Sure, they provide the soundtrack of spring and are often lovely to look at. But a new study may offer the best reason yet to appreciate birds: the general absence of gigantic insects from our daily lives.
Today insects are among the smallest creatures on Earth, but about 300 million years ago, huge bugs were fairly common. The dragonfly-like griffinfly, for example, had a wingspan of about 70 centimetres—a little bit smaller than a crow’s. Today’s widest-winged insects are butterfly and moth species that span about a foot (30 centimeters).
The prehistoric bugs’ incredible growth was fueled by an atmosphere that was more than 30 percent oxygen, compared with 21 percent today, experts say. The extra oxygen gave bugs more energy per breath, allowing them to power bigger bodies.
But things changed about 150 million years ago, during the Jurassic period, when the first birds appeared alongside dinosaurs. After birds took to the skies, winged insects stopped growing bigger—even as oxygen levels rose.
As to why the big bugs might have fallen to birds, the maneuverability of any sort of flying thing really scales with size. Small things are much more maneuverable than large things. In other words, large insects may have been easy targets. Another possibility is that birds may simply have eaten the big bugs’ lunch. The birds may have m0re successfully competed for food sources.
The largest insects today could perhaps be three times as large as they currently are, based on current oxygen levels – hip, hip, hooray for birds!!! Learn more here.