Physiological ecology of incubation of ptarmigan eggs at high and low altitudes
Carey, C. & Martin, K. 1997: Physiological ecology of incubation of ptarmigan eggs at high and low altitudes. - Wildl. Biol. 3: 211-218.
The broad altitudinal distribution of ptarmigan Lagopus spp. makes this group an excellent model with which to ask how morphological and physiological specializations foster successful reproduction of birds at their distributional limits. Eggshell conductance and permeability to gases, shell surface area, shell thickness, daily water loss, and egg volume were measured in willow ptarmigan Lagopus lagopus breeding at 720 m a.s.l. and white-tailed ptarmigan Lagopus leucurus breeding between 3,600 and 4,100 m a.s.l. Of these characteristics, only egg volume and shell surface area differed significantly between the two species. Since the rate of daily water loss is similar at the two breeding locations, embryos develop in similar hydric environments inside the shell. High altitude embryos facilitate oxygen delivery with acclimatory adjustments in certain cardiovascular and cellular characteristics.
Key words: egg mass, eggshell conductance, high altitude, incubation, water loss, white-tailed ptarmigan, willow ptarmigan
Cynthia Carey, Department of EPO Biology, University of Colorado, Boulder, Colorado 80309 USA
Kathy Martin, Canadian Wildlife Service, 5421 Robertson Road, Rural Route 1, Delta, British Columbia, Canada V4K 3N2
Associate Editor: R.J. Gutiérrez