Which Male Bird Produces Milk For Its Young?

In the animal kingdom, nursing young is a role almost exclusively carried out by female mammals. However, there is one unique species of bird in which the male takes on lactating duties – the Dayak fruit dove of Southeast Asia.

If you’re short on time, here’s a quick answer to your question: The male Dayak fruit dove produces crop milk to feed its young hatchlings.

In this comprehensive article, we will explore the biological phenomenon of crop milk production in male Dayak fruit doves. We’ll examine the mechanisms behind this ability, the evolutionary benefits it confers, and how it sets the Dayak fruit dove apart from other birds in its singular parental care.

Dayak Fruit Dove’s Production of Crop Milk

Composition and Creation of Crop Milk

The Dayak Fruit Dove, scientifically known as Ptilinopus hoedtii, is a unique bird species found in the rainforests of Borneo. What sets this bird apart from others is its ability to produce crop milk, a substance rich in nutrients that is used to feed their young.

Crop milk is not actual milk, but a secretion produced by the male dove’s crop, which is an enlargement of the esophagus.

The composition of crop milk is fascinating. It contains a high concentration of proteins, fats, and carbohydrates, making it an ideal source of nutrition for their hatchlings. This substance is produced by the male dove through the regurgitation of partially digested food.

The crop acts as a storage pouch where the food is broken down and mixed with saliva, creating a creamy and nutritious liquid.

Regurgitation Feeding of Hatchlings

Once the crop milk is produced, the male dove regurgitates it to feed their hatchlings. This unique feeding behavior is commonly observed in bird species that lack nipples or mammary glands. The male dove regurgitates the crop milk directly into the mouths of their young ones, ensuring they receive the necessary nutrients for their growth and development.

The crop milk is an essential part of the Dayak Fruit Dove’s reproductive strategy. It allows the male dove to contribute significantly to the care and nourishment of their offspring, alongside the female dove.

This cooperative breeding behavior is crucial for the survival of their species and demonstrates the remarkable adaptability and creativity found in nature.

Comparison to Mammals

The production of crop milk by the Dayak Fruit Dove is a rare phenomenon in the avian world. While mammals are known for their ability to produce milk to nourish their young, the crop milk production in birds is an exceptional case.

This unique behavior challenges the traditional notion that milk production is exclusive to mammals.

Although crop milk and mammalian milk serve the same purpose of providing nutrition to offspring, there are notable differences between the two. While mammalian milk is produced by mammary glands, crop milk is produced through the regurgitation of partially digested food.

Additionally, the composition of crop milk differs from mammalian milk, with varying nutrient profiles.

Understanding the Dayak Fruit Dove’s production of crop milk provides valuable insights into the diversity of reproductive strategies in the animal kingdom. It highlights the incredible adaptability and evolutionary innovations that have allowed different species to thrive in various environments.

Physiological Adaptations for Crop Milk

Birds are known for their diverse and fascinating reproductive strategies. While most people are familiar with mammals producing milk to nourish their young, it may come as a surprise that some male birds also possess the ability to produce a substance called crop milk.

This unique adaptation allows them to provide essential nutrients to their offspring, ensuring their survival and growth.

Specialized Glandular System

The secretion of crop milk is made possible by a specialized glandular system found in certain bird species. This gland, known as the crop sac or the pigeon’s milk gland, is located in the crop, an enlargement of the esophagus.

The crop sac is lined with a highly vascularized epithelium that produces a milky substance rich in proteins, lipids, and other essential nutrients.

This glandular system has evolved in birds such as pigeons, doves, flamingos, and some penguins to fulfill the nutritional needs of their young. It serves as an alternative to mammalian milk, ensuring the survival of the offspring in environments where resources may be scarce or unpredictable.

Hormonal Control of Lactation

Just like in mammals, the production of crop milk in male birds is regulated by hormones. The hormone prolactin plays a crucial role in promoting the development and functioning of the crop sac. It stimulates the growth of the glandular tissue and promotes the synthesis and secretion of the nutrient-rich crop milk.

Interestingly, the hormonal control of lactation in male birds is similar to that of female birds during egg-laying and brooding. Prolactin levels rise during the breeding season, triggering the development of the crop sac and the production of crop milk.

This hormonal regulation ensures that the offspring receive the necessary nutrients during the critical early stages of their development.

Nutrient Transport and Metabolism

Once the crop milk is produced, it is regurgitated by the male bird and fed directly to the chicks. The crop acts as a temporary storage organ, allowing the male bird to produce crop milk in advance and provide a continuous supply of nutrients to the offspring.

Inside the crop, the nutrients from the crop milk are absorbed into the bloodstream and transported to the growing chicks. The young birds rely solely on crop milk for their nutrition until they are able to digest solid food on their own.

