Estimating the population and related dynamics of the cave-dwelling Edible-nest Swiftlet in the Andaman Islands, India

Abstract

Apodids (Swifts and Swiftlets) are among the under-studied bird species. They are hard to identify, and their breeding habitats are inaccessible, making studying their population estimation and related dynamics challenging. In this study, we aimed to estimate the populations using the capture-mark-recapture (CMR) and nest count methods. Conducted at the Baratang cave complex in the Andaman Islands, our study used stratified sampling to choose 12 study caves based on the breeding population for capture and recapture in all possible caves occupied by Edible-nest Swiftlet (Aerodramus fuciphagus). The use of the Lincoln Index to estimate the populations of the Edible-nest Swiftlet in each cave by analyzing the capture-mark-recapture data and using the program MARK with the Live Recaptures. The Lincoln Index and total population count estimated 486 and 505 birds, respectively, with no significant difference (p > 0.05). The best-fit model indicates that the annual survival rate was consistent throughout the study period (0.97–1.00), and the capture probability was 0.35 ± 0.02. The study evidently showed that using only one method is inadequate for accurately estimating the Edible-nest Swiftlet populations. The CMR method is recommended as an alternative when it is necessary to understand related population dynamics, and the nest and roost count methods are not feasible. The study confirms the effectiveness of the CMR method when used in combination with other traditional methods.