by Carl Strang
The dark-eyed junco may be our most familiar winter visitor among the birds. They nest in Canada and the northern states, so we see them here only from September to April.
Their nesting habitat is forests, especially forest edges. What do they prefer in winter? Yesterday I showed how two local breeding birds prefer woodlands, to the near total avoidance of open areas. Such is not the case for juncos. At Mayslake Forest Preserve over two years I have a total of 36 observations in open habitats, 307 in savanna, and 61 in forest. Expectations based on the proportional acreage in those habitats are 125, 174 and 105, respectively. Though they spend some time in the open, and some time in forest, like Goldilocks they find the intermediate mix just right. Given that their winter diet is mainly seeds they pick up off the ground, this is not surprising as savannas provide both seeds and shelter, forests provide shelter but fewer seeds, and open areas have abundant seeds but limited shelter of the kind juncos like.
The other winter species for which I had enough data to look at habitat preference is the American tree sparrow.
Here the observations number 62 in the open, 55 in savanna, and 37 in forest. Corresponding expectations based on habitat areas are 48, 66, and 40. It will come as no surprise to readers familiar with this species that the open appears to be preferred, but these observations are not far from the expectations and in fact the difference is not statistically significant. It appears that the tree sparrows are taking full advantage of the seed stocks available in the open as well as the shelter provided by wooded habitats. They nest north of where juncos spend the summer, in open tundra areas and zones of mixed tundra and scattered trees, so the differences between the two species on their wintering grounds are consistent.