Do Birds Produce Milk?
Everywhere you turn in East Africa, doves are quietly making their mark – perched on branches, fluttering around waterholes, or cooing in the distance. But these seemingly ordinary birds have some extraordinary secrets. From their unique way of drinking to their surprising ability to produce a milk-like substance for their chicks, doves are full of fascinating behaviours that challenge what we think we know about birds.
How Doves Drink Differently
If you’ve ever watched birds at a waterhole, you’ve likely noticed their peculiar way of drinking. Most birds follow the “sip and tip” method: they dip their beak into the water, lift their head to let the liquid flow back to their crop, and then repeat the process. But what is a crop? The crop is a small pouch-like organ located in the bird’s throat, just before the stomach. It acts as a temporary storage space where food or water can be held before digestion. This organ is particularly useful for birds, allowing them to eat or drink quickly and then process it later, away from predators or harsh conditions.
Doves, however, break the “sip and tip” rule. When a dove drinks, it submerges its beak slightly in the water and keeps it there. By using capillary action – a natural process where water is drawn up through narrow spaces – they pull water into their beaks. Simultaneously, they use their tongue like a piston to pump the water directly into their throat. This adaptation allows doves to drink quickly and efficiently, a vital trait in the often arid environments they inhabit.
Pigeon Milk? A Remarkable Parenting Strategy
Beyond their drinking habits, doves also boast an extraordinary way of nourishing their young. Both male and female doves produce a nutrient-rich substance known as pigeon milk in their crop. This milk is fed to their chicks during the first critical days after hatching, giving them a strong start in life.
Although pigeon milk and mammalian milk evolved independently, they share some surprising similarities. For instance, both are regulated by the hormone prolactin, which plays a key role in parenting across many species. In mammals, prolactin stimulates the production of milk in the mammary glands. In birds, including doves, it triggers the production of crop milk. Essentially, prolactin is the “parenting hormone,” responsible for initiating behaviors and processes that support the growth of offspring.
While mammalian milk is a liquid secretion – likely an evolved form of sweat – pigeon milk is made up of specialised cells that are shed from the lining of the crop. These cells form a paste-like substance packed with nutrients that chicks consume directly from their parents’ mouths. Pigeon milk is a powerhouse of nutrition, consisting of approximately 60% protein and the remainder mostly fat. These nutrients are essential for the rapid growth and development of young chicks.
Remarkably, pigeon milk doesn’t just nourish, it also protects. Similar to mammalian milk, it contains antibodies that help bolster the chicks’ immune systems while their own defenses are still developing. Studies have shown that even other species, such as chickens, benefit from consuming pigeon milk. One experiment found that chickens fed pigeon milk developed stronger immune systems compared to those given a similar nutritious diet without the milk.
Another fascinating parallel between mammalian and pigeon milk is their role in gut health. Mammalian milk often contains beneficial bacteria, which help establish a healthy gut microbiome in newborns. These bacteria are essential for proper digestion and overall health. Similarly, pigeon milk introduces beneficial bacteria to the chicks’ digestive systems, giving them a head start in developing a robust and efficient gut.
While crop milk is extraordinary, it’s not exclusive to doves. Flamingos and male penguins also produce crop milk to feed their young. However, the consistency, composition, and shared traits with mammalian milk make the process in doves particularly remarkable.
Next time you find yourself at a waterhole, take a moment to appreciate the humble dove that comes fluttering down. From its efficient drinking habits to its sophisticated parenting strategies, this seemingly ordinary bird is anything but. Their adaptations not only highlight their resilience but also underscore the intricate ways in which nature ensures survival and growth.
