COW BUNTING. 
215 
the foster mother as attentive to it as she could have 
been to her own. I ought to acknowledge here, 
that, in none of these instances, could I ascertain ex- 
actly the time required to hatch the cow bird’s eggs ; 
and that of course none of them are decisive ; but is it 
not strange that the egg of the intruder should be so 
uniformly the first hatched? The idea of the egg 
being larger, and therefore from its own gravity finding 
the centre of the nest, is not sufficient to explain 
the phenomenon ; for in this situation the other eggs 
would be proportionably elevated at the sides, and 
therefore receive as much or more warmth from the 
body of the incumbent than the other.* This principle 
would scarcely apply to the eggs of the bluebird, for 
they are nearly of the same size ; if there be any dif- 
ference, it would be in favour of the eggs of the builder 
of the nest. How do the eggs get out of the nest ? 
Is it by the size and nestling of the young cow bird ? 
This cannot always be the case ; because, in the instance 
of the bluebird’s nest in the hollow stump, the cavity 
was a foot deep, the nest at the bottom, and the ascent 
perpendicular; nevertheless, the eggs were remoyed, 
although filled with young ones ; moreover, a young 
cow-pen finch is as helpless as any other young bird, 
and so far from having the power of ejecting others 
from the nest, or even the eggs, that they are sometimes 
found on the ground under the nest, especially when 
the nest happens to be very small. I will not assert 
that the eggs of the builder of the nest are never 
hatched ; but I can assert, that I have never been able 
to find one instance to prove the affirmative. If all 
the eggs of both birds were to be hatched, in some cases 
the nest would not hold half of them; for instance, 
those of the sparrow, or yellow-bird. I will not assert, 
that the supposititious egg is brought to perfection in 
less time than those of the bird to which the nest 
. * The ingenious writer seems not to be aware that almost all 
birds are in the habit, while sitting, of changing the eggs from the 
centre to the circumference, and vice versa , that all of them may 
receive an equal share of warmth. 
