Size, organic composition, and energy content of Leach's storm-petrel ( Oceanodroma leucorhoa ) eggs with reference to position in the precocial–altricial spectrum and breeding ecology

• Published in: Canadian Journal of Zoology
• Main Authors: Montevecchi, W. A., Kirkham, I. R., Roby, D. D., Brink, K. L.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1983
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Oceanodroma leucorhoa
• Online Access: http://dx.doi.org/10.1139/z83-195; http://www.nrcresearchpress.com/doi/pdf/10.1139/z83-195

Leach s storm-petrel eggs are very similar in composition to those of birds whose young develop precocially. In comparison with altricial species, eggs are relatively large (22% of adult mass), contain large yolks (41% of fresh egg contents) and have high yolk to albumen ratios. As in other precocial species, water content was low, making up 70% of the whole egg, 87% of the albumen, and 50% of the yolk, but accounted for much intraspecific variation in egg mass. The low water content is notable in view of the petrel's long incubation period, though low porosity of the eggshell and high humidity in the nest burrow must help the embryo conserve water. High lipid levels in the yolk (27%) are similar to those of precocial birds. Fresh yolk and albumen each contained 14% protein. About 80% (55.3 ± 2.5 kJ) of the total energy in the egg (60.7 ± 3.8 kJ) was contained in the yolk. The energy density of wet egg contents (7.27 ± 0.48 kJ/g) falls in the range of precocial birds. The egg's high energy content can be explained in terms of the maintenance requirements of the embryo during the long incubation period and the precocity of the hatchling. On the basis of standard metabolic rate estimates and interspecific comparisons, it does not appear to be energetically costly for a female to produce an egg. Single egg clutches and absence of relaying following egg loss suggest that the pelagic feeding ecology of Leach's storm-petrel imposes severe constraints on parental feeding rates and meal size, which effectively limit viable brood size to one.