I have muscovies which are NOT small birds. My duck house is a hoop coop made of cattle fencing. Over the top is a tarp which is relatively tight. the bottom 4 feet also has a layer of redbrand wire 2X4" Seriously can't imagine a 7 pound hen getting through that. never had a predator problem but the last few days the hen hatching ducklings has escaped. she comes back to perch on top when she cant get back in. On Sunday I ran some more wire over the back arch thinking maybe she was getting on top the straw bales and somehow getting through the cattle fencing 4 feet up and escaping through the cattle panels ( but under the tarp). Once again she escaped. Yesterday evening the eggs started hatching. So being out of hardwire, I added chicken wire to the front arch and over the door. Predators are not a problem and I have 6 adult ducks currently living down at the pond, but the ducklings have a hard time surviving the turtles till they get bigger so I really want to keep the ducklings in the coop a few weeks and the best way to do that is keep mamma there. I sure hope I have finally found her escape route. I have a second hen sitting in the coop but her eggs are a month out from hatching so she isn't as antsy and I havent seen her leave the nest at all. Please keep your fingers crossed she doesnt escape again. Last clutch to make it to the pond at hatch, I have 3 out of 13.