Videographic monitoring at caves to estimate population size of the endangered yǻyaguak (Mariana swiftlet) on Guam

Endangered Species Research
By: , and 

Links

Abstract

The yǻyaguak (Mariana swiftlet; Aerodramus bartschi) is an endangered cave-nesting species historically found on Guam and the southern Mariana Islands, Micronesia. The population on Guam has been severely affected by the introduction of the brown treesnake Boiga irregularis. Population status assessments have, however, been challenging due to the limitations of traditional counting methods, which rely on visual observations at cave entrances and are prone to inaccuracies. To improve count accuracy, we estimated yǻyaguak population size and relative nesting activity using thermal and near-infrared videography. The population on Guam was surveyed at the island’s 3 known occupied caves (Mahlac, Maemong, and Fachi) between 2019 and 2023. Mahlac Cave harbored the largest colony, which ranged from 506 to 665 birds; Maemong Cave held 144 to 196 birds; and Fachi Cave, which is sometimes flooded, had 28 (in 2019) and 35 birds (in 2023). Our estimates indicate a slight decline in the yǻyaguak population over the study period. This study demonstrates the potential of thermal and near-infrared videography for improved monitoring of yǻyaguak colonies and nesting activity, which will contribute to our understanding of population dynamics and the effectiveness of management strategies such as brown treesnake control.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Videographic monitoring at caves to estimate population size of the endangered yǻyaguak (Mariana swiftlet) on Guam
Series title Endangered Species Research
DOI 10.3354/esr01296
Volume 53
Year Published 2024
Language English
Publisher Inter-Research
Contributing office(s) Fort Collins Science Center, Pacific Island Ecosystems Research Center
Description 11 p.
First page 139
Last page 149
Country United States
Other Geospatial Guam
Google Analytic Metrics Metrics page
Additional publication details