Foster eggs or chicks of waders 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

35%
Certainty

30%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

If the wild populations of a species are very small then it may not be possible to foster offspring to conspecifics. However, it may be possible to foster chicks and eggs to a similar, but more abundant species, if one is present. This can increase the reproductive output of the wild population of the endangered species, or even allow for the reintroduction of a population into parts of its former range.

Study locations

Key messages

A replicated and controlled study from the USA found that killdeer Charadrius vociferus eggs incubated and raised by spotted sandpipers Actitis macularia had similar fledging rates to parent-reared birds.
A replicated and controlled study from New Zealand found that cross-fostering black stilt Himantopus novasezelandiae chicks to black-winged stilt H. himantopus nests significantly increased nest success, but that cross-fostered chicks had lower success than chicks fostered to 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

A replicated and controlled experiment on two islands in Lake Michigan, USA, in 1987-9 (Powell & Cuthbert 1993) found that killdeer Charadrius vociferus eggs incubated and raised by spotted sandpipers Actitis macularia did not have significantly different hatching or fledging rates, compared to parent-reared eggs and chicks (47% hatching success, 0.8 fledglings/pair and 48% fledging success for cross-fostered chicks, n = 16 broods vs. 54%, 0.6 fledglings/pair and 27% for parent-reared chicks, n = 24 broods). There were no significant behavioural differences between parent-reared and cross-fostered chicks and one cross-fostered chick was seen two years after fledging, when it courted and mated with wild killdeer. No parent-reared chicks were seen again but the authors note that killdeer have low site-fidelity and so may not be seen again.
Study and other actions tested
Referenced paper
Powell A.N. & Cuthbert F.J. (1993) Augmenting small populations of plovers: an assessment of cross-fostering and captive-rearing. Conservation Biology, 7, 160-168.
A replicated and controlled study in mountain streams and rivers in South Island, New Zealand, in the austral springs of 1981-7 (Reed et al. 1993) found that fledging success of managed black stilt Himantopus novasezelandiae nests was at least ten times that reported from unmanaged nests (13-27 chicks fledging in the population each year, a 20-42% fledging rate vs. 2% reported in another study for unmanaged nests). Eggs were removed from black stilt nests and artificially incubated (see ‘Artificially incubate and hand-rear birds in captivity’), before being returned as they were hatching. If replacement in the original nest was not possible then eggs were placed in a foster nest, either another black stilt nest or a black-winged stilt H. himantopus nest. Fledging rates and recruitment to the local population were higher for chicks fostered by black stilts than cross-fostered chicks (66% of 50 chicks fostered by black stilts were resighted and five recruited locally vs. 19% of 21 cross-fostered chicks, with a single recruit). The authors note that cross-fostered chicks followed their foster parents on migration, probably leading to low recruitment.
Study and other actions tested
Referenced paper
Reed C.E.M., Nilsson R.J. & Murray D.P. (1993) Cross-fostering New Zealand's black stilt. Journal of Wildlife Management, 57, 608-611.

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

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Bird Conservation

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