Growth-rate associated changes in the energy-requirements of tern chicks

To obtain infonnation on the energetic implications of intraspecific growth rate differences we measured the energy requirement for development in chicks of Common Tern Sterna hirundo and Sandwich Tern S. sandvicensis under laboratory conditions. Both maximum (kJ.day-l) and total gross energy intake for development (kJ during prefledging period) increased with growth rate and were reduced by almost 40% and 25%, respectively, in the slowest compared to the fastest growing individuals in each of the two species. These results imply that the range of food availability within which a chick can grow to adulthood, is wider than hitherto believed. However, one should bear in mind that slow growth also may result in higher nestling and postfledging mortality.