1600. Cypsiurus batasiensis batasiensis

(1600) Cypsiurus batasiensis batasiensis (Gray).
THE BENGAL PALM-SWIFT.
Tachornis batasiensis batasiensis, Fauna B. I., Birds, 2nd ed, vol. iv, p. 336.
Cypsiurus batasiensis batasiensis, ibid. vol. viii, p. 681.
This tiny Swift has a range rather similar to that of Micropus a, nipalensis, being an Eastern bird of heavy rainfall areas running into the South-West coast, whereas the Western form, paler in colour, is restricted to areas of smaller rainfall. It is found through¬out Bengal and Bihar ; Assam, North of the Brahmapootra as far East as the Dibong ; Orissa, Madras and Ceylon. The birds of the Travancore and Malabar coast appear to be also of this race, showing again how the avifauna of this wet South-West corner of India is much closer to that of the North-East of India than it is to that of the far nearer districts of North-West India.
It is a bird of the plains and haunts open country, very confiding and often found in gardens, parks and even the main streets of towns and villages. It makes its nest generally under the leaf of a Palmyra-palm, but occasionally also under the leaves of Cocoanut, Date, or Betelnut-palms.
The nests are always built under leaves which hang over and so form complete shelters from bad weather. Hume gives a good description of those built under the leaves of the Toddy-palm :— “The large fan-shaped leaves of this palm get bent by the wind and hang down so that the points of the leaves turn somewhat inwards ; and it is to the under surface of that portion of the leaf which is bent inwards to which the nest is attached.
"The bent portions of the leaf stand at an angle of 40 to 70 degrees, so that the under surface becomes in fact the upper surface and presents a sloping furrowed bank in which the nest is attached.
"In one of these furrows formed by the large plaits of the leaf, and always about the centre of this latter, a tiny watch-pocket-shaped nest, composed of fine down of the Argemone mexicana and other plants, or in other cases of fine feathers cemented together with the saliva of the bird, is firmly glued. The actual pocket of the nest is rarely above 1.1/2 inch in circumference and 3/4 of an inch in depth, but the back portion of the nest runs up the plait from 2 to 3.1/2 inches It is a curious fact that while the rest of the neat is pretty soft the edge of the pocket in front is matted into a sort of cord, just as in the case of the watch-pocket a piping is run round the edge. In one or two nests that I have seen the birds have incorporated the soft petals of the white poppy (so largely grown for opium in Bihar, where this species is specially abundant) with the other materials of the nest,”
I have often found the nests made entirely of soft vegetable down and saliva, yet at other times entirely of soft small feathers and saliva. One nest was made of all of these, pure white, except one black feather, far larger than the rest, hanging like a plume from the bottom,
Hume gives the measurement, of a nest (vide supra) as 1.1/2 inch in. circumference. This is probably a mistake for diameter, as a good many nests measured by myself vary from 1.1/4 to 1.5/8 inch in diameter, and none are anything like as small as 1/2 inch.
The birds breed either singly or, more often, in colonies. Generally five or six pairs breed in the same tree, each pair having a leaf to itself ; at other times as many as twenty or more pairs form a colony in a group of trees or even on one tree, and I have seen as many as three nests in one leaf. Inglis found a large colony breeding in some Areca-palms, but in no instance was there more than one nest to a leaf.
They breed practically all the year round and must have two or more broods. In Calcutta I found nests with eggs from November to March and again in July and August ; Inglis took eggs in March, April, July and other months as well, and records his earliest eggs as the 26th February and his latest as the 2nd August. Hume received eggs in April and June.
In Ceylon Legge gives the breeding season as October to April and I have received eggs from Phillips taken in December. Davidson says that they breed in Mysore in Betel nut and Cocoanut-palms in January and February.
The normal clutch of eggs is two, but three are not very uncommon.
They are typical tiny Swifts’ eggs. Fifty average 18.2 x 11.5 mm. : maxima 19.1 x 11.5 and 18.3 x 12.1 mm. ; minima 16.6 x 10.3 mm.
Both sexes incubate and both assist in the building of the nest, but I think the male only brings material, all of which he catches floating in the air.

BookTitle: 
The Nidification Of Birds Of The Indian Empire
Reference: 
Baker, Edward Charles Stuart. The nidification of birds of the Indian Empire. Vol. 3. 1934.
Title in Book: 
1600. Cypsiurus batasiensis batasiensis
Spp Author: 
Gray
Book Author: 
Edward Charles Stuart Baker
CatNo: 
1600
Year: 
1934
Page No: 
460
Common name: 
Bengal Palm Swift
M_ID: 
7701
M_SN: 
Cypsiurus balasiensis balasiensis
Volume: 
Vol. 3
id: 
14753

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