Wood Frogs are usually the first to start calling every spring, often before the snow and ice are gone. They often call for only one or two days, since they call and lay their eggs in vernal pools--bodies of water that dry up usually by late spring.
They were calling at Springbrook yesterday, and I was only able to get these poor quality photos. The pool is big this year--because of the big snow melt.
The males set up small territories in the middle of the pool. They call while floating on top of the open water, and they fight for the few open spaces. In the top photo you can see one approaching the closer one. The next picture I call a "muddle." Three or more males converge and "wrestle" underwater to determine who gets the spot. This lasts for five or ten seconds. And then five or ten minutes later it happens again.
Wood Frogs inflate air sacs on the sides of their upper chest area and expel the air to make their short croaking--barking calls. The easiest way to find them is to look for the ripples in the water that the frog makes when making the call.
You can see the air sacs on the lower photo--sorry for the quality.
These frogs were about 75 feet away so even with a 500 mm lens they were tiny in the view finder, and these pictures are cropped out of the original much bigger picture.
Still, it is always a great pleasure to hear the wood frogs the once every three or four years I am able to catch their calls on the one day they are there.