First couple of photos show not only what the traps look like, but just how many customers we had. Chickadees and Sparrow in first one - male and female Cardinal with Sparrow in the second.
The third picture gives you a good look at what the door looks like - if this Chickadee steps on it, his own weight will make it shut.
Can you see the band on the Chickadee's leg? It tells us that this bird was not so unduly traumatized by his banding experience that he doesn't still stay around. You can also see in the enlarged last photo how safe the bands are - there is space between the band and the bird's leg, and obviously not altering his ability to go about his business.