The polygamous ruff (Machetes pugnax, Fig. 37) is notorious for his
extreme pugnacity; and in the spring, the males, which are considerably
larger than the females, congregate day after day at a particular spot,
where the females propose to lay their eggs. The fowlers discover these
spots by the turf being trampled somewhat bare. Here they fight very
much like game-cocks, seizing each other with their beaks and striking
with their wings. The great ruff of feathers round the neck is then
erected, and according to Col. Montagu sweeps the ground as a shield
to defend the more tender parts ; and this is the only instance known
to me in the case of birds of any structure serving as a shield. The
ruff of feathers, however, from its varied and rich colours probably
serves in chief part as an ornament. Like most pugnacious birds, they
seem always ready to fight, and when closely confined, often kill each
other; but Montagu observed that their pugnacity becomes greater during
the spring, when the long feathers on their necks are fully developed;
and at this period the least movement by any one bird provokes a
general battle. (7. Macgillivray, History of British Birds, vol. iv.
1852, pp. 177-181.) Of the pugnacity of web-footed birds, two instances
will suffice: in Guiana bloody fights occur during the breeding-season
between the males of the wild musk-duck (Cairina moschata); and where
these fights have occurred the river is covered for some distance with
feathers. (8. Sir R. Schomburgk, in Journal of Royal Geographic
Society, vol. xiii. 1843, p. 31.) Birds which seem ill-adapted for
fighting engage in fierce conflicts; thus the stronger males of the
pelican drive away the weaker ones, snapping with their huge beaks and
giving heavy blows with their wings. Male snipe fight together,
tugging and pushing each other with their bills in the most curious
manner imaginable. Some few birds are believed never to fight; this is
the case, according to Audubon, with one of the woodpeckers of the
United States (Picu sauratus), although the hens are followed by even
half a dozen of their gay suitors. (9. Ornithological Biography,
vol. i. p. 191. For pelicans and snipes, see vol. iii. pp. 138, 477.)
The males of many birds are larger than the females, and this no doubt
is the result of the advantage gained by the larger and stronger males
over their rivals during many generations. The difference in size
between the two sexes is carried to an extreme point in several
Australian species; thus the male musk-duck (Biziura), and the male
Cincloramphus cruralis (allied to our pipits) are by measurement
actually twice as large as their respective females. (10. Gould,
389