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Temperature-dependent sex ratio in a bird.
1Animal Behaviour Laboratory, Department of Psychology, Macquarie University, Sydney, NSW 2109, Australia. ann@galliform.bhs.mq.edu.au
Biology Letters
|December 7, 2006
Summary
Incubation temperature influences sex ratios in Australian brush-turkeys, with skewed ratios at extreme temperatures. This temperature-sensitive embryo mortality, not sex chromosomes, determines offspring sex in these unique birds.
Area of Science:
- Avian biology
- Reproductive ecology
- Thermoregulation
Background:
- Incubation temperature's role in sex determination is well-established in reptiles but largely unproven in birds.
- Megapodes, a unique avian group, utilize environmental heat for incubation, presenting a novel system to study temperature effects on reproduction.
Purpose of the Study:
- To investigate the impact of incubation temperature on sex ratios in the Australian brush-turkey (Alectura lathami).
- To explore the underlying mechanisms of temperature-influenced sex determination in megapodes.
Main Methods:
- Controlled incubation experiments manipulating temperatures.
- Monitoring of hatching success and sex ratios across different temperature regimes.
- Analysis of chick weight and size in relation to incubation temperature.
Main Results:
- Incubation temperature significantly affected sex ratios in Australian brush-turkeys.
- Lower temperatures produced more males, higher temperatures produced more females, and intermediate temperatures yielded a 1:1 sex ratio.
- Chick weight was reduced at lower temperatures, but size was unaffected.
Conclusions:
- Temperature-dependent sex-biased embryo mortality, rather than temperature-dependent sex determination, is the likely mechanism for skewed sex ratios in megapodes.
- This finding challenges conventional understanding of sex determination in birds and highlights megapode uniqueness.
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