Monday, March 16, 2009
This week for ABC Wednesday I thought I was going to end up having to post about ice! But thankfully the weather has taken a major upturn and I am now able to think beyond the frozen tundra we have been enduring for the last few months to something that happens in the spring for many species. My post this week is I for Incubation.
This word comes from the Latin incubare which translates as 'to lie upon.' The word is used in various different contexts but today I am using it in terms of incubating eggs. For the female Green Honeycreeper Chlorophanes spiza in these pictures it means providing enough heat to allow the embryo to develop and then hatch successfully. She will hatch altricial chicks, that means the chicks are blind, bald and totally dependant on their parents to feed them, protect them and keep them warm.
In contrast, when the Button Quail Coturnix chinensis has successfully incubated her eggs to hatch, her work is largely done. She hatches precocial chicks which have downy feathers, their eyes are open, they are fully mobile and able to forage for themselves. When alarmed she will crouch and spread her wings to cover the hatchlings.
Reptiles have a much more 'hands-off' approach to incubation. Animals like turtles and crocodiles bury their eggs in the ground or decaying vegetation and depending on how warm the eggs get, this will define the gender of the emerging hatchlings. For example, the Nile Crocodile Crocodylus niloticus, if the temperature inside the nest is below 89.1 °F, or above 94.1 °F, the offspring will be female. Males can only be born if the temperature is within that narrow 5-degree range.
For the Blandings Turtles Emydoidea blandingii that we work with in our conservation project more females are produced at higher incubation temperatures and more males are produced at lower incubation temperatures.
For many great 'I' posts, check out ABC Wednesday.
Photo Credits - CJT & Dan Thompson
- ► 2011 (25)
- ► 2010 (32)
- ▼ March (8)