In both countries, sheep-runs have been greatly deteriorated in value by the abundance of rabbits, which destroy the herbage; and in some cases they have had to be abandoned altogether.] [Footnote 11: Later observers have proved that two eggs are laid and usually two young produced, but it may be that in most cases only one of these comes to maturity.] [Footnote 12: _Origin of Species_, p.59.Professor A.Newton, however, informs me that these species do not interfere with one another in the way here stated.] [Footnote 13: Winwood Reade's _Martyrdom of Man,_ p.

520.] [Footnote 14: _Nineteenth Century,_ February 1888, pp.

162, 163.] [Footnote 15: The Kestrel, which usually feeds on mice, birds, and frogs, sometimes stays its hunger with earthworms, as do some of the American buzzards.

The Honey-buzzard sometimes eats not only earthworms and slugs, but even corn; and the Buteo borealis of North America, whose usual food is small mammals and birds, sometimes eats crayfish.].