(520) Enicurus immaculatus Hodgs.
THE BLACK-BACKED FORKTAIL.
Enicurus immaculatus, Fauna B. I., Birds, 2nd ed. vol. ii, p. 61.
The Black-backed Forktail breeds in the sub-Himalayas from Garwhal, where it is very rare, to Eastern Assam and thence throughout the Burmese lower hills South to the Malay States. I have nowhere found this to be a really common bird, like the Slaty- backed and Spotted Forktails, but it breeds in some numbers in the foot-hills and adjacent plains, so far as the ground is broken and forested, in Assam. They breed occasionally as high as 2,000 or even 2,500 feet and I have a single record of one pair breeding at about 3,200 feet, a quite exceptional record.
Although this little bird breeds generally on small streams in dense forest, its nest may also be found some distance from these in among rocks and boulders in ravines through which a little water always trickles, except in the driest months. In Assam we found it nesting in very dense forest, the ground much broken up and the heavy undergrowth mixed with outcrops of rock, covered with moss, ferns and orchids, over which little cascades of water fell when the rain was heavy. Such rock-faces seemed a very favourite site, the nest being tucked away on a ledge or in a crevice over which the water fell either in considerable volume or just dripped according to the rainfall. After heavy rain the birds had to dive through the cascade to get to their nests. On the whole
I think they were better concealed in these places than are most Forktails’ nests, but other sites were often chosen, such as hollows in fallen trees, on the banks of streams etc., just like those selected by the two preceding species.
In Assam they breed chiefly in April and May, a few birds laying during the last weeks in March. In the Bhamo Hills Wickham found them breeding later than the other Forktails, taking nests in May. In Pegu Oates took a nest with three eggs on the 20th April, whilst still further South Hopwood found one, also with three eggs, on the 16th of March. In the Chin Hills Mackenzie, Hopwood and others report them as breeding from the end of March to May.
The nest is quite typical of the family : the usual cup-shaped nest of bright green moss lined with skeleton leaves, the body of the nest sometimes containing roots and a few dead leaves, whilst under the skeleton leaves there is a layer of fine moss-roots in about one nest in five. The eggs generally number three only, four being rather exceptional.
Most eggs are rather like small pinkish eggs of the Spotted Forktails, but are rather feebly marked with indefinite freckles and small irregular blotches rather than well-defined spots. Although I have only a comparatively small series of these eggs, some of the clutches are quite unusual. One, the first I ever took, has a pale stone- grey ground-colour profusely speckled all over with dark purplish brown, the markings even more numerous at the larger end than elsewhere. The nest was the normal type of the family and the birds were caught on the nest, or it would have been hardly possible to accept them as Forktail’s eggs. Another clutch has a pale sea-green ground with rather large blotches of light reddish-brown and lavender, dense and coalescing at the bigger end and sparse at the smaller. Yet a third clutch of three is of the normal type but has the freckles confined to the extreme larger end, where they form small caps.
In shape the eggs are broad, short ovals, much less pointed at the small end than the eggs of the Spotted Forktails.
Twenty-eight eggs average 20.8 x 15.8 mm. : maxima 21.6 x 16.0 and 21.2 x 16.3 mm. ; minima 20.0 x 15.6 and 20.3 x 15.1 mm.
An abnormally large clutch of eggs taken by Hopwood in Tharra¬waddy measure from 23.2 x 16.0 to 25.0 x 16.0 mm.
As usual in this genus both sexes incubate and both assist in the building of the nest.
520. Enicurus immaculatus
(520) Enicurus immaculatus Hodgs.