Golden-crowned sparrows arrive in my yard each year on Sept. 18 plus or minus two days. I buy my black oil sunflower seeds the week before in anticipation of their arrival, and they never disappoint. There are always about 20 that line up for breakfast. Two weeks later, a modest collection of about 10 dark-eyed juncos descend from the hills to join them. Again, I can set my calendar by their arrival. These are predictable events.
Then there are less predictable occurrences. After four straight winters of few or no varied thrushes on the valley floor, they are widespread this year. Varied thrushes look quite a bit like robins but have a distinctive black band across the chest. They also have an orange line over the eye and orange marks on the wing. They look enough like robins that they are called Alaska robins by some (usually Alaskans).
Where robins may fly high or parade about openly on a lawn, varied thrushes keep to the shadows. Because of their secretive behavior, one of the first indications they are present is usually their song.
In spring, the simple but beautiful song is loud and clear. It is a long, drawn-out burry whistle on a single pitch lasting 3 to 5 seconds fading into silence. There is a pause, and then the next song begins on a different pitch either higher or lower.
It is especially impressive in the silence of the redwoods. In winter, the songs are subdued, but they still are distinctive.
You may find them feeding on madrone berries alongside the robins and cedar waxwings in the canopy. However, they are more likely to be on the forest floor picking up fallen fruit. Unlike robins, they are leaf flippers. Where towhees scratch up leaves to discover hidden morsels beneath, varied thrushes flip leaves to the same end. This probably explains why their bills are longer than a robin's.
Why are varied thrushes visiting this year but not in the previous few years? Great question. The better than average madrone berry crop this year offers a partial answer. It's more likely that conditions farther north in Alaska and British Columbia, where most of these birds breed, could offer a better clue.
And it's more than thrushes this year. Across North America, many birds of the boreal forest of Canada and Alaska are appearing in yards and feeders south of their normal range and in greater numbers. Locally, this includes a large number of red-breasted nuthatches, small flocks of red crossbills and scattered chestnut-backed chickadees.
The answer usually lies with the food resource, but the diets of these birds are varied and include seeds, fruits and insects. It's not likely that all food resources failed simultaneously. Can they predict the weather months in advance? I don't see how. For now it's another of the mysteries that keeps me going to field and forest.
If you are not fortunate enough to have varied thrushes visiting your yard, Lithia Park is a good place to see them. In spring a few remain to breed locally. Their concerts can be heard in the shadows up Wagner Creek and among the towering forests about Union Creek. And, of course, you always can head to the redwoods.
Stewart Janes is a biology professor at Southern Oregon University. He can be reached at firstname.lastname@example.org.