When choosing attributes, start with those that are most prominent and certain. For example, if you cannot surely say that a bird is green (parakeet) or black (crow), but are uncertain, don't choose colour at all. Instead choose whatever is prominent - beak (pelican), crest (hoopoe). If there are too many results, you can always select more attributes to narrow it down.
Use the keyword search as a last resort - it searches in the description etc. but there's no guarantee that the word you search for will be present, even if it seems obvious.
Each bird has a link to the relevant Wikipedia page for more in-depth coverage.