Nature Rambles | Silent Autumn



As summer wanes, a September harvest moon rises over the eastern horizon on a beautiful Friday the 13th. The winds have turned, and come from the northwest, bringing in cool breezes. During this time of year, under these conditions, birders have come to expect that the new dawn will be greeted with a flurry of migrating birds to greet the morning sun.

The Cornell Lab of Ornithology’s BirdCast website forecasted that conditions were perfect for migration. Birders greeted the crisp morning on Saturday, Sept. 14. The problem is that the migrating birds weren’t there to greet them. A one-hour walk at Tawny Oaks brought 40 species of birds to the observer, but only four of those species were migrants. Was it just too early? Where the conditions just not right? It wasn’t just the observers at Tawny Oaks who were disappointed. Their disappointment was echoed throughout the birding world on internet message boards and list-serves. Bird Banding Stations, such as the one run by Vernon Kleen at Lincoln Land Community College, also noted the scarcity of birds. Vern only captured and banded 16 birds the entire day. He notes that this season’s bird numbers are unusually low. Something just doesn’t seem right.

On the same day as September’s Harvest Moon, a study was published in Science magazine. The authors have been researching the effects of widely used neonicotinoid pesticides (also called neonics) on songbird populations. Neonics have been shown to negatively impact bees and other pollinating insects in the wild as well as birds in lab studies. This new study looked at the effects of neonics on wild populations of seed-eating birds. The authors found that White-throated Sparrows that ingest plant seeds that have been laced with neonic pesticide show reduced feeding behavior, reduced body weight and delayed migration.

Most seeds that are used in the agricultural setting are treated with neonics to reduce insect predation. Being a systemic pesticide, that toxin is spread throughout the plant and can even be found in trace amounts in seed produced by plants. While the dose that migrating birds are ingesting isn’t likely a lethal amount, this study shows that it doesn’t take a lethal amount of a pesticide to adversely affect a bird. Migration is a dangerous time for birds. The dangers of the travel, the exposure to storms and the amount of energy that it takes to fly thousands of miles all takes a toll on the migratory bird. When a bird has less body fat to fuel its flight and then is late to migrate, its prospects aren’t very good.

Some would say that I shouldn’t blame the pesticide use for a slow birding day. True, I don’t have scientific proof that an empty prairie was caused by the prevalent use of neonics. But there is scientific proof that non-target species are adversely affected by this pesticide. That should be enough for us to all take note. Rachel Carson’s “Silent Spring” showed us all too well the folly of complacency. We don’t need a sequel to be written called “Silent Autumn.”

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