Here's an idea for a cheap, homemade nestbox trap. My neighbor has a large horse barn and lets the House sparrows breed in it. I hear them cheep, cheep, cheeping when I walk by and after it's first year, I knew I'd have to do something. I learned last year that if I put up my nice (cheap), homemade trap between his barn (property line is the fence just behind the box) and all my bluebird / tree swallow and martin housing, that I frequently trap the HOSP before they interfere with any of my other nesting birds.
This is a 2 chamber nest box trap. The door on the left is a trap door for Trios that was sent to me by someone on the PMCA forum a while back. I just mounted it to the front of this 'box' that I screwed together out of left over wood. The other chamber has a Van Ert trap in it. On the back are 2 doors, 1 for each chamber.
I had a problem with the blue birds and tree swallows insisting on trying to nest here, so I finally closed down the box on the right and cut a smaller hole out of a sour cream lid, then duct-taped it over the larger hole on the door. Since then, I've only caught HOSP in this trap. The roof rests on top of the two T-posts and to keep it from tipping, I have 2 screws on each side, just far enough apart to let the trap slide down the t-posts.
Either I've gotten really lucky, or my idea of 'distract & intercept the HOSP' before they get to the other nest boxes was spot on. I like the portability of this trap too. I've actually opened the door and the HOSP refused to come out. So, I would lift the trap off the posts, take it home and put it in a large garbage bag and open the back door to get him / her out. Then just put the trap back.


