LIFE AND BEHAVIOR OF THE CUCKOO 
183 
Durham Weir, who then gave one of the best accounts of the be- 
havior of the nestling cuckoo which we still possess. 
Those who rejected Jenner's account relied either upon nega- 
tive evidence or upon analogical reasoning, as in the case of Charles 
Watterton, whose bitter attacks upon Audubon, mainly rested 
upon the same fallacies. ''The young cuckoo," said Watterton 
'^cannot by any means support its own weight during the first 
da}^ of its existence. Of course, then, it is utterly incapable of 
clambering rump foremost up the steep side of a hedge sparrow's 
nest, with the additional weight of a young hedge sparrow on 
its back. The account carries its own condemnation, no matter 
by whom related or by whom received." 
Blackwall, who placed a young cuckoo, hatched by a titlark, 
in the nests of other birds and watched the eviction of their eggs 
and young, made this significant remark: ''T observed that this 
bird, though so young, threw itself backwards with considerable 
force when anything touched it unexpectedly." It has been 
stated that while this cuckoo will inevitably evict a live bird it 
permits a dead one to remain, but this seems likely to be an error. 
The peculiar hitching movement by means of which this bhnd 
nestling is able to get rid of its nest-mates possibly arose as a 
reflex response to a contact stimulus of a disagreeable kind. The 
repeated stimuU call into play both legs and wings, and indeed the 
whole body, and after one trial at evicting an egg, Hancock 
saw the little cuckoo fall back into the nest as if in a state of ex- 
haustion; two hours sometimes elapsed before any fresh attempt 
was made. In every case where this highly specialized instinct 
has been shown to be well developed, we are inclined to believe that 
any object simulating an egg or young bird would seldom fail to 
awaken this response, when the evicting instinct is at its height, 
although the stimulus afforded by a struggling live bird would be 
greater than that of a dead or passive object, whether nestling 
or egg. This would seem to explain the observation by Jenner 
that after the third day, when this instinct is on the wane, an egg 
is tolerated when an active bird would be expelled. 
We come now to consider a series of contrary statements made 
