 Well, in this module, we will be discussing reproduction in birds. So birds, they have retained the important adaptation for life on land and that evolved in early reptiles. These are the same, these are the same adaptations in the reptiles. Or over here, we see that they are continuing in birds. With little, as you can see, changes, little, rather additional changes. Now, with the exception of most waterfowl, birds lack penis. So this is an intrametant organ which is used to introduce, to introduce sperms into the female. Now, males simply deposit semen against the cloaca for internal fertilization. They can, as a birds be, just they meet their cloaca and introduce the sperms into the female. But there are certain animals which have this organ, the penis, which is used to introduce the sperms into the female. Now, the sperms then migrate. When these sperms, they enter the body of the female. Now these sperms, they travel up, they travel up, up to the point. It's a very convoluted ovidot and up to the point where they very close the ovary. And the egg released at that time, that is just in the form of a yolk. That is a yolk which is surrounded by a membrane, which is the vitiline membrane. And then the shell formation is after fertilization. After that, as the fertilized egg moves down along the ovidot, then the remaining part of the egg, like the albumin or the cloaca, or the cloaca is the spirals, the proteinaceous albuminus. And after that, the egg is membrane. And then lastly, the shell egg is developed by the shell glands on it. And when the egg is laid down, this is a complete well-protected house in which there is further development. Now all birds are oviparous and the eggshells are much thicker than those of the reptiles. Because the calcium in it is more brittle as compared to the egg shell or egg of the birds. Now thicker shells permit birds to sit on their eggs and warm them. This is processes called incubation. So these birds build nests, which is a very comfortable bed, and then they lay down on the eggs in that place. And then they provide warmth by sitting on to the egg. That is why their shells are harder as compared to those of the reptiles. Because reptiles do not incubate the eggs. They do not sit on the eggs. They do not provide warmth to the eggs. Now the boosting, the brooding, the brooding or incubation is Sun's early development. The winter-side feathers are also removed and it becomes a brooding patch which gives it a moist environment, a humid environment and a temperate environment. And that is the most appropriate, the best environment for the development of the egg. Now when many young birds hatch, they are incapable of surviving by their own. Because when the young bird comes out of the egg, this process is called as incubation of the egg. This is hatching of the egg. Now extensive parental care, when the young one comes out of the egg shell, then the parents provide feed. You must have seen that chirping is their sound. And that is a call for the parents to bring food. And then they introduce open beaks to the parents. So the extensive parental care, this is what is called a parental care. So in the beginning, it protects the young ones under its wings and provides warmth. So the young ones are common among birds, then fishes, amphibians and reptiles. And these three groups of animals, the protection of the birds is maximum. So in this diagram, we are seeing that these are the eggs and this chick has come out. And in the beginning, this chick does not look like this, its feathers are wet. But in a few hours, it becomes fluffy. And at this point, it is a one day chick. And after that, this is another bird. And these are the young ones and the mother is feeding them. In both cases, both the parents feed the young ones. And their growth at this point is very rapid. It seems that the output of their development is much higher as compared to the input, the food, the energy which is moving. So it is just, it is no doubt, it is something marvelous. It is inborn. It is something that they do not have to do. This is the process of feeding. The parents have to do it. The nature of their brain is kept quiet. This is what is being translated in this form. So in this way, we can call this protection in birds. It is much better as compared to its previous group, that is the reptiles. So in this, after development, after its so-called birth and its hatching, even after that, they nurse the parents, the young ones. And they keep nursing until they can grow their wings. And they cannot fly. And they cannot get their own feed. So this is all about reproduction in birds.