Chickens do not drink milk from their mothers because they belong to the biological class Aves, which does not produce this substance. Unlike mammals, chickens and other birds nourish their hatchlings using pre-stored nutrients and the immediate consumption of external food. Their reproductive strategy, which involves laying eggs, is fundamentally linked to this non-lactating biology.
The Biological Basis: Why Birds Do Not Produce Milk
Lactation is a defining characteristic of mammals, which possess specialized structures called mammary glands designed to produce true milk. Chickens, classified as Aves, lack the biological infrastructure necessary for synthesizing and delivering this substance. The production of milk involves complex hormonal and anatomical systems unique to mammals, systems that birds simply do not share.
The energy investment strategies of these two classes differ significantly based on their reproductive methods. Mammals sustain their young internally and then through lactation, requiring continuous parental energy output. Birds package all the necessary resources into the egg before it is laid. This strategy ensures the chick receives its entire initial supply of sustenance from the egg’s contents rather than post-hatch parental secretions.
Nutritional Sources for Newly Hatched Chicks
A newly hatched chick’s first source of energy is internal, supplied by the residual yolk sac that is fully withdrawn into the abdominal cavity just before hatching. This yolk provides concentrated fats and proteins, sustaining the chick for the first 24 to 72 hours of life. The stored yolk is metabolically sufficient to meet the chick’s initial needs, providing a buffer until they locate external food and water.
The yolk sac typically takes between 3 and 5 days to be fully absorbed. Chicks are classified as precocial, meaning they are mature, fully feathered, and mobile immediately after hatching, allowing them to begin foraging at once. The immediate consumption of external feed, which provides necessary carbohydrates, is required for the chick to properly utilize the dense fat reserves within the remaining yolk. While some bird species, such as pigeons, produce “crop milk,” chickens do not possess this adaptation and rely solely on the yolk and external foraging.
The Mother Hen’s Role in Teaching Foraging and Hydration
The mother hen compensates for the absence of milk by providing intensive behavioral instruction to her brood immediately upon hatching. She guides her chicks to appropriate food and water sources, actively teaching them the skills necessary for finding sustenance and avoiding danger. The hen uses distinct clucks to communicate with her young, including specific calls to draw attention to newly discovered edible items.
She physically demonstrates foraging techniques, such as scratching the ground to uncover hidden insects and seeds, which the chicks instinctively mimic. This parental guidance also includes leading the chicks to water and dipping her own beak to encourage them to drink, as hydration is a learned behavior. Brooded chicks exhibit better socialization, reduced fear responses, and more developed foraging habits than those raised without a mother hen.