Temperature regulation in mounds of three sympatric species of megapode (Aves : Megapodiidae) in Papua New Guinea: testing the 'Seymour Model'

Abstract

Most megapode species rake organic material into mounds in which they incubate their eggs. To test predictions of a model proposed for temperature regulation in incubation mounds (the ‘Seymour Model’), I collected data on the physical characteristics of these mounds of the sympatric wattled brush-turkey (Aepypodius arfakianus), brown-collared talegalla (Talegalla jobiensis) and New Guinea megapode (Megapodius decollatus) in Papua New Guinea. Data from mounds supported several predictions of the Seymour Model: (1) there is a critical mass needed for mounds to heat to incubation temperatures, (2) mounds are stable homeotherms, (3) mounds cool after they are abandoned, and (4) mounds with different proportions of organic material differ in size. Data did not support predictions that (1) mound size will change with changes in ambient air temperature, and (2) mounds in high-rainfall areas will be convex to shed water. Mounds of New Guinea megapodes and brown-collared talegallas were similar and differed from those of wattled brush-turkeys in size, composition, temperature profile and location of eggs. These differences were consistent with the Seymour Model. The Seymour Model is robust enough to explain differences in mounds of sympatric megapodes, which differ in their taxonomy, behaviour and ecology.