(1608) Collocalia unicolor unicolor (Jerdon).
THE INDIAN EDIBLE-NEST SWIFTLET.
Collocalia unicolor unicolor, Fauna B, I., Birds, 2nd. ed. vol. iv, p. 346.
This Swiftlet occurs over the greater part of Southern India wherever there are suitable places for breeding in. Great numbers breed in various islands off the coast and others breed in the Nilgiris, Palni and other hills of Mysore and in the Travancore hills also up to some 4,000 feet but generally under 2,500 feet. In Ceylon it is even more common, here also breeding at all levels from the small coastal rocks and islands to above 4,000 feet in the hills.
There are numerous accounts of its breeding in Hume’s ‘Nests and Eggs.’ Davison and Cardew describe its breeding in the Nilgiris, Jerdon in Pigeon Island, Vidal on the Vingorla and Malvan Rocks, Terry in the Palni Hills and Bourdillon in Travan¬core. In Ceylon its breeding is described at length by Legge.
All these accounts agree with one another and also with those given by Campbell, Packard, Williams, Wait and all the later writers.
The birds always breed in colonies, though these vary greatly in size. Sometimes no more than a dozen or twenty pairs may occupy a cave, while at other times they may be very much more numerous. Bourdillon counted 250 nests in a cave in Travancore, while Legge says that about 300 pairs bred in one of the best-known caves at Hapatale in Ceylon. They make their nests in caves of any size, some very small, others very large, while they often also nest in railway-tunnels and similar places. Williams found a colony breeding under the Wenlock Bridge on the Wellington-Coonor road in April 1926. Always, however, the nests are placed in the darkest recesses of the cave or tunnel, where hardly any light or no light at all reaches the nests. These are built up against the roof and higher parts of the sides of the cave and very seldom within easy reach of the hand. If the cave is big and the colony small the nests may he scattered about it singly but, more often, they are built in clusters, half a dozen to a score or more of nests all touching one another at the sides, while those above and below them are but an inch or two apart, Vidal gives a very good account of the nests, and says :- "None of the nests I have got from the Vingorla Rocks are pure white. The nests are all mixed with grass and feathers, the saliva being pure only where the nest is attached to the rock and on the rim of the saucer. The nests vary a good deal in size and shape. They are very shallow, seldom deeper than half an inch, and have a diameter of about 2 inches. Externally the saliva, freely mixed with grass and feathers, is smooth and coagulated. Inside the cup it forms a network of fine shreds. They look at a little distance exactly like deep oyster-shells with one side flattened, the saliva where it is smoothed down having a pearly appearance.” In order to obtain pure white nests Vidal again and again sent men to the breeding places or went himself with the men who farmed the nests, but all were the same, grass and feathers mixed to some extent with saliva.
I have had one or two nests sent me which were more than half saliva, but ninety-nine out of a hundred, whether first nests or not, are as described by Vidal, though the material may differ a little in different nests. Both Davison and Cardew say that in the Nilgiris the bulk of the material used is a grey thread-like lichen.
The birds stand a great deal of bullying before they will desert their breeding caves. The nests are farmed out for exportation to China and the Indo-Chinese countries, the farmers collecting all the first nests and often the second lot as well, while the third lot is left, and the birds then lay and bring up their young in peace. The weight of the nests so collected may be anything from 5 to 50 pounds, though the weight of the saliva when the nests have been boiled down is nothing like half this amount.
The breeding season is generally April, May and June, but Jerdon visited Sacrifice Rock in March when a few of the nests had eggs in them, and Jerdon says that the first lot of eggs had already been taken.
The full clutch of eggs is always two ; Bourdillon writes of one egg only being laid, but as these were nearly all fresh, two only being incubated, most may have been incomplete clutches and the others second layings, as the farmer had already taken one batch of nests from the colony. They are typical little Swifts’ eggs, white, fragile and glossless, long blunt ovals in shape.
Eighty eggs average 20.9 x 13.5 mm. : maxima 22.2 x 13.4 and 21.0 x 14.1 mm. ; minima 19.7 x 13.1 and 20.8 x 12.6 mm.
Legge has an interesting note on some young birds, and says the partially fledged young which were procured for me on this occasion and which I kept for the night scrambled out to the exterior of the nests and slept in an upright position. This is evidently the normal mode of roosting of this species.”
It is, we may add, the normal method of roosting with most Swifts.
1608. Collocalia unicolor unicolor
(1608) Collocalia unicolor unicolor (Jerdon).