are frequently re-orientated or redirected in a most peculiar fashion; but several of them also show particular, and probably significant, resemblances to certain patterns of such diverse species as the Ring-bill, the Laughing Gull, the Black-headed Gull, and the Little Gull. Some of the aerial hostile displays of Bonaparte's Gull appear to be equally distinctive in physical form, if more conventional in orientation ; but the whole aerial hostility of this species is more like that of the Black-headed Gull and less like that of the other gulls.