IIO BIRDS OF LA PLATA 
experimenting, pressing d@¥n the bird’s head and 
trying to bend him by main force into some other 
position; but the strange rigidity remained unre- 
laxed, the fixed attitude unchanged. I also found, 
as I walked round him, that as soon as I got to the 
opposite side and he could no longer twist himself on 
his perch, he whirled his body with great rapidity the 
other way, instantly presenting the same front as before. 
Finally I plucked him forcibly from the rush and 
perched him on my hand, upon which he flew away ; 
but he flew only fifty or sixty yards off, and dropped 
into the dry grass. Here he again put in practice 
the same instinct so ably that I groped about for 
ten or twelve minutes before refinding him, and was 
astonished that a creature to all appearance so weak 
and frail should have strength and endurance suff- 
cient to keep its body rigid and in one attitude for 
so long a time. 
Some recent or at all events later observations 
appear to show that some species of Bittern possess 
a similar instinct to that of the bird described—the 
faculty of effacing themselves as it were in the presence 
of an enemy. Doubtless any Bittern, its colouring 
being what it is, would make itself invisible among 
partially decayed and dead vegetation by extending 
and stiffening its body and keeping its breast towards 
its intruder. The peculiar thing in the case of the 
small Heron is that the whole action of the bird 
appears to be framed and designed expressly to make 
it look exactly like a dead yellow tapering bulrush. 
