Iridescent ‘moustachial stripe’ of the Ruby-cheeked Sunbird

posted in: Morphology-Develop., Sunbirds | 0

“My favourite sunbird of the garden is the Brown-throated Sunbird (Anthreptes malacensis) as we have established a long friendship with these birds in our garden. In the jungle my favourite is the Ruby-cheeked Sunbird (Chalcoparia singalensis singalensis) – another very friendly and approachable sunbird, often allowing me to watch close up even when with young.

“I naturally have lots and lots of images and would like to share a few to illustrate a feature that may be overlooked in the field and not mentioned in many field guides and books – the iridescent ‘moustachial stripe’.

“Although it could be argued that it is not a ‘true’ moustachial stripe as it does not extend from the base of the bill, it does have the same ‘location’ in bird topography (I am no expert on bird topography and am happy to be corrected). Most books on birds in my region (looked up six) do not show this feature in the illustrations or it does not show up in photographs displayed.

“Madoc (An Introduction to Malayan Birds, 1956) goes so far as to say ‘the Rubycheek lacks the moustachial steaks’ when comparing the bird to the Brown-throated Sunbird. Wells (The birds of the Thai-Malay Peninsular, Volume 2, 2007) states that ‘…side of neck … bordered ventrally by a stripe of metallic violet blue running from below ear-coverts to upper breast-level.’

“I will start off with two pictures, one in excellent light showing of the colours well (a bit off focus) (above left) and an older one close up (above right) showing the iridescent ‘moustachial stripe’ as purple-pink in good light.

“… picture on the left … shows that if the head is turned or in poor light, the brilliance of this ‘moustachial stripe’ is not appreciated and it can look just like a darkish line or band (left).

“…a juvenile male who is just developing this ‘moustachial stripe’ to illustrate how easy it is to miss when lighting is poor. Compare the pictures of the same bird taken within seconds of each other (below). When the head is turned the brilliance of this ‘moustachial stripe’ is not appreciated and it can look just like a darkish line or band. I am not sure if this is the early feature of adult plumage in most juvenile male Ruby-cheeked Sunbirds. In this bird it is the first metallic plumage to develop; apart from the deepening orange-rufous throat that indicates the transition to adulthood. In my previous juveniles observed and photographed the first metallic plumage has developed in various parts of the body, often the tail.

“In my experience over the past 4-5 years of many families, all the family units have been two juveniles, even in the nest. One usually more mature than the other in plumage, this often being the male (below). I suspect it is usually one male (developing clear male adult plumage) and one female juvenile (just a deepening of the orange-rufous throat so less striking) but have insufficient follow up data to be sure.

“Parent usually split up to look after the feeding of the young but are within close reach of each other. These juveniles were old enough to feed themselves but were still being fed occasionally by adults.

“…adult female with caterpillar (below left) – loves to forage ‘upside down’ looking for spiders and insects. In my observation over the past 4 years, arthropods, insects, caterpillars and larvae are important parts of their diet. They are especially fond of spiders. They also enjoy small berries and other small fruit. I have yet to observe an adult feeding on nectar. …my first observation of a Ruby-cheeked Sunbird feeding on Straits Rhododendron (Melastoma malabathricum).

“Differentiating an adult female from an older female juvenile can be difficult. The iris colour is a good feature – adults red and juveniles brown (below right).”

Dato’ Dr Amar-Singh HSS
Kledang-Sayong Forest Reserve, Ipoh, Perak, Malaysia
18-19th September 2010

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