Maybe it’s already happened to you in years past: you walk into your garage, ready to take your first bike ride of the year now that it’s finally warm enough, but you lift your old helmet only to find that it is full of moss, leaves, and twigs. What?! You may think it’s a late April Fool’s joke, but actually it is the product of a lot of hard work by a small cavity-nesting bird that has found a safe place to put their home. Depending on where you live, it could be any number of species, but the most common by far are the Carolina Wren and House Wren.

Clockwise from top left, submissions are by Joe Hoelscher, David Hutchinson, Mike Smith, and Sophie Lyon.