Les aus pertanyen al grup dels vertebrats. La seva característica principal és que poden volar. Per això disposen d’un cos aerodinàmic, amb les extremitats anteriors transformades en dues ales de forma i mida idèntiques. Com a excepció, l’estruç, l’emú, el kiwi i el pingüí són de les poques espècies d’aus que no poden volar.

Com a trets característics, les aus tenen el cos cobert de plomes, respiren per pulmons i en comptes de dents tenen bec. La reproducció de les aus és de tipus ovípar. És a dir, que després d’aparellar-se, ponen els ous i els deixen madurar fins que neixen les cries.

Les aus són la classe més abundant del Planeta. Al món n’hi ha més de 9.000 de diferents.

Birds belong to the vertebrates group. Their principal characteristic is that they can fly. To do this they have an aerodynamic body, and their front limbs have evolved into two wings of identical shape and size.  The ostrich, emu and penguin are amongst the few exceptional bird species that cannot fly.

Other characteristics of birds include having a body that is covered in feathers, breathing through lungs, and having a beak instead of teeth. Birds are oviparous, that is to say that after mating they lay eggs and leave them to incubate until their young are born.

Birds are the most abundant species on earth. There are more than 9,000 different types of birds.

Birds belong to the vertebrates group. Their principal characteristic is that they can fly. To do this they have an aerodynamic body, and their front limbs have evolved into two wings of identical shape and size.  The ostrich, emu and penguin are amongst the few exceptional bird species that cannot fly.

Other characteristics of birds include having a body that is covered in feathers, breathing through lungs, and having a beak instead of teeth. Birds are oviparous, that is to say that after mating they lay eggs and leave them to incubate until their young are born.

Birds are the most abundant species on earth. There are more than 9,000 different types of birds.