I have just come from the bluebird trail that I have managed for 4 years now. Once again, I found the top off a box and the baby birds (about 3 days old last Monday) gone. Something (the trail is on a golf course but I am assuming a non-human predator) has become quite good at prying the lids off the boxes. This is the 5th time I have found this situation this year. Our boxes have slanted lids with a long piece of wood that slides into the box and (supposedly) is held in place behind a dowel. The lids are about an inch wider than the top of the box and need a firm grip on the edge to get them off (they don't come off by rocking them). 

I know that many of you have experience with different types of bluebird boxes and I would appreciate any help I can get about box designs where the tops are harder to get off. Maybe I should install some sort of latch? We need fairly easy (for humans) access to the box because we check them once a week and keep records on the broods. We also need to replace some of the older boxes so are interested in about where and how we can get new boxes.

Thanks,
Doris Brody