LECTURES. at 
very imperfectly,—if thrown into the company of birds of a different 
species it will modify its nest and make one approximating to those 
of its companions. But the imitation of the nest of another species is 
never perfect, but is suited to the structure of the bird building it. 
Pigeons which have weak feet and clumsy bill could never do more 
than lay twigs on the top of one another, and a parrot which uses 
both feet and beak for every movement is incapable of making a nest 
and lays her eggs in a hole. That the instinct is capable of consider- 
able modification we see from the nests of chimney martins and 
jackdaws, who now often build in church towers. What did these 
birds do formerly? The very earliest chimneys in this country being 
built in the 12th Century and church towers also being a compara- 
tively late introduction in the history of the world. 
Song and nest building are then, at any rate in some degree, 
imitative ; what about fear of natural enemies. Here at least 
we might expect a pure instinct, since escape from enemies is 
necessary for the preservation of life, but again we find an acquired 
fear passes by tradition from one generation to another. I will 
do no more here than just give the results of some of Mr. Hudson’s 
observations in La Plata. He tells us that the rhea, the American 
ostrich, was till quite lately hunted by Spaniards on horseback, and 
that in the two hundred years the Europeans had inhabited the 
continent they had acquired a fear of mounted man, but showed no 
anxiety at the sight of a pedestrian. During the last twenty years 
they have become accustomed to give cries and will no longer allow 
man to approach. The same observer experimenting ‘with young 
birds of his own rearing, used at times to imitates the snorting alarm call 
of the old bird, immediately they rushed to him and tried to hide 
themselves by pushing their heads and necks into his trouser leg. 
And if he always made this call at the approach of a person dressed 
in white they soon acquired a habit of avoiding anyone so clothed, 
There is a curious instance given of the cowbird, which like our 
cuckoo is a parasite, that is, the eggs are placed in the nest of 
another bird. The rightful occupants of the nest crouch with 
terror when they hear the warning note uttered by the parent on the 
approach of man, but the cow-bird not understanding the cry shows 
no terror and will even take worms from his hand. On the contrary 
directly the cow-bird associates with his own species he becomes 
imbued with class-prejudice and shuns the approach of his forme 
benefactor. No observations have been made along these lines with 
regard to our own cuckoo.—Here is the opportunity for the Collectior 
of Facts. 
