Earlier today, I was looking at a list I made in May, 2014 of migrants I had seen in my yard. And I was struck by the fall-off in numbers from 2014 to today. By this time of the month in 2014, I had seen dozens of individuals across ten species of warbler. This year, I've seen maybe five individuals across two species. So what on earth happened?
I could be completely off base, but I'm blaming sparrows. Bird feeders have caused the number of house sparrows to explode in this neighborhood. Their numbers are up maybe tenfold or more over three years ago. And as sparrow numbers go up, might not the number of everything else -- most conspicuously May migrants -- go down? As sparrows' spring diet turns from seeds to insects, they start hoovering bugs out of all the trees and shrubs in the neighborhood, leaving the the larder somewhat bare.
If you're wondering whether sparrows could really have this much effect on insect populations, consider what happened in China during the Great Leap Forward. When Mao tabbed the Eurasian tree sparrow (a species closely related to our own invasive house sparrow) as one of the Four Pests to be eliminated, people began persecuting the sparrow with such enthusiasm that the species was nearly wiped out. Result? Locust populations, previously kept in check by sparrows, boomed. The ensuing famine killed at least 25 million people.
So if you're worried about locusts, by all means, keep a feeder. But if you're worried about our native birds, particularly during their migration, consider the effect of your feeder on the local ecology. It's instructive to take a walk around the block in Prospect Hill, and really listen for what birds you hear around you. I think you'll be shocked at the omnipresence, and sheer numbers, of house sparrows.
If you're wondering whether sparrows could really have this much effect on insect populations, consider what happened in China during the Great Leap Forward. When Mao tabbed the Eurasian tree sparrow (a species closely related to our own invasive house sparrow) as one of the Four Pests to be eliminated, people began persecuting the sparrow with such enthusiasm that the species was nearly wiped out. Result? Locust populations, previously kept in check by sparrows, boomed. The ensuing famine killed at least 25 million people.
So if you're worried about locusts, by all means, keep a feeder. But if you're worried about our native birds, particularly during their migration, consider the effect of your feeder on the local ecology. It's instructive to take a walk around the block in Prospect Hill, and really listen for what birds you hear around you. I think you'll be shocked at the omnipresence, and sheer numbers, of house sparrows.
No comments:
Post a Comment