The Remarkable World of the Blue-throated Bee-eater

The Blue-throated Bee-eater (Merops viridis) is a member of the bee-eater family and is widely distributed across Southeast Asia, where it inhabits subtropical and tropical environments, especially mangrove forests. Its main diet includes bees, wasps, dragonflies, and other flying insects. This small bird is famous for its striking colors, featuring a reddish crown and nape, deep green wings, a pale green chest, and the distinctive blue patch on its throat.

Young birds have a less colorful appearance compared with adults. Juveniles usually have greenish heads and wings with lighter green underparts, gradually developing the bright adult plumage as they mature. These birds also produce a wide range of vocal sounds, including powerful long-distance calls that help individuals communicate through dense forest environments.

Blue-throated Bee-eaters display asynchronous hatching, meaning that their chicks do not all hatch at the same time. This often results in competition between siblings and may lead to siblicide. Older chicks usually have an advantage because they are larger, stronger, and better able to compete for food supplied by their parents. These birds also undertake seasonal movements, including migrations between islands in Southeast Asia and mainland regions. One notable migration route begins in Sumatra, crosses the Strait of Malacca, and reaches the western coast of Malaysia. Some populations also travel from Southeast Asia to breeding areas in western China.

The species is currently classified as Least Concern because of its broad geographic range and relatively stable population. However, habitat destruction caused by deforestation remains a major concern, as the loss of forests can reduce suitable living areas and affect overall bird diversity.

Taxonomy and Classification

The Blue-throated Bee-eater belongs to the family Meropidae, which includes bee-eaters and around 27 related species. It is also sometimes known by another common name, the Chestnut-headed Bee-eater.

Two subspecies are generally recognized:

Merops viridis viridis (Linnaeus, 1758): Found from southern China through Indochina and the Greater Sunda Islands.

Rufous-crowned Bee-eater (Merops viridis americanus) (Statius Müller, 1776): Found in the Philippines and considered by some researchers to represent a separate species.

Previously, M. v. americanus was treated as the same species as M. v. viridis in classifications published by Sibley and Monroe during the 1990s. Only more recent studies have recognized them as separate subspecies.

Physical Description

Adult Blue-throated Bee-eaters usually reach about 21 cm in body length, with an additional 9 cm contributed by their elongated tail feathers. Their body weight typically ranges from 34 to 41 grams.

Fully grown birds have exceptionally colorful plumage. They display a reddish crown and neck area, dark green wings, a blue tail, light green breast feathers, a white belly, and the characteristic blue throat patch. Juveniles develop their adult colors gradually and are mostly green in appearance, with darker green heads and wings and lighter green chests.

Both adults and young birds have dark eye markings. Their eye color can vary from reddish shades to brown or a mixture of both.

Vocalizations and Communication

Blue-throated Bee-eaters use a diverse collection of sounds, including long calls, warning calls, chirps, soft chirps, purring sounds, sharp coos, trills, and feeding-related calls.

Their long calls are especially important for communication across long distances. These calls are produced either while flying or while sitting on a perch. During the display, the bird stretches its neck and points its bill upward, creating a recognizable posture known as the long-call position.

Short chirping sounds are usually sharper and repeated at regular intervals, often being used during activities such as digging.

Distribution and Habitat

The Blue-throated Bee-eater has a broad range extending from southeastern China to the Greater Sunda Islands. The species is especially common in Singapore, Malaysia, southern Cambodia, and southern Thailand, with additional populations found in regions such as Borneo and Java.

These birds generally live at lower elevations, usually between sea level and around 670 meters. They occupy many open habitats, including agricultural fields, suburban gardens, riverbanks, coastal dunes, and sandy open areas.

During the winter season, some individuals move into forest canopies and mangrove waterways. Unlike many other bee-eaters that dig nests into steep sandy cliffs, Blue-throated Bee-eaters usually create horizontal tunnels in flat ground, making their nesting sites easier to access.

They may breed in colonies containing around 50 to 200 pairs, although some individuals also live independently in open landscapes.

Breeding Behavior

Blue-throated Bee-eaters have an estimated generation length of approximately 6.2 years. Their breeding strategy involves asynchronous incubation, meaning parents begin caring for eggs at different stages, resulting in chicks hatching at different times.

Eggs usually hatch over a period of about ten days, with an average difference of several days between the first and last chick. The timing of hatching affects chick size, with the earliest-born chick usually being the largest.

A breeding pair typically produces two to seven eggs, but only zero to three chicks usually survive until they are ready to leave the nest. Younger and weaker chicks often die first because of competition from older siblings.

Siblicide occurs when older chicks attack younger ones using a temporary sharp hook on the upper bill. This structure later disappears as the birds mature. Older chicks are better protected because they develop stronger bodies and more feathers, while younger chicks are more vulnerable to injuries.

Sibling competition becomes more intense when food supplies are limited. Since parents usually deliver insects one at a time, stronger chicks can easily dominate access to food. Larger broods do not necessarily improve survival rates, and chicks with lower body weight are more likely to suffer injuries and eventually die.

Feeding Habits

Blue-throated Bee-eaters mainly consume flying insects, especially bees and wasps. They also capture flies, beetles, and other insects, including prey measuring up to about 42 mm in length.

Dragonflies make up a significant portion of their diet, and hunting success is highest during sunny weather. They usually stop feeding during rainfall and immediately afterward.

Their feeding activity follows seasonal weather patterns, with the highest feeding rates occurring during the breeding period when sunny conditions become more common after the rainy season.

Migration Patterns

Every spring, Blue-throated Bee-eaters (Merops viridis) and Blue-tailed Bee-eaters (Merops philippinus) migrate from Sumatra across the Strait of Malacca toward the western coast of Malaysia.

During migration, they use a combination of flapping and gliding flight. They sometimes take advantage of ocean breezes and rising air currents to gain altitude while crossing the sea.

After reaching land, migrating birds may stop on structures such as lighthouses or tree branches to rest before continuing their journey. Observations made between 2000 and 2001 recorded more than 2,200 migrating bee-eaters, including over 200 Blue-throated Bee-eaters.

The highest migration numbers were recorded during strong thermal conditions, which allowed birds to soar more efficiently. Strong winds from the west also appeared to encourage migration toward Malaysia.

Some populations also travel to western China during breeding season, as shown by their known distribution range.

Relationship with Humans and Conservation

Human activity represents the greatest threat to Blue-throated Bee-eater habitats. Although the species is currently considered Least Concern due to its large distribution and stable numbers, habitat destruction remains a potential long-term problem.

Logging and rainforest removal can negatively affect individual bird species as well as overall biodiversity. Studies in Malaysian tropical forests have shown that bird communities can recover within several decades after logging, with older recovering forests supporting greater species diversity than recently disturbed areas.

Although not commonly kept, Blue-throated Bee-eaters are occasionally maintained in captivity for ornamental purposes or horticultural collections.