Foster eggs or chicks of parrots with wild conspecifics
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
Background information and definitions
Natural variations in reproductive output can be detrimental when populations are very small, for example if pairs fail to produce fertile eggs or some pairs repeatedly fail to raise offspring successfully. One way to minimise this problem is to foster eggs and chicks between nests. Eggs and chicks from nests with more offspring than they are likely to be able to raise can be moved to those with infertile eggs. Alternatively, if a pair produces fertile eggs or healthy chicks but consistently fails to raise chicks then it may be possible to transfer offspring to a more successful pair.
In other circumstances it may be possible to foster chicks with other species (‘cross-fostering’). Studies describing this intervention are discussed in the following section ‘Foster eggs or chicks with wild non-conspecifics (cross-fostering).’
Supporting evidence from individual studies
A 1998 review of a yellow-shouldered Amazon Amazona barbadensis release programme on Margarita Island, Venezuela (Sanz & Grajal 1998), found that, of 53 nestlings fostered to wild nests between 1989 and 1996, 44 (83%) chicks eventually fledged. The population on the island increased from 750 to approximately 1900 individuals between 1989 and 1996 as a result of recruitment increasing from zero in 1989 to 53 birds/year following management. This study is discussed in more detail in ‘Release captive-bred individuals’, ‘Artificially incubate or hand-rear birds in captivity’ and ‘Use education programmes and local engagement to help reduce pressures on species’.Study and other actions tested
A replicated study in 2005-2006 (part of a longer study from 2000-2009) in 18 monitored yellow-shouldered Amazons Amazona barbadensis nests in tropical forest habitat on Margarita Island, Venezuela (Briceño-Linares et al. 2011) found that fostering fledglings and assisted breeding significantly decreased poaching rates. The use of foster nests and assisted breeding in 2005 decreased poaching from 56% at the end of 2004 to 18% in 2005 and 0% poaching in of monitored nests in 2006. Fledglings from high-risk nests (further away from the base) in the study area were moved to foster nests (possessing similarly aged fledglings) near the field base. All fledglings from each nest were then removed and placed them in a labelled wooden box in a secure facility after sunset, and returned to the nest at sunrise. This strategy was initiated once the parents stopped spending the night inside the nests, around 30–40 days after hatching. This study is also discussed in ‘Relocate nestlings to reduce poaching’, ‘Use education programmes and local engagement to help reduce pressures on species’, ‘Employ locals as biomonitors’ and ‘Foster eggs or chicks with wild conspecifics’.Study and other actions tested
Referenced paperBriceño-Linares J.M., Rodríguez J.P., Rodríguez-Clark K.M., Rojas-Suárez F., Millán P.A., Vittori E.G. & Carrasco-Muñoz M. (2011) Adapting to changing poaching intensity of yellow-shouldered parrot (Amazona barbadensis) nestlings in Margarita Island, Venezuela. Biological Conservation, 144, 1188-1193.