Frankly, I found a number in the millions surprising. It was my math, so a second effort definitely was needed.
The answer was the same: Birds using 61 nests at the Wayzata Country Club (WCC) consumed over 5 million insects during the recent nesting season.
Maybe the number is more, maybe less. I was using research numbers for total insects fed to each nestling of four bird species while the newly hatched birds were in the nest. I did not do the counting. Grad students doing thesis work somewhere did that (thank you).
I’ve maintained nesting boxes at WCC for about 12 years. The best nests for numbers, however, always belong to swallows that build on their own, with no help from me.
Barn swallows nest under the eaves of the club skeet shack. Cliff swallows nest under eaves of an old barn, once used for horses, now for storage.
There are 30 or so cliff swallow nests, each on average holding five chicks. That makes seven birds per nest (parents count) times 30 nests or around 200 cliff swallows. The chicks are in the nest for 20 days, give or take. (Birds are fairly reliable but not precise; the numbers are rounded off to reflect that.)
That grad student, whoever she was, reported that each of those birds can eat up to 720 insects per day, parents feeding the young birds. (Insects here refers to adult and larval stages, flying and crawling species.) Seven birds per nest multiplied by 720 insects per bird per day multiplied by 30 nests for 20 days equals just over 3 million bugs total.
There are 15 barn swallow nests. The numbers are very close to the cliff swallows. Credit the barn swallows with removal of 1.5 million bugs.
Both species of bird feed young continually during daylight hours. Both species exclusively eat flying insects.
Now for the nest boxes, or bird houses if you prefer. There are 30 spread around the course and grounds. This year eight were occupied by Eastern bluebirds and eight by tree swallows. We had one incomplete nest for both house wren and black-capped chickadee. There always are boxes not used; 60% occupancy is usual.
We usually have at least one chickadee nest and two wren nests. I don’t know why this year is different, but the world rapidly is becoming different.
The bluebirds average four eggs/nestlings, the tree swallows five. The swallows again are aerial insectivores. Using the same math, those eight nests would account for removal of an estimated 460,000 flying insects.
The bluebirds, which find their food on the ground, can be credited with removal of about 350,000 insects.
We have 4.5 million bugs for barn and cliff swallows plus 810,000 for tree swallows and bluebirds, equaling 5.3 million insects total for those birds this season. This does not include the insects eaten by the birds before nesting or after leaving the nest and awaiting fall migration.
WCC is one of three golf courses in my general neighborhood to have nesting-box programs. There are many more golf courses in the state with similar programs, plus countless boxes tended in yards and parks by people who love birds.
The numbers reflect the importance of insects for these and many other bird species. Baby songbirds depend on an insect diet. Throughout the world, right now, insect numbers are in steep decline. This story should not alter that truth.
Lifelong birder Jim Williams can be reached at woodduck38@gmail.com. Join his conversation about birds at startribune.com/wingnut.
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