The Odour of Sex: Sex-Related Differences in Volatile Compound Composition among Barn Swallow Eggs Carrying Embryos of Either Sex

Abstract

Avian communication has been traditionally believed to be mainly mediated by visual and auditory channels. However, an increasing number of studies are disclosing the role of olfaction in the interaction of birds with their social environment and with other species, as well as in other behaviors such as nest recognition, food location and navigation. Olfaction has also been suggested to play a role in parent-offspring communication not only in the post- but also in the pre-hatching period. Volatile compounds produced during embryogenesis and passively released through the eggshell pores may indeed represent the only cue at parents’ disposal to assess offspring quality, including the sex composition of their clutch before hatching. In turn, sex identification before hatching may mediate adaptive strategies of allocation to either sex. In the present study, we analyzed odour composition of barn swallow eggs incubated in their nest in order to identify any sex-related differences in volatile compounds emitted. For the first time in any bird species, we also investigated whether odour composition is associated with relatedness. The evidence of differences in odour composition among eggs containing embryos of either sex indicates that parents have a cue to identify their brood sex composition even before hatching which can be used to modulate their behavior accordingly. Moreover, odour similarity within nests may represent the prerequisite for kin recognition in this species.

Non‐destructive characterization of egg odor and fertilization status by SPME/GC‐MS coupled with electronic nose

“…(j)). This meant that each group of the two kinds of VOCs might carry some biological information about fertilization but the relation or mechanism between them w complex and unknown …”

“…Subsequently, the VOCs emitted from eggs were extracted by a 50/30 μm divinylbenzene/carboxen/polydimethylsiloxane on 2 cm Stable Flex fiber (Supelco, Bellefonte, PA, USA) with a depth of 28–30 mm for 60 min at 38 °C (Fig. ) …”

“…24 Nonanal, decanal, octanal, hexanal, heptanal and 6-methyl-5-heptan-2-one were detected in (Fd) barn swallow eggs. 25 As a result, it could be concluded that 6,10-dimethyl-5,9-undecadien-2-one may be a species-specific volatile of chicken egg and the composition or profile of odor from eggs between chickens and barn swallows were more similar to each other than to that of quail.…”

“…1). [24][25][26] GC-MS Volatile organic compounds from eggs with different fertilization status were collected by HS-SPME, and then immediately desorbed in a gas chromatography (GC) injector port for 5 min at 250 ∘ C in splitless mode. The VOCs were separated on a HP-5MS capillary column (30 m × 0.25 mm × 0.25 mm film thickness) using a 7890B-5977A GC-MS instrument (Agilent Technologies, Palo Alto, CA, USA).…”

Blue petrels recognize the odor of their egg

“…Recent evidence shows that egg odor can vary with embryo sex, fertility and development (Costanzo et al, 2016;Webster et al, 2015). However, the ability of birds to assess information encoded by egg odor has scarcely ever been investigated.…”