What Mesh Size Should I Use for Small Birds?

24mm

This is the smallest standard mesh size, usually used only for hummingbirds. Some banders prefer this size for capturing kinglets and the smallest wood warblers, but birds even as small as Song Sparrows will sometimes bounce out of this net; species that take sizes larger than 0 or OA are best captured with a larger size mesh.

30mm - 32mm

This net works well at capturing typical wood warblers, wrens, smaller sparrows (Chipping, Field, etc.). Loosely set, it will capture birds as large as Northern Cardinals, but it works best for birds that take sizes 0 and 1.

36mm - 38mm

36mm and 38mm mesh is the "all-purpose" size for a wide range of passerines. Although hummingbird, chickadees, and kinglets may slip through this mesh, with enough bag it will usually catch wood warblers and sparrows, plus most birds that take 1A or 1B band sizes.

60mm 

This net is ideal for jays, all but the smallest woodpeckers, mourning doves, robins, grackles, etc. It's also best for small owls and small raptors. Birds the size of chickadees and wood warblers can slip through almost without stopping. In general, this size works well with birds that wear band sizes 2 through 5.

-Bill Hilton, Jr