On 14th June 2008, a pair of Yellow-vented Bulbul (Pycnonotus goiavier) suddenly arrived in my garden and perched on the branches of a tree. They vocalisation of the pair was unfamiliar.

Usually, these bulbuls would make their familiar gurgling noises at their dawn chorus during certain periods of the year. These characteristic sounds can also be heard at other times of the day.

But the sound I heard was new to me – crack-crack-crack, to be answered by crick-crick-crick.

One of the bulbuls was quivering its wings and at the same time spreading and fluttering them. The tail feathers were somewhat spread and partially cocked. The plumage was fluffed (top).

Suddenly, one of the birds flew off, to return about a minute of so later with a long strand of fibre in its bill (left). Nesting material?

They then left the scene, leaving me puzzled. Obviously, this was a form of courtship behaviour.

The Whiskered Treeswift (Hemiprocne comata) is distinctive in its white facial stripes. It is a forest species and resident in Malaysia. In Singapore it is a rare, non-breeding visitor, although it used to be a fairly common resident before.

Mark Chua a.k.a cajuka managed to document the intimate moments of a pair of Whiskered Treeswifts that ended in copulation.

The image on the left shows the male with his chestnut ear-coverts that is lacking in the female on his left.

It appears that very little is known of the breeding behaviour of this species and every little observation helps to increase our knowledge of this bird.

The nest is a half-saucer of feathers and saliva attached to a thin branch. A single egg is laid. Both the adults incubate the egg and tend to the young.

The images above and below show the male in the process of mounting the female to effect cloacal contact that lasts only a few seconds.

An earlier post gives the nesting behaviour of the Grey-rumped Treeswift (Hemiprocne longipennis).

All images by Mark Chua.

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 Eurasian Sparrowhawk (Accipiter nisus) is a forest and open woodland species. Although Thiollay (1994) reported it to be not usually found in urban gardens and parks, Hume (2002) says that it is “bold enough to hunt in gardens and parks.”

The bird is found throughout Europe, except Iceland. During the 1950s and 1960s populations decreased significantly through accidental pesticide poisoning. However, since the 1970s, numbers have increased as a result of enlightened attitudes, protection and controlled use of pesticides.

It builds a simple platform of twigs on flat branches close to the trunk and lays 4-5 eggs. It raises only one brood a year, around March-June. It feeds almost exclusively on small and medium-sized birds like tits, finches, thrushes and pigeons. The image above shows an adult male with prey in a garden in Cheshire, England.

According to Dave, the “male chooses the nest site at the end of February, builds a platform of nest, then the female helps 7/10 days later (below). They come every morning spending approximate one hour, then back around 1130 hours.

“Every time they meet they do courtship ritual, and early May courtship could be up to 12 times a day especially when male brings in a kill. She takes it off him, he goes to check the nest then comes back to mate without fail. Then they sit side by side, preening.

“As soon as 5 eggs are laid she doesn’t like him to come close but she has let him come closer than last year. When he visits her on nest, she is more tolerant. When she is ready to lay an egg, she totally ignores him. If he brings a kill, she will allow him to approach or she will come to him, take the prey and hide it in the ivy in the willow tree and have it later.

“I have put small pond under the chopping block and she used it instantly to drink, hope she bathes in it as I have a cam on it.

Check out Dave’s webpage HERE and a footage of the sparrowhawk nesting in his garden HERE.

References:
1. Hume, Rob (2002). Birds of Britain and Europe. London: Dorling & Kindersley.
2. Thiollay, J. M. (1994). Family Accipitridae (Hawks and Eagles). Pp. 52-205 in del Hoyo, J., Elliott, A. & Sargatal, J. eds. Handbook of the birds of the world. Vol. 2. New world vultures to guineafowl. Barcelona: Lynx Editions.

Images by Steve Magennis; and Chris Sperring MBE provided various assistance.

In the earlier post on the courtship behaviour of the Blue-eared Barbet (Megalaima australis) by Adrian Lim a.k.a wmw998, there was a mention of a prominent black throat pouch that the male displayed when making its mating call (below).

The male was described as puffing and blowing to expand his throat pouch. As the pouch expanded, it pushed aside the black feathers that make up the black upper breast band, exposing a smooth, rounded, black sac.

Adrian is of the view that “the sac is only a tool for making the call, I doubt it is for attracting the female. If you look at the shots carefully, you will notice that the breast of the male bird sinks in whenever the sac inflates or puffs up.”

Dr Geoffrey Davison was consulted and responded: “The throat of most birds bulges a bit when they call, but this looks rather extreme. I would have guessed that its crop is stuffed with food, and then when it is calling as well the upper part of the breast would swell even more.

“I have watched other species of barbets calling, and have not seen such an extreme swelling. On the photo it looks as though part of the patch is bare skin, and black - or is this perhaps a patch of feathers that have got wet and sticky from its food? If it is bare black skin then this does imply a signal function. The bases of the feathers within this patch are black.“

On seeing an enlarged image of the pouch, Geoff added: “Quite dramatic, isn’t it? The black skin is very clear in your tweaked version of the photo. I’m not familiar with the literature on anatomy, but many fruit-eating birds are able to store quantities of food in a gular pouch, for later regurgitation. It’s the equivalent of the macaques’ cheek pouches, though a different part of the anatomy (lower down in the oesophagus). I would be inclined to avoid the word ’sac’ for such a structure.

“Presumably a female barbet would be able to distinguish at a glance a male who has a supply of fruit ready (bigger black pouch = more food), and more inclined to allow copulation. I remember seeing something recently… about male birds rewarding the female who allows copulation by giving her fruit after she has submitted, rather than using fruit to tempt her beforehand.

