Which place has fewer birds: a city? or a cornfield?
When birders visit cities they often think, “There are no birds here.” This isn’t accurate, but I think so too until I realize there’s a very high quantity of birds but low quality — lots of pigeons, starlings and house sparrows. It’s the lack of diversity that prompts the comment.
Bird diversity is highest where the habitat provides a wide variety of food, cover and nesting sites. A 20-year study of abandoned fields on Long Island found that bird diversity increased with the foliage height. Since there’s not much foliage in cities the birds we find here are those who nest on or in buildings and eat human refuse or handouts — and the birds who prey on them. (Peregrines!)
Most songbirds eat insects and invertebrates which are hard to come by in the asphalt jungle. Even hummingbirds who sip nectar feed insects to their young. If you want birds you must have insects.
Places without insects are biological wastelands because they’re also missing everything that depends on insects, all the way up the food chain. Here’s a picture of a wasteland. There are no birds here.
I bet you’re thinking, “That’s not possible. There are plants in that cornfield. There have got to be insects and birds there too.”
Nope. Today in the U.S. we use more pesticides than we did when Rachel Carson warned us about them in Silent Spring.(1)
90% of the corn we grow is genetically engineered to survive the assaults of herbicides, fungicides and insecticides. This allows cornfields to be sprayed frequently(2) without hurting the corn. Seed is also pre-treated with insecticide.
There are no insects in cornfields, no birds, and no plants except corn. I was amazed when I found out about this at Cornstalks Everywhere But Nothing Else, Not even a Bee.
Not even a bee. Hmmmm…
(credits: photo of Pittsburgh from the Fort Pitt Bridge and a cornfield, both from Wikimedia Commons. Click on the images to see the originals. Today’s Tenth Page is inspired by page 620 of Ornithology by Frank B. Gill.)