External Anatomy

The external anatomy of the chicken is made up of the comb, wattle, spurs, and feathers. These parts, other than the spur, can be found on both the male and female, with the only difference being the size tends to be a bit larger in males. While the comb and wattle are most likely used for sexual display, the spurs and feathers are used as protection. 

Comb

The comb is a fleshy growth located on the dorsal midline of the head. It begins to develop roughly within 6-15 weeks of hatching. It varies in size and shape among breeds due to the prevalence of different strains of sex hormones, though it tends to be much larger and brighter in roosters than in hens. The most common shape of comb is the single comb. It does, however, come in a variety of shapes such as the pea comb, the rose comb, the cushion comb, the V-shaped comb, and the strawberry comb. Though it is normally red in color, it can also vary in color such as a blackish blue in certain breeds.  An unhealthy bird’s comb may appear bleached or dark purple in color and lopped or shriveled. Some studies suggest that the main purpose of the comb is to act as a cooling system due to the chicken’s inability to sweat while others claim it to be ornamental and serve as a display for courtship. 

Wattle

The wattle refers to a pair of red, fleshy caruncles that hang off of the ventral side of the head. Like the comb, wattles tend to begin developing around 6-15 weeks after hatching. The main purpose of the wattle, like the comb, is to cool the chicken down but also to attract potential mates.

Spurs

The spur is a sharp, bony growth on the leg of the chicken. It is covered in epidermis but is not classified as a digit. Though usually only found on roosters, hens also have the ability to grow spurs. The spur may begin to develop within a few weeks of hatching but generally take about a year or more to fully develop and become sharp. It serves as a defense mechanism for fighting. 

Note: The spur is not labeled because we had a female chicken and females usually do not have spurs.

Feathers

The presence of feathers is known to be the most characteristic trait of the class Aves. Feathers grow from an epidermal follicle found in the epidermal core and like hair in mammals, are made up of keratin. The feathers assist the birds in maintaining and regulating body temperature, keeping the bird dry, camouflage, flight, and even sometimes attracting a mate. Feathers can be classified as two types, contour and down. Contour feathers assist in flight while down feathers cover the body to help regulate body temperature. Feathers can also be categorized as scapulars (shoulder feathers), primaries (feathers forming the contour of the wing), and secondaries (large feathers found between primaries and the innermost of the large feathers on a wing.) The feathers are replaced once or twice a year and the bird molts in such a way that it does not lose enough flight feathers to render it flightless.