@Chlidonias I have seen quite a number of hummingbird species in Costa Rica, Ecuador and in lesser extent Panama, and only a few I could identify at first sight. Some are very distinctive like the Violet Sabrewing, but many are quite alike. To make it even more difficult, male and female of the same species can look very different. Take the Purple-throated mountaingem for example, a species I saw recently in Chiriquí and some years ago in Selvatura: male is dark green with blue crown and purple throat, female has no crown and a orange throat and belly. So, my procedure with hummingsbirds was to take a lot of photos and checking these with my bird guide on the side back in the hotel.
I'm used to sunbirds, which may have similar iridescent plumage, and where the sexes are quite different (and females of several species tend to look similar) - but hummingbirds have always struck me as probably being more difficult than sunbirds.
I would agree with AWP here.......ID of some species is pretty easy since they have a feature (size, colour, tail shape or length) that is diagnostic, but many in Costa Rica are green and roughly the same size. You do get your eye in after a while though. I also just took lots of pictures of everything I saw, and then used a field guide and help of a local birder to finalise it. In the end I found that I had pics of many more different species than I had originally thought.
