Breeding ecology of the Little Tern 4: Feeding

The plumage of the Little Tern (Sterna albifrons) during the breeding season shows a prominent black cap on the head and a yellow bill tipped with black (above). The plumage of the juvenile is distinct from that of the adult (below).
Normally all the birds would be facing the persistent wind direction, be it morning or evening. Hence, the adults always got into a bit of trouble positioning themselves for landing in the mornings. Fish was sometimes dropped as a result. Passing on the fish to the juvenile were mostly done without problems in the evenings. The juveniles were normally near-hysterical whenever the parent arrived with fish (above). They would wave their wings to attract the attention of the arriving parent. The other juveniles normally remained patient and waited their turns. The parent that was keeping an eye on the juveniles would then fly off to get food for the other chick. Should the other chick managed to snatch the fish, the rightful chick would normally chased it around until the fish was dropped and retrieved it. Originally the chicks were fed with bits and pieces of fish. As the chicks grew they were slowly fed the entire fish caught by the parents (above). The parent bird would hold the fish just behind the head and direct it into the gaping mouth of the juvenile, head first. This would prevent the sharp spines of the fins damaging the throat as the fish slithered down the throat into the stomach. With a larger fish it was not possible to place it inside the gape. The juvenile had to receive the fish, gripping it just below the head. It then had to manipulate the fish so that it was swallowed head-first (below). Courtship feeding, as described earlier (a, b) continued throughout this period when the parents were continuously feeding the juveniles.

Input and images by Dr Jonathan Cheah Weng Kwong.

Migratory habits of Black Baza

Black Bazas (Aviceda leuphotes) were commonly seen in late November 2006 around Punggol, Sarimbun, Khatib Bongsu and Lake View Promenade (Chinese Garden, Jurong). These birds were of course winter visitors.

On the 26th of that month Chan Yoke Meng encountered a flock of ten Black Bazas. The birds were very skittish, hunting insects that they brought back to their favourite high perches to be consumed. And whenever these bazas were around, there was quietness all around. Only when they moved off did the bulbuls and pigeons reappeared and began calling and singing.

Bazas look like mynas when flying but their flight pattern is distinctly different. Once you are familiar with the two flight patterns, it is easy to differentiate the two birds from afar. This baza encounter brought back memories of an exciting earlier encounter more than two years ago. On the morning of 31st October 2004, Tang Hung Bun was fortunate enough to witness the spectacular sight of a flock of more than 30 Black Bazas circling the sky above Sime Forest.

And a few weeks later, he had the opportunity of seeing a few Black Bazas foraging in the wooded areas behind his office. There were at least three of them. They hid themselves behind the branches and leaves. When they found something, they flew to it and landed in a rather awkward manner on a bunch of leaves to catch it. They would then fly to a branch to enjoy the meal. As Tang recounted, “The little green insect that you see in the black baza's beak in one of the photos (above) must be the black baza favourite food. I have seen the black bazas eating them quite a number of times.”

Tang’s earlier posting of his experience attracted the attention of R. Surachai who wrote to inform that Asian Raptor Research and Conservation Network (ARRCN) Thai volunteers counted thousands of these bazas flying south towards the Thai-Malaysia border towards the end of October of that year. This would mean that the birds were heading towards Peninsular Malaysia. The few birds that Tang encountered were obviously part of the large flocks that the Thais counted, birds that ended far south into Singapore.

Our bird specialist R. Subaraj has this to add: “I have personally seen a single flock of 100 birds spiralling on a thermal over Mount Faber. They can be seen anywhere in Singapore, with the largest flocks recorded over southern and central parts of the island. Many are also seen along the east coast at places like Loyang and Ubin.

"Small wintering flocks have always over-wintered at sites like the Central Catchment, Pulau Ubin and Sungei Buloh, to name a few.”

Input by Chan Yoke Meng, R. Surachai, Tang Hung Bun and R. Subaraj; images (from top) by Yoke Meng, Johnny Wee and Tang (lower two).

Breeding ecology of the Little Tern 3: Life and death

Things are not always smooth sailing for the chicks of the Little Tern (Sterna albifrons) once they hatch. There is no guarantee that they would develop normally to eventually fledge. In fact not all chicks survive the 20 odd days to fledging.

