Years ago most of my bird pictures were taken at the nest. My hero of that time was Eric Hosking and he inspired me to follow this line. Today, not many people involve themselves with this type of approach, for various reasons. The main argument is that it harms the birds. This is true if you do not know how the basic methods need to be employed, and I think that a lot of photographers of this moment cant be asked to learn the techniques, and want immediate results. As a result, you see a lot of cliched pictures of subjects taken at well known sites or others using "rent-a-hide.
Pentax k1000, Agfa, 200mm, Tower hide, Hanimex flash.