My first ecology text in college had the subtitle “Distribution and Abundance.” And if you think about it, that covers much of what we study in the field of ecology. Why is this species common here but rare somewhere else? What limits the distribution of a species? Is it climate, competitors, predators, disease, food or something else entirely?
We have one of those interesting little puzzles here in the valley. Black-billed magpies with their bold black and white plumage and overly long tails are found around the world. They live in the hedgerows of England. They glean reindeer carcasses in Scandinavia. You will find them across Siberia. In Alaska, they are on the gravel bars of many rivers attempting to steal a mouthful of salmon from some gluttonous brown bear. And they are common throughout the juniper and sagebrush country of Central and Eastern Oregon, including the Klamath Basin.
And in the Rogue Valley? You may never have seen one, but they are here. And they have been here for a long time. When I first arrived in the Rogue Valley many years ago, birders informed me where I could find magpies. The most dependable place was in the oaks along the Greensprings Highway between mile posts 10 and 12. You could reliably see them as they flushed from the roadside or perched high in one of the scattered pines. Then there was a small group around the landfill at the end of Valley View Road in Ashland. A third family group could sometimes be seen in the oaks behind Roxy Ann Peak.
Little has changed over the decades. The Greensprings mob is still there. The Valley View family is harder to find with the closing of the landfill, but I am told it is still there. And hikers on Roxy Ann still report seeing the occasional magpie. In recent years a new group has been discovered in the oak-filled canyon along Dead Indian Memorial Road about mile post 7. Despite this recent addition, stability is the word for this bird.
Why just in these locations? A great many species increase and decrease in number and expand and contract their range a bit from year to year, but not our magpies. What limits them?
This is a mystery to me. Not much preys on magpies, so there is no obvious answer here. Regarding food, magpies eat just about anything that has calories. I don’t see diet as an explanation either. And they coexist comfortably with ravens throughout the Old World and New.
A possible answer may involve competition with crows. Crows are common anywhere there are human activities in the Rogue Valley, but they are not common among the oaks in the foothills. Crows are common in the Willamette Valley but there are no magpies present even though magpies inhabit the same soggy habitat in England. Crows are uncommon east of the Cascades where magpies flourish. This complementary distribution suggests competition as a possible answer, but I am not yet convinced. There are many oaks in the foothills of the Cascades without magpies. I will leave this puzzle to some young and upcoming ecologist to solve.
Stewart Janes is a biology professor at Southern Oregon University. He can be reached at email@example.com.