It’s always fun to get reacquainted with once familiar bird friends. Growing up in California most of these were common, everyday birds, but now having lived in MN for the past 35 years, they have become more exotic than common.
Acorn woodpeckers are not only beautiful to look at but fascinating to watch. They are close cousins of our Midwestern Red-headed Woodpecker, and share some of their interesting behaviors, like food caching and “helpers at the nest” in which last year’s offspring help feed the current crop of chicks.
A somewhat exotic bird, even by California standards — the Wrentit, whose closest relatives are the long-tailed Tits of Asia. This is the only American representative of that family. Its call reminds me of that of the Field Sparrow — a bouncing ping pong ball. The white iris is distinctive and unusual in birds.
Bewick’s Wren is a perky little bird that flits about in the brush, never still, unless it has stopped momentarily to scold you for getting too close. Its behavior is very similar to our Midwestern House Wren.
The western version of the Slate-colored Junco is so much prettier then the Midwestern race. On the west coast it is called an Oregon Junco, but it is genetically pretty much the same bird we see in the rest of North America. I’m not sure if this race is migratory or not,
White-crowned Sparrows are found everywhere in brushy habitat on the west coast. Most of them breed at northern latitudes all the way into Alaska or in high montane meadows, but spend the winter in mild California climates. This was the bird that got me interested in field biology research back in my undergraduate days. They look a lot like the eastern White-throated Sparrow, and are in the same genus.
I never realized how common these two species were in grassy California meadows where they can poke around looking for fallen seed. I always thought Golden-crowned Sparrows (left) were rare, while the White-crowned Sparrows were common, but it is just the reverse in the oak-grasslands of the northern bay watersheds (around San Leandro reservoir). The west coast race of the Fox Sparrow (right) is grayer than our (prettier) chestnut version found in the Midwest.
Spotted Towhees occupy western habitats, and the almost identical Eastern Towhee is found all over eastern North America. When I took ornithology, they were the same species, but taxonomists have decided they should be split. However, they do interbreed where their ranges overlap in the Great Plains. In addition to their spots on their wings, Spotted Towhees only sing part of the Eastern Towhee’s song: “drink your teaaaaaaaa” is truncated to just “teaaaaaaa”.
What I’ve illustrated here are several examples of what happens when animals are isolated geographically, and develop locally slightly differently on the two sides of a barrier. What happened in Towhees, Fox Sparrows, Juncos, White-breasted Nuthatches, and scores of other bird species was the result of an east-west separation for thousands of years during glaciations that split North America down the middle and pushed bird species like these into distinct western and eastern North American populations that slowly diverged over generations from their parental lineage.