Jonathan has been monitoring the White-winged Tern (Chlidonias leucopterus) at Kranji since 2005.

In that early period when he was new to birds, he was rather puzzled by the “chocolate chip” tern he photographed and had difficulty getting it identified (below left). He now knows that it is a White-winged dressed in a transitional plumage.

The White-winged, also known as White-winged Black Tern, breeds in Siberia. It winters south, moving down the Malay Peninsula to Singapore and beyond to as far as Australia.

In Singapore, it is possible to see the bird both in its non-breeding (above right) and breeding plumages (below). The image below shows the breeding plumage, although “not quite though, judging from the white flecks on the head” – according to our bird specialist R Subaraj. Similarly, the “chocolate chip” bird at the top shows early transitional stage, as only some black feathers have developed.

Adds Subaraj: “White-winged Terns usually start arriving as migrants in September. They occur in numbers, particularly during passage, in coastal and offshore areas (and freshwater too). Numbers have declined over the years due to a reduction in foraging areas around our coastlines; such as the original Sg. Serangoon estuary where pig swill would empty out of the Sg Serangoon Kecil from the pig farms and this would attract hundreds of terns.

“Northbound return passage is often late in April/May and during that latter period is when you may have more birds in transitional or near-breeding plumage, as they moult in preparation for their return to their breeding grounds in the north.”

All images by Dr Jonathan Cheah Weng Kwong.

bklim photographed an adult White-throated Kingfisher (Halcyon smyrnensis) showing its brilliant colourful plumage – dark chestnut, blue and white. In addition, it has a red bill, dark brown iris, red orbital skin and legs. The female may have a slightly paler head and belly while the juvenile’s plumage is slightly duller. Whatever the sex or age, the bird is a spectacular specimen, guaranteed to impress anyone.

There is a popular misconception that the brilliance of the kingfishers’ colours is dependent on the angle of light, a result of iridescence. But iridescence does not come into play here, nor are the colours a direct result of the pigments.

What are responsible are the microscopic structures of the feather.

The mature feather covering is made up of a hard protein sheath of keratin. Just below this sheath is a layer of keratin cells filled with tiny pockets of air. As white light strikes the feather, the short wavelengths are scattered by the air pockets. As shades of blue (blue, indigo and violet) have the shortest wavelengths, they are scattered the most and in all direction. Thus we see the blue from any angle.

Just below the layer of cells containing the light scattering air pockets are melanin, pigments that absorb most of the longer wavelengths of light. This creates a dark background, thus intensifying the blue we see.

Other non-iridescent colours besides blue are also produced structurally. When the light-scattering air pockets are a bit bigger (bigger than the wavelength of blue light), the result is green (since blue is no longer scattered, and green wavelengths are now scattered the most), as in some parrots.

With even larger air pockets, no wavelengths are scattered, but all are reflected, producing white light and thus plumage that we perceive as white; white does not exist as a pigment in birds.

All images by bklim.

Reference:
Clark, G. A. Jr. (2004). [‘Form and function: The external bird.’]. Pp. 3.1-3.70 in Podulka, S., Rohrbaugh, R.W. Jr & Bonney, R. (eds.) Handbook of bird biology. Ithaca, NY: The Cornell Lab of Ornithology.

This post is a cooperative effort between NaturePixels.org and BESG to bring the study of bird behaviour through photography to a wider audience.

According to the literature, the prominent black sac seen in the Blue-eared Barbet (Megalaima australis) is a gular sac, also called vocal sac. See earlier posts 1, 2 and 3.

Birds produce most of their sounds with their syrinx, the sound producing organ sited where the windpipe divides into two. What is less known is that there are secondary acoustic structures that modify the sounds produced by the syrinx – whether to spread, amplify or reverberate. One of these is the vocal sac, prominent and exaggerated in some species.

According to Dantzker & Bradbury (2006), the bare vocal or gular sacs seen in the North American grouse and the Neotropical cotingas are inflated only in acoustic display. As most of these sacs are brightly coloured, they are probably also involved in visual signaling. The pan-tropical frigatebirds (below left) and two storks, the Old World Marabou (Leptoptilos crumeniferus) (below right) and New World Jabiru (Jabiru mycteria), also inflate their necks and vocalise, but not always at the same time.

