Interspecific Interference Competition--Nest Sites for Blue and Great Tits

Abstract

SUMMARY (1) Interspecific competition for nest sites was studied in blue and great tits nesting in boxes in Wytham Woods, Oxfordshire. (2) The breeding density of both blue and great tits was dependent on the density of nest boxes over the range of two to eight boxes per hectare. (3) Changes in blue and great tit densities, from one year to the next, were negatively correlated at low densities of nest boxes and positively correlated at high nest-box densities. The relative density of blue tits increased as the density of available nest sites increased. The spatial variance of blue tit mean density was dependent on great tit density over the same range of nest-box densities. The spatial variance of the great tit population was independent of blue tit density. (4) Blue and great tits do not maintain interspecific territories or space out their nest sites. They do compete for the same favoured nest sites. (5) Great tits are good interference competitors and are relatively more successful than blue tits where nest sites are limiting. Blue tits are good exploitation competitors and are successful where high breeding densities result in competition for food during the breeding season.