Edible-nest Swiftlets forage high above the canopy, while Glossy Swiftlets forage at the
canopy level and near the ground. Johnson (1969) suggested that insects move upwards in air with an increase in ambient temperature. This may be the reason for the shift of Edible-nest Swiftlets to higher altitudes during foraging and Glossy Swiftlets, being smaller and more agile to maneuver in confined spaces, to move towards relatively cooler zones inside the canopy at the
forest edges or stream banks close to open paddy lands for foraging. Variations in microhabitat use signify resource partitioning among Edible-nest and Glossy swift lets at Chalis-ek with Edible-nest Swiftlets having affinity for categories, .10 m Above Forest
Canopy, .30 m Above Ground, and Above Forest Canopy, and Glossy Swiftlets for Inside Forest
Canopy and Inside Stream Bank Canopy in descending order. Variations in foraging maneuvers
indicate variations in food preferences by both species as demonstrated by gut content and
bolus analysis (Medway 1962, Harrison 1972, Hails and Amiruddin 1981, Waugh and Hails
1983, Charles 1987, Collins 2000, Laurie and Tompkins 2000). The Edible-nest Swiftlet’s affinity towards .30 m Above Ground in open land for foraging was unusual as the species has been known to prefer forested areas. The plasticity in food selection by Edible-nest Swiftlets (Charles
1987, Laurie and Tompkins 2000) suggests two microhabitats, .10 m Above Forest Canopy and .30 m above ground, may have similar insect diversity. This demonstrates that forested habitat
and microhabitats above forest canopy level are important for Edible-nest Swiftlets. Glossy Swiftlets also had affinity towards both available habitats. We infer, in concurrence with previous studies, that cave-dwelling Edible-nest Swiftlets are dependent on forests and will be adversely affected by the present rate of deforestation and habitat alteration. Changes in land use away from caves used for breeding sites will also lead to population declines of Edible-nest Swiftlets because of its wider foraging ranges. However, habitat alteration around breeding caves may not have a marked effect on foraging activities of Glossy Swiftlets, which have more elasticity in habitat use.