Some economists report that insects consume or destroy up to 10 percent of an industrialized nation’s gross national product and up to 25 percent of developing nations’.
Despite the fact that this number seems staggering, it could very well be more than twice as much if it weren’t for birds.
Birds consume such an amazing amount of harmful insects and weeds that one of the main aspects of the Migratory Bird Treaty Act of 1918 was the economic interest of protecting birds.
In an old book about birds by Walter Schutz, he mentions the economic value of common birds. The book laid out a study conducted by the U.S. Department of Interior that documented the economic value of some of the most common birds measured by their consumption of insects and weeds. Although it didn’t lay out exactly how many insects each bird species eats, it did breakdown the percentage of their diets based on insects or weeds.
Since I wasn’t able to find a copy of the study online, here are a few examples of the economic value of common birds.
The diet is about 68 percent insects, including beetles, grasshoppers, caterpillars and 15 other noxious bugs. The other 32 percent are weed seeds, such as wild blackbery, ragweed and Virginia creeper.
– Black Phoebe:
This bird has one of the most economically beneficial diet with 89 percent being noxious insects and click beetles. Some click beetles are major agricultural pests to potatoes, strawberries, corn and wheat.
– South Carolina Chickadee:
Grapevine insects and black olive scale, a highly infectious pest of citrus trees, comprise 83 percent of the diet while the remaining 17 percent are mostly weed seeds.
– House Wren:
The small songbird eats all harmful insects like grasshoppers and beetles and about 2 percent weed seed and grass.
The members of the Colinus genus have an extremely beneficial diet because 40 percent comes from destructive agricultural pests like the Colorado potato beetle, cucumber beetle, weevil, cotton boll weevil, cutworms and squash ladybug. The other 60 percent comes from the worst weed seeds.
Almost 90 percent of the birds’ diet in the Tyrannus genus is nearly entirely noxious insects and pests. Like the Black Phoebe, the diet of the Kingbirds is one of the most beneficial.