Observations on alloparental care of fledglings in Osprey Pandion haliaetus (Aves, Pandionidae)

We describe the adoption and alloparental care of fledglings by an Osprey pair during two consecutive breeding seasons (2008-09) in the small and semi-colonial cliff nesting population of Tenerife (Canary Islands). The intruding broods (two fledglings each year) switched nest a few days after fledging (≤ 10 days in 2008 and ≤ 6 in 2009). They used the recipient nest and perches together with the genetic broods, and received alloparental feeding. The short distance between neighbouring nests and advantageous terrain characteristics of the recipient territory seem to be the main reasons that led to these behaviours.