The Asian Koel: A Study of Sexual Dimorphism, Breeding Behavior, and Global Distribution

 *Heri Tarmizi

The Asian Koel (Eudynamys scolopaceus) is a fascinating bird known for its distinctive calls and interesting behaviors, particularly its brood parasitism. Found widely across South and Southeast Asia, including Indonesia, this bird is a common sight in urban areas like parks, gardens, and bushes. The Asian Koel exhibits sexual dimorphism, with males and females differing significantly in color. Moreover, this species is notable for its migratory patterns and unique breeding behaviors.

Description and Sexual Dimorphism

The Asian Koel is a member of the cuckoo family, Cuculidae. The species exhibits striking sexual dimorphism. The male Asian Koel is predominantly glossy black with a greenish-blue sheen and striking red eyes. Its plumage can appear almost iridescent under the right lighting conditions, giving it a glossy, sleek appearance. On the other hand, the female is much less conspicuous. She has a brownish body with white and buff spots, and her underparts are heavily streaked. These contrasting colors between the sexes are believed to play roles in their mating and nesting behaviors.

Asian koel Female Image source e-bird

Asian koel Male Image source e-bird

Vocalization

One of the most distinctive features of the Asian Koel is its loud and unique call, which is more commonly heard than the bird is seen. The male’s call is a series of loud, repetitive "ko-el" sounds, which can be heard throughout the day and sometimes even at night. The female’s call is different, consisting of shrill and repetitive "kik-kik-kik" sounds. These vocalizations are often associated with the breeding season and are crucial for communication between mates and for territorial purposes.

Breeding Behavior and Brood Parasitism

The Asian Koel is renowned for its brood parasitism, a behavior where it lays its eggs in the nests of other bird species, particularly those of the crow family (Corvidae). This behavior relieves the koel of the need to build its own nest and rear its chicks. The female koel will lay her eggs in the host's nest, leaving them to be incubated and raised by the unsuspecting host parents.

The breeding season for the Asian Koel varies by region but generally occurs during the warmer months when food is plentiful. In Indonesia, this typically aligns with the local climate and food availability. The female koel is known to lay her eggs in the early morning when the host birds are away foraging. The koel chick hatches earlier than the host's eggs and often exhibits aggressive behavior, such as pushing the host's eggs or chicks out of the nest to eliminate competition for food.

 Distribution and Habitat

The Asian Koel is widely distributed across the Indian Subcontinent, China, Southeast Asia, including Thailand, Malaysia, and the Indonesian archipelago. In Indonesia, the koel is found on several islands, including Java, Sumatra, and Bali. It is a migratory bird in parts of its range, particularly in regions where seasonal changes affect food availability.

In urban environments, the Asian Koel is commonly found in parks, gardens, and areas with abundant tree cover. Its ability to adapt to human-altered landscapes has facilitated its spread across various regions. Koels are also seen in rural areas, especially in agricultural regions where they can find plenty of food and suitable host nests for breeding.

 Global Distribution

Globally, the Asian Koel's range extends from the Indian subcontinent in the west to China and Southeast Asia in the east. They are known to migrate to warmer regions during the colder months. In Australia, the koel is considered a summer visitor, arriving in the northern parts of the country to breed during the southern hemisphere’s spring and summer.

Conservation Status

The Asian Koel is listed as Least Concern by the International Union for Conservation of Nature (IUCN). This status is due to its wide distribution and large, stable population. However, habitat destruction and changes in land use could impact local populations. Despite these potential threats, the koel's adaptability to various habitats, including urban areas, has helped maintain its population numbers.

 Conclusion

The Asian Koel is a remarkable bird with distinctive sexual dimorphism, unique vocalizations, and intriguing breeding behaviors. Its widespread presence across South and Southeast Asia, including Indonesia, underscores its adaptability and resilience. Understanding the koel's behavior and ecology not only enriches our knowledge of avian biodiversity but also highlights the complex interactions between species in shared ecosystems. As urbanization and habitat changes continue, the Asian Koel's ability to thrive in diverse environments serves as a testament to its adaptability and the intricate balance of nature.

Bibliography

- Payne, R. B. (2005). The Cuckoos. Oxford University Press.

- Ali, S., & Ripley, S. D. (1983). Handbook of the Birds of India and Pakistan. Oxford University Press.

- Rasmussen, P. C., & Anderton, J. C. (2012). Birds of South Asia: The Ripley Guide. Lynx Edicions.

- Erritzoe, J., Mann, C. F., Brammer, F. P., & Fuller, R. A. (2012). Cuckoos of the World. Bloomsbury Publishing.

- BirdLife International. (2024). Eudynamys scolopaceus . The IUCN Red List of Threatened Species 2024.