Studies have shown that crop milk is a highly nutritious substance, containing high levels of proteins, fats, and other essential nutrients. It provides the growing chicks with the energy and building blocks necessary for their rapid growth and development.

While the production of crop milk is a remarkable adaptation, it is important to note that not all bird species possess this ability. It is limited to certain taxonomic groups and is most commonly observed in species that nest in colonies or have extended parental care.

Understanding the physiological adaptations for crop milk in male birds sheds light on the incredible diversity of reproductive strategies in the animal kingdom. It showcases the ingenuity of nature in ensuring the survival and success of offspring, even in challenging environments.

Evolutionary Benefits of Male Lactation

Male lactation, the ability of male birds to produce milk for their young, is a fascinating phenomenon that challenges traditional notions of parental roles in the animal kingdom. While female lactation is widely observed in mammals, it is relatively rare in the avian world.

However, in a few species of birds, males have evolved the ability to produce milk, providing numerous benefits both for themselves and their offspring.

Increased Offspring Survival

One of the key evolutionary benefits of male lactation is increased offspring survival. In species where males produce milk, the male bird takes on a more active role in nurturing and feeding the young.

This can be particularly advantageous in environments where food resources are scarce or unpredictable. By producing milk, male birds are able to ensure a steady supply of nutrition for their offspring, increasing their chances of survival and overall reproductive success.

Division of Parental Duties

The ability of male birds to produce milk also allows for a more equitable division of parental duties. In many bird species, the female is solely responsible for incubating the eggs and caring for the hatchlings.

However, in species where males have evolved lactation, they are able to actively participate in the rearing of their offspring. This division of labor not only lightens the burden on the female but also strengthens the bond between the parents, leading to more successful breeding pairs and healthier offspring.

Monogamous Pair Bonding

Male lactation has also been linked to the formation of monogamous pair bonds in certain bird species. In monogamous relationships, males and females form long-term partnerships, sharing the responsibilities of raising their young.

Male lactation plays a crucial role in reinforcing this bond, as it allows the male to actively contribute to the nourishment and care of the offspring. This shared parental effort promotes cooperation and mutual investment between the parents, leading to stronger pair bonds and increased reproductive success.

The evolutionary benefits of male lactation in birds highlight the incredible adaptability and complexity of parental roles in the animal kingdom. By challenging traditional gender norms and assumptions, these species have found innovative ways to ensure the survival and well-being of their offspring.

The study of male lactation in birds continues to provide valuable insights into the evolution of parental care and the diverse strategies employed by different species to ensure their reproductive success.

Uniqueness of Male Milk Production in Birds

Limited to Dayak Fruit Doves

When it comes to male birds producing milk for their young, this unique phenomenon is limited to a specific species known as the Dayak Fruit Doves. These beautiful birds, scientifically known as Ptilinopus hoedtii, are native to the rainforests of Borneo.

The males of this species have developed a remarkable adaptation that allows them to produce a substance similar to milk to nourish their chicks.

The milk-like substance produced by male Dayak Fruit Doves is not identical to the milk produced by mammals, but it serves a similar purpose. It is rich in nutrients and provides essential sustenance for their growing offspring.

This adaptation is thought to have evolved as a response to the unique dietary needs of their chicks and the scarcity of food resources in their environment.

Interestingly, the ability to produce milk is not present in all male Dayak Fruit Doves. Only a select few individuals possess this ability, making it even more fascinating and rare within the avian world.

Contrast with Other Bird Species

The male milk production phenomenon in Dayak Fruit Doves stands in stark contrast to the traditional roles of male and female birds in reproduction. In most bird species, it is the female who takes on the responsibility of incubating the eggs and feeding the young.

However, in the case of Dayak Fruit Doves, the males play an active role in parental care by producing milk for their offspring.

This unique behavior challenges the conventional understanding of bird reproduction and highlights the incredible diversity and adaptability found in nature. It showcases the ability of organisms to evolve and develop innovative strategies to ensure the survival and success of their species.

Future Research Directions

The male milk production in Dayak Fruit Doves remains a fascinating area of study for researchers. While some aspects of this phenomenon have been explored, there is still much to uncover. Future research may focus on understanding the physiological mechanisms behind male milk production and the genetic basis for this adaptation.

Scientists are also interested in discovering how male Dayak Fruit Doves acquire the necessary nutrients to produce milk and whether there are any trade-offs or costs associated with this behavior. Additionally, further investigation into other bird species may reveal similar instances of male milk production and shed light on the evolutionary significance of this unique trait.

For more information on bird reproduction and the fascinating adaptations found in the animal kingdom, you can visit National Geographic’s Birds page.


The parental strategy of crop milk provision uniquely equips male Dayak fruit doves to take over the critical role of nourishing hatchlings.

This fascinating deviation from normative avian biology underscores how dynamic and varied nature’s solutions can be for giving offspring the best chance at survival.

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