Patterns, correlates, and paternity consequences of extraterritorial foray behavior in the field sparrow (Spizella pusilla): an automated telemetry approach

Abstract

Abstract: In many territorial species, occasional movements beyond territory boundaries (extraterritorial forays) have been documented in many species. While many explanations for the occurrence of extraterritorial forays have been proposed, a logical and proposed function of extraterritorial forays is to engage in extra-pair copulations with extra-pair mates outside of their territories. We used an automated radio-telemetry system (ARTS) to examine the patterns and correlates of foray behavior of male and female field sparrows (Spizella pusilla) and investigated if forays were associated with extra-pair paternity (EPP) and cuckoldry. We found that male and female field sparrows regularly engaged in extraterritorial forays. In males, age and time of foraying (day vs. night) were important factors explaining foray rates (foray/h); older (ASY) males forayed more than younger (SY) males and, while we detected many nocturnal forays, most forays occurred during the day. For females, fertility stage and age appeared to be important in explaining foray rates; older females forayed more during pre-fertile period than fertile and post-fertile periods. Unlike foray rates, the duration of forays (min) was not explained by any of the variables examined. Surprisingly, despite the large number of forays documented (>3500), greater foray rates or duration of forays were not associated with higher probability of EPY for males or females or with cuckoldry in males. Forays may play a role in prospecting and acquiring information about their social and ecological environment, which ultimately may help them to achieve greater reproductive success, but not necessarily in the form of EPP. Significance statement: Despite many territorial species are known to conduct extraterritorial forays (movements beyond their territory), very little is known about this behavior. We used an automated radio-telemetry system (ARTS) to examine the patterns, correlates, and paternity consequences of extraterritorial foray behavior in male and female field sparrows (Spizella pusilla). We documented more than 3500 forays and found that both male and female field sparrows regularly engaged in extraterritorial forays; however, different factors explain their foray rates (age, time of foraying (day vs. night), and fertility stage) but not the duration of forays. Surprisingly, greater foray rates or duration of forays were not associated with higher probability of EPY in males or females or with cuckoldry in males. Rather than exclusively acquiring extra-pair matings, forays likely serve multiple purposes, such as prospecting and acquiring information about their social and ecological environment, which ultimately may help individuals achieve greater reproductive success.