Blue-throated Bee-eater (Merops viridis)(Linnaeus, 1758)

1. Overview

There are 25 species of Bee-eaters (Meropidae) worldwide [1]. They are a family of colourful birds related to the similarly colourful kingfishers and rollers. They are so called because their diet contains bees and wasps. They feed on other insects as well. Like swifts and swallows, they catch their prey on the wing.Singapore has 2 species, Blue-throated bee-eater, and Blue-tailed bee-eater. The blue-throated bee-eater is recognisable by its bright blue throat, chestnut head and back, and black eye stripe. Its upperparts and wing feathers are predominantly green, while its lower back,rump, and tail are a brilliant blue. Adults have distinctive long tail feathers. Juveniles lack the long tail feathers and have a bluish green head. Adults measure about 28cm in length, including their tails.Their flight is jerky and undulating, with a few rapid wing beats followed by a long glide. Their call sounds like “berek berek”, giving rise to its Malay name, and is frequently uttered in flight. Both Blue-tailed and Blue-throated Bee-eaters have long streamer tails, have similar calls, live in the same habitat. Both have blue tails, but the Blue-throated Bee-eater has a blue throat, whereas the Blue-tailed Bee-eater has a rufous throat. And the latter lack the chestnut head of the former. Also, they are found in Singapore at different times of the year with a slight overlap: Blue-throated from April to September, Blue-tailed from August-March [2].

2. Morphology:

As a member of the Coraciiformes, the blue-throated bee-eater possesses syndactyl feet whereby the second and third digits are joined. Males and females do not possess any significant visible sexual dimorphism. Juveniles (bottom), however, have a deep green crown instead of chestnut brown and lacks the blue throat. The green feathers are shed during the post-juvenile moulting and replaced with chestnut brown feathers over time. “Patchy” (individual on the left) appearance of the crown and mantle is indicative of a younger age.

3. Vocalization:

4. Biology:

4.1 Feeding:

As its name suggests, bee-eaters prey on bees along with other invertebrates, mostly insects such as wasp, dragonflies, and butterflies. Blue-throated Bee-eaters are aerial insectivores[4]. They hunt and capture invertebrate prey mid-air using their beak. This is followed by the knocking of the prey on a hard surface which removes the stinger (below). During this process, the prey is highly stressed causing it to release its venom before it is being consumed (above). Such a behaviour can be observed in other members of the Coraciiformes such as kingfishers and rollers[5].

4.2 Bathing:

Like many other birds, blue-throated bee-eaters are host to various parasites[6][7]. In order to keep themselves healthy, they take daily baths to remove parasites such as chewing lice and to keep their feathers clean. Bathing involves fluffing of feathers while beating at the water while dipping its head into it every now and then. Following which, the bee-eater removes excess water off by shaking away the remaining droplets and flying off to further dry itself. If water is not available, bee-eaters can also indulge in sand bathing. They roll about in loose sand fluffing their feathers and shaking vigorously. It is believed that the sand particles help absorb oil, removes dry skin and parasites that can damage the feathers or suck the blood of the birds[8].

Grooming of feathers usually comes after bathing. It is crucial to keep each filament of the feather, free and clean for flight. Thus the bird preens itself by passing each primary through the beak cleaning it in the process[8] (above).

4.3 Courtship

Courtship often begins with males calling out and raising of throat and wing feathers as a form of display[9]. This is usually followed by an offering of food prey as a form of "nuptial gift". Once the gift is accepted, copulation follows. More often than not, multiple gifts are required before the female accepts her mate. The pair would be perched in proximity and the male slide up to the female which most likely lean forward to facilitate mounting. The male then mounts the female and use his bill to push her head down. As copulation begins, the male will mount the female while flapping his wings to maintain balance. At the same time, females will hang tightly onto the perch so as not to be displaced. This entire process is completed rather quickly in a matter of seconds[10].

4.4 Nest Building

Blue-throated Bee-eaters build their nest in underground tunnels on soft soil (above). The birds fly directly onto the ground, dig the soft soil with their feet to slowly excavate the tunnels. As the depression deepened, they use their beaks to dislodge the soil and feet to displace the loosened particles backwards. Each bout of digging took a few minutes before the birds flew off to rest. Excavation continued until the nests were ready. While their beaks make good picks for digging, their small feet is not suitable for such an activity. As such, beaks are used to break up the soil while the feet rapidly kick back loose earth, with the curved wings forming a ‘half-pipe’ to elevate the legs allowing ease of movement and to direct the loose soil. Each time the birds approached the nest entrance to start the digging, they would look out around for dangers before digging (below)[6][11].

4.5 Egg Laying

As the time for egg laying arrives, females would retreat into the nest to lay the eggs. A clutch of approximately 2-7 eggs is laid over a few days apart from which zero to three young were raised. This is to facilitate asynchronous hatching resulting in chicks of variable size and age from a single clutch. Sometimes, larger clutches of eggs can be observed. These clutches were suspected of containing eggs dumped by extra-pair females. Incubation takes around 30 days during which time the male will feed his partner while she incubates the eggs. Bee-eater broods hatched over periods of up to 10 days[6].

4.6 Brood Care

When the chicks hatch they are supplied by a minimum of the two parents. Most nests, however, were supplied by 3-5 birds. Along with the parents, feeding was carried out by older birds who may have lost a partner and in particular by genetically related younger birds from the last brood. These younger birds could be identified by a lack of the central, elongated, tail feathers as well as remnants of green feathers on their heads giving a patchy appearance. These young adults seem to be highly efficient hunters given the high frequency by which they returned to the nest with food[6][11]. Losses of chicks occurred throughout nesting period but it’s reported to be most frequent during the early stages. Due to the nature of asynchronous hatching, chicks varied in sizes. Mortality often begins with smaller and younger individuals due to the lack of food and attacks from their larger siblings. This behaviour has inferred from peck or puncture wounds on the upper body and head of naked or downy chicks[6].

5. Distribution

The blue-throated bee-eater is a widespread Southeast Asian species that can be found in countries such as Brunei, Cambodia, China (vagrant), Hong Kong (vagrant), Indonesia, Laos, Malaysia, the Philippines, Singapore, Taiwan (vagrant), Thailand, and Vietnam[2][3][4].

In Singapore, their habitats include secondary forest, scrub, old plantation and occasionally parklands. Birds nest communally, excavating nest burrow in sandy banks on quarry faces and man-made sand piles. Birds usually breed in Singapore from March to June but migrate to Indonesia from September on[2].

6. Conservation

7. Taxonomy and Systematics

7.1 Type Specimen

The holotype of the Blue-throated Bee-eater was collected from Myanmar and described by Carl Linnaeus in 1758 under Systema Naturae.
It is currently deposited at Museum für Naturkunde, Berlin[13].

7.2 Taxonomic hierarchy

[1]

[16]

7.3 Blue-throated Bee-eater vs Rufous-crowned Bee-eater

[17]

7.4 Other Closely Related Species

7.4 DNA Barcode

8. References

This page was authored by Tee Yu Xun

Last curated in 2016