When we have warm days in the winter something alerts the basking turtles and up to the pond's surface they come. It always amazes me -- exactly what triggers the behavior? Water temperature changes slowly so I don't think that alerts them. So what, then? I must find a herpetologist and ask.
If you know, please leave a comment...
The turtle above is a male yellowbelly slider (Trachemys scripta scripta). Sliders are very common here.
A log full of basking turtles. If we could have gotten close enough, you would see that the backs of many of these turtles are covered with mud and algae, signs of where they are spending most of their winter days.