26o FLEAS, FLUKES AND CUCKOOS 



If the intended foster parents surprise the cuckoo near their nest 

 they make frantic efforts to drive her away, buffeting and pecking her 

 in a courageous manner. The cuckoo never fights back — it would 

 certainly not be in her interest to injure the future foster parents of her 

 own chick — but she is very persistent and even if driven off returns 

 time and again and generally succeeds in laying her egg in the chosen 

 nest. Sometimes one or more males accompany the female and try to 

 divert the fosterers' attention while she quickly and furtively deposits 

 her egg. Chance has remarked that at times the victims behave as if 

 they were mesmerised by the cuckoo. Some pairs of meadow-pipits 

 which he had under observ^ation appeared to welcome her attentions 

 and seemed to fly up to her as she sat watching their activities and 

 "virtually invite her" to their nest. He also noted that sometimes after 

 a cuckoo had laid her egg the fosterers would at once begin to brood, 

 although their own clutch was not yet complete, as if the visitation was 

 regarded in the nature of an honour conferred upon them. At any rate 

 it can be said that the presence of the cuckoo is a disturbing and 

 exciting influence, which can upset the normal rhythm of their 

 behaviour. 



A frequent result of the cuckoo's visit to a nest is its desertion by the 

 intended fosteiers. One of the adaptations to brood-parasitism is the 

 development of eggs resembhng those of the fosterers, but in the case of 

 the European cuckoo the adaptation is by no means perfect and the 

 birds often notice the strange egg and remove it, build over it or merely 

 abandon the nest. Some species of bird desert much more readily than 

 otheis and consequently keep the cuckoo at a safe distance. Many 

 warblers, for instance the chiffchaff and wood-warbler, will abandon 

 their nests if a fight has taken place, and Capek found that 77 per cent, of 

 cuckoos' eggs which had been placed in the nest of the latter species 

 were destroyed, whereas in the same district the common redstart 

 accepted and reared all but five per cent. 



It has already been explained that the cuckoo tries to lay her egg 

 either before the fosterer's clutch is complete, or immediately upon 

 completion. In this she succeeds in about 70 per cent, of her layings. 

 The young cuckoo develops more rapidly than the foster nestlings and 

 hatches out one to four days before them if brooding had not commenced 

 prior to the introduction of the cuckoo's egg into the nest. Correct 

 timing is of great importance, for the parasite is thus given several days' 

 start, a definite advantage over the rest of the brood. 



