Foraging Habitat Selection and Seasonality of Breeding in Germain's Swiftlet (Aerodramus inexpectatus germani) in Southern Thailand

Abstract

Habitat degradation is major threat that limits animal populations and knowledge of foraging habitat selection is important to support the survival of organisms. Germain's swiftlet (Aerodramus inexpectatus germani) produces highly valuable nests and has an important ecological role in ecosystems as an insect predator. However, little is known about the foraging habitat preferences, vertical distribution and factors affecting the timing of breeding, knowledge which may be helpful for managing swiftlet populations. We aimed to determine 1) the preferred foraging habitats, diurnal and seasonal variation on foraging, 2) vertical foraging pattern and 3) the variation in breeding chronology between the west and east of peninsular Thailand, areas with relatively large swiftlet populations. The intensity of foraging within five major habitats was investigated from prey capture attempt and related to insect availability (estimated as biomass). Breeding activities of total 85 breeding pairs were observed using an IP camera at four colonies for three breeding cycles and related to insect biomass in its major foraging habitats. The highest foraging intensity was over water bodies, forest and open paddy land where insect abundance was higher compared to tree-dominated agriculture and urban areas. Foraging intensity was greater in twilight period than midday, the wet season showed higher intensity of foraging compared to the dry season and related to insect biomass. Vertical foraging height influenced by vegetation foliage height where were rich of insect prey. This suggested that food supply affected habitat use and it can affect swiftlet breeding strategies. Breeding time in the western colonies was earlier than the eastern colonies of peninsular Thailand probably due to differences in prey availability which is influenced by the timing of rainfall. Consequently, better protection and management of wetlands, forest and open paddy land within their foraging range would likely improve the availability of natural insect prey. Nest harvest time should be varies by geographical variation in breeding chronology. This has implications for the sustainability of the swiftlet industry across the species range.