Stay or shift: does breeding success influence the decision in a cave-dwelling swiftlet?

Decision rules allow individuals of a species to decide whether or not to return to the same site in the following year or season, based on their immediate breeding success. We checked the decision rule phenomenon and simultaneously tested the prior-experience hypothesis for the cave-dwelling Edible-nest Swiftlet (Aerodramus fuciphagus inexpectatus; ENS) in the Baratang Cave Complex, Andaman and Nicobar Islands, India. We used the capture-mark-recapture method to understand the decision rule in ENS. Assuming that breeding success affects the decision, we monitored 234 individuals for two consecutive breeding seasons (2017 and 2018). We also documented habitat variables (cave morphometry and microclimate) to understand the correlates of breeding success. We captured 88% (207 birds) of adult birds from the study caves in 2017 and recaptured 66% (137 birds) of adults from the same caves in 2018, which confirmed fidelity towards the cave by the species. There was no significant correlation between the rates of breeding success in 2017 and 2018. Multiple regression models revealed an insignificant relationship between cave structure and breeding success of the species. Additionally, microclimate variables (temperature and humidity) did not influence the breeding success of the birds. Our results indicate that ENS individuals seem to chose decision rule by rejecting the prior-experience hypothesis. The existing conservation strategies associated with enhancing the ENS population in the Andaman and Nicobar Islands can benefit from our findings. We further recommend long-term studies and population monitoring to understand the breeding cave fidelity in ENS.