RUBEGA, M.A.*; HEATH, K.M.: Skeletal development in hatchling avocets and stilts: the effects of salt stress on growth and ossification.

Post-hatching skeletal development in non-galliform precocial birds is less well-known than is embryonic development, and the effects of stress during growth are even less studied. Many studies have shown that high salinity levels are lethal to hatchling birds, but the effects of sublethal levels of salt stress on ultimate adult form and function are completely unknown. We examined normal and salt-stressed American avocet (Recurvirostra americana) and black-necked stilt (Himantopus mexicanus) chicks (0 – 14 days post-hatching) for the effects of salt stress on skeletal development. Measurements of cleared and stained specimens revealed that salt stress stunted growth in avocets, but did not suppress ossification. Salt-stressed avocets were smaller because of reduced bone growth, but proportionally more ossified because ossification proceeded despite salt stress. The patterns of salinity effects on the development of the skeleton in stilts were more ambiguous. These patterns suggest that the ontogeny of ossification may be invariant, and thus may partly explain observations of reduced ultimate adult size in birds subjected to other forms of stress during the postnatal growth phase.