Swiftlet behaviour responses to Predators in proximity to their nests
When they have the opportunity, swiftlets nest in totally dark parts of caves. This prevents most predation on eggs, young and incubating adults. However, a few predators are able to either reach the nests or prey on birds flying to and from nests. In response, swiftlets have developed anti-predatory behaviour. To reduce predation, adult birds enter and exit caves in groups, increase flight speed at the entrance (where most predators attack), and feed their young less frequently than comparable species that do not nest in caves. Where there have not been predators consistently at entrances the birds do not form groups but fly singly and slowly. In most colonies a few birds use alternative entrances. Predation at the nest is reduced by adults clumping their nests on high, smooth, overhanging rock surfaces. When such safe surfaces are not available or predators are able to climb the walls, swiftlets respond by spacing nests widely, reducing the chance that a predator will find them.
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