Mate Preference of Female Blue Tits Varies with Experimental Photoperiod

Laura B Reparaz,Samuel P Caro,Claire Doutrelant,Kees Van Oers,Marcel E Visser,Marc Naguib,Paul A Bartell

doi:10.1371/journal.pone.0092527

Abstract

Organisms use environmental cues to time their life-cycles and among these cues, photoperiod is the main trigger of reproductive behaviours such as territory defence or song activity. Whether photoperiod is also important for another behaviour closely associated with reproduction, mate choice, is unknown. In many bird species, mate choice occurs at two different times during the annual cycle that strongly differ in daylength: in late winter when photoperiod is short and social mates are chosen, and again around egg-laying when photoperiod is longer and extra-pair mates are chosen. This duality makes the role that photoperiod plays on mate choice behaviours intriguing. We investigated the effect of photoperiod on mate choice using three experimental photoperiodic treatments (9 L:15 D, 14 L:10 D, 18 L:6 D), using blue tits (Cyanistes caeruleus) as a biological model. We show that female choice was stronger under long photoperiods. In addition, female blue tits spent significantly more time near males with long tarsi and long wings. This latter preference was only expressed under long photoperiods, suggesting that some indices of male quality only become significant to females when they are strongly photostimulated, and therefore that females could select their social and extra-pair mates based on different phenotypic traits. These results shed light on the roles that photoperiod may play in stimulating pair-bonding and in refining female selectivity for male traits.

Highlights

In temperate zones, most animal species start breeding remarkably regularly each year
The choice to engage in extra-pair copulations is made around egglaying [16,17,18,19], while the social mate is typically chosen much earlier, in late winter [20,21]. This illustrates that mate choosing behaviours are important before reproduction starts, and during the breeding season, for selecting individuals with whom to potentially engage in extra-pair copulations. Given that these two time periods strongly differ in their day length, the role that photoperiod plays on mate choice behaviours in these species is intriguing
The work performed in the field was approved by the prefectural office of Corsica and the Regional Direction of Environment (DIREN) committee

Summary

Introduction

Most animal species start breeding remarkably regularly each year. Exposure to increasingly longer photoperiods triggers a cascade of neuroendocrine reactions that prepare animals for breeding: e.g., genes are activated in the brain, reproductive hormones increase in concentration in the blood, and gonads mature and start producing gametes [3,4,5,6] These physiological changes in turn stimulate the expression of a complex and well-organized suite of reproductive behaviours such as territory defence, courting, nest preparation and communication displays, like songs in songbirds [1]. This illustrates that mate choosing behaviours are important before reproduction starts, and during the breeding season, for selecting individuals with whom to potentially engage in extra-pair copulations Given that these two time periods strongly differ in their day length, the role that photoperiod plays on mate choice behaviours in these species is intriguing. If birds choose different kinds of mates (social vs. extra-pair) based on different indices of quality, we predict that some of these morphological and behavioural traits will only affect mate choice behaviours under some photoperiods and not others

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Discussion