Backyard Birds – Common Birds Count

David Wilcove wrote in the Cornell Ornithology Lab newsletter: “Sentiment aside, important ecological reasons exist for paying closer attention to common birds. Studies all over the country show that insectivorous songbirds significantly reduce populations of leaf-consuming caterpillars in forests. In aggregate, obviously, more abundant species eat more insects than the rare ones.”

“Take, for example, Yellow-rumped Warbler,” he said. “Partners in Flight estimates that 127 million Yellow-rumps breed each summer in the boreal forests of Canada and the U.S. That translates into roughly 3.4 million pounds of Yellow-rumps. Assume that each warbler consumes roughly 35% of its body weight per day in insects. During the spring and summer this one species eats well over a million pounds of insects!”

“This offers,” he said, “an intriguing way to view North American birds. “Who would have imagined that more than five million pounds of Red-eyed Vireos and six million pounds of Swainson’s Thrushes breed in our forests each year? Or that more than 50 million pounds of American Robins scour lawns, gardens, and forest floors for insect prey during the summer?

“Many studies suggest that numbers of many long-distance migrants declined dramatically in recent decades. Have other species, perhaps permanent residents such as chickadees or short-distance migrants such as bluebirds, increased by taking advantage of the greater food supply of insects, or have the insects simply increased?”

When we report the common birds, we help scientists track populations of the birds that make a difference. We get excited about rarities, but they don’t have the biological importance of keeping track of robins, Yellow Warblers, House Finches, and House Wrens. Although we certainly need to protect the rare and endangered birds, we also need to ensure that the common birds remain common.

Our Denver Urban CBC tracks common birds well, and we have records for 34 years. This year we had an average number of species — 81 — yet the lowest number since 2001. We counted an average number of individuals – 39,983, but the mix differed substantially from average. Non-natives dropped noticeably: 679 starlings compared with an average of 4,139; 119 House Sparrows (ave, 1,285), 1,208 Rock Pigeons (ave. 2,000.). House Finches dropped to 474 (ave. 1,123). Several species dropped to 60% or less of average: Tree Sparrow (140 cf 213), Dark-eyed Juncos (234 vs. 385); Downy Woodpecker (23 / 43), Northern Flicker (138 / 201). Raptors came in at 8% of average, with Bald Eagles (30 / 47) and Kestrels (18 / 34) showing striking drops.

A few species did increase: 131 American Goldfinches (2nd highest, ave. 59), 887 Crows (661), and the second-highest count–149—for Eurasian Collared-Dove.`. And ducks: a mixed bag: Counts dropped precipitously for Mallard, Ring-necked Duck, Common Goldeneye, and Common Merganser. Two species have registered consistent increases: 276 Buffleheads (highest count – ave. 73) and 243 Hooded Mergansers (2nd highest; ave. 102).

Urling and I have reported our yard birds daily since we moved here in 1997 (and fairly regularly when we lived in residential Denver. I haven’t tried to calculate the changes to their occurrences over the 25 years– that would take a couple of weeks.

I do notice that we have more Spotted Towhees this winter than in the winters of 2003-2008. House Finch and American Goldfinch numbers seem about the same. We have almost no Tree Sparrows this winter, whereas we have had half a dozen or more most winters, though the numbers seem to vary.

We also lack Pine Siskins – though a couple of neighbors have many. That’s why they and we both should send in data – our feeders don’t represent birds at other feeders.

So track the common birds – and send reports from your feeders to eBird — every day or as often as you can.