Providing evidence to improve practice

Individual study: Impact of supplementary feeding on breeding behaviour of Florida scrub-jays Aphelocoma coerulescens at Archbold Biological Station, Florida, USA

Published source details

Schoech S.J (1996) The effect of supplemental food on body condition and the timing of reproduction in a cooperative breeder, the Florida scrub-jay. The Condor, 98, 234-244


As part of an investigation into the role of food availability in the decision (whether and) when to breed, this study investigated the impact of supplementary food provision on the reproductive behaviour of the cooperatively breeding Florida scrub-jay Aphelocoma coerulescens at Archbold Biological Station (27°10'N, 81°21'W), Florida, south-eastern USA.



During 1993, from late January until females had finished laying, dried dog food, peanuts and mealworms were provided twice daily at feeding stations in the middle of the territories of 10 scrub-jay breeding groups (comprising 10 breeding pairs and 23 non-breeders). A further 32 groups (32 breeding pairs and 23 non-breeders) were left unsupplemented, as controls.

Nests of supplemented and control groups were checked every two to three days to determine the clutch initiation date and clutch size. Following their capture in Potter traps and mist-nets, adult scrub-jays were weighed, and their level of body lipids (a measure of body condition) was estimated based on their lean body mass (estimated using total body electrical conductivity with a Dickeyjohn DjME100 Ground Meat Tester).



Breeding females in food-supplemented groups initiated clutches significantly (on average 16 days) earlier than control females. No significant difference was detected between the average clutch size of supplemented and control females. Supplementary feeding was found to have a significant effect on the body condition of adults, with the average body lipid levels of supplemented birds nearly four times higher than for control birds among breeding females, and nearly two times higher among breeding adults.
No significant difference was observed in the number of supplemented (five of 23) and unsupplemented (four of 23) non-breeders that became ‘breeders’ (i.e. paired courted and established a territory) during 1993, suggesting that food availability was not the only factor affecting the decision to forgo breeding in this species.
Note: If using or referring to this published study, please read and quote the original paper, which can be accessed from