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Providing evidence to improve practice

Action: Foster eggs or chicks of cranes with wild non-conspecifics (cross-fostering) Bird Conservation

Key messages

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Two studies from the USA found low fledging success for cranes fostered to non-conspecifics’ nests.

 

 

Supporting evidence from individual studies

1 

As part of the planning for a whooping crane Grus americana reintroduction programme, a replicated study in Florida, USA, in 1982-7 (Nesbitt & Carpenter 1993) found that 22% of 23 wild Florida sandhill crane G. canadensis pratensis pairs successfully fledged chicks from captive-laid greater sandhill crane G. c. tabida eggs fostered in their nests. A further 35% hatched at least one egg but failed to fledge any chicks, 26% began incubation but then abandoned the substituted eggs and 17% immediately abandoned the eggs. Overall, survival of 34 cross-fostered eggs was 39% (from hatching to leaving the territory), lower than the 56% survival of captive-bred and released cranes, discussed in ‘Release captive-bred individuals’. The eggs came from a combination of wild birds in Idaho, USA, and captive birds from Florida. Greater sandhill cranes are migratory, whilst Florida sandhill cranes are not. Migratory movements of fostered birds were larger than a control group of Florida sandhill cranes, but not significantly so.

 

2 

A study in Idaho, USA, between 1975 and 1991 (Kuyt 1996) found that 215 wild-sourced and 73 captive-bred whooping crane Grus americana eggs that were cross-fostered into sandhill crane G. canadensis nests had high hatching success (210 eggs hatching, 73% of total) but low fledging success (85 birds fledging, 30%), low survival (13 individuals alive in 1991, 5%) and no pairs formed between fostered individuals. Causes of mortality included predation by coyote Canis latrans and birds, collisions with fences and powerlines and disease. This study is also discussed in ‘Use captive breeding to increase or maintain populations’, ‘Foster eggs or chicks with wild conspecifics’ and ‘Release captive-bred individuals’.

 

Referenced papers

Please cite as:

Williams, D.R., Child, M.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.K.H.J. & Sutherland, W.J. (2019) Bird Conservation. Pages 141-290 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.