“The Black-Naped Oriole (Oriolus chinensis) is the only oriole species that can be found in Singapore. They can be commonly seen in our parks and gardens, and even in our housing estates. With its bright yellow and black plumage, they can be quite conspicuous. However, as they like to stay hidden in the foliage, they can be difficult to observe.

“Recently, a Black-Naped Oriole was briefly encountered in a mangrove boardwalk. The oriole was rather skittish and it disappeared into the mangrove forest after only three quick shots. It was only after downloading and reviewing the pictures that I realised that instead of the usual symmetrical yellow and black patterns on its back, this bird appeared to lack symmetry in its tail feathers. One black feather was either missing or have yet to grow on the right side of its tail (above left). From the appearance of the plumage, I would guess that this is an immature bird that is growing or moulting into a full adult.

“Images of an adult (left) and a juvenile (above right), showing the different stages of the oriole’s plumage are attached for comparison. The adult’s plumage showed black in its central tail feathers and had a black eye band while the juvenile’s black in those areas are still not visible. The immature’s plumage falls in between the two.

“The photos of the adult and juvenile were taken separately during an earlier outing when they were found to be seeping(?) nectar from the flowers of a bottle brush tree. The Black-Naped Orioles are known to have a varied diet consisting of mainly fruits and insects. I did not know that Black-Naped Orioles can be harvesting nectar from flower to flower.”

Kwong Wai Chong
Singapore
28th July 2010

Since May 2010 when I started scattering birdseeds in my garden that attracted a Spotted Dove (Streptopelia chinensis), only a single bird visited in the mornings and evenings. I have always wondered whether this was the same bird or was there another. As both sexes look the same but can we recognise one individual from another?

At every opportunity I photographed the bird in an effort to look for distinguishing features. Of the features on the head, the dark black line that extends from the gape to the eye appears to vary on the same individual, depending on the position of the head.

It was only in late June that I had the opportunity to compare features of two individuals when the regular dove brought its mate to feed in the garden (above left). And the mate has a distinguishing mark that is different from the regular bird. The black line on both sides of the face has a gap near the bird’s gape (left: bird below has a gap in the black line).

An added bonus was that on one of the days when the pair of doves visited the garden, they brought a juvenile *Peaceful Dove (Geopelia striata) with them (above right). That was the only day the juvenile Peaceful Dove was seen. Maybe it did come on other days but was not spotted by me.

But which is male and which is female has still to be resolved. It may be possible that the regular visitor (the one with the continuous black line) is the female and the recent arrival the male. If the doves were brooding their chicks earlier, the male would be on duty during the day and only the female would be free to forage. Thus the regular visitor would naturally be the female. Once the chicks fledged, the pair of adults would be free to visit regularly together with the juveniles. But why only the female came most of the time, and the juvenile seen only once? Did the male accompany the juvenile elsewhere?

Earlier parts can be accessed here: 1. Introduction, 2. Feeding behaviour; 3. Comfort behaviour; and 4. Eyelids.

*Thanks to Phil who alerted me on the error in ID - see comments.

A bird’s eye has three eyelids: an upper eyelid, a lower eyelid and a nictitating membrane. The upper eyelid has limited movement, thus the lower moves up to cover the eye. The nictitating membrane or the third eyelid is a translucent membrane that moves sideways, although in the owl this membrane moves diagonally. The nictitating membrane cleans the eye and keeps it moist. It also protects the eye from particles, etc. especially when the bird lunges into the undergrowth to catch prey.

In the case of the Spotted Dove (Streptopelia chinensis), the upper eyelid can be lowered half way over the eye (above left). As observed during a preening session, the closing of the eye is achieved by moving down the upper eyelid to meet the lower eyelid that moves up (above centre and right). Apparently the lower eyelid does not move up totally, but halfway.

During foraging in grassy patches where the eyes may be submerged in vegetation, the closing of the eyelids may come into play to protect the eyes (above).

Now what has happened to the nictitating membrane?

Earlier parts can be accessed here: 1. Introduction, 2. Feeding behaviour and 3. Comfort behaviour.

Coppersmith Barbet (Megalaima haemacephala) is found from the Indian subcontinent except the north-west, Sri Lanka, SW Yunnan, Sumatra, Java, Bali and the Philippines.

Nine subspecies of barbets are recognised. These can be divided into two basic groups. Subspceies celestinoi, delica, haemacephala, indica and mindanensis have yellow above and below the eye and yellow chin and throat. In the other group of subspecies, mainly rosea, homochroa, intermedia and cebuensis, the yellow is replaced by red.

The Singapore subspecies is indica (above left), which has a range of NE Pakistan E to S China, S to Sri Lanka, Singapore and Vietnam. Subspecies rosea (above right) is found in Java and Bali.

Images by David Tan.

“Attached are cropped images showing the head of a male Brown-throated Sunbird (Anthreptes malacensis) that were taken at close proximity. The nictitating membrane and lower eyelid were captured in action.

“The nictitating membrane, also known as the third eyelid, is believed to be used to protect and moisten the eye. It is either transparent or translucent; thus helping to keep some visibility when it is deployed.

“In the first set of images, the sunbird’s translucent nictitating membrane was visible. It could be seen to commence from the front part of the eye, moving across horizontally past the pupil (above left), before completely covering the entire eye (above centre). After less than a second, it retracted to re-expose the eye to its normal condition (above right).

“The second set of images managed to capture the sequence of the eyelid moving in tandem with the nictitating membrane. [Note the distinct lower eyelid (left) that is not obvious in the image above-left when the eyelid is not about to be raised.] Interestingly, the nictitating membrane was closed before the lower eyelid moved upwards to show a half-closed eye (below left and centre). Less than a second later, the nictitating membrane was retracted to uncover the eye that was not covered by the lower eyelid (below right). However, the white and opaque lower eyelid remained drawn for a relatively longer period of about 3 seconds before resuming its normal open-eye position. The upper eyelid was not seen in action.

“Could this sunbird be catching a wink? The sunbird was somewhat inactive during the brief moment that its lower eyelid was shut. But it resumed to its active chirping self immediately after that. Unfortunately, the other eye was not in view. Hence, whether it was for one eye or both eyes cannot be determined.”

Kwong Wai Chong
Singapore
14th June 2010

Note: The whitish patch of skin appearing as the lower eyelid moves upwards is rather unusual. This patch has a distinct lower border. We sent the images to Dr David R Wells who replied: “Yes; the bird is extending its nictitating membrane (‘third eyelid’) then closing its eye by raising the lower lid (upper lid smaller, less mobile). The pale patch you see below the eye is simply the featherless skin of the stretched lower lid.”

Check out the eye movements in the Buffy Fish Owl (Ketupa ketupu) HERE.