I've had a small nest box in my backyard for years. I think this may be the third or fourth rendition of the box. It's a small box suited to small birds. The entrance is high up in the box and is a small diameter to let in only little birds.
Over the years I've had many residents that have raised families. It's fascinating to first watch for nest competition , nest building, egg incubation, young birds and then leaving the nest. I've had Red breasted nuthatches, Tree swallows, Black-capped chickadees, Boreal chickadees and House sparrows. Several nests were abandoned.
Now bout a week ago I noticed a small gray bird quickly enter and leave the box. It was so fast I couldn't identify the bird. I have no idea how long the birds were at the nest before I saw them. After a few days I could see that they were Boreal chickadees. Great! I get a bird family this summer.
Well, not so fast Red. Today house sparrows showed up. Actually quite a few House sparrows were at the nest. Then I noted House sparrows carrying nest material to the box. So the Boreal chickadees had to abandon their new nest.
It's sad to see bird's nests be destroyed . but I realize it is the order of the day in the wild. However, I will harass those dirty rotten House sparrows so that they will wish they'd never met me.
A great photo of a boreal chickadee by Angela Maclean