INTER‐SPECIFIC RELATIONS BETWEEN SOME ANDEAN BIRDS

Summary. Four types of partly nectarivorous and partly insectivorous “honey creepers”, Diglossa lafresnayei lafresnayei, D. carbonaria aterrima, D. cyanea cyanea and Conirostrum cinereum fraseri are more or less common near Quito, Ecuador. They compete with one another to a very considerable extent, since their ranges are broadly overlapping, they occur in many of the same habitats, and they feed on many of the same flowers and types of insects in exactly the same places. The relations between these birds are so distinctive and so obviously specialized that they may be considered to form a special social group or “complex”. Some of the reactions between individuals of different species in this complex are quite different from both their intra‐specific reactions and their reactions to other species (not belonging to the complex). This differential responsiveness is shown in three ways.1 Individuals of different species of this complex never (or almost never) come close together, due to the fact that they deliberately refrain from approaching one another. They also keep apart from other individuals of their own species (except members of the same family group), but they do this by defending territories against such individuals, not merely by refraining from approaching them. They do not refrain from approaching individuals of any other species. 2 Individuals of different species of this complex never (or almost never) become openly aggressive toward one another; but they do show such hostility toward most other individuals of their own species and (usually to a lesser extent) individuals of all other species. 3 Individuals of different species of this complex usually refrain from singing simultaneously. They do not show the same degree of restraint when other individuals of their own species are singing, and they usually ignore the songs of other species.All the distinctive features of the behaviour of the different species of this complex toward one another seem to be adaptations (or the results of adaptations) to permit them to live in the same areas and habitats, during the same general periods of time, and still remain segregated from one another at any given moment. There is reason to believe that this type of segregation may be more advantageous than inter‐specific fighting. It seems likely that the members of this complex have been in contact with one another for a long time. Some of the morphological and behaviourial characters of lafresnayei, cyanea , and fraseri seem to be adaptations to the presence of aterrima. Theoretical considerations would suggest that there will be strong selection pressure against both further divergence and convergence of these forms as long as it continues to be advantageous for them to maintain the same interspecific relations with one another.