Incubation energetics of the Laysan Albatross.

The energy expenditure of incubating and foraging Laysan Albatross (Diomedea immutabilis, mean body weight 3.07 kg) was estimated by means of the doubly-labelled water technique. During incubation, the energy expenditure was similar to that of resting birds that were not incubating an egg. The energy expenditure of foraging albatross (2072 kJ/day) was 2.6 times that of resting birds. It was concluded that the energy expenditure of the tropical Laysan Albatross was not less than that of species foraging over cold, high-latitude oceans. An energy budget compiled for an incubating pair of albatross revealed that the energy expenditure of the female was greater than that of the male bird, during the incubation period.

The initiation of pulmonary respiration in a bird embryo: blood and air cell gas tensions.

The gaseous stimuli for pipping and the initiation of pulmonary respiration were examined in th Wedge-tailed Shearwater (Puffinus pacificus) by measuring blood gas tensions in the chorioallantoic vein and air cell gas tensions (Pao2 and Paco2) prior to and during the pipping process. External pipping (shell fracture) was the first observed pipping event and preceded internal pipping (penetration of air cell and initiation of pulmonary ventilation). This sequence of cracking the eggshell prior to the initiation of pulmonary respiration resulted in higher Pao2 and lower Paco2 values than the pre-pip air cell gas tensions. Pip-cracks in the shell allow greater diffusion than could normally be obtained across the intact eggshell. This also favors the establishment of large partial pressure gradients of O2 and CO2 across the chorioallantois, thereby improving gas exchange across the inner resistance barrier. The gaseous stimuli for pipping may be attenuated and thus favor the 5-6 day pip-to-hatch interval in this species.

The initiation of pulmonary respiration in a bird embryo: tidal volume and frequency.

Pulmonary ventilation in embryos and hatchlings of the Wedge-tailed Shearwater (Puffinus pacificus), measured with a barometric plethysmograph, revealed a progressive rise in tidal volume (VT) and minute volume (VE) during the paranatal period to achieve hatchling levels. VT and VE in internally pipped eggs (penetration of air cell) was 0.06 ml +/- 0.03 (SD) and 3.11 ml . min-1 +/- 1.80, respectively. Ventilation was significantly higher (P less than 0.05) in eggs with pip-holes (VT = 0.15 ml +/- 0.04 and VE = 7.09 ml . min-1 +/- 2.76). A significant difference (P less than 0.05) was also obtained for VT and VE between embryos and hatchling chicks. The respiratory frequency (f) was approximately 47 breaths . min-1 for both embryos and chicks. Acute changes in ventilation were examined in response to 2% CO2, 5% CO2, and 10% CO2 in air. For embryos, VT increased significantly (P less than 0.05) only with 10% CO2 and was accompanied by a significant decrease (P less than 0.05) in f. Hatchling VT increased significantly (P less than 0.05) with each test gas and VE increased significantly (P less than 0.05) with acute exposure to 5% CO2, from 16.5 ml . min-1 +/- 2.0 in normoxic air to 53.9 ml . min-1 +/- 8.6. The shearwater embryo is relatively insensitive to high levels of CO2, suggesting a respiratory adaptation to naturally inspired air cell gas concentrations during the internal pipping phase and rebreathing.

Embryonic oxygen consumption and growth of Laysan and black-footed albatross.

The constraints placed on diffusive gas exchange by the eggshell and the adaptive features of embryonic respiration and metabolism in large Laysan and black-footed albatross eggs (300 g) during prolonged incubation (65 days) were examined in naturally incubated eggs on Sand Island, Midway, in the Northwestern Hawaiian Islands. A low eggshell gas conductance and slow growth rate were associated with a relatively low oxygen consumption (MO2) throughout incubation. Just prior to internal pipping (IP) of the inner shell membrane and penetration of the air space, the MO2 (pre-IP MO2) was approximately 1,250 ml O2 (STPD).day-1 for both species, resulting in air cell O2 and CO2 tensions of 106 and 40 Torr, respectively. During the 4- to 5-day pipping-to-hatching interval, O2 uptake increases rapidly as pulmonary respiration is initiated. Hatchling O2 consumption averaged 3,700 ml O2 (STPD).day-1 or about three times the pre-IP MO2. Data support the hypothesis that embryonic metabolism among Procellariiformes is related to the extent to which the incubation period deviates from the expected value based on initial egg mass.