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Providing evidence to improve practice

Individual study: Supplementary feeding may increase reproductive success and adult fitness in northern goshawks Accipiter gentilis in New Mexico, USA

Published source details

Ward J.M. & Kennedy P.L. (1996) Effects of Supplemental Food on Size and Survival of Juvenile Northern Goshawks. The Auk, 113, 200-208


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Provide supplementary food for raptors to increase adult survival Bird Conservation

A randomised, replicated and controlled trial in mixed conifer forests and scrub in New Mexico, USA, in 1992-3 (Ward & Kennedy 1996), found that northern goshawk Accipiter gentilis adults from territories provided with supplementary food during nesting were heavier than adults from control (unfed) territories, but sample sizes were too small for statistical tests (females: average of 1,007 g for six birds from fed territories vs. 975 g for five controls; males: average of 689 g for five fed territories vs. 660 g for two controls). Supplementary food consisted of dead Japanese quail Cortunix japonica provided every other day starting the day after hatching and continuing until most control birds left the area. This study also examined differences in chick growth and survival, discussed in ‘Provide supplementary food to increase reproductive success’.

 

Provide supplementary food for raptors to increase reproductive success Bird Conservation

A randomised, replicated and controlled trial in mixed conifer forests and scrub in New Mexico, USA, in 1992-3 (Ward & Kennedy 1996), found that northern goshawk Accipiter gentilis nestlings from territories supplied with supplementary food had significantly higher survival than those from control (unfed) territories in 1993 but not 1992 and only when chick, rather than nest was the unit of analysis (1993: 90% survival for ten fed chicks vs. 37% survival for eight controls; 80% survival for five fed nests vs. 40% survival for five controls; 1992: 80% survival for 15 fed chicks vs. 100% survival for 16 controls). The authors suggest that this is due to increased attendance by females, as most nestling losses were due to predation and there were no significant differences in nestling size between treatments (average of 590-682 g for fed chicks and 541-676 g for controls). Supplementary food consisted of dead Japanese quail Cortunix japonica provided every other day starting the day after hatching and continuing until most control birds left the area. This study also examined differences in adult goshawk weights whilst provisioning, discussed in ‘Provide supplementary food to increase adult survival’.