3972 The Zoologist — May, 1874. 



at all. Here are both Mr. Blaclcwall's opinions as recorded by 

 himself: — 



" In the year 1834 I advocated the opinion prevalent among ornitholo- 

 gists, that the loss of the feathers alluded to above is attributable to the 

 habit which the rook has of thrusting its bill into the ground in search of 

 food. An extensive examination and comparison of specimens had led me 

 to observe that the nudity extends further and is more complete in some 

 individuals than in others, that the more prominent and exposed parts are 

 first deprived of feathers, and that short fdiform processes bearing a close 

 resemblance to new feathers enveloped in membrane, frequently occur on 

 the less prominent and less exposed parts, particularly on the flaccid skin 

 which occupies the angle at the base of the lower mandible. In addition 

 to these facts, I may remark that an opportunity had presented itself of 

 inspecting a rook whose mandibles were so greatly curved in opposite 

 directions, and consequently so much crossed at the extremities, that it 

 could not possibly thrust its bill into the ground ; and the base of that 

 organ and the anterior part of the head did not manifest the least deficiency 

 of plumage. With such evidence in its favour, I was induced to adopt the 

 popular hypothesis, which I now abandon in consequence of having recently 

 proved by experiment that it is erroneous. 



" Being supplied by Mr. Davies with two young rooks taken from a nest 

 in his rookery at Cyffdry on the 17th May, 1843, I put them into a large 

 wooden chicken-pen, purposing, when they could take food without assist- 

 ance, to remove one of them to a garden enclosed with walls, where it 

 might have an opportunity of employing the means of procuring sustenance 

 common to the species, and let the other remain in the pen. This plan 

 was frustrated by the unexpected death of one of the young birds soon after 

 it came into my possession ; but the result of the experiment, as will be 

 seen in the sequel, was not at all affected by this untoward circumstance. 

 In the month of August the surviving rook lost only a few feathers from 

 various parts of its body, but did not moult regularly till July and August, 

 ]8i4, when the feathers at the base of the bill and on the anterior region 

 of the head were cast off and were not renewed, though the bird was 

 remarkably healthy, and was never on any occasion suffered to leave the pen 

 for a moment. On the 20th June, 1846, an unfortunate accident terminated 

 its existence. It lived long enough, however, thoroughly to establish the 

 fact that after the feathers are once shed from those parts in the act of 

 moulting they are not renewed, as the denudation became rather more 

 extensive and complete after the bird had moulted a second time, in the 

 summer of 1845, and continued unchanged to the day of his death, affording 

 a convincing proof that this conspicuous feature in the adult rook, which 

 strikingly affects its physiognomical expression, must be regarded as a 

 specific character." — P. 100. 



