Elucidating mutual mate choice: effects of trial design on preferences of male zebra finches

Abstract

Understanding the dynamics of mutual mate choice requires investigation of mate preferences of both sexes using a variety of designs, but fewer studies have focused on male choice in avian models. Here we conducted two experiments on preferences of male zebra finches to study the impact of trial design on results. Experimental design varied in number of trial participants, inclusion of observer (“audience”) males, and housing design for stimulus females. Females were reared on one of two diets to enhance variation in mating quality: those reared on a protein-supplement diet (HI-diet) were predicted to be more attractive to males than (LO-diet) females that did not receive supplements. Results differed among trial types. Notably, males showed the predicted preference for HI-diet females only in the Group Choice experiment, where two male subjects simultaneously chose from a field of four females, and all six birds interacted freely. In the Dyadic Preference (DP) experiment, a single male was allowed to interact with two stimulus females that were physically isolated; in half of these trials, audience males were present. In DP trials without audience males, test males did not express a preference consensus; however, with audience males present, test males preferred LO-diet females. Results are consistent with a small but growing literature indicating that results of mate choice experiments can be highly sensitive to design considerations.

Female differential allocation in response to extrapair offspring and social mate attractiveness

“…Since egg mass is heritable (Christians, 2002; Potti, 1999) and can be influenced by female early‐life environment—with better environments associated with heavier eggs and larger clutches (Griffith & Buchanan, 2010; Monaghan et al., 1996; Potti, 1999)—high‐quality males may have secured mates that were more fecund. Assortative pairing in zebra finches has been reported in both free‐pairing colony experiments (Burley, 1986; Burley & Foster, 2006) and mate choice experiments (Holveck & Riebel, 2010), but it is unclear whether such assortment extends to fecundity, since mixed results are reported for males’ tendency to choose based on female fecundity (Martin & Burley, in press; Wang et al., 2017). Thus, the relative contributions of differential allocation and assortative mating to the egg mass patterns found here remain unclear.…”