Chemical labels differ between two closely related shearwater taxa

Abstract

Chemical signals may be the basis of interspecifi c recognition and speciation in many animals. To test whether a chemical label allowing recognition between closely related species exists in seabirds, we investigated two closely related taxa breeding sympatrically at some localities: Cory ' s and Scopoli ' s shearwaters. Procellariiform seabirds are ideal for this study because they have a well-developed olfactory system and unequalled associated capabilities among birds. We analysed and compared the relative volatile compounds composition of the uropygial gland secretions of Cory ' s and Scopoli ' s shearwaters. As the volatile components from uropygial secretions might also provide some critical eco-chemical information about population origin and sex, we also examined variations in the volatile compounds between populations and sexes in Cory ' s shearwater. Th e chemical data were obtained using gas chromatography -mass spectrometry techniques looking for the presence of these three particular labels: species, population and gender. We found diagnostic diff erences in uropygial secretions between the two species of shearwaters and smaller but signifi cant variation between populations of Cory ' s shearwater in the Atlantic. No signifi cant diff erences were observed between males and females. Individuals might thus use the chemical variation between species to recognize and mate with conspecifi cs, especially at localities where both species breed sympatrically. Geographical variation in chemical composition of uropygial secretions suggests that selective forces might vary according to locality, and might represent a key in the species recognition. Further behavioural bioassays are needed to determine whether or not these species labels are signals allowing reproductive isolation between these two taxa. Finally, one of the aims of our study was to test easier methods than freezing for storing uropygial gland secretions in the fi eld. We describe here a new possibility for the storage of uropygial secretion samples at ambient temperature in the fi eld, providing an alternative, simple protocol for the sampling of avian chemosignals.

Preen oil chemical composition encodes individuality, seasonal variation and kinship in black kites Milvus migrans

“…In numerous avian species, the chemical composition of preen oil encodes information on various bird characteristics, such as sex, age, individuality, seasonal variation, species affiliation or genotype (Hagelin 2007, Mardon et al 2010, Wyatt 2014, Caro et al 2015, Gabirot et al 2016, Krause et al 2018. Although the biological meaning of these differences has rarely been investigated, a few studies have shown that most of these odour cues can be recognized by birds Nevitt 2004, Mardon andBonadonna 2009) and influence social behaviour (Balthazart and Schoffeniels 1979, Hirao et al 2009, Caspers et al 2015.…”

Sex and age, but not blood parasite infection nor habitat, affect the composition of the uropygial gland secretions in European blackbirds

“…Similar results were found by Leclaire et al (2011) in black‐legged kittiwakes Rissa tridactyla during the bird breeding season. However, the composition of the uropygial gland secretion did not differ between sexes in other species, such as crested auklet (Hagelin et al 2003) and Cory's and Scopoli's shearwaters (Gabirot et al 2016). In addition, non‐significant differences between sexes were found in the composition of the volatile fraction of uropygial gland secretions of juvenile house sparrows (Díez‐Fernández et al 2020a), further suggesting that sexual differences may be only apparent in adult/sexually mature birds.…”

“…The composition of this secretion varies among species (Haribal et al 2009) and age classes (Shaw et al 2011) and may differ between sexes (Whittaker et al 2010). Sexual differences in the composition have been detected in some species such as Bengalese finches Lonchura striata (Zhang et al 2018) and dark‐eyed juncos Junco hyemalis (Soini et al 2007), but not in others, such as crested auklets Aethia cristatella (Hagelin et al 2003), Cory's shearwaters Calonectris borealis and Scopoli's shearwaters C. diomedea (Gabirot et al 2016). The uropygial secretion contributes to a large extent to bird odour (Moreno‐Rueda 2017), and differences in its composition may therefore play an important role in bird intraspecific and interspecific communication (Caro et al 2015).…”

Pigeon odor varies with experimental exposure to trace metal pollution

“…Although sexual dimorphism in chemical cues from feathers or preen secretions has been reported in several bird species (Amo et al 2012;Leclaire et al 2011;Whittaker et al 2010;Zhang et al 2010), it is not ubiquitous. For instance, king penguins (Aptenodites patagonicus) and Cory's shearwaters (Calonectris borealis) seem to exhibit no sex-differences in scent (Gabirot et al 2018;Gabirot et al 2016). Pigeons display sexual polymorphism in iridescent coloration of neck feathers (Chatelain et al 2017;Leclaire et al 2014a), and might, therefore, use this other trait to discriminate between sexes.…”