Saturday, 21 July 2012

Blue-throated Bee-eater nesting in Penang

Blue-throated Bee-eater pair (male on the left)

One of my best images some years ago was of a Blue-throated Bee-eater (Merops viridis) with a dragonfly in it’s bill. I developed a love for these birds and the other members of the Bee-eater family. They are magnificent fliers and hunters, are elegant and with a nice blend of colors.
Late last year I took up residence upon retirement on Penang island with more time to pursue my photographic passion. As soon as the Bee-eaters arrived to nest I was in my element. First it was the Chestnut-headed Bee-eaters, which will be the subject of a separate article. The Blue-throated Bee-eaters suddenly appeared in a flock of about 12-15 in mid February. There were not many Chestnut-headed Bee-eater nesting, possibly about 12-15 nests so there was no major territorial disputes.
Male and female Blue-throated Bee-eaters look the same and only when they are adjacent can differences be seen; the male (left, below) is slightly bigger, has longer tail feathers and a larger forehead.
For the first few weeks the Bee-eaters got used to their environment by perching in the surrounding higher trees and swooping at insects. Research shows that have a better than 70% strike-rate on flying prey and can spot a fly 70 metres away. Pairs were most likely already formed and the couples explored various sites to drill their nest holes. There are usually several exploratory drills before a serious nest hole is formed. Bee-eaters are all elegance and grace while in flight and it seems incongruous that they have to become miners to make their nests. Their bills make ideal picks but the dainty little feet are not great shovels. The bills are used to break up the soil while the little feet rapidly kick back the loosened soil, with the curved wings forming a ‘half-pipe’ to elevate the legs to augment their freer movement and to direct the tailings.


Blue-throated Bee-eaters are beautifully colored and elegant birds
Couples are likely paired for life and greet each other with great excitement
Some territorial disputes occur over restricted perching sites
In digging a nest hole the long bill is used to loosen the soil
The loosened soil is then kicked backwards with the wings forming a channel

Mating occurred around this time. The pair would be perched in proximity and the male would sidle up to the female who would most likely lean forward to facilitate mounting. The male would then mount the female and use his bill to push her head down while coupling took place in a flurry of wings and legs. By this time the colony had expanded to approximately 200 birds.
The male may bring gifts of insects to the female to initiate mating or gift-giving may not be required. There is a phase of gift giving in another week or two, which was also common to the Chestnut-headed Bee-eaters. It is believed this period with the male supplying the females is to assist her nutritionally with the rigors of egg-laying.
According to research 4-5 eggs are laid some days apart, so there is an asynchronous development of the eggs and chicks. Chicks I saw emerging from one nest came out singly over a period of three days. Incubation takes around 30 days during which time the male will feed his partner while she incubates the eggs. When the chicks hatch they are supplied by a minimum of the two parents. Most nests I observed however were supplied by 3-5 birds. As well as 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.  These sub-adults appeared to be prolific hunters judging by the frequency they arrived with 'cargo'.

Mating is initiated by the female leaning forward
Here coupling occurred in the early morning light 
Gift-giving may precede mating but occurs more frequently around egg-laying time
 As the chicks matured the activity around a productive nest hole was hectic with birds lining up with cargo, like planes on a runway holding pattern, waiting for their turn in the nest. The development of the chicks in the nest cavity also took around 30 days. On the day of the fledging the suppliers ceased bringing insects to the nest in order to draw out the chick. I observed 4 fledgings and the chick was not seen until it rapidly came to the surface and flew into adjacent trees. You can tell fledging is imminent because incoming insects are deposited at the threshold of the nest.

There are frequent trips into the nest as the eggs are incubated and feeding starts
As the chicks mature there is a constant stream of insects being supplied
 Juveniles, from the last nesting, help supply the nest
A mature nest is a busy place with constant arrivals and departures
Fledged chicks are large and have green colored heads.
Blue-throated Bee-eaters are not endemic to this nesting area however the newly fledged chicks could be seen in subsequent days with adults, likely their parents.  On several occasions they were apparently getting lessons in the finer points of excavation. The newly-emerged chicks are the same size as the parents but have no elongated, central tail feathers and have a green head instead of the brown of the parents.
Nest holes were drilled in small banks or on the flat ground, some entrances were obvious while some were very cryptic within the surface grass or sundry vegetation.  Raising chicks within the ground presents some problems; parasites are abundant and bee-eaters spend a considerable time preening and dust bathing to remove unwanted passengers. I observed one chick that was forced from the nest prematurely when the cavity was invaded by termites. Wild boars also caused some ground perturbation around nest entrances. 
Blue-throated bee-eaters are a colonial species and the nesting grounds are 'alive' with the chirping sounds of their characteristic communication. There were a number of raptors flying over from time to time and these are kept under surveillance by a number of pairs of eyes. With the adults' flying skills and the sequestering of the chicks until maturity they are not in danger from the skies. It is important that such nesting grounds are respected and protected during this busy period. Fortunately at this site circumstance has allowed for this, so far at least. 

Bee-eaters are constantly preening to remove parasites 
This Bee-eater is dust and sunbathing to remove parasites
Group surveillance; an eagle is tracked

Graeme Guy July 2012


4 comments:

  1. Fantastic write-up Graeme - the pictures and the words complement each other perfectly. I think the dragonflies are Pantala flavescens (the golden one which quarters open areas in vast squadrons) and Orthetrum sabina (the stripy one - also common in open areas but more terrestrial).

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  2. Hi Graeme

    Your nature photography depresses me - for the best possible reasons. I used to be an avid bird watcher and when the Rainbow Bee-eaters arrived here on their southward migration we would strike out to the more arid areas north and east of Adelaide, looking for sandy banks and dunes. I can't recall ever having a view through the binoculars as good as the portraits you present here. So far as photographing them, forget it!

    It is tempting to assume that the Blue-throated Bee-eater is more approachable - but probably not. I am sure that your success is the result of an understanding of the birds' habits and great dedication on your part. I am in awe.

    Cheers!
    Robert

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  3. Dear Graeme
    Perhaps you could help me with a bird identification. I live in Chiang Mai Thailand and was watering my longon trees. I noticed a hole in the ground about 7-8 cm in diameter. Thinking it was a gopher hole (they will gnaw on tree roots and kill the tree), I filled it with water. To my surprise a green (on the back at least) bird about 15 to 20 cm emerged and flew off. I've lived here over 20 years and have seen these hole occasionally but never a bird. Any idea what it is?
    Regards
    Allan

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  4. Hi Graeme,
    Fantastic shots! I was wondering, what kind of lens that you used for these shots?
    Regards,
    Jephte

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