I never visit the Mere without an hour round the collection, as you say close ups of birds you rarely see close or are never likely to see ,Where else will you see a dozen Male Smew at a few feet :) I think my enjoyment of this stems from being a small child in a very poor family and my holiday each year was a single day in my Summer Holidays where my mother would take me to Southport for a day trip and when we got there knowing we had a very limited amount of money my mother used to say where do you want to go pick 2 places and I used to reply 3 places .The Bird Zoo ,The Aquarium, and Southport Zoo and those 3 places filled my day out for several years during the late 1960's,early 1970's,So I think the collection at Martin mere is an adult version of going back to those simpler times :)
I do agree Tim, I remember studying Smew at close quarters at Slimbridge and getting shots I could only dream of. I do know of a couple of unscrupulous wildlife photographers who, in the past, have passed off shots of birds in collections as wild birds!! Also the WWT have restocked birds into the wild in the past so as a conservation tool this works too
After distant views of both Temminck's Stint and Little Stint at Martin Mere, Tony and I wandered around the static collection listenening out for warblers. I remember Bill Oddie on Springwatch recommend the collection. I would too. Test your ID skills then marvel at plumage details close-up. The relative sizes of birds side by side changes too without optics - Lesser Whitefront Geese and Buffleheads are staggeringly tiny. As are captive Avocets. Wood Ducks are just beautiful close up. Some species of bird and animal most of us will only ever experience in a zoo or collection first. Either way our impressions will be different from the usual context in which we encounter them.