Birds in the greenhouse! Sounds kind of like "Snakes on a Plane" although not as problematic.
Nearly every year, we get a few wayward birds that fly into the greenhouse, more often the back greenhouse. Usually, I just duck down, walk behind the birds and shoo them towards the door and they fly out. This works unless the birds are young or dumb. This year, a young mockingbird got in greenhouse #3 and couldn't get out. I tried shooing, but although he'd fly toward the front, he'd veer off to the side instead of flying out the door. Mockingbirds can be nasty, but this one was just dazed and tired. He was flapping against the front wall, so I scooped him in a bucket, threw a box over the top end get him outside. He flew away unscathed.
Mourning doves are also difficult, because they're too dumb to fly out on their own. Usually have to throw a towel over them and rescue and release.
Recently, we had a tougher challenge. Walked into the greenhouse, heard a strange noise, looked up and saw a hummingbird hovering near the top of the greenhouse. Once, when I worked in the garden center, we had a hummingbird inside~we got it out eventually, but it took a while and wasn't easy. Luckily, John was home when this happened.
The poor thing was tired from hovering constantly. It perched on the frame around the fan on the back wall. John got up on the bench with a bucket, figuring he‘d scoop her (it was e female) into the bucket. The little thing hopped on the edge of the bucket end sat there. John handed me the bucket and I slowly walked out of the greenhouse with it perched there the whole time. It sat on the bucket a few minutes to recover then flew off and rested in a tree.
Then I go into greenhouse #2 and see a small wren hopping around on the floor. By the time I got John and we came back in, we couldn't see it. It was way in the back though, and we hadn‘t seen it fly out. Looked on the back wall and saw it stuck in the web of one of the large, writing spiders that live there, John released it and we scooted it out, only to be met by Lucy! She didn‘t hurt it~it hopped under a tree and eventually flew away. I'd much rather have toads in the greenhouse!