This is sort of continuing in the same vein of the last post in terms of what is visiting my backyard this fall. I love Golden-crowned Kinglets, and they love my 2 Hackberry trees. This fall they seem to be particularly numerous. In fact, Cornell Lab's Birds of North America site says:
Formerly breeding almost exclusively in the remote, boreal spruce-fir (Picea-Abies) forests of North America, the diminutive Golden-crowned Kinglet has been expanding its breeding range southward at lower elevations into spruce plantings in Pennsylvania, Illinois, Indiana, and Ohio and into white pine hemlock (Pinus strobus-Tsuga) forests in eastern Tennessee, northeastern Georgia, and the western Carolinas.
So the southward expansion of their breeding range may possibly explain why I have been seeing them with greater frequency in this area, which is just north of Chicago. Within this breeding range, R. satrapa is very much tied to old growth conifer forests. There has been a lot of rehabilitation of this type of habitat, and most likely this has helped their numbers in the eastern part (my part!) of the range. In any regard, when the leaves of the hackberries turn bright yellow in fall, I know to look up to find these little birds busily flitting about the branches.