There's no question that Trinidad is the prime birdwatching site in Trinidad and Tobago, but that doesn't mean that Tobago isn't worthwhile too. There are a number of birds in Tobago which you won't see in Trinidad, and some of the birds which are common here aren't seen much in Trinidad.
Initially I wasn't too thrilled by the prospect of visiting Little Tobago, which my guidebook assured me was an "arid, hilly island" just off the North-East coast. I was told that it's good for viewing sea-birds, but somehow that didn't seem too exciting. However, I was pleasantly surprised, especially because of the flamboyant red-billed tropicbirds which nest on the island and the Brown Boobies, but also because of a good supply of colorful tropical birds from the mainland.
Tobago has an abundant supply of blue-crowned motmots and rufous-tailed jacamars, neither of which is seen as often on Trinidad (in fact, I didn't see either). Both of these are really spectacular birds, mostly because of their colors, but also because of their shapes.