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, however, is
very inferior in force and rapidity to that of a hawk.
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