Oological data on egg and breeding characteristics of brown pelicans

Abstract

Mean clutch size in 236 sets of North American Brown Pelican eggs was 2.95 and did not vary geographically between North American populations. Shell weight varied from 8.05 g to 10.99 g along a geographic continuum. Shell thickness averaged 0.510 mm for P&cams occidentalis occidentalis, 0.5544557 mm for P. IJ. carolinensis, and 0.569- 0.579 mm for P. o. cdifornicus. The ranges of breeding dates for the more southern populations were wider than those of northern ones.....Small numbers of eggs taken in Texas and Florida after 1949 were 20 per cent below normal weight; 1962 eggs from California were 26 per cent below normal; and three taken in Panama, 15 per cent below normal. Shell thickness had likewise decreased 15-27 per cent.