Gas conductance and metabolism of shorebird eggs: variation within and between species

Abstract

Fresh egg mass (M 0; g), water vapor conductance of the egg shell (G H 2O ; mg·[Torr·d] −1), and neonate mass (M n; g) were measured in the ruff ( Philomachus pugnax), common redshank ( Tringa totanus), northern lapwing ( Vanellus vanellus), black-tailed godwit ( Limosa limosa), and Eurasian curlew ( Numenius arquata). In addition, the development of embryonic O 2 consumption (Ṁ O 2 ; ml·d −1) and CO 2 production (Ṁ CO 2 ; ml·d −1) were measured in these species, except the ruff. In northern lapwing and black-tailed godwit eggs the coefficients of variation for G H 2O were 3.8 and 2.3 times higher, respectively, than those for M 0. In these two species only about 10% of the variation for G H 2O was attributable to M 0, and about 77% to differences between clutches, suggesting a strong maternal component. In the northern lapwing, embryonic Ṁ O 2 plateaued prior to internal pipping, but not in the common redshank and black-tailed godwit. The latter result is in contrast to embryonic patterns previously described for other precocial species. In shorebirds the occurrence of an embryonic Ṁ O 2 plateau is not related to the neonatal level of cold-induced thermogenesis.