Brown-throated Sunbird – moulting

posted in: birds, Morphology-Develop., moult | 0

Post 1. Unsure of the sex of this juvenile.

I have not been paying enough attention to two Brown-throated Sunbirds (Anthreptes malacensis malacensis) in the garden who have been enjoying the nectar from our Callistemon spp (Bottlebrush tree) and Albizia spp (Mimosa Tree).

Post 2.

Some images of the self-feeding male, moulting. This could be a juvenile/immature moulting into adult plumage, but there hardly any ‘convincing’ gape present and bare parts look adult.

Post 3.

There is no data on eclipse plumage phase for adults but it may be possible. I am uncertain why the tail in this bird is so short. The calls the bird made were like those of an adult. Note that juvenile bills are usually lighter with some pale pink/orange.

Post 4. A composite image of 4 different birds showing the transition from juvenile to adult plumage.

Post 5. This is a juvenile female. Note the lighter, orange lower, proximal mandible and gape.

I cannot be sure of the sex of the first juvenile in Post 1. After reviewing all my observations of immatures moulting, the first metallic plumage to appear are usually some feathers in the face/neck giving the appearance of a moustachial steak, and a few feathers in the scalp. This is followed by changes at the nape. Mantel changes are late.

Post 6. This is a male in strong light with a blood-red iris.

Post 7. A sonogram of the calls of this male.

The above is the sonogram of the calls of the male, common calls made by this species and usually repeated in varying frequency – can be rapid in sequence (every second) or 3-5 seconds apart. Handbook of the Birds of the World Alive (2020) describes these 2-3 note calls as the ‘song’ and translates them as “sweet-sweet”, or “swit-swit-sweet”. The sonogram is fascinating in its structure, showing far more complexity to the ‘song’ than what we hear with our ears.

 

Amar-Singh HSS (Dato’ Dr) – Ipoh, Perak, Malaysia

Habitat: Urban environment

Date: 25th July 2020

Equipment: Equipment: Nikon D500 SLR with Nikon AF-S Nikkor 500mm f/5.6E PF ED VR, handheld with Rode VideoMic Pro Plus Shotgun Microphone

 

 

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