Select Page

Avian biology provides insight into the unique adaptations of birds throughout their evolutionary history. One such adaptation is the egg tooth, which plays an essential role in a bird’s hatching process and subsequent development.

This article will explore what happens to the egg tooth once it has served its purpose during hatching. The structure and function of the avian egg tooth are integral components of the hatching process for many species of birds.

Egg teeth vary in size and shape depending on the species, but they all serve as an invaluable tool that helps chicks break through their hard-shelled eggs when they are ready to hatch. Through research on this particular adaptation of birds, biologists have been able to gain valuable insights into how eggs develop and begin life outside of their shells.

Chick hatching
Newborn yellow chicken hatching from egg

Structure And Function Of The Egg Tooth

The egg tooth is a hard protrusion found in many species of birds and reptiles. Its purpose is to assist the embryo with breaking through the outer shell of its egg during hatching. It is made up of keratin, which makes it strong enough to puncture the tough surface of an eggshell.

This structure can be seen on embryos as early as day nine or ten after incubation has begun, and usually falls off within 1-2 days after a chick hatches. The specific anatomy of an egg tooth varies between species, however research suggests that they are generally triangular or conical in shape with a sharp tip.

A study by Deeming (1993) examined the internal structures associated with the egg tooth in several bird species and discovered that it was connected to cartilaginous tissue near the upper mandible region. Moreover, this tissue had well developed blood vessels that could supply nutrients necessary for growth and development prior to hatching. Thus, demonstrating the importance of this structure for successful embryonic development before birth.

Hatching Process For Different Species

The egg tooth of a bird is an evolutionary adaptation that helps young birds break out of their shells. It’s like a tiny pickaxe on the tip of a chick’s beak, helping it to chip away at its prison walls until finally hatching free from the shell.

The size and shape of this tool varies according to species but all perform the same basic job – allowing fledgling chicks to take their first breath in the world outside.

Incubation techniques and egg nutrition are two important elements for successful hatching, as both influence how developed the egg tooth will be when the time comes for breaking out; the stronger and more resilient it is, the easier it will be for baby birds to emerge into their new lives.

But no matter what species we look at, once hatched each one has gone through a remarkable process involving a unique little feature – namely, its egg tooth.

Development Of The Egg Tooth

The development of the egg tooth in birds is an important adaptation that aids in hatching. The presence and size of this structure, which is composed of a hardened keratinous material, varies among different species but typically forms on the tip of the beak or upper mandible during incubation. It serves as a useful tool to aid chicks with breaking through their shells when they are ready to hatch.

Incubation timing has been found to be one factor influencing the formation and growth rate of the egg tooth; studies have demonstrated that longer incubation times result in larger egg teeth at hatching compared to those hatched earlier.

Additionally, nutrition of the developing embryo can influence its development; higher levels of carotenoids have been linked to increased egg tooth size while deficiencies in calcium can cause delayed maturation or even complete failure for it to form.

Ultimately, these adaptations ensure successful hatching rates amongst bird species by providing direct access into their eggs.

Role Of The Egg Tooth In Bird Evolution

Avian evolution has been characterized by a number of adaptations, including the presence of an egg tooth. This specialized structure is located on the beak or upper mandible and provides birds with the ability to create a small hole in its own shell upon hatching.

The presence of this trait is thought to have played an important role in the dietary preferences of modern avian species. The egg tooth allows young hatchlings to access their food source more quickly than if they were limited to relying on the strength of their parents alone.

Studies indicate that greater eggshell thickness comes at a cost: increased energy expenditure for adults during incubation. Thus, it appears that avian diets may play a decisive role in determining which reproductive strategies are favored among various species.

Those individuals able to capitalize on more abundant food sources as fledglings would enjoy higher survival rates due to fewer constraints placed on parental resources. As such, the development and prevalence of an egg tooth can be seen as being integral to bird evolution over time.

Variation In Egg Tooth Size And Shape

Avian egg tooth shape and size vary among species. Egg teeth are located on the embryo’s beak or upper jaw, typically at an angle of 45° from the midline. The purpose of these projections is to aid in hatching by providing a mechanical advantage when pip-breaking behavior occurs during embryonic development.

The egg anatomy varies between avian species; however, most birds have a single egg tooth that is composed of epidermal tissue with a hard calcareous tip containing dentine-like structures. During embryonic growth, calcium deposition increases as the egg tooth grows and becomes more pointed as it reaches full maturity just prior to hatchling emergence.

This structure can remain attached after hatching, sometimes referred to as a ‘snood’ due to its appearance resembling a rooster’s wattles and snoods.

A variety of factors contribute to differences in egg teeth size and shape across different bird species: beak morphology, clutch size, rate of incubation, shell hardness/thickness, number of chicks hatched simultaneously, and strength requirements for pip breaking all play roles in determining the characteristics of each species’ respective egg tooth. Furthermore, research suggests that individual variation may also exist within certain populations based on genetic make-up or environmental conditions.

Chick hatching

Post-Hatching Fate Of The Egg Tooth

Following the hatching of a chick, the egg tooth begins to regress. It is composed primarily of soft tissue and calcium carbonate and disappears as quickly as it appeared during incubation, showing no signs of calcification or ossification in post-hatch chicks.

The anatomy of an egg tooth consists of two parts: (1) corneous material that protrudes from the tip of a specialized beak structure; and (2) a small area of connective tissue below the epidermis that serves as the attachment point between the egg tooth and underlying jawbone structures.

Physiologically, an egg tooth acts as an effective tool for breaking through hard shells by providing additional pressure against them while also acting as a wedge to help widen cracks in the shell surface.

Research has shown that embryos with higher levels of hydration were more likely to hatch successfully due to increased flexibility in their egg teeth allowing them to exert greater force on their shells when attempting escape.


The egg tooth is an important tool used by birds to break out of their shells when hatching. Its role in the evolution of avian species has been essential, and its size and shape can vary between bird species.

After hatching, however, the egg tooth eventually falls off or dissolves away as the beak continues to grow. This begs the question: what purpose does this structure serve after it has fulfilled its primary role?

It appears that the development of the egg tooth may have broader implications for evolutionary processes within a particular species than originally thought. The data from recent studies suggest that the presence of an egg tooth could influence characteristics such as reproductive behavior and adult morphology, thus providing insight into how modern birds evolved over time.

Further research into these aspects will help us better understand how birds adapted to new environments throughout their long history on Earth.