In the above species, the sacs are often held fully inflated for lengthy periods in a strictly visual display and only used occasionally in sound production.

Three other groups have vocal sacs that are equally impressive but not devoid of feathers. Perhaps the most striking is the kakapo (Strigops habroptilus), an endangered flightless parrot from New Zealand that seems to inflate its whole body when booming. Many medium to large bustards, like the Kori Bustard (Ardeotis kori) (below left) inflate sacs that are often covered in elaborate feathering; and some but not all inflating bustard species vocalise while inflated (Collar, 1996; Dantzker & Bradbury, 2006).

According to Johnsgard (1983), certain calls among yearling crowned cranes involve the inflation of the gular sac. This is thought to serve as a resonator that may provide increased carrying power. In the Australian Crane (Grus rubicundus), the gular sac of the male is inflated during display and possibly helps to resonate low-frequency sounds. The Grey Crowned Crane (Balearica gegulorum) of Africa is shown above (right).

Strangely, there is no mention of barbets having gular sacs, not even in the most recent monographs of these birds. It is now obvious that the Blue-eared Barbet’s black sac plays a role in vocalisation, possibly also in fruit storage. And according to Adrian, other species of barbets also have these sacs. Obviously, there is much to be learnt about gular sacs and barbets. Happily, bird photographers like Adrian are currently at the forefront of this investigation.

References:
1. Collar, N. J. (1996). Family Otididae (Bustards). Pp. 240-275 in: del Hoyo, J., Elliott, A. & Sargatal, J. eds. Handbook of the birds of the world. Vol. 3. Hoatzin to Auks. Barcelona: Lynx Editions.
2. Dantzker, M. S. & Bradbury, J. W. (2006). Vocal sacs and their role in avian acoustic display. Acta Zoologica Sinica (Suppl.) 52:486-488.
3. Johnsgard, P. J. (1983). The cranes of the world. Bloomington: Indiana University Press.
4. Short, L. L. & Horne, J. F. M. (2001). Toucans, barbets and honeyguides: Ramphastidaer, Capitonidae and Indicatoridae. Oxford University Press.
5. Short, L. L. & Horne, J. F. M. (2002). Family Capitonidae (Barbets). Pp. 140-219 in: del Hoyo, J., Elliott, A. & Sargatal, J. eds. Handbook of the birds of the world. Vol. 7. Jacamars to Woodpeckers. Barcelona: Lynx Editions.

Image of barbet by Adrian Lim, others by YC.

In the earlier post on the prominent black pouch of the Blue-eared Barbet (Megalaima australis) by Adrian Lim a.k.a wmw998, there was a discussion of the pouch being used as a possible storage for food.

Adrian was adamant in his belief that the pouch was for vocalisation and not for food storage. He wrote, “I had watched the birds for days, and I can safely tell you the pouch wasn’t used for the purpose of holding food, like a hamster! At all times, I had observed the food to be delivered directly from the male’s beak, not regurgitated food.

“I strongly believe that the pouch was for sound production to attract the female (soft note, sounds exactly like blowing a football referee’s whistle lightly, one note at a time ) and perhaps to warn other males of its presence (the chiok chiok sound). I had seen the bird perching on a branch, making both sounds, both using the pouch. The soft sound, as I had mentioned earlier, was made in between feeding the female, when the female happened to be away ‘temporarily’, eg. flown away from the feeding perch because of disturbance. And if you look carefully, the entire breast and belly of the male bird sunk in whenever it made such sound, to inflate the pouch.

“Please check into my posting in NaturePixel a couple of months back… I had some photos of the same male doing the blowing and puffing thing.“

The images above and below show the sequence of pouch inflation. In the absence of food in the bill and a female around, it would seem that the pouch is more involved in vocalisation.

Adrian added, ”This bird comes to the tree near my balcony and blows nonstop, a few times a day. No other bird joins it…

“…I think all barbets, except the Brown, and possibly the Lineated, do the same blow job. So far, I have also captured the Golden-throated doing the same thing. Funny though, they do not open the beak while blowing.”

