Why don't birds have teeth?

More than 100 million years ago, one of the main dinosaur lineages branched off and evolved into the birds we know today.
Unlike their fearsome, sharp-toothed ancestors, birds are edentulous, which means they lack teeth.
While some species have toothlike structures, including jagged beaks for gripping food or a so-called “egg tooth” for hatchlings to break and escape their shell…
… all species of modern birds lack traditional teeth.
Numerous explanations have been proposed to explain why birds evolved to have toothless beaks.
Initially, it was thought that a lack of teeth was an evolutionary benefit that made eating easier.
Scientists reasoned that beaks allowed birds to better pursue their prey and consume seeds and nuts without having teeth getting in the way.
Another potential explanation was that the absence of teeth made it easier for birds to fly by decreasing their body weight.
However, more recent research has put forward a new hypothesis.
Teeth take a long time to form within an embryo—so long that tooth development could take up to 60% of a dinosaur’s incubation period.
Birds may have evolved to lose their teeth in order to shorten incubation times and the immobile, vulnerable position it leaves eggs in.
Without teeth, modern birds are able to hatch much quicker than their dinosaur ancestors, within weeks or even days of eggs being laid.
Today, scientists still haven’t proved one theory or another as to why birds no longer have teeth.
But that doesn’t mean these explanations are “for the birds”—no matter what, these hypotheses still offer insights to better understanding why birds evolved the way they did.