Question: Do birds have four limbs and how are the fore limbs modified

Cheryl Andisi answered on 25 Jan 2017:

@Steph,
Hallo! Very good question!
I teach a subject called Introduction to Zoology- study of animals to first years and this is one of the questions we almost always have on the exam paper.
Birds fall in a group of vertebrate animals that have four limbs also known as superclass tetrapoda. The other group of animals under vertebrata will be those that have fins ie fishes and are referred to as superclass pisces.
In birds, the fore limbs are modified for flight and that is what we generally refer to as wings. The hind limbs are modified for walking, perching or swimming. Some of these modifications include:

-they have feathers made of keratin-same substance that makes your hair and nails. The feathers on the wings and tail provide lift and for steering and balance in order to enable flying.
– Birds posses a modified sternum that allows for attachment of flight muscles that extent to its wings

Other adaptions for flight include that birds have hollow bones, which reduces their weight without sacrificing the strength, have only a single ovary and keep their reproductive organs small unless it is breeding time, they lack teeth, they have efficient respiratory systems, their bodies are covered with feathers for insulation and they have a large brain connected to sharp eyes which enables them have very good sight and quick processing and perception of what they see as they fly