In the T&C playing fields I found about 20 Purple Martins perched on the light posts. In years past, these playing fields have been a roosting site for large groups of Purple Martins around this time of year. After breeding, martins assemble in large communal roosts which may or may not be related to their upcoming southward migration. In the next few weeks watch for larger and larger groups of these birds over the playing fields, in particular over the large baseball diamond. Here's a post I made about the martins gathering here in July of 2007.
Near the footbridge I was excited to find an adult Cooper's Hawk in the creek bed. Cooper's Hawks are common winter residents in our neighborhood, but only a few breed here during the summer. And it's always fortunate to see one because they usually stay hidden in the forest canopy. They specialize in hunting other birds, so they have relatively short wings and a long tail for maneuvering between tree branches when they're chasing their prey. This one soon flew back into the woods as I approached, but I got this poor picture showing its dark cap and red eye.