My world is very earthlike and I am looking to create a bird that primarily eats bone marrow. I wanted my bird to crack the bones of the carcasses to eat the marrow inside. What would the ideal beak shape for breaking bones and removing marrow be? I was thinking something like a parrot would be best, but I'm not sure if it would work.
Woodpeckers are perfect for eating marrow. They love fat and are always at suet feeders in winter. They already drill their way into trees. Then they extend their long tongues to lap up the morsels within. A giant woodpecker could hold a bone, peck through its cortex and use its tongue to get at the marrow inside.
This seemed so plausible that I wondered if it had ever been observed. It turns out woodpeckers do use their bills to drill through bone and do use their tongues to eat what is inside - in this case, brains.
What happens next may upset you (and in fact, if you’re sensitive to bird-on-bird violence, you may want to stop reading here). Before the chicks even realize there’s an enemy at the gates, the woodpecker cocks its head back and starts to peck … their skulls. The Gila’s head moves like a pneumatic hammer, up and down, up and down, drilling into flesh and bone with the force of 1,000 G’s. Soon both chicks’ skulls have been opened up like coconuts. At this point, the woodpecker begins extracting brain and blood with its long, sticky tongue.
I bet woodpeckers eat marrow bones now. I will keep searching...
almost there... https://www.dailymotion.com/video/xoxpvs
Just like so many of our creature-design questions, the answer to this one is: "nature beat you to it."
Presenting the Lämmergeier, or Bearded Vulture, a species of vulture that specializes in consuming bone marrow, just like your fictional bird!
These vultures leave the hard work of breaking open the bones to our old friend, gravity. By simply carrying bones to great heights and dropping them onto rocks, the Lämmergeier breaks open the bones without even using its beak!
As you can see from the above image, the Lämmergeier's beak is curved, with the top segment extending past the bottom part in a downward-curving hook, designed to scoop and scrape marrow from cracked and broken bones as efficiently as possible. Your fictitious bird could employ the same strategy of dropping bones from a height and have a near-identical beak shape, or, instead of inventing a bird, you could simply co-opt this one if it suits your purposes.
Think about what this bird needs to do to get to and eat the marrow. It first has to break through bone, so the beak needs to be thick or tough. Next, after a hole in the bone is made it needs to gather enough food from what it can reach through the hole, so a long, narrow beak would be beneficial. If it is a bigger bird, it may be strong enough to simply snap the bones in half, but the second problem still remains, it must be narrow enough to fit its open beak into the bone and long enough to eat more.
Like a woodpecker crossed with a hummingbird.
I recommend looking at the various types of Galapagos finch, discovered by Charles Darwin.