Over the seven years we've lived outside of Bozeman, Montana, the change we've noticed is dramatic. We just don't see the birds we used to. Tree swallows used to raise young in the nest boxes we provided, as well as in natural tree cavities. Now we no longer see swallows at our home. And this year, the house wrens are absent. None are in the nest boxes and we've yet to hear one this spring. I could list additional species that have become less common (including at some of the birding spots we frequent), but you get the idea.
A recent study found that bird numbers have plummeted 30% in recent decades. This decline in North American birds signifies an erosion of the health of our environment, according to the report summarized here.
Just as remarkable is the change in insect populations we've observed near our home. Moths, bees, butterflies, beetles, even house flies have markedly declined over the last seven years. Might the change in bird numbers be partly correlated to dwindling insects, as well as the other factors at play? The late evolutionary biologist E. O. Wilson once noted, “If all mankind were to disappear, the world would regenerate back to the rich state of equilibrium that existed ten thousand years ago. If insects were to vanish, the environment would collapse into chaos.”