not all
Basic : All birds have feathers, beaks/bills, two feet, wings, and lay eggs. More complex: All birds have crops, gizzards, a four chambered heart, and are warm-blooded.
Birds have two legs with wings and bills.
All birds are warm-blooded, lay eggs, and have bills.
ducks.geese.canadian geese
what
Birds don't have teeth, but some have serrated bills.
they have bills.
If think you mean What is a distinct characteristic of birds. If so, then one characteristic of all birds is feathers. A few more is that they are all warm-blooded, they all are vertebrates, they all lay hard-shelled eggs, and they all have beaks/bills.
Sadly, like all birds, flamingos do not have teeth. They have bills and tiny baleen used to filter the water.
black bird Crow
they have duck bills/beaks
Birds in cold climates have special bills that help them access food sources like seeds or insects hidden under snow. Birds in aquatic environments have bills that are adapted for catching fish or filtering water for food, allowing them to thrive in water habitats.