(1575) Tockus birostris (Scop.).
THE COMMON GREY HORNBILL.
Lophoceros birostris, Fauna B. I., Birds, 2nd ed. vol. iv, p. 301.
Tockus birostris, ibid. vol. viii, p. 679.
I can add nothing to the distribution of this Hornbill as given in the ‘Fauna,’ which is as follows :—From the base of the Hima¬layas, throughout the better-wooded parts of the Indian Peninsula, except on the Malabar and Travancore coasts ; it does not occur in Sind, the Punjab or the greater part of Rajputana but has been found on Mt. Abu ; it extends to Western Bengal and Bihar but not to Eastern Bengal or Assam.
This is one of the common birds of the Indian plains, being found everywhere in well-wooded country and breeding freely round towns and villages and even in gardens, when these contain suitable trees with holes for breeding purposes. C. Home, quoted by Hume (‘Nests and Eggs,’ vol. iii, p. 74), gives an excellent and exhaustive account of this bird’s breeding. He writes:—“In April 1908 I received news of two nests and found that both had been made in the trunks of Cotton-trees (Bombax heptaphyllum), the bird having dug out and enlarged with his bill holes in the soft wood, which had been previously used by Parrots.
“In each case I obtained 3 eggs ; and the hole, at a great height from the ground, appeared to have been plastered up with cow¬dung, or something resembling it.
“I was, however, fortunate at the close of the same month (April 1808), On my lawn, surrounded by other trees, stood a noble sissoo-tree (Dalbergia sissoo) ; and where the first great fork diverged was a hole, I had often wished the Hornbills to use this and they, on April 28, made up their minds to do so. The hole was nearly a foot in depth, and roomy inside. On the 29th the female went into the nest and did not come out again.
“The hole being about 10 feet from the ground and opposite my verandah, I could watch everything perfectly with a glass.
“On April 30th I observed the female working hard at closing the orifice with her own ordure. This she plastered right and left with the flat side of her beak, as with a trowel.
“I never saw the male bring anything but food. The male bird would alight near, then fly to the hole and knock with his beak. On this, the points of that of the female appeared and received the food, when the male flew off.
“The hole was at first perhaps 6 inches in height and 3 or 4 wide. When closed up, the opening at the widest part was a little larger than would admit a finger. The plastering operation took two or three days, after which the ordure was thrown out.
“The natives, who know the habits of these birds well, told me that the female digs herself out directly her newly-hatched young need food,”
Horne learnt much by his observations, but on the 7th May he took the three eggs the nest contained, so that all further details as to incubation etc. and whether the female did dig herself out were lost.
The above description would do for almost all the nests of this bird. As a rule they select holes low down, between 10 and 20 feet from the ground and, only exceptionally, much higher than this.
Mr. J. D. Finlay (Journ. Bomb. Nat. Hist. Soc. vol. xxxiii, p. 444, 1929) gives some very interesting notes on this bird. He found a nest 25 or 30 feet up in a Mango-tree which he opened up on May 13th and took the two fresh eggs which were in it. On June the 2nd, 6th and 16th he paid further visits to the nest. Each time no eggs were found, though the female was inside and "had repaired the blocking of the entrance.” The last time she was taken away, and it was found she had moulted her primaries, the new quills being half developed. There were no signs of more eggs in the ovaries, so that in this instance the hen bird must have shut herself in until it was safe for her to come out with her powers of flight fully restored.
It has often been asked what is the object of blocking up the entrance to a nest-hole when a bird of the defensive power of a Hornbill indulges in it. The Horn hills, however, have very powerful enemies in the shape of the larger snakes and lizards with which they certainly could not cope unaided, and I have no personal doubt that protection against these is the raison d’etre of the masonry work.
General Osborne’s note on this subject (op. cit. vol. xiv, p. 715) show that not only does the hen bird moult her wing-quills during incubation but that at this period she is not physically at her best for protective fighting.
The breeding season is from the middle of March to the end of May, most birds laying in April.
The normal clutch of eggs is three, though Hume speaks of seeing four young birds and that, though he has not seen as many as five, such a number has been reported.
Thirty eggs average 41.9 x 30.0 mm. : maxima 46.0 x 32.0 mm. ; minima 39.1 x 29.2 and 39.2 x 27.5 mm.
1575. Tockus birostrls
(1575) Tockus birostris (Scop.).