death would cause theirs during the period of infancy." It is
remarkable that some of the species, but not all, both of the Cuckoo
and Molothrus, should agree in this one strange habit of their
parasitical propagation, whilst opposed to each other in almost every
other habit: the molothrus, like our starling, is eminently sociable,
and lives on the open plains without art or disguise: the cuckoo, as
every one knows, is a singularly shy bird; it frequents the most
retired thickets, and feeds on fruit and caterpillars. In structure
also these two genera are widely removed from each other. Many
theories, even phrenological theories, have been advanced to explain
the origin of the cuckoo laying its eggs in other birds' nests. M.
Prevost alone, I think, has thrown light by his observations [9] on
this puzzle: he finds that the female cuckoo, which, according to most
observers, lays at least from four to six eggs, must pair with the male
each time after laying only one or two eggs. Now, if the cuckoo was
obliged to sit on her own eggs, she would either have to sit on all
together, and therefore leave those first laid so long, that they
probably would become addled; or she would have to hatch separately
each egg, or two eggs, as soon as laid: but as the cuckoo stays a
shorter time in this country than any other migratory bird, she
certainly would not have time enough for the successive hatchings.
Hence we can perceive in the fact of the cuckoo pairing several times,
and laying her eggs at intervals, the cause of her depositing her eggs
in other birds' nests, and leaving them to the care of foster-parents.
I am strongly inclined to believe that this view is correct, from
having been independently led (as we shall hereafter see) to an
analogous conclusion with regard to the South American ostrich, the
females of which are parasitical, if I may so express it, on each
other; each female laying several eggs in the nests of several other
females, and the male ostrich undertaking all the cares of incubation,
like the strange foster-parents with the cuckoo.
I will mention only two other birds, which are very common, and render
themselves prominent from their habits. The Saurophagus sulphuratus is
typical of the great American tribe of tyrant-flycatchers. In its
structure it closely approaches the true shrikes, but in its habits may
be compared to many birds. I have frequently observed it, hunting a
field, hovering over one spot like a hawk, and then proceeding on to
another. When seen thus suspended in the air, it might very readily at
a short distance be mistaken for one of the Rapacious order; its stoop,
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