Medway (1962) reported wider foraging ranges of Edible-nest Swiftlets in the non-breeding season, leading to changes in activity near breeding sites. Swiftlets at Chalis-ek, traveled
away from the caves even during the preincubation period, possibly due to non-availability
of food near caves. Food availability for swiftlets depends on the density and diversity of insects which in turn depend on weather conditions (Johnson 1969). Glossy Swiftlets were more active in early and late morning hours, but did not have significant diurnal variations in activities (Fig. 2). Asynchronous breeding in the Andaman and Nicobar Islands by Glossy Swiftlets may have resulted in no variation in diurnal activities. Fly/glide was the most frequent behavior apparently used for scanning foraging areas while traveling to other foraging areas. Both species spent substantial time in fly/glide which depends on availability of insects. Insect density varies chronologically, spatially, and seasonally (Johnson 1969), thus, affecting fly/glide in the two species. Feeding attempt was the second major activity after fly/glide. All individual activities, except feeding attempts, had temporal variations in their proportions by month. No diurnal variation in feeding attempts and calls was recorded. Call and follow were presumed to be mating/pairing displays as well as a response to foraging competition. Call and follow activities by Edible-nest Swiftlets, and follow by Glossy Swiftlets were higher during nest construction (Jan–Feb). This suggests that follow must be more
related to mating. Insect diversity was assumed to affect the occurrence of different foraging maneuvers with the presumption that different foraging maneuvers are used to prey on different type of insects. This dependence resulted in temporal (monthly and hourly) variations in the proportions of different foraging maneuvers.