Sex recognition by odour and variation in the uropygial gland secretion in starlings

Abstract

Summary1. Although a growing body of evidence supports that olfaction based on chemical compounds emitted by birds may play a role in individual recognition, the possible role of chemical cues in sexual selection of birds has been only preliminarily studied. 2. We investigated for the first time whether a passerine bird, the spotless starling Sturnus unicolor, was able to discriminate the sex of conspecifics by using olfactory cues and whether the size and secretion composition of the uropygial gland convey information on sex, age and reproductive status in this species. 3. We performed a blind choice experiment during mating, and we found that starlings were able to discriminate the sex of conspecifics by using chemical cues alone. Both male and female starlings preferred male scents. Furthermore, the analysis of the chemical composition of the uropygial gland secretion by using gas chromatography-mass spectrometry (GC-MS) revealed differences between sexes, ages and reproductive status. 4. In conclusion, our study reveals for first time that a passerine species can discriminate the sex of conspecifics by relying on chemical cues and suggests that the uropygial gland secretion may potentially function as a chemical signal used in mate choice and ⁄ or intrasexual competition in this species.

Evidence that the house finch (Carpodacus mexicanus) uses scent to avoid omnivore mammals

“…Our records indicate that before knocking at the door, all birds were oriented towards the chamber they subsequently entered. The knocking on the door did not affect the preference of birds in previous studies with the same species and apparatus (Amo et al 2012b), or in other tested species (Amo et al 2012a). The device was carefully cleaned with commercial antibacterial, neutral pH soap, and allowed to air dry between trials.…”

“…The validity of first choice as a measure of the interest of birds, including this species, in particular chemical stimuli has been previously demonstrated (e.g. Bonadonna and Nevitt 2004;Bonadonna et al 2006;Amo et al 2012a, b, Krause et al 2014. To minimise the length of the trials, if the test bird did not leave the central chamber after 1 min, we gently knocked on the middle of the entry door of the central chamber to prompt it to move to one of the choice chambers.…”

“…However, recent evidence suggest that, besides assessing predator chemical cues, birds use olfaction in several other contexts, from foraging (e.g. Nevitt 2011, Amo et al 2013a to social interactions including discrimination of species (Zhang et al 2013, Krause et al 2014, sex (Whittaker et al 2011, Amo et al 2012a) and even the relative quality/condition of individuals (Amo et al 2012b). The importance of olfaction has been demonstrated amongst others in different species of Procelariiformes (e.g.…”

Rollers smell the fear of nestlings

“…Northern shovelers Anas acuta and common eiders Somateria mollissima, when alarmed during the incubation period, spray faeces on their eggs that deter mammal predators [15]. Surprisingly, the possible role of substances produced during interspecific chemical defence as intraspecific signals has not been investigated in birds [8], although the ecological relevance of avian olfaction is receiving growing interest [16][17][18][19][20][21].…”

Olfactory discrimination ability of South African fur seals (Arctocephalus pusillus) for enantiomers

“…Water shrews, another semi-aquatic mammal, preferentially use their olfactory system to detect their prey underwater (Catania et al 2008). Similarly, the birds' sense of smell was long thought to be poor on the basis of anatomical findings (Bang & Cobb 1968, Welty 1975, but behavioral studies have demonstrated that several species of birds possess highly sensitive olfactory systems (Benvenuti et al 1977, Caspers & Tobias 2011, Amo et al 2012. Similarly, it has been found that the number of olfactory receptor genes is not a reliable predictor for an animal's olfactory capacity.…”