When Jonathan Cheah was documenting the breeding ecology of the Little Terns (1,, 2), he noticed a larger chick limping through the viewfinder of his camera. As he moved closer he noticed one leg bleeding as the chick hobbled over a sand mound. He went over and found it lying motionless, a usual reaction when a chick is approached. Lifting the chick off the ground, he noticed a foreign object lodged on the chick’s webbed foot. After removing the object he gently placed the chick on the sand and it scuttled off happily (below). And he also experienced death of chicks. As Jonathan recounts, “The first two days of hatching are very crucial to the survival of the chicks. Failed nests can occur by bad choice of nesting grounds, too many eggs, even stress of parent by predators. Once the chicks can move, the survival rate increases.“ Around the nesting grounds he observed chicks dying (above) but the parent birds do not normally accept the fact that the chicks were dead. In one instance the parent covered the chick's beak with a rock to prevent ants from entering the carcass. It even continued to sit on the remaining egg and dead chick, whilst being harassed by the sudden increase in flies and ants (below). Unfortunately the remaining egg did not hatch, most probably due to a super heated ground. Obviously a poor choice of nesting location.

Input and images by Dr Jonathan Cheah Weng Kwong.

Territorial Nightjars

"The Grey Nightjar (Caprimulgus indicus) is an uncommon but annual migrant to Singapore. It breeds from northern Thailand all the way up to Siberia. Like the Oriental Scops Owl (Otus sunia) it is a nocturnal bird that is usually silent away from it's breeding grounds. In recent years, a few birds have been observed throughout the "winter" period (October - March) around the MacRitchie and Sime Forest areas of the Central Catchment Nature Reserve, proving that the species winters here. One to two birds have wintered around the Treetop Walkway area for the past two years or so and have been seen and photographed, during the day, roosting on branches of adjacent trees.

"In all my years of local bird observation, I have only heard this nightjar calling twice... at Sentosa. Calling may be an indication that the bird is holding a winter territory.

"On November 16th, 2006, while conducting an evening bird survey at the Treetop Walkway (above), I was pleased to hear a Grey Nightjar calling loudly at dusk. The call was a quickly repeated "tuc" note in a series of several in a row. The call was coming from a large Terentang tree (Campnosperma auriculatum) where this species has been regularly seen roosting before. Along with Benjamin Lee and Janet Hong, who were with me at the time, we quickly moved closer. What followed was both unexpected and exciting.
"The calling Grey Nightjar was being harassed by a resident Large-tailed Nightjar (Caprimulgus macrurus) (above). The latter may not have been pleased about this visitor calling loudly within what it considered it's territory. Instead of retreating and going silent, as expected, the Grey chased off it's larger cousin before returning to the tree to call loudly from a branch. This scene was replayed twice or thrice more, before the Grey chased the Large-tailed away. We could see the chase below us before they both disappeared into the darkness. Subsequently, the Grey was heard calling loudly again from a different tree.

"What can we make of this scene and the behaviour witnessed? Well, many migrants do not call because they are not at their breeding grounds defending their territory or seeking a mate. However, there are many others who call constantly while here. Why the difference? In many cases, this may be the difference between passage migrants and wintering visitors.
"A passage migrant simply passes through Singapore, on its way to further south... probably Indonesia. They may stop to feed for a few days or if the weather is unfavourable (as well as when there is a thick haze in the way) but they do not stake out a feeding territory for their short stint here, hence no need to call. Some, like the Yellow-rumped Flycatcher (Ficedula zanthopygia), may stopover for a bit longer and sets up a temporary territory by calling from selected perches. Others, like the Blue-winged Pitta (Pitta moluccensis) (above) only call once or twice, at dawn or dusk... contact call to any of their kind that may be about? Who knows?
"A winter visitor actually spends the cold northern winter here in tropical Singapore, often staying a few months before returning to their breeding grounds in spring. As they are here for quite a while, they set up a territory in which they feed and sometimes drive away others of their kind, like the Common Kingfisher (Alcedo atthis) (above) does. Throughout the "winter" months (this period varies from species to species), we are treated to the calls of Arctic Warblers (Phylloscopus borealis), Asian Brown Flycatchers (Muscicapa dauurica), Brown Shrikes (Lanius cristatus) (below), Siberian Blue Robins (Luscinia cyane) and many, many more northern visitors.
"So, the calling and aggression displayed by the Grey Nightjar on Thursday may simply be further proof that this species is now a winter visitor in Singapore."

Submitted by Subaraj Rajathurai, 18th November 2006

Images by YC (Treetop Walkway), Chan Yoke Meng (Blue-winged Pitta, Brown Shrike), KC Tsang (Common Kingfisher) and Tang Hung Bun (Large-tailed Nightjar).

Moulting 1

On and off I have been picking up various types of feathers in my garden and along my driveway (above: Javan Myna contour feather, top left; down, top right; tail, middle; Black-naped Oriole tail feather, bottom). During the time when I was interested in plants (and not in birds), I considered these as discarded feathers, detached as a result of fights between birds. Now that I am a “sometime-birdwatcher”, I am slightly more enlightened.

