Spring and early summer is the mating/nesting season for many of the inhabitants of the South
Bay Parks. Turkeys are everywhere, and the males are showing their tail fans to impress the females. 
Around my neck of the woods, Santa Teresa County Park is a great place to see turkeys. Even closer to home, the “unofficial” Coyote Los Alamitos Canal Trail that runs behind my house in the Santa Teresa Foothills is also a good spot to see the amorous gobblers (more on that unofficial trail below). Here is a Quicktime video of some of these turkeys that I took on the canal trail.
Geese and Ducks are also in the mating mood, and during last weekend’s stroll
around Almaden Lake I encountered numerous fowl sitting on eggs. Almaden lake is also a great place to see egrets and other birds. There is a small “bird sanctuary” island in the middle of the small lake, and if you are patient it’s a good 
place to take pictures of birds in flight as many of them fly frequently between the island and the shore.
Meanwhile, over at the Palo Alto Baylands, the Barn Swallows are busily building mud nests in the rafters of the visitors’ center. It’s quite a sight to see as hundreds of swallows swarm back and forth between the visitors’ center and the mudflats where they gather up the mud used to build their nests. I believe the birds actually swallow and then regurgitate the mud at the nest. See the photo below. If you’ve never seen this spectacle before I strongly
encourage you to visit the Baylands in the next few weeks.
I also want to take a moment here to discuss the unoffical Coyote Los Alamitos Canal Trail. The San Jose
water department has an easment alongside the canal for this land, but most of it is owned by private individuals. The trail is posted with several “no trespassing” signs but if you visit the trail on the weekend you will see that literally hundreds of joggers and bike riders readily ignore them. I’ve found this trail to be a very accessible 
place to see wildlife. In addition to the turkeys shown in the video link above, I’ve encountered snakes, rabbits, bobcats and hundreds of lizards on my evening walks or bike rides.
There are several reasons often given for why the city has not been able to make this a legal trail. One of the primary reason usually touted is that the residents who live along the
trail value want to preserve their privacy. This is a totally bogus argument since the trail is already
heavily used and making it official would assure that it is maintained and patrolled on some regular basis. My backyard is only about 100ft from the trail and I would strongly welcome the city turning it into an official trail that I could enjoy without concern that I am breaking the law.
Ronad Horii has a web page with lots of information about and pictures of the Coyote Los Alamitos Canal trail.