Characteristics and Competition for Nest Cavities in Burrowing Procellariiformes

Abstract

We examined the dimensions, nearest-neighbor distance, density, vegetation cover, shelter, and substrate of nest cavities in a multispecific colony of Procellariiformes: Cory's Shearwater (Calonectris diomedea), Little Shearwater (Puffinus assimilis), Bulwer's Petrel (Bulweria bulwerii), and Band-rumped Storm-Petrel (Oceanodroma castro). We investigated differences in nest cavity dimensions between species, the influence of nest cavity characteristics on hatching success of Cory's Shearwater and Band-rumped Storm-Petrel, and intra- and interspecific competition for nest cavities by using natural and artificial nests. Dimensions of nest cavities were highly correlated with species' body size. Physical features of the nests of Cory's Shearwater differed from those of small petrels. Physical features of the nests of small petrels overlapped extensively. Physical features helped to explain hatching success of Cory's Shearwater, and crowding influences contributed to hatching success of Band-rumped Storm-Petrel. Sheltered nest cavities had higher hatching success, but nest cavity characteristics interacted with the quality of breeders. Breadth and volume of eggs laid by Cory's Shearwater in artificial nests were significantly smaller than those in nearby natural nests, indicating that young breeders likely occupied artificial nests. Cory's Shearwater laid in half of the artificial nest cavities built for them, and excavated natural and artificial nest cavities of small petrels. We suggest that the breeding population of Cory's Shearwater includes high numbers of new breeders and is regulated by the availability of nest cavities. Results indicated that interference competition within and between Cory's Shearwater and small petrels is important in the structure of this procellariiform breeding community.