202 The Naturalist in La Plata. 
ward of the flock, and when opposite to it suddenly 
wheel and charge it at full speed, uttering loud 
shouts, by which the birds are thrown into such terror 
that they are incapable of flying, and are quickly 
despatched. 
I have also seen gaucho boys catch the Silver-bill 
(Lichenops perspicillata) by hurling a stick or stone 
at the bird, then rushing at it, when it sits perfectly 
still, disabled by fear, and allows itself to be taken. 
I myself once succeeded in taking a small bird of 
another species in the same way. 
Amongst mammals our common fox (Canis azare), 
and one of the opossums (Didelphys azare), are 
strangely subject to the death-simulating swoon. 
For it does indeed seem strange that animals so 
powerful, fierce, and able to inflict such terrible 
injury with their teeth should also possess this safe- 
guard, apparently more suited to weak inactive 
creatures that cannot resist or escape from an enemy 
and to animals very low down in the scale of being. 
When a fox is caught in a trap or run down by dogs 
he fights savagely at first, but by-and-by relaxes 
his efforts, drops on the ground, and apparently 
yields up the ghost. The deception is so well 
carried out, that dogs are constantly taken in by it, 
and no one, not previously acquainted with this 
clever trickery of nature, but would at once pro- 
nounce the creature dead, and worthy of some praise 
for having perished in so brave a spirit. Now, when 
in this condition of feigning death, I am quite sure 
that the animal does not altogether lose conscious- 
ness. It is exceedingly difficult to discover any 
evidence of life in the opossum; but when one with- 
