The afformentioned are all good tips...Merritt Island if you have transport and don't mind taking a 30-40 minute drive...Gatorland is close...and you might try Lake Toho as well for possible eagle sightings. On Disney grounds, there are a few places to reliably find birds...there is a nice path running through the forest between Wilderness Lodge and Fort Wilderness Campground...the grounds of Saratoga Springs from the Treehouse Villas on one end, to the walkway from Congress Park to Marketplace on the other, are filled with trees, near water, and always has a good diversity of water birds and tree birds. The boat from Marketplace to Port Orleans goes through narrow canals with lots of water birds. And the pathway from Boardwalk Resort to Disney's Hollywood Studios is about 3/4 mile, and follows a waterway on one side and lots of trees along the other. Even within the theme parks, you will always reliably find birds, especially egrets, herons, cormorants, grebes, ibis, and various ducks.
As for temps, I'd amend the above - by May, you're more likely going to see temps in the UPPER 80s and quite possibly 90s. The past 3 years have been progressively hotter and for much longer than ever before in Florida history - while most of the US and Europe has been walloped by cold winters, we've had 3 of the warmest winters on record in our state's history for the past 3 years...by April, we're deep into the upper 80s and water temps have moved up to 84-86 degrees. May, the humidity returns full-force, usually in the mid-80% range...so it's sweat-city. Drink lots of water!