Regional differences in shell conductance and pore density of avian eggs

Minidesiccators were attached to the middle and to the blunt and pointed ends of avian eggs of six different species and from their mass change over time the regional shell gas conductance was determined. Later the pore density and shell thickness of these areas were measured. All species showed a decline in regional shell conductance and pore density from the blunt end to the pointed end. With the blunt end over the air cell as a reference point, the regional conductance of the middle and the pointed end declined to 88 and 63%, while pore density fell to 81 and 63%, respectively. The six species represent four orders of birds, and the results suggest that differences in regional conductance may be a relatively common characteristic of bird eggs, that differences in regional pore conductance are proportional to the pore density, and that therefore the conductance of individual pores in any one species is relatively constant.