Egg Temperature and Embryo Metabolism in Some High-Latitude Procellariiform Birds

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Abstract
The embryos of Procellariiformes develop slowly, reportedly, at least in part, as a result of low incubation temperatures, and some species such as Wilson's and Leach's storm petrels experience long periods of chilling. Incubation temperatures of eggs of Leach's storm petrel (on Kent Island, New Brunswick), Wilson's storm petrel, and the southern giant fulmar (Palmer Station, Antarctica) averaged 35.9, 35.7, and 35.5 C, respectively. These are well within the range of temperatures for other species of birds and indicate that the prolonged incubation periods of petrels are not attributable to low incubation temperatures. We measured the depressing effect of cooling ( ) on rate of heartbeat of small embryos and rate of oxygen consumption of larger embryos. Values of increased at lower temperatures but in most cases did not differ from, or in some cases even exceeded, the values for embryos of species that lack cooling tolerance. Large embryos of the giant fulmar, which has slow embryonic development but continuous incubation, did not survive prolonged chilling, indicating that not all slowly developing embryos tolerate protracted cooling, at least in their late stages of development. Rates of oxygen consumption by storm petrel embryos were about two-thirds the level of the similarsized but rapidly growing Japanese quail embryo. Giant fulmar embryos exhibited low rates of oxygen consumption, as do other Procellariiformes, but, surprisingly, so did the rapidly growing skua embryos.