The Ciickods Foster- Parent 265 



than both his foster-parents put together, and they waited 

 on him like slaves. It was really distressing to see their 

 unrevyarded toil. Now, no argument will ever convince 

 me that the robin or the wagtail, or any other bird in whose 

 nest the cuckoo lays its egg, can ever confound the intrud- 

 ing progeny with its own offspring. Irrespective of size, 

 the plumage is so different ; and there is another reason 

 why they must know the two apart: the cuckoo as he 

 grows larger begins to resemble the hawk, of which all 

 birds are well known to feel the greatest terror. They will 

 pursue a cuckoo exactly as they will a hawk. 



I will not say that that is because they mistake it for 

 a hawk, for the longer I observe the more I am convinced 

 that birds and animals often act from causes quite distinct 

 from those which at first sight appear sufficient to account 

 for their motions. But about the fact of the lesser birds 

 chasing the cuckoo there is no doubt. Are they endea- 

 vouring to drive her away that she may not lay her egg in 

 either of their nests ? In any case it is clear that birds 

 do recognise the cuckoo as something distinct from them- 

 selves, and therefore I will never believe that the foster- 

 parent for a moment supposes the young cuckoo to be its 

 own offspring. 



To our eyes one young robin (meaning out of the nest 

 on the hedge) is almost identical with another young 

 robin ; to our ears the querulous cry of one for food is con- 

 fusingly like that of another : yet the various parent birds 

 easily distinguish, recognise, and feed their own young. 

 Then to suppose that, with such powers of observation 

 with the keenness of vision that can detect an insect or a 

 worm moving in the grass from a branch twenty feet or 

 more above it, and detect it while to all appearance engaged 

 in watching your approach to suppose that the robin does 