According to Short & Horne (2001): “Most barbets.. sing to proclaim and maintain a territory; since these species largely occur in pairs or social groups, the female is usually near or with her mate. …the basic form of the song is not elaborate in most barbets, in which a series of low-pitched ‘hoot’ or ‘hoop’ or ‘ooo’ notes are uttered perhaps ad nauseum, seemingly, as in some tinkerbirds and the Coppersmith Barbet.”

In another communication, Short & Horne (2002) state that “most barbets give a relatively low-pitched ‘hoot’, ‘hoop’ or ‘pop’ notes that may be repeated in short to long series as a song, uttered with the bill closed or nearly so.

“…Aggressive calls generally are noisy, and commonly include fast, chattery, squawky, honking, rattling and grating sounds, usually repeated in short to long phrases and often compounded, as in a squeaky grating or squeaky chatter.

“…the more hooping, popping or hooting songs seem ventriloquial, and may vary in volume simply as a result of the barbet turning its head as it sings.”

We will discuss the role of the pouch, or gular sac, in another post.

All images by Adrian Lim.

References:
1. Short, L. L. & Horne, J. F. M. (2001). Toucans, barbets and honeyguides: Ramphastidaer, Capitonidae and Indicatoridae. Oxford University Press.
2. Short, L. L. & Horne, J. F. M. (2002). Family Capitonidae (Barbets). Pp. 140-219 in: del Hoyo, J., Elliott, A. & Sargatal, J. eds. Handbook of the birds of the world. Vol. 7. Jacamars to Woodpeckers. Barcelona: Lynx Editions.

This post is a cooperative effort between NaturePixels.org and BESG to bring the study of bird behaviour through photography to a wider audience.

The Javan Myna (Acridotheres javanicus) that was passed on to me by Lin Yangchen on 21st February 2008 spent a quiet night in its cardboard box. It made soft chirping sounds when I opened the cover of the box the next morning.

Initially widening its gape reluctantly, it did so without persuasion as it was hungry. It was fed mashed bread in water and pieces of banana. Small lumps needed to be directed into the gape before the chick swallowed them. Pieces of mashed fish were also given. It made minimum sound when fed.

As it developed, the chick was more responsive, making more sounds and opening its bill when food was offered (left). It began to grab at the food offered when placed in the centre of the gape, rather than passively allowing the food to drop in.

Usually, it accepted two to three offerings of food at a time, after which it will not accept more. It needs to be fed regularly and often.

As it grew, it made more sounds and moved about inside the box. It also responded when I approached, making chirping sounds, asking to be fed.

Four days after rescue (X+4, X=21st February), the chick began to stand upright and hopped around a bit when places on the grassy ground. It was also seen preening its feathers along the sides of the belly.

The colour differential began to develop. The juvenal feathers around the nape became darker grey than those around the flanks (right top). The wings, other than those feathers showing white, were distinctly black.

On the morning of day X+5, the chick began to preen its wing feathers and scratched its head. It was also seen stretching its wings as well as flapping them.

This was the first time I noticed how it slept. Supporting itself on its tarsi and rump, it placed its head on one side of its shoulder, raised its lower eyelids to close the eyes and then went to sleep (right bottom). It also slept by resting its entire body on the ground, the head similarly touching the ground and wings slightly unfolded (right top). The legs were still not totally strong enough for the bird to stand most of the time.

On day X+6, the chick made louder noises in the morning from inside the box, obviously begging for food. It also flapped its wings vigorously. Unlike previously when anything that was placed into the throat was swallowed, this time the food offered, even when placed inside the throat, was first subjected to a vigorous shake of the head resulting in most being flicked away.

On day X+7, the chick was standing more, even hopping about more. With time the legs got stronger and it was able to stand most of the time. The image below (left), showing the chick supporting itself on its pair of tarsi, was taken on day X+5. That on the right, taken on day X+11, shows it standing upright.

The bird had the habit of turning around to defecate. This happened after taking a few mouthfuls of food. It would turn around, its back facing me, and defecate. Initially puzzled, I later realised that this is what it will do inside the nest.

The chick would be fed from outside the nest and the chick needs to turn around to force its faecal matters from its vent out of the nest. After all, it is not wise to pollute the nest as this will attract predators.