When wildlife conservationist Olya Weekley was a little kid, she noticed something incredible from her apartment window.

I was born and raised in Ukraine, and we were living on the third floor, and in the corner of our window in the kitchen every year, house martins came and made a mud nest.

They construct an enclosed nest from mud and spit, often under the eaves of homes and city buildings.

And my grandma would be furious because they would just make a whole big mess on the glass, and she would grumble about it and be like, "Oh, these darn house martins." But at the same time, we both would be glued to them and watching the parents come and feed the babies, and seeing the little yellow baby mouths sticking out.

And then eventually we could see each one of them leave the nest, and then we would wait for them to come back the next year.

[laughs]