During the last several years I have done a number of organized natural history tours. Most of my experiences have been very positive. These included trips to Europe and Turkey. I found the leaders very knowledgeable of the best locations and the local plants, birds, and butterflies. A bonus for me was that they were often knowledgeable photographers as well. It was very helpful to have arrangements for accommodations and usually meals arranged by somewhat else when off the beaten path in another country and in another language. Participants are typically very interested in and often very knowledgeable of plants, birds and/or butterflies.
Two companies I have had very positive experiences with are Bob Gibbons’s Natural History Travel and Ian Green’s GreenTours. Both companies are based in England and cover many areas throughout the world. They typically stay in local moderate hotels and stay away from touristy locations. Another company recommended by fellow travelers is NatureTrek.
Even if you are not a group person I recommend looking at the catalogues or websites of natural history travel companies. They may give you ideas about places to go, what you might see there and when to go. When traveling independently, it doesn’t hurt to first check to see where the pros go. You might also find a trip you would like to do but wouldn’t want to try on your own.