Action: Release birds in ‘coveys’
Key messagesRead our guidance on Key messages before continuing
- A replicated study in Saudi Arabia found that houbara bustard Chlamydotis undulata macqueenii survival was low when chicks were released in coveys with flightless females.
- A review of cackling goose Branta hutchinsii conservation and a replicated study in England found that geese and grey partridge Perdix perdix releases were more successful for birds released in coveys than for young birds released on their own or adults released in pairs.
Coveys are ‘family groups’ of birds (normally gamebirds): broods of chicks with an accompanying adult. Groups of birds may be safer from predators than individual chicks and the presence of parents or foster parents may also help survival.
Supporting evidence from individual studies
A replicated study reviewing a houbara bustard Chlamydotis undulata macqueenii release programme in central Saudi Arabia between 1991 and 1993 (Jaime et al. 1996) found that releasing coveys of chicks into a large (4 km2) enclosure designed to exclude mammalian predators had low levels of success. Eight coveys with a total of 15 chicks were released along with eight females (rendered flightless). Of these only five birds integrated into wild flocks with five leaving the enclosure and being predated by mammalian predators; two were killed inside the enclosure and three died of disease. Other release techniques and descriptions of the captive-breeding programme are discussed in ‘Use captive breeding to increase or maintain populations’, ‘Use artificial insemination in captive breeding’, ‘Release captive-bred individuals’, ‘Use holding pens at site of release’ and ‘Use holding pens at site of release and clip birds’ wings’.
A before-and-after study from the Aleutian Islands, Alaska, USA on the cackling goose Branta hutchinsii recovery programme (USFWS 2001) found that releasing geese in family groups proved a better strategy than releasing young geese (captive or wild, see ‘Release birds as adults or sub-adults, not juveniles’). The authors note that the release of captive-bred geese was not very successful overall. This study also investigates the effect of Arctic fox Alopex lugopus control on breeding islands (see ‘Predator control on islands’).
A replicated study on four farms in Gloucestershire and Oxfordshire, England, in 2007 (Rantanen et al. 2010) found that grey partridge Perdix perdix released in coveys in autumn had significantly higher survival (78% survival of 92 monitored birds over 13 days) than adult birds released in pairs in spring (42% survival for 70 birds). The authors suggest that the differences were due to different habitat use: spring-released birds spent a lot of time in fields and field margins, whilst autumn birds spent more time in game cover crops. Use of field margins was negatively associated with survival, whilst use of crops was positively associated.
- Jaime M.S., Combreau O., Seddon P.J., Paillat P. & van Heezik Y. (1996) Restoration of Chlamydotis undulata macqueenii (Houbara Bustard) Populations in Saudi Arabia: A Progress Report. Restoration Ecology, 4, 81-87
- (2001) Aleutian Canada goose road to recovery. U.S. Fish & Wildlife Service report.
- Rantanen E.M., Buner F., Riordan P., Sotherton N. & Macdonald D.W. (2010) Habitat preferences and survival in wildlife reintroductions: an ecological trap in reintroduced grey partridges. Journal of Applied Ecology, 47, 1357-1364