Wings 329 
and bushes; while goldfinches and woodpeckers swing 
past in long undulations, a loop and a catch, a loop and 
a catch,—with wings wide extended, then quickly closed. 
Hummingbirds have a remarkably insect-like flight; the 
rapid reflex whirr of the wings holding them perfectly 
still, poised in mid-air. 
When ornithologists think that they have formed a 
correct theory of flight and that, given such and such 
conditions, certain results must follow, such a bird as the 
Crested Screamer soars into their mental atmosphere and 
upsets every calculation. Such a bulky and short-winged 
bird, by all good “rules” of flight, should confine itself 
to short laboured efforts, barely skimming the low bushes 
of its South American haunts! But it refuses to be thus 
limited. Of this species it is said: ‘‘The Screamer is a very 
heavy bird, and rises from the ground laboriously, the 
wings, as in the case of the swan, making a loud noise. 
Nevertheless it loves soaring, and will rise in an immense 
spiral until it wholly disappears from sight in the zenith, 
even in the brightest weather; and considering its great 
bulk and dark colour, the height it ultimately attains 
must be very great. On sunny windless days, especially 
in winter and spring, they often spend hours at a time 
in these sublime aerial exercises, slowly floating round 
and round in vast circles, and singing at intervals. How 
so heavy and comparatively short-winged a bird can sus- 
tain itself for such long periods in the thin upper air to 
which it rises has not yet been explained.” 
I find in my journal the following account of a flight 
of vultures which we saw in a desolate alkali desert in 
