It didn't have a grey cap, (here's a side view
) so I'm leaning to the Trogon too. I just spent an hour looking through 20 pages of Google web images of Trogons, but as most of the birds shown are male, I couldn't spot it for sure. I'm wondering if it's the mate of the motmot (also from the Trogon family) that is often in my garden. The male has a racquet tail though, and this one doesn't.
I have only one guidebook, "A Photographic Guide to Birds of Costa Rica". Unfortunately there are only 252 species shown, less than one third that occur in this country. Books are incredibly expensive here, but in retrospect, I should have bypassed the vastly expensive one, and bought the horrendously expensive one!
Thanks bhs, I appreciate your time and effort! Edited to add:
Heavens, I think I just found her - I checked the grey capped cuckoos, and on the image page was a Squirrel Cuckoo
. I think that's the same bird?