Action: Foster eggs or chicks of waders with wild conspecifics
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- Two small trials in North America found that piping plovers Charadrius melodus accepted chicks introduced into their broods, although in one case the chick died later the same day.
- A replicated study from New Zealand found that survival of fostered black stilts Himantopus novasezelandiae was higher for birds fostered to conspecifics rather than a closely related species.
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 small trial on a beach in Nova Scotia, Canada in July 1983 (Flemming 1987) found that a pair of piping plovers Charadrius melodus adopted a chick introduced to their brood after it was abandoned by its parents when one day old. The foster parents brooded the chick but, following heavy rains on the day of introduction, it disappeared and is assumed to have died. The author suggests that its weakened condition, due to being abandoned by its parents meant that it could not survive the rainstorm, whereas its ‘stepsiblings’ could and were later seen flying.
A small trial on a beach in Connecticut, USA, in May 1990 (Midura et al. 1992) successfully introduced an orphaned piping plover Charadrius melodus chick into a foster family with four similarly-aged chicks. No aggressive behaviour was observed towards the foster chicks and all five young were seen flying in July. The chick was originally released within 11 m of the foster family when it was one day old.
A replicated study in South Island, New Zealand (Reed et al. 1993), investigated the survival of black stilts Himantopus novasezelandiae, fostered by both conspecifics and black-winged stilts H. himantopus. This study found that there was higher recruitment into the local population from chicks fostered by conspecifics. The study is discussed in more detail in ‘Foster eggs or chicks with wild non-conspecifics (cross-fostering)’ and ‘Artificially incubate and hand-rear birds in captivity’.
- Flemming S.P. (1987) Natural and experimental adoption of piping plover chicks. Journal of Field Ornithology, 58, 270-273
- Midura A.M., Beyer S.M. & Kilpatrick H.J. (1991) An observation of human-induced adoption in piping plovers. Journal of Field Ornithology, 62, 429-431
- Reed C.E.M., Nilsson R.J. & Murray D.P. (1993) Cross-Fostering New Zealand's Black Stilt. The Journal of Wildlife Management, 57, 608-611