Journal Article

Shell resistance and evaporative water loss from bird chicken eggs: effects of wind speed and egg size

Weinheimer, Christina J., Spotila, James R., Paganelli, Charles V.

1981

Overview

Wind speed had a negligible effect on the rate of evaporative water loss from chicken eggs. Mean water loss was 0.132 mg cm⁻² h⁻¹ in still air, and 0.138 mg cm⁻² h⁻¹ at 400 cm s⁻¹. Boundary-layer resistance ($r_{b}$) decreased from 2.17 s cm⁻¹ in still air, to 0.91 s cm⁻¹ at 100 cm s⁻¹, to 0.54 s cm⁻¹ at 400 cm s⁻¹. The boundary layer had no effect on water loss because shell resistance ($r_{i}$) was the limiting variable with values of 384.0 s cm⁻¹ at still air, 385.0 s cm⁻¹ at 100 cm s⁻¹, and 374.9 s cm⁻¹ at 400 cm s⁻¹. Shell resistance changed with time. During the first 2 h of our experiment in still air,$r_{i}$was 294 s cm⁻¹ and gradually increased during hours 2-5 and 5-24 to 366 and 395 s cm⁻¹. This change was less apparent at 100 and 400 cm s⁻¹ wind speeds. Boundary-layer resistance increased as egg size increased. For a finch egg (0.8 g), a goose egg (190 g), and an ostrich egg (1,480 g)$r_{b}$was 1.63, 2.40, and 5.00 s cm⁻¹, respectively. Boundary-layer effects and wind speed are of little importance in the gas exchange of bird eggs, even the very large eggs of the ostrich and recently extinct elephant bird, Aepyornis.

• Publisher: University of Chicago Press
• Subject: Bird nesting / Birds / Boundary layers / Chicken eggs / chickens / Desiccators / Eggs / Evaporation / Water loss / Water vapor / Wind velocity