“The other possibility is that this is a hollow structure, part of the air sac system, used as a resonance chamber to enhance sound production as it calls. These are not mutually exclusive possibilities (there could be both a resonating chamber in the air sac system and a pouch in the oesophagus) but not quite so easy to visualise how the two would work together.”

Morten Strange had this to say: “Bizarre image… This bird is not calling, the gular pouch seems to be stuffed to the brim with fruits…” while Wang Luan Keng suggested a ventriloquism function.

Yes, the pouch stores fruits, plenty of fruits. This species of barbet apparently has to offer a fruit for each act of copulation and usually a series occur one after another.

According to the literature, the skin of the throat or the neck on many non-passerine birds is bare, loose and distensible. In many instances it forms a pouch, especially in fruit-eating birds like hornbills (Kinnarid & O’Brien, 2007). The pouch comes in useful in the transporation of fruits to the nest to feed the chcks and/or mate.

In pelicans the pouch is for catching and holding fish for the young birds. That of the male Great Bustard (Otis tarda) is inflated in display (Garrod, 1874). In male frigatebirds (Fregata spp.) (above left), Marabou Stork (Leptoptilus crumeniferus) (above right), among others, similar pouches are inflated and displayed in courtship or social displays.

In grouse and Painted-Snipe (Rostratula benghalensis), the pouches increase the vocalisations by enlarging the sound resonating chamber (Stettenheim, 2000). Morten also pointed out that the Chestnut-winged Babbler (Stachyris erythroptera) produces low-pitched notes by inflating its neck, barring two patches of skin. The puffed-out neck-skin is a conspicuous blue or violet. His image is published in Collar & Robson (2007).

Image of barbet by Adrian Lim, those of frigatebird and stork by YC.

References:
1. Collar, N. J. & Robson, C. (2007). Family Timaliidae (Babblers). Pp. 70-291 in: del Hoyo, J., Elliott, A. & Sargatal, J. eds. Handbook of the birds of the world. Vol. 12. Picathartes to Tits and Chikadees. Barcelona: Lynx Editions.
2. Garrod, A. H. (1874). On the “showing-off” of the Australian bustard (Eupodotis australis). Proc. Zool. Soc. London 1874, No. 31:471-473.
3. Kinnarid, M. F. & O’Brien, T. G. (2007). The ecology and conservation of Asian hornbills: Farmers of the forest. University of Chicago Press.
4. 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.
5. Stettenheim, P. S. (2000). The Integumentary morphology of modern birds - An overview. Amer. Zoologist 40:461-477.

Adrian Lim a.k.a wmw998 documented a pair of courting Blue-eared Barbet (Megalaima australis) in Malaysia sometime in May 2008

The female was perching on a branch of a tree doing nothing in particular. Suddenly there was a loud call, made by a male nearby. He had food in his bill but this did not prevent him from making “such sweet music” as described by Adrian (left). The male was puffing and blowing to expand his throat pouch. As the pouch expanded, it pushed aside the black feathers that make up the black upper breast band, exposing a smooth, rounded, black sac.

The female was attracted to the male’s display but waited for him to come close and make his courtship offering of food. Only then was there copulation. Each act of copulation was preceded by an offer and actual transference of a succulent fig to the female (below). No fig, no sex! *

This courtship feeding of fruits followed by copulation went on for a number of times, as is typical of barbets (below).

In the image below the male is covering the female with his wings in another act of copulation.

The courtship feeding of the Blue-eared appears different from that of the Coppersmith (M. haemacephala). Whereas the former offered one fig per act of copulation, the latter often got away with less number of fruit as compared with number of copulations - often getting away with two for the price of one. Such behaviour was confirmed by another observation where the Coppersmith managed to copulate with the female, to only release the fruit after and not before. And then he mounted her a second time without offering a second fruit. Two for the price of one!

During mating, singing by the pair is incessant and simultaneous, with head bobbling, side to side tail movement, all these in an aggressively looking manner (Short & Horne, 2002).

Adrian confirms the above with his statement about the male: “Blue-eared Barbet seems to make very loud noise most of the time, when it is not having a female or attracting a female… Normally, it sounds like ‘CHIOK CHIOK’, and it can be doing that for minutes at a time. I have a feeling that it is trying to make its presence known to other males. This is a ‘territorial behaviour’ perhaps!

“However, when it is courting a female, or trying to attract a female to a certain perch or tree, the noise is much gentler and softer, and totally different from the ‘CHIOK CHIOK’. I can’t describe the sound to you in words, but in both cases, you can see the black sac.”

There seems to be no mention of the prominent black throat pouch in the literature. As such, this can be a first record in the Blue-eared Barbet, or any barbet for that matter. Discussion of this throat pouch will be posted in the next few days. So stay tuned!

Addenda:
“I have to clarify here that the courtship is a process that is likely to continue for a few days at the least, between the pair. It is not a case of a male going out to have a ‘good time’, spotted a female and making a lot of noise to attract it! In my opinion, the birds had already ‘accepted’ each other, and so the offer of food was like feeding a young, nothing spectacular, no noise making at all, even when the ACT was over. The only time that the gentle sound was made was when the female bird flew off for reason such as disturbance by other birds or animals, and the male wanted to call it back to the same tree.” Adrian, 1st June 2008

*Adrian has written in to clarify that there were occasions when “…the male bird would feed the female continuously, and only once in a while, got on top of her, though still with the food held in the beak and about to offer her.” 4th June 2008.

Reference:
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.

All images by Adrian Lim.