How Strong Is a Macaw's Beak? Cracking the Hardest Nuts

What can a macaw’s beak crack?

Large macaws feed on some of the toughest foods in tropical forests. The hyacinth macaw of Brazil, Bolivia and Paraguay specializes in palm nuts, such as those of the acuri and bocaiuva palms, whose shells are so hard that a person would need a hammer to open them. The bird holds the nut in its foot, wedges it inside the bill and works along a natural seam until the shell splits.

The scarlet macaw and other large macaws eat hard seeds, palm fruits and unripe fruit with tough husks. In southeastern Peru, macaws have been recorded opening the thick, woody fruits of the Brazil nut tree, which most animals other than agoutis cannot get into.

Cracking food that others cannot open is an important advantage. A macaw can harvest seeds before the fruit is ripe and before competitors arrive.

How does a macaw’s beak work?

A parrot’s beak is built differently from that of most birds:

• A hinged upper bill. In parrots the upper mandible joins the skull with a flexible hinge, so it can move up and down independently. This gives a wide gape for big nuts and lets both halves of the bill work together like a nutcracker.
• Powerful jaw muscles. Large muscles on each side of the skull close the bill, and parrots have an unusual arrangement of jaw muscles, including one found in no other birds, that adds to the force.
• A sharp hook and a chisel. The curved tip of the upper bill grips and tears, while the cutting edge of the lower bill works like a chisel against it.
• Ridges inside the bill. Fine ridges on the underside of the upper mandible hold a slippery seed in place while the bird turns it.
• A muscular tongue. The thick, dry tongue moves seeds into position, peels away husks and feels for the weak point of a shell.

The beak is a bony core covered by a sheath of keratin that grows continuously and is worn down by daily cracking and chewing. That constant use keeps the edges sharp.

Why bite-force numbers for macaws are unreliable

Websites often state that a macaw bites with 500, 1,000 or even 2,000 pounds per square inch (psi), sometimes comparing it to a big cat or a crocodile. These numbers are repeated widely, but none can be traced to a published study that measured a live macaw’s bite.

There are several problems:

• No standard measurement. Bite force in animals is normally measured in newtons with a force sensor, under controlled conditions. “Psi” is a pressure, which depends on how small the contact area is, so it is not the right unit for comparing bites.
• Hard to measure. Measuring a large parrot’s full bite safely is difficult, and birds rarely bite at full strength on demand.
• Copied claims. The same unsourced figures spread from website to website and are not supported by scientific studies.

The safest conclusion is that large macaws have one of the most powerful bites of any bird for their size, capable of crushing shells that need serious tools for people, but the exact force is unknown. Compare how scientists measure real bite force in mammals in How strong is a jaguar’s bite?

The beak as a third foot

A macaw uses its beak for much more than eating. When climbing, it grips a branch with the bill, pulls its body up and then moves its feet, so it climbs using the beak almost like a third limb. A 2022 study of rosy-faced lovebirds climbing a vertical surface found that the head and neck produced forces comparable to those of the legs, confirming that parrots really do climb on three points.

The bill also helps the bird:

• Hold food while the foot turns it, working together with the zygodactyl feet, which have two toes forward and two back.
• Preen its own feathers and its partner’s.
• Enlarge nest cavities by chewing away rotten wood inside a tree hollow.
• Defend itself, with a bite and a loud display of spread wings and raised feathers.

Many parrots also show a preference for using one foot to hold food, often the left, much as people favor one hand.

How does a macaw’s beak compare with other birds?

Among birds, only a few other groups specialize in cracking very hard seeds. Hawfinches in Europe can crack cherry and olive stones with a bill that is tiny by comparison but backed by enormous jaw muscles. Grosbeaks and crossbills open seeds and cones in their own ways. The big macaws, however, combine sheer size with the hinged parrot design, and the hyacinth macaw, the longest parrot in the world, has the largest bill of the group.

Clay eating is another part of the macaw diet that often goes with hard, bitter seeds. Read about it in Why do macaws eat clay?

Is a macaw bite dangerous to people?

A large macaw can bite hard enough to cause deep cuts and serious injuries to fingers, and parrot keepers and zoo staff treat these birds with care. In the wild, macaws avoid people and pose no threat. If you meet a tame or captive macaw, do not try to touch or handle it unless its keeper tells you it is safe, and for any serious bite seek medical help.