Crimson Sunbird: Adult and juvenile male plumage

posted in: Morphology-Develop., Sunbirds | 5

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The male Crimson Sunbird (Aethopyga siparaja) is eye-catching because of its prominent crimson head, back, throat and upper breast.

In a juvenile male bird, the crimson is not apparent until later when individual crimson feathers develop as the bird moults from a juvenal to a breeding plumage. As individual breeding feathers develop, the redness appears in scattered patches as seen in the image above (right)

However, an adult male during the non-breeding period sheds most of his crimson feathers on his head and breast, taking on an eclipse dress. When the next breeding season comes, he will develop his colourful plumage once again.

So is the bird above (right) a juvenile male or a male in eclipse dress? Or is he a young adult in eclipse dress?

Choo Teik Ju
Singapore
August 2008

Reference:
Cheke, R. A., Mann, C. F. & Allen, R. (2001). Sunbirds: A guide to the sunbirds, flowerpeckers, spiderhunters and sugarbirds of the world. New Haven & London: Yale University Press.

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.

5 Responses

  1. Hi Yeow Chin,

    While I cannot say if the Crimson Sunbird adopts an eclipse plumage elsewhere, that does not seem the case in Singapore. Here, we see full plumaged males throughout the year, whether they are breeding or not.

    Perhaps this may be due to our weather being more or less consistent throughout the year, allowing for a longer breeding season. There appears to be, for example, evidence of nesting between December – September, for the Olive-backed Sunbird.

    The bird in the right photo should be considered a immature that is slowly moulting into the adult male plumage. This seems to be confirmed by the orange gape, which is an indication of an immature/juvenile.

  2. That is great to know. Thanks for the info.

  3. Thinking about this further, I realise that in most cases that I can recall, a Crimson Sunbird showing blotches of red is normally an immature in moult to adulthood.

    However, there have been instances where a Crimson Sunbird has only shown red on the throat and have also been assumed to be immature males. However, I cannot recall if these birds had pale gapes that would confirm their immaturity. Perhaps it would be worthwhile for everyone to look out for such birds and perhaps obtain photos to confirm if they are indeed immatures or could they be males in eclipse!

  4. […] An earlier moulting stage of this sunbird can be seen HERE. […]

  5. I notice that there is a difference in the undertail-pattern. While the juvenile/immature has a blackish tail with white tips to the outer two tail feathers and a white outer web to the outermost tail feathers, while the adult male seems to have a uniform brown tail.

    if this character is true than a mottled male with a adult-tail pattern would be in an eclips plumage while a mottled male with a patterned tail is a moulting immature. A complete adult male with a patterned tail would be an immature then.

    I have no time to check this om photo’s, but it would be inetresting

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