Re: Megapode nest heating question

[Dann Pigdon <dannj@alphalink.com.au>]

On Thu, Aug 12th, 2010 at 10:48 AM, GSP1954@aol.com wrote:

> Does any know how much WARMER than the 
> GROUND TEMPERATURE the EGG TEMPERATURE in plant fermenting megapode nests can 
> get? Am looking for the maximum differential. 

You would obviously need to know both maximum and minimum daily surface 
temperatures at the 
nest site in order to get the maximum temperature difference. Megapode 
researchers have 
obviously measured nest temperatures, but I wonder how many have also measured 
surface 
temperatures at the same time?

Malleefowls have a 60-90 day incubation period, with a breeding season between 
September (early 
spring) and March (early autumn). Given the relatively constant incubation 
temperatures in 
Malleefowl mounds (32-34C), the daytime surface temperature in the Mallee would 
actually be 
higher than the nest temperature during the summer months (December to 
February). Mean daily 
minimums tend to drop to around 15-16C during mid summer, and to as low as 6C 
in September 
(the start of the breeding season). These are of course air temperatures, so 
the temperature of the 
substrate might be a few degrees warmer depending on how much daytime heat thay 
retain.

Early on in the breeding season, nest temperatures might be as much as 25C 
higher than surface 
temperatues during the coolest parts of the night (at a guess). That would be 
when the amount of 
decomposing plant matter in the nest was at its maximum, so it's not unexpected.

Towards the end of the breeding season, when the amount of decomposing plant 
matter remaining 
in the nest mound is low, Malleefowls are known to remove sediment from the top 
of the nest 
mound in order to boost the internal temperature via solar energy:
http://www.malleefowl.com.au/malleefowl.aspx

-- 
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Dann Pigdon
Spatial Data Analyst               Australian Dinosaurs
Melbourne, Australia               http://home.alphalink.com.au/~dannj
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