There are 10,000 species of birds in the world and more than 10,000 ways for those species to live.
So it's not often that you find a trait which is truly universal in every single bird species.
Flight? [buzzer sound]
Hollow bones? [buzzer sound]
But they do exist. Let's learn some truly universal traits in birds.
Every single bird in the world is bipedal meaning it walks on two legs.
Also at a very basic level all birds are endothermic,
generating their own body heat, and homeothermic, maintaining a consistent body temperature.
Birds are kind of famous for this but all birds lay eggs with hard shells.
All birds are vertebrates meaning they have a backbone.
And all birds have feathers. These soft fluffy keratin covers are truly universal among birds.
All birds have toothless beaked jaws.
All birds produce beta keratin in their feathers,
talons, beaks, and anywhere else that keratin goes.
Beta keratin is tougher than the alpha keratin used by mammals
We don't have enough time to get into it now but bird lungs are
very very very complex and they are universal in birds.
All birds have a gizzard. It's a fleshy bag in their bodies that they use to physically
squish food and make it easier to digest. It's kind of like chewing.
All birds have a four chambered heart compared to some reptiles which have three.
All birds have a bone in their eyes, the sclerotic
ring that surrounds their pupil. This gives them voluntary control over their iris muscles.
All birds have a bony septum in the middle of their heads separating their eyes.
Inside their ears all birds have a flat cochlea. not a spiral like we do.
All birds use the ZZ ZW sex chromosome system,
where if they have two chromosomes that are the same they are biologically male
and if they have two that are different they are biologically female.
Also it goes without saying that all birds share assorted
organs like kidneys but we're not going to go into them all.
Here are some things which are almost but not quite universal in birds.
Flight [buzzer sound]
Exceptions: Kakapo, Penguin, Ostrich, and a bunch of other birds.
Hollow bones [buzzer sound]
Exceptions: Penguins and Loons.
High metabolic rate [buzzer sound]
Exception: Dusky Munia.
Good vision [buzzer sound]
Exception: Kiwi
Poorly developed sense of smell [buzzer sound]
Exception: also the kiwi
Single ovary [buzzer sound]
Exception: the kiwi again!
This one caught me by surprise
Wings [buzzer sound]
Exception: Moa and Elephant Bird, both of which are extinct. Probably because they
didn't have wings. But they did go extinct within human history.
Uric acid production [buzzer sound]
That white part in bird droppings?
Universal in birds except for hummingbirds which can produce ammonia.
An all-purpose cloaca [buzzer sound]
A single opening for both feces and urine.
Exception: Ostrich
We're making new discoveries about birds every single day. Over time some of these universal
traits may turn out to have an exception. Like maybe we find a bird that lays soft-shelled eggs
but that will be a good day because that means that we still have things to learn.
Because there is one more universal characteristic of birds,
which is that every single one is amazing!
Thanks for learning about birds this week. You can explore the universe of birds by watching
another video on this channel, or you can subscribe to know when a new video comes out.
Thanks for stopping by this week to learn what makes Life awesome!