Harper EJ, MacDonald DW. 1999. Energy metabolizability and nutrient digestibility in the magpie (Pica pica). In Proceedings of the Third Conference on Zoo and Wildlife Nutrition, AZA Nutrition Advisory Group, Columbus, OH.
A number of studies have been conducted to determine energy requirements in avian species. However, this is a complex area and one which is driven by a number of factors. For example, environment is one of the major factors which governs energy requirements, and the metabolizable energy requirements of avians housed in controlled conditions probably do not reflect the normal basal requirements of free-living birds. Environmental temperature is a strong determinant, and energy requirements decline as temperature increases (NRC, 1984; Bryant and Furness, 1995; Prinzinger et al, 1989; Ellis, 1984). Phylogeny is also very influential in determining energy requirements in avian species, and species-dependent characteristics such as body conformation and composition, flight duration, posture and feather coverage all exert an effect; factors which complicate inter-species extrapolation of energy data and may explain why energy equations derived from data on one species do not correlate well with data derived from others.21_HARPFULL.pdf     16 KB