Purple Heron (Ardea purpurea) Science Article 1
[…]. During the breeding season, the Purple Heron Ardea purpurea is a central place forager and periodically visits the nest with the food necessary for nestling development. The tradeoffs between the costs (mostly energy used in travelling and foraging) and benefits (food) of foraging, should allow the birds to obtain sufficient energy for themselves and their offspring (Bell, 1991). In stable environments, the net energetic gain for adult birds is a good indicator of their behaviour (Kacelnik & Cuthill, 1987) although variations may arise depending on the foraging habitat (Bateson & Whitehead, 1996). […].
Campos, F. & Lekuona, J. M., Ardeola 47(1), 2000, 105-107