The release weight of a fostered Swift

Contributed by Judith Wakelam

Weight is an important indicator of the health of a bird. When a bird is being fostered or rehabilitated, the rehabber takes its weight regularly as she feeds it up, not essaying a release until it reaches a healthy release weight, ideally around 40-45 grams, though some small Swifts can go at considerably less than this, even as light as 36 grams

50 grams is heavy for a Swift
Photo Judith Wakelam

I took delivery of a brood of three nestlings rescued from a roof in Ely last year (reported here), all of which eventually flew. The tiniest of them proved to be the one with the biggest appetite! Here it is weighing in at a colossal 50 grams. 

In the nest, chicks regularly exceed their release weight, but then they progressively lose the excess in the two or three days between the parents leaving them alone in the nest and the moment when they finally pluck up courage to launch themselves into the air.