Niedrige Ei- und Körpertemperatur („Hypothermie“) bei brütenden Gelbschnabelsturmtauchern (Calonectris diomedea)
Body and egg temperatures of Cory's Shearwater were recorded in an Aegean colony. Body temperatures of breeding birds were 2 ° C lower than those of non-breeding, resting adults and accounted for 36.7±0.41 ° C in ♂ and 37.6±0.59 ° C in ♀. Incubation temperature, determined telemetrically inside incubated eggs, was 29.6±0.6° C.
Comparative egg attendance patterns of incubating polar petrels
Background The internal environment of eggs in most birds is regulated by transferring heat energy through contact incubation, maintaining nest microclimate, and frequent egg turning by the incubating parent on its nest. However, we lack information about egg attendance patterns in birds that breed in polar environments where variations in life history are expected to influence incubation behavior. Moreover, crevice/burrow nesting petrels in high-latitude regions are known for periodically leaving their egg unattended (hereafter ‘egg neglect’), but there is little reporting on the internal condition of unattended eggs. At Dumont d’Urville Station, Antarctica, we studied the incubation behavior of 24 snow ( Pagodroma nivea ) and 15 Cape ( Daption capense ) petrel pairs using egg loggers that recorded egg turning rates, orientation changes, and temperatures at 1 Hz for durations of 3–6 days. Results Egg turning frequency (1.31 ± 0.33 vs. 1.38 ± 0.39 turns h −1 ), angle change per turn (43.1 ± 43.2 vs. 48.6 ± 43.7° turn −1 ), and egg temperature (34.1 ± 2.3 vs. 34.1 ± 2.0 °C) were nearly identical for snow and Cape petrels, respectively. However, egg neglect was only observed in snow petrel nests (based on egg temperature changes) where loggers recorded mean durations of 1.34 ± 1.15 days (maximum duration of 3.63 days). During periods of neglect, eggs cooled to 5.5 ± 1.8 °C over an average of 91 min, but were rewarmed by parents in only 76 min at a rate of 0.33 °C min −1 . Conclusions Egg temperatures of both species during regular incubation were within 1–2 °C of other high-latitude petrel species, but neglected snow petrel eggs remained several degrees above freezing, which was likely attributed to crevice nesting where neglected eggs are buffered by environmental conditions. Using egg rewarming rates, thermal capacity of eggs, and published metabolic rates, we estimate egg rewarming costs in snow petrels to be 1.5 to 1.9 × BMR. Excluding egg neglect periods, turning rates for both petrel species were lower than other seabirds studied using biologging devices, which may be associated with the prolonged incubation periods that are characteristic of procellariiform seabirds.
Metabolism of Avian Embryos: Ontogeny of Oxygen Consumption in the Rhea and Emu
Oxygen consumption of Rhea (Rhea americana) and Emu (Dromiceius novaehollandiae) eggs increases exponentially during the first 70% of incubation and reaches a maximum about three-quarters of the way through incubation. Rate of O₂ consumption then declines to about 75% of the peak value, increasing again just prior to pipping. We suggest the decline in rate of O₂ consumption is due to a decline in growth rate, and that growth of the embryo of ratites is essentially complete at the time of the peak in O₂ consumption. Completion of growth prior to the normal end of incubation may permit ratite eggs of different ages to synchronize hatching within a clutch. Rates of O₂ consumption just prior to the initiation of pulmonary respiration are 104 ± 7 cm³ h⁻¹ in Rhea eggs and 75 ± 7 cm³ h⁻¹ in Emu eggs. Calculated and measured air-cell gas tensions at this stage of incubation vary systematically with egg size between species of birds. Large eggs have higher air-cell O₂ tensions and lower air-cell CO₂ tensions than do small eggs. Water vapor conductance of Emu eggs is 46.2 ± 9.6 mg·day⁻¹ torr⁻¹, much lower than predicted on the basis of egg size and incubation period.