Evolution of nest-building behavior in Agapornis parrots
Five species in the African lovebird genus Agapornis are the only parrots, other than Monk Parakeets (Myiopsitta monachus), that construct nests. Four species (A. personata, A. fischeri, A. lilianae, and A. nigrigenis) build domed nests within cavities, and a fifth (A. roseicollis) builds a cup-shaped nest within a cavity. The other members of the genus have nesting behavior that is more typical of other parrots: A. cana and A. taranta nest in cavities that are lined with nesting material, and A. pullaria excavates burrows in arboreal ant or termite nests. To reconstruct the evolution of nest-building behavior in Agapornis, I sequenced a 622-bp portion of the cytochrome-b gene (mtDNA) and used the sequence data to build a phylogenetic tree. The phylogeny shows that the divergence between the nest-building species and cana, taranta, and pullaria occurred early in the evolution of the genus. The nest builders form a monophyletic clade, and the small amount of sequence divergence between personata, fischeri, lilianae, and nigrigenis indicates that they probably should be considered subspecies of a single species. A reconstruction of the evolution of nest-building behavior on the phylogeny indicates that the construction of a domed nest is derived from the habit of lining the nest, because the nesting material is used to build progressively more complex nest structures. Within Agapornis, nest building is associated with colonial breeding. The construction of a nest within a cavity may allow breeding pairs to modify and use cavities that otherwise might be unsuitable. This would, in turn, give pairs added flexibility in nest-site choice, thereby facilitating colonial breeding.