Dr Scott McDonald DVM has an interesting PDF regarding beak growth. The PDF contains graphic, disturbing pictures of malformed beaks so I'm not providing a link. You can find it with a search engine if you want. Here is an excerpt:
Key Point: No matter how deformed or overgrown a beak appears, it almost
never prevents a bird from eating.
Introduction
The beak includes the bones of the upper and lower jaws and their keratinized
sheaths or rhamphotheca. This horny covering functionally replaces the lips and
teeth. There is tremendous variation in the shape of the beak depending on
how different species feed and live. In psittacines, the upper beak is massive
and curved, whereas the lower beak is small and horseāshaped. This is why
parrots are called hook bills. A parrotās beak is adapted to cracking large nuts
and seeds as well as tearing and shredding wood from trees to provide nest
sites. It is also used for grasping, climbing, preening, and displaying. It can be a
formidable weapon yet also function as a delicate utensil for feeding newborn
chicks.
Microscopically, the horny beak resembles skin, consisting of dermis and a
modified epidermis. The epidermis is very thick and its cells contain free
calcium phosphate and hydroxyapatite crystals, in addition to abundant keratin.
This is what helps make the beak so hard. Keratin is an insoluble protein and is
the principal constituent of the epidermis in hair, nails, and the beak.
The outer layers of the beak are continuously being replaced by normal wear
and tear. Many bird owners erroneously believe that the upper beak grows
from the cere and continues to the tip (or edges) where it is then worn off
(likewise with the lower beak). On the contrary, beak tissue grows continuously
outward (towards the surface) over much of the beak. As the keratinized
epithelium reaches the surface, it is either worn off or may move distally a short
distance before it is lost. Only towards the edges and tip does the beak tissue
truly move rostrally.
The surface of the beak in juvenile parrots is smooth because the growth is new.
However, as the bird reaches its first year and older, the beak takes on a more
irregular appearance. This is a result of the normal wearing off of the outer
keratin layers. Sometimes these layers flake off or peel, leaving behind ledges
on the beakās surface. These ledges are what make the beak look rough and
scaly. These ledges can also be misinterpreted as cracks, which they are not.
How irregular a birdās beak appears can also be related to diet. A diet low in
vitamin A (seeds lack Vitamin A) can lead to hyperkeratosis, which clinically
causes the beak to become thickened and overgrown. Such beaks can appear
very scaly. The beak can also appear rough if the bird does not adequately rub
it on hard inanimate objects, such as a lava stone or concrete and sand perches.
Part of the physical examination of each bird includes an evaluation of the beak.
Most healthy parrots have beaks in which the surface is slightly irregular and
the tip a bit long. Such birds often receive a ācosmeticā beak trim. A cosmetic
trim is not necessary for the health of the bird, but by doing so, the bird looks
better, which in turn makes the client more appreciative.
Some birds have a pathologic condition which can change the normal outward
appearance of the beak and affect some beak functions. In such cases
ācorrectiveā beak trimming is necessary. Aside from losing the entire upper or
lower beak due to traumatic injury, overgrowth or deformity of the beak rarely
affects a birdās ability to eat.never prevents a bird from eating.
Introduction
The beak includes the bones of the upper and lower jaws and their keratinized
sheaths or rhamphotheca. This horny covering functionally replaces the lips and
teeth. There is tremendous variation in the shape of the beak depending on
how different species feed and live. In psittacines, the upper beak is massive
and curved, whereas the lower beak is small and horseāshaped. This is why
parrots are called hook bills. A parrotās beak is adapted to cracking large nuts
and seeds as well as tearing and shredding wood from trees to provide nest
sites. It is also used for grasping, climbing, preening, and displaying. It can be a
formidable weapon yet also function as a delicate utensil for feeding newborn
chicks.
Microscopically, the horny beak resembles skin, consisting of dermis and a
modified epidermis. The epidermis is very thick and its cells contain free
calcium phosphate and hydroxyapatite crystals, in addition to abundant keratin.
This is what helps make the beak so hard. Keratin is an insoluble protein and is
the principal constituent of the epidermis in hair, nails, and the beak.
The outer layers of the beak are continuously being replaced by normal wear
and tear. Many bird owners erroneously believe that the upper beak grows
from the cere and continues to the tip (or edges) where it is then worn off
(likewise with the lower beak). On the contrary, beak tissue grows continuously
outward (towards the surface) over much of the beak. As the keratinized
epithelium reaches the surface, it is either worn off or may move distally a short
distance before it is lost. Only towards the edges and tip does the beak tissue
truly move rostrally.
The surface of the beak in juvenile parrots is smooth because the growth is new.
However, as the bird reaches its first year and older, the beak takes on a more
irregular appearance. This is a result of the normal wearing off of the outer
keratin layers. Sometimes these layers flake off or peel, leaving behind ledges
on the beakās surface. These ledges are what make the beak look rough and
scaly. These ledges can also be misinterpreted as cracks, which they are not.
How irregular a birdās beak appears can also be related to diet. A diet low in
vitamin A (seeds lack Vitamin A) can lead to hyperkeratosis, which clinically
causes the beak to become thickened and overgrown. Such beaks can appear
very scaly. The beak can also appear rough if the bird does not adequately rub
it on hard inanimate objects, such as a lava stone or concrete and sand perches.
Part of the physical examination of each bird includes an evaluation of the beak.
Most healthy parrots have beaks in which the surface is slightly irregular and
the tip a bit long. Such birds often receive a ācosmeticā beak trim. A cosmetic
trim is not necessary for the health of the bird, but by doing so, the bird looks
better, which in turn makes the client more appreciative.
Some birds have a pathologic condition which can change the normal outward
appearance of the beak and affect some beak functions. In such cases
ācorrectiveā beak trimming is necessary. Aside from losing the entire upper or
lower beak due to traumatic injury, overgrowth or deformity of the beak rarely
. But each to his or her own.
