Comparative Analysis of Communication Systems in Two Large Taxa of the Order Charadriiformes: Gulls and Terns

摘要

Ritualized feeding of the mate during the formation of breeding pairs is an important part of communicative systems in both gulls and terns In the course of the breeding cycle this behavior is transformed into provisioning of mate during regular relieving of birds at nest Modes of food transportation are quite different in gulls and terns. Gulls carry food in their stomachs to regurgitate it for the partner and later for chicks, while terns transport it in their bills ("direct feeding"). In the latter case, the prey itself, being carried by the bird, is an important optical stimulus determining main features of communication process organization in terns. Differences in the feeding behavior between gulls and terns not only specify distinctions in their entire communication process schemes but also affect some particular features of communication signals, In contrast to gulls, terns are characterized by stereotype ritual aerial interactions. In some key situations, they use rhythmical vocal constructions whose effectiveness and distant signals depend both on the high recurrence rate and high signal frequency. Terns lack some displays characteristic of gulls, which may be derivatives of regurgitation behavior. By analogy with what is revealed in terns, the so-called "appeasing" displays in gulls may be just defensive behavior. Large differences in communication systems of gulls and terns make it possible to treat them as valid families. Terns are similar to generalized waders in their signal behavior and nest building pattern integrated in their communication system. This may indicate a possible phylogenetic relationship between both taxa.