Large Crested Tern,a true sea bird

by K. G. H. Munidasa

The Large Crested Tern Sterna bergii velox Cretzschmar is a common breeding resident in the Wet and Dry Zones of Sri Lanka. It is known to breed “on the islets off Ambalangoda on the West coast and on the sites around the coast during May” (Annotated Checklist of the Birds of Ceylon-1948).

“Breeding colonies exist on sand banks on Adam’s Bridge and on rocky islets of the Southern Province. I believe, too, that breeding takes place on the shores of the Hambantota lewayas (salt pans) as I have seen many there in full breeding plumage in June, flying inland carrying fish in their beaks” (A guide to the Birds of Ceylon, First Edition 1955).

“It has been found to breed in June on the sand banks between Mannar and India... and end of April or early May on rocks off the South coast” (Manual of the Birds of Ceylon, Second Edition - 1931).

The Large Crested Tern, a true sea bird, has never been known to come inland for breeding purposes. However, in July 1974 the writer discovered a breeding colony of this tern in a land-locked lagoon on the outskirts off the Hambantota town.

First visit

It was my first visit to the Koholankala lewaya. The morning was exceptionally bright and cool breeze blew over in spite of the prevailing arid condition. I surveyed the expanse of dry bed in the centre of the lewaya with my binoculars.

A villager in loincloth passed me and strolled towards the embankment that zigzagged along the bed, apparently designed to divert sea water to the Maha Lewaya (main saltpans) across the highway, beyond.

After plodding through the ankle-deep mud the man stopped beside the embankment about a quarter-mile from the margin. I watched him closely and presently saw him looking at some white objects at his feet which to the distance appeared like a collection of mushrooms. He turned back and walked off in the direction of the coast.

The moment the man reached the embankment there was a great commotion of birds, and scores of terns were circling above him.

There were hundreds of White-shafted Litele Terns and a quite larger from with darker upper parts, which I could not distinguish from the distance. I decided to go there and see things for myself. Through the glutinous mud progress was pretty hard, and in certain places I sank up to my knees in the slush.

Once on the embankment, I progressed faster and reached the spot I aimed for. In one place I came upon 13 large eggs lying in the moist sand spit, 10 to 15 inches apart, without any nest. About fifteen feet from these there were 72 similar eggs on a bed of dead mollusc, three inches deep.

The smaller terns (white-shafted species) started to mob me and the larger ones, some 30-40 of them, circled higher up. They were all Large Crested Terns, in full breeding plumage. They uttered a loud crraaaw note in alarm. Their ordinary call note was a grating craaa.

The eggs were oval in shape, pointed at one end and greyish-white or greyish-buff in colour (some resembled hens’ eggs) with purplish-grey clouds and blotched or speckled with black (sepia). Some were seemingly more pointed than the others.

Having no measuring instrument in hand I recorded a rough measurement on my notebook with the help of my ball-point pen. From that I later arrived at an average of 63x45mm. against 62x43mm. given by G. M. Henry.

Sitting on eggs

I watched from a distance and found 10 to 12 birds sitting on the eggs and the rest circling above the colony. Resting in the shallow water away from the breeding place I later found 30 to 40 Large Crested Terns.

The next week I arrived at the lewaya at 5.30 in the morning. My intention was to obtain measurements with a calliper of as many eggs as possible. From the distance I could hear a commotion in the lewaya to my right.

In the dim light I could not see anything, but managed to differentiate the alarm calls of the Large Crested Terns. I waited on the bund until it was broad daylight and walked across to the brooding colony. There were no eggs on the sand dune and it was strewn with remains of egg shells.

I looked around and there wern’t any tern either. There was fewer White-shafted Little Terns, too. Then I heard the familiar Cra-aa and looked up to find two Large Crested Terns in the air.

They circled above me and raised an alarm, which brought dozens of little terns rushing up to the place Subsequently, more and more Large Crested Terns flew over to investigate. But they did not remain long, and returned the way they had come, while the little terns continued to mob me, all alone.

Seated in the embankment. I took stock of the situation. Further scrutiny of the sand bed solved the puzzle.

On the sand, superimposed on my footprints of the previous day and that of the man I was watching examining the eggs, were the pug marks of a pack of jackals (or dogs). Incidentally, I had observed a pack of fourjackals by the scrubby margin at 9 a.m. during my previous visit.

After gobbling away the eggs, the predator had clawed the sand in a couple of spots and climbed the bank to attack the breeding colony of the White-shafted Little Terns. I found that out of close upon 30 eggs and a dozen chicks there only nine eggs and three chicks had escaped the predators’ eyes.

Large assembly

Back on the perimeter bund, I found a large assembly of Large Crested Terns in a shallower part of the lewaya about 150/200 individual in breeding plumage. Some of them perched on stakes driven into the bed by the National Salt Corporation.

These could have been the birds which made the commotion, earlier in the morning. The following Sunday, I arrived at the lewaya at 8.00 a.m. and found 13 Crested Terns on the margin, where I had seen the large flock in my previous visit.

Seven days later on visiting the colony in the morning I found 17 Crested Terns in the water not far from their breeding site. Except a few, all of them were in full breeding plumage.

On the sand close to this place I found an undamaged egg, which I presumed was one that had escaped the predator’s attention. I passed on the egg specimen to the Secretary of the Ceylon Bird Club in Colombo, who in tern handed it over to the Colombo National Museum authorities, requesting for a report. The egg measured 59.95x 39.40mm.

At the National History Section of the Museum, the egg specimen was examined and confirmed in size and colour as that of a Large Crested Tern. On the approval of the CBC it was duly cleaned up and incorporated into the museum collection.

Meanwhile, Major W. W. A. Phillips a former Secretary, Chairman of the CBC, then in retirement in England had in a letter to the Club said “The Large Crested Terns used to breed annually on the small rocky islets off Ambalangoda; they probably still do if the disturbance is not too great...

It is most interesting that a colony has been found breeding in the Koholankala lewaya I have never heard of this species breeding inland from the sea, until this report...it is quite new to hear of them breeding in a lewaya. I also remember finding a large breeding colony of these Terns, with eggs, on one of the low rocky islets off the East Coast, many years ago”.