I now know that these feathers have been discarded naturally as a result of moulting. Now why do birds discard their feathers?

Feathers are important to birds. They insulate them from the cold and enable them to fly. But feathers undergo wear and tear. They become brittle, frayed and sometimes get damaged by ectoparasites. Worn and damaged feathers cannot function well and this can prove fatal if the bird cannot fly properly.

As feathers are dead structures, they need to be replaced regularly. And this process is known as moulting. In moulting, the growth of the new feather pushes out the old from its follicle.

Moulting may be partial or complete. Partial moult occurs when only certain feathers or groups of feathers are replaced. Complete moult occurs when all the feathers are replaced. Thus when birds develop their winter plumage or change from juvenile to adult plumage, moulting was at work.

The image below is a moulted breast or more likely belly feathers of a Buffy Fish Owl (Ketupa ketupu), picked up below the owl's roost by Melinda Chan. Our field ornithologist Wang Luan Keng has this to say: “Birds do have a season to moult, usually after their breeding season. In Singapore, most birds breed from Feb/March till July/Aug, maybe Sep. Many species here overlap moult and breeding slightly so they will start moulting in July/Aug and end by Oct/Nov when the NE monsoon starts. Many species, especially passerines, have straight forward sequential moult; others like cuckoos, hawks, herons, fruit doves etc have very complicated multiple moult series and yet some species like rails, grebes and probably bitterns moult all feathers at once and go flightless during that period. And mind you, we are only talking mainly about primary feather moult. We know even less about other flight feather moult and almost nothing about body feather moult.”

Input and images by YC; expert information by Wang Luan Keng and owl's feather provided by Melinda Chan.

Breeding ecology of the Little Tern 2: The first few days

Most of the newly hatched chicks can be grouped into two main groups. They can be hatched helpless, with eyes closed, naked or sparsely covered with down, in which case they are altricial. On the other hand they can be hatched with their eyes open, covered with down and can soon walk or swim, then they are precocial. The chicks of the Little Tern (Sterna albifrons) are neither altricial nor precocial - they are semi-precocial. Although the chicks can move about within a few hours after hatching and are covered with down the next day, they are hatched with their eyes closed and partially covered with down (above). The advantage here is that the chicks do not need total parental care in a habitat that is exposed and dangers lurks at every corner. By the second day the chicks are fully covered with down (above). They lie motionlessly and await the calls of their parents. When the parents are nearby and no threat seems to be around, they pop out with gaping mouths, sometimes chirping (below). At any instance of danger, they remain motionless again. Otherwise they prop up and open their beak when they hear the calls of their approaching parents (above). The parents feed them non-stop, having no time to preen themselves after splashing in sea water to refresh. The chicks find comfort having the parent close by (below). The days of the adult involves warming the chicks, protecting the chicks from the environment and feeding the chicks. Feeding usually take the form of broken down fish parts since the chick cannot swallow. Feeding is rotational and also cycles between the chicks.

Input and images by Dr Jonathan Cheah Weng Kwong.

Food for the Yellow-vented Bulbuls' nestlings

“Over a period of two weekends, this pair of Yellow-vented Bulbuls (Pycnonotus goiavier) were observed to be feeding their young (from the noise made, probably two of them). Regular visits, at the peak times, were about 10-15 minute intervals. The parents' foraging grounds were all around the garden and a big piece of wasteland behind my house. It's quite amazing that they were able to find that much food so easily.
















“I've attached a series of pictures of the parents, and also the Chiku tree (Manilkara zapota) where the nest was hidden (above). I don't have any pictures of the nestlings as I didn't want to disturb the nest. The Chiku tree was pruned at that point in time, and had just begun to sprout new growth - just enough to keep the nest out of sight from prying eyes.
















“Both parent birds returned to the same perch, the sawn off branch, and held whatever prey that they had secured whilst perched there (above). They scanned the surroundings for a few seconds, as if making sure that there were no predators in the vicinity, before plunging into the nest to feed their young. As they did so, the chirps of the nestlings could be heard loudly, as presumably, they competed for the food. “The range of food items fed to the nestlings was quite impressive, varying from fruits, to spiders, caterpillars and even a cicada (top, above and below)!"















“All shots taken with a Nikon D2X and the 80-400mm VR lens mounted on a tripod, and shot from my 2nd storey balcony. This explains the almost eye-level shots.“
Note: Most of the food fed to the chicks consisted of various invertebrates, mainly insects except what looks like a fig (Ficus sp.) (above). Growing chicks need lots of proteins and thus the animal food.

Input and images Khew Sin Khoon.