Mate guarding and territorial aggression vary with breeding synchrony in golden whistlers (Pachycephala pectoralis)

Abstract

Male paternity assurance behaviour during the female fertile period has been widely documented amongst birds. In contrast, how sex-specific behavioural strategies vary with local breeding synchrony levels remains largely unknown. This is important because, in many species, intra-population patterns of extra-pair fertilisation rates, and hence cuckoldry risk, are known to vary with the number of simultaneously fertile females. Each sex may therefore differ in how they behave towards male conspecifics during different degrees of breeding synchrony. Here I provide evidence of such sex-specific differences in the golden whistler (Pachycephala pectoralis), a species in which within-pair paternity assurance is negatively associated with breeding synchrony. Via simulated territorial intrusions using decoy males, I show that males, but not females, increase levels of aggression to male intruders during periods of low synchrony, possibly because cuckoldry risk is greatest during this period. In addition, males appear to invest more effort into mate guarding after, but not before, territorial intrusions during this period. These inter-sexual differences may reflect conflicts in interest between the sexes, with females consistently showing interest in males during the fertile period regardless of synchrony levels and males investing more resources into expelling intruders when the risk of paternity loss is greatest. This study thus provides evidence that males may be able to detect variation in breeding synchrony and cuckoldry risk and adjust their paternity assurance behaviour accordingly.

Male decisions or female accessibility? Spatiotemporal patterns of extra pair paternity in a songbird

“…Thus, when EPCs are mainly male initiated, as suggested by previous work in pied flycatchers (Björklund and Westman 1983;Alatalo et al 1987), a negative relationship between synchrony and EPP rates would occur when males prioritize avoiding cuckoldry over seeking paternity outside the pair bond (Birkhead and Biggins 1987;Westneat et al 1990). Accordingly, when the risk of cuckoldry is high, fairy martin males (Petrochelidon ariel) guard their mates more intensively, (Hammers et al 2009) whereas golden whistler males (Pachycephala pectoralis) are more aggressive towards intruders and remain closer to their mates (van Dongen 2008).…”

Prenatal exposure to low doses of atrazine affects mating behaviors in male guppies

“…Aggression between rival males is an important factor in gaining fertilizations because winning contests allows access to females (Bertram et al, 2011;Brown et al, 2007;Hurtado-Gonzales and Uy, 2010). More aggressive males will also guard mates to prevent sperm competition (Bateman and Toms, 1998;van Dongen, 2008;Watts, 1998). Hence reduced aggression towards rival males can lead to lowered reproductive success.…”

Mate-guarding intensity increases with breeding synchrony in the colonial fairy martin, Petrochelidon ariel

“…We have insufficient information to comment on these assumptions but clearly a more detailed understanding of the EPC behaviour of both males and females would help to reveal the mechanism underlying this relationship between mate guarding and synchrony (Westneat & Stewart 2003). The observed increase in mate-guarding intensity with breeding synchrony is at odds with two previous studies that found males guarded less intensely when synchrony was high (Chuang-Dobbs et al 2001;van Dongen 2008). One possible explanation for this difference is that these other studies were on territorial species which would have regular interactions with far fewer conspecifics than the colonial fairy martins.…”

“…When synchrony is low, only a few females in the population will be concurrently fertile, and these individuals may attract more male-initiated EPC attempts than more synchronous females (Westneat et al 1990), promoting the necessity for mate guarding (Wagner et al 1996). Consequently, all else being equal, guarding may be expected to be most intense when the proportion of fertile females in the population is low (Wagner et al 1996;van Dongen 2008). Alternatively, males may invest more effort into seeking EPC when a higher proportion of females in the population are fertile (greater synchrony) and/or synchrony may facilitate the ability of females to compare and choose among extrapair males, promoting their propensity to engage in EPC (Stutchbury & Morton 1995).…”