Putative function of green lining in black sparrowhawk nests: mite-repellent role?

WE INVESTIGATED WHETHER THE FRESH green plant material with which black sparrowhawks (Accipiter melanoleucus) line their nests functions to repel insect pests and ectoparasites. When insect pest levels were elevated by means of securing an attractant (decaying meat) to the nest periphery, significantly more, and only highly volatile, Eucalyptus leaves were brought to the nest by the adult birds. At another black sparrowhawk nest, an outbreak of the haematophagous mite, Ornithonyssus bursa, was recorded one month after the birds had stopped lining the nest selectively with leaves containing high concentrations of phenolic lipids. This outbreak happened when the young had already fledged and were probably less susceptible to infestation than nestlings. The selective use of nest-lining material may serve to prevent chemically the transfer of mites from adules to the nest, and thus reduce infestation of nestlings. We discuss hypotheses and suggest future study directions for understanding the relationship between mites, their hosts, and the selective use of volatile plant chemicals. [ABSTRACT FROM AUTHOR]