Severally, I have come across the raging argument: is chicken a mammal or a reptile? Proponents of chicken being a mammal readily point out that, like mammals, chickens are warm-blooded vertebrates. On the other side, we have proponents of chicken being a reptile arguing that, like reptiles, chickens lay eggs. So then, what is a chicken?
Chickens are neither reptiles nor mammals, despite sharing some features across the board. Chickens are classified as aves, a breed of domesticated fowl, kept for eggs and meat production. Like birds, chickens have feathers, wings, beaks, lay, and hatch eggs. However, in the special case of chickens, their chicks are precocial in that they only need warmth, water, and food to grow, surviving independently of their parents.
How about we adeptly explore what separates chickens from mammals and reptiles? What unique features do birds boast also?
Why is a Chicken Not a Mammal?
Before we dive extensively into the signature characteristics of a mammal, there are three fundamental differences between chickens and mammals.
First, unlike mammals, chickens don’t have mammary glands. Therefore, chickens don’t breastfeed their chicks.
Also, except for the likes of the western long-beaked echidna and the duck-billed platypus, mammals don’t lay eggs but give birth to their live young ones. Chicken, instead, lays eggs.
Lastly, while mammals have fur or hair covering their bodies, chickens make do with feathers.
Birds belong to the Aves class, with an estimated 9,000 species of birds roaming the planet today. Generally perceived as descendants of dinosaurs, here are some of the prominent features of birds.
Birds Have Wings
Which bird doesn’t have wings? NONE! But what many don’t get is that a bird has wings doesn’t automatically translate into an ability to fly.
A bird’s wings are essentially paired forelimbs, majorly responsible for propelling the bird from the ground. Birds that live on the ground have reduced wings, while aquatic birds like puffins and penguins that don’t fly have their wings adapted as flippers, helping in propelling them through water.
The shape of the wing is a critical determinant of the bird’s capacity to fly. Some wing shapes give the specific bird more speed, some wing shapes aid the bird with more aerial maneuverability, while other wing shapes make flying less energy demanding for other birds.
Take the falcon and its narrow wings with very sharp tips. Such wing anatomy gives the falcon the speed advantage.
For albatrosses, their wings are longer but lacking in width. Such a shape gives them the advantage of vertical propulsion or loftiness. In songbirds, they have elliptical wings that enhance their maneuverability when flying through constricted spaces.
Birds Have Feathers
Feathers are undoubtedly signature characteristics of birds. Just any species of bird alive today is furnished with feathers.
These feathers are composed of keratin. Feathers are typically fluffy and to feel.
In birds, feathers shoulder an array of responsibilities, from keeping them warm to helping them fly. Particularly, contour feathers are vital to a bird’s flight capacity, just like flight feathers are important in aiding the bird’s loftiness.
In many cases, male birds parade their feathers to woo their mates. Depending on the species, a healthy bird would molt its feathers at least once or twice in 12 months.
Birds Have Beaks
Have you seen those distinct protrusions at the mouths of birds? Those are beaks. A unique feature of birds, beaks are made of a bony core bordered by a keratin layer.
Beaks deputize for the absence of conventional teeth in the generality of birds. Such lack of teeth in birds would have severely handicapped their feeding as they would be unable to chew on food.
But thanks to their beaks, birds can rip through their food, severing them into smaller pieces comfortable enough for them to swallow.
The beak’s sharpness is typically adapted to the feeding regimen of the bird. Correspondingly, you would have carnivorous birds like hawks and owls having hooked and sharper beaks. This is specialized for tearing their foods.
At the other end, pickers like ducks have flatter beaks adapted to picking food out of water. Finally, when it comes to birds whose diet is predominantly seeds, they have beaks shaped like cones and are significantly robust. These beaks help the bird penetrate the shells of the seeds they eat.
Lastly, Birds Lay Eggs
Just any bird you can think of lays eggs. Most birds lay these eggs in protected enclaves, typically nests.
The bird egg’s shell is hard thanks to its rich composition of calcium and hardened mucus. The growing embryo has its nutritional needs satisfied by the egg white and the yolk.
Having established some of the signature characteristics of birds, let us learn three core characteristics of mammals.
Mammals Produce Milk for Their Babies
First things first, mammals have their young ones live born. That means they don’t lay eggs like chickens. When these live babies are born, the mother produces milk to feed them via lactation.
Typically, this milk is secreted via the mother’s mammary glands, from which the babies feed. Aside from nutrition, milk also enhances the immune protection of the young ones.
Mammals are Covered with Hair or Fur (and in Some Cases, Both)
Yes, depending on the species, mammals either have hair or fur or, in other cases, combine hair and fur. The likes of cattle and dogs have a sustainable hair coat that covers their bodies for life.
Periodically, they shed this coat. Wolves and semiaquatic mammals like the otter and seals have their body plated with a thick layer of fur.
The hair or fur covering serves both protective and insulating functions. While many mammals like dogs have body covering for insulation, porcupine and hedgehogs have covering adapted into quills which protects them from predators.
Mammals are Warm Blooded
Mammals have special adaptation capacities, courtesy of their ability to retain warmth even in colder temperatures. This is in contrast to reptiles and other cold-blooded folks whose temperature is directly determined by their environments.
Therefore, you don’t see mammals warming up like reptiles. When they feel too cold, mammals can independently regulate their metabolic process to enhance warmth.
Mammals – just like birds – are homeothermic. This means internally, mammals have a stable body temperature, normally higher than the environmental temperature. The environment does not influence this internal temperature.
Reptiles are unique, too, differing from birds. Reptiles are vertebrates, thanks to having backbones. The majority of reptiles lay eggs, with their eggshells strong exteriorly.
For more clarity, let us point out that not all reptiles lay eggs. Viviparous reptiles like lizards and snakes don’t directly lay eggs. This category of reptiles has their eggs reaching maturation within the mother’s oviduct after fertilization. After maturity, these eggs come out as little babies of the adult, not eggs to be hatched outside.
Reptiles are ectothermic, otherwise known as cold-blooded. Unlike mammals, reptiles derive their body temperature from their environment as they lack internal heat production or regulation capacity.