Ann and I just returned from a trip to Belize. We spent four of our days there birding. I was afraid that with our early warm-up here there would be nothing left. Fortunately, there were many birds. We birded in two areas: Lamanai and Cockscomb/Hopkins. We were fortunate to have two really great guides and we wanted to pass along their contact information in case you ever head down that way.
We stayed at Lamanai Outpost Lodge in the north and used their resident birder, Eduardo Ruano (<eduardo...>). He was amazing. He'd put the scope on a bird five layers deep in the brush. He'd hear things we couldn't and then find the bird. We birded four different areas on foot and by boat (be sure to go out for the nighttime Spotlight Nature Safari) and saw 125 species.
Later, we birded with Jonathan Urbina (<anibru.feathers...>) in the Cockscomb/Hopkins area in the south. Jonathan's approach to birding was a bit different. We drove to several different spots and then waited for the birds to come. No calling, though a very little pishing. Sure enough, the birds came. Cockscomb is jungle which makes it darn near impossible to see anything in the jungle itself. Jonathan's approach was to find specific habitats with a clearing and then survey the edges. He could also hear more birds than we could and identify them all. In all we saw 111 species. Jonathan works closely with Roni Martinez (<roni.a.martinez...>) and is out in the field a lot. If you can't reach him directly, contact Roni.
Both of these guides are really great people and fantastic birders. We had a great time with them. Give them a try when you're in the area.