Megapods are the only birds that rely upon external heat sources for incubation. In Australian brush-turkeys Alectura lathami, males build large mounds of organic material, in which several females then bury their eggs. Incubation heat is produced by microbial decomposition of the organic material and can range from 30-38 degrees Celsius, averaging 34 degrees Celsius. We incubated freshly-laid eggs at 31 degrees Celsius, 34 degrees Celsius and 36 degree Celsius and found that, while the ratio of males to females at 34 degrees Celsius was almost 1:1, there was a significant difference in sex ratio between 31 degrees Celsius and 36 degrees Celcius: more females hatched at the higher temperature and more males at the lower one. Chicks from the hot and cold temperatures were of similar size, but they differed considerably in weight. 'Cold' chicks were significantly lighter, most likely because they had used up all their yolk reserve during the much longer incubation period. Behavioural observations revealed that heavier hatchlings dug themselves out of their underground nests more rapidly. In nature, they would hence disperse with a larger remaining yolk reserve. Incubation temperature is thus likely to have an effect on survival. Results also raise the intriguing possibility that adults could actively manipulate sex ratios through the choice (by females) and maintenance (by males) of incubation sites. We anticipate that the effects of incubation temperature will prove to be critical for understanding the behavioural ecology of megapodes.
|Number of pages||1|
|Publication status||Published - 2005|
|Event||ASSAB/AES 2004 - Adelaide Zoo, South Australia|
Duration: 15 Apr 2004 → 19 Apr 2004
|City||Adelaide Zoo, South Australia|
|Period||15/04/04 → 19/04/04|