Foster eggs or chicks of cranes with wild non-conspecifics (cross-fostering)

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
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How is the evidence assessed?

Effectiveness

14%
Certainty

35%
Harms

10%

Calculating overall effectiveness category

Background information and definitions

There two species of cranes Grus spp. are resident in North America: the endangered whooping crane G. americana which migrates from central Canada to the southern USA; and the sandhill crane G. canadensis which contains several subspecies, some of which are migratory and some sedentary. Sandhill cranes offer the potential to foster whooping cranes, but there is uncertainty over the ability of whooping cranes to migrate successfully following if they are raised by another species.

Study locations

Key messages

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

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

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.
Study and other actions tested
Referenced paper
Nesbitt S.A. & Carpenter J.W. (1993) Survival and movements of greater sandhill cranes experimentally released in Florida. Journal of Wildlife Management, 57, 673-679.
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’.
Study and other actions tested
Referenced paper
Kuyt E. (1996) Reproductive manipulation in the whooping crane Grus americana. Bird Conservation International, 6, 3-10.

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. (2020) Bird Conservation. Pages 137-281 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

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This Action forms part of the Action Synopsis:

Bird Conservation

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Foster eggs or chicks of cranes with wild conspecifics Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link