Imagine having fingers on your elbows: these birds have claws on their wings
Meet the Hoatzin, the only living birds with functional claws on their wings
Growing up, I’m sure your parents told you you were unique; one-of-a-kind; like no-one else on this wonderful Planet Earth!! (No? Oh… That’s too bad. My parents certainly told me stuff like that all the time!)
But the truth is, even if you are one-in-a-million, there are and the world is full of eight billion people, that means there are eight thousand people just like you.
Hoatzins, though - they really are one-of-a-kind. Their chicks are the only living birds with functional claws on their wings (a trait they lose as adults). Not only can they walk and fly, they can crawl like lizards. And they are the only bird in the world that digest their food the same way cattle do.
Let’s explore how, and why!
The Hoatzin is a gorgeous bird that lives along slow-moving rivers and lakes in the Amazon Basin.
But because of their habit of building their nests over bodies of water, Hoatzin chicks have had to learn to swim, or sink.
Each Hoatzin chick hatches with two claws on each wing - but these claws stay on for only the first 3 months of its life. If a Hoatzin nest is approached by a predator, the chicks will drop from the nest into the water below!
Hoatzin chicks have evolved to be surprisingly capable swimmers. They paddle to safety and hide along the bank until the predator moves on.
That’s when they use their little claws to climb back up the tree and into the nest.
Wing claws in birds aren’t actually something totally novel: they are found in other birds, like chickens, ducks and ostriches, and even in the long-extinct Archaeopteryx, a bird-like dinosaur. But, for all other bird species, these claws are just vestiges of their ancestry. This is like how humans have tailbones - a nod to how we’ve evolved from tailed primates. In fact, most humans grow a tail in the womb, which disappears by eight weeks. Humans have evolved to no longer need tails once they learned to walk upright.
Back to birds: the claws of Hoatzin chicks are unusual because they aren’t mere vestiges of a dinosaur ancestry. The claws serve an important, modern-day function in the survival of young birds!
Not only do Hoatzin chicks have claws on their wings, they even ‘crawl’ with them
A closer look at the muscles and tendons of the Hoatzin chicks show us they they actually use the claws to grasp, and crawl. Their ‘crawling’ movement is most similar to that of animals such as lizards and dogs - and, it goes without saying, this has never before been documented in birds!
There’s more: Hoatzins have stomach like cows
When will the list of amazing fun facts about the Hoatzin end?!
The Hoatzin is the only bird in the world that digests their food the same way cows, goats and sheep do. These animals are called ruminants and have a specialised ‘gut compartment’ that is filled with helpful bacteria that help them digest their food.
Just like cows, a Hoatzin’s diet consists almost entirely of plant matter. For the Hoatzin, it’s tough leaves, which need to be broken down with the help of bacterial fermentation. Foul-smelling bacterial vapors exhaled by the Hoatzin are apparently what gave this species it’s nickname: “stinkbird.”
Many of the same bacteria strains found in a Hoatzin’s gut compartment are also found within the stomachs of cows. I guess that could be why cow farts are so lethal - in fact, the methane produced is also said to contribute greatly to climate change.
But this unique digestion process isn’t the most efficient. In fact, in cows, the entire digestion process takes them anywhere from one to three days to fully digest their meal. And For Hoatzins, the digestion process takes up to 45 hours.
So these birds apparently spend about 80% of their time lounging around just digesting their food. They often aren’t able to fly at all, when they are full of fermenting leaves.
Truly one-of-a-kind
Hoatzin chicks are the only living birds with functional claws on their wings. Although a few other species (like chickens and ducks) have the vestiges of claws on theirs, they are not used by these other species.
Hoatzin chicks are able to crawl like a lizard with their wings and wing-claws
Hoatzins digest food the same way cows and sheep do - and they stink the same way, too!
Thanks for coming along with me on this bird learning journey. Through this article, I learnt about the wonderful world of Hoatzins, and even how human babies grow tails in the womb! The natural world is so interconnected and it’s great to learn about it.
BTW, I want to thank you for supporting me: knowing that you open and read my articles really, really push me to keep writing more! :D
ngl the chick looks straight out of my nightmares