Intraspecific and interspecific chemosignals in birds: a review

This review of chemosignals in birds considers intraspecific oriented chemosignals such as pheromones, interspecific chemosignals, and chemical interactions with parasites. Intraspecific chemosignals are known in some seabirds, especially burrow- or crevice-nesting auklets and petrels that breed in large colonies and are often nocturnal on land. Crested Auklets secrete a distinctive scent closely associated with courtship and important in sexual selection. Individually distinctive odours of petrels allow them to identify their own nest and can have a significant role in social relationships. Substances considered as sex pheromones, diesters of 3-hydroxy fatty acids, are produced by female mallards in their uropygial glands during the mating season. In many species of Charadriiformes during nesting monoester waxes are substituted with mixtures of less volatile diester waxes, less easily detected by mammals searching for nests. The tissues, mainly skin and feather of the New Guinean Passerines of the genus Pitohui and Ifrita contain steroidal alkaloids from the batrachotoxin group probably as a chemical defense. The variation of preen gland secretion in some other Passerines is apparently due to selective pressures caused by ectosymbionts. The auklets' odour, considered as a signal of mate quality, has also a function as ectoparasite repellent: aldehyde constituents of this odour kill and repel ectoparasites. Parasitic nematodes influence grouse digestion and thereby scent emission, making parasitized birds more vulnerable to depredation by mammals. Conversely, scents of some mammalian predators can function as a bird repellent.