Blue-eared Barbet’s pouch: Vocalisation rather than storage

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.

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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.“

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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.

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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.

Input and 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.

An account of this barbet’s gular sac has now been published: Lim, A. T. H., L. K. Wang & Y. C. Wee, 2009. The Blue-eared Barbet Megalaima australis and its gular sac. BirdingASIA 11: 98-101.

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

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