PORTUGUESE EAST AFRICA (SOUTH) 89 
standing with one of its long legs forward and the other back- 
wards, as if about to start a race, and for it to remain like this for 
hours, until moved bodily into another position. Their sphinx-like 
postures were not disturbed in the slightest by any noise, move- 
ment, or the introduction of every conceivable kind of natural 
food. Specimens that behaved in this way were no use persevering 
with and so they were liberated. Others were induced to begin 
feeding by placing their natural food—water-lily seeds and insects 
—in a shallow pan of water so that they could paddle through it. 
My difficulties were not at an end even when J had several birds 
apparently quite happy and feeding well, for some of them devel- 
oped staggering fits. In this complaint the head was held back to 
such an extent that frequently the victim would roll over back- 
wards. This was rather puzzling for I knew that it was through 
no fault in their diet, and I could find nothing that had any 
effect as a cure. The symptoms usually appeared within a few days 
of capture, but when I arrived at the London Zoo with three 
apparently perfect specimens, I was surprised a few days later to 
find that one had developed the same trouble, and it died quite 
suddenly. A post-mortem examination revealed nothing organ- 
ically wrong, to the naked eye, so the blood was examined micro- 
scopically for parasites, and was found to contain filaria worms in 
great quantity. This solved the mystery of the previous cases of 
fits. These minute worms are introduced into the bloodstream by 
the bites of mosquitoes, and it is only natural that swamp-dwell- 
ing birds should be the most likely to be preyed on. It shows that 
many parasites are quite harmless to birds and mammals in their 
wild state, but the slightest falling off in condition, due to change 
of diet or temperature such as may occur in captivity, disturbs the 
delicate balance between the parasites and their host. 
One day I caught a very young jacana in a floating cage-trap 
that I had set among the water-lilies in the hope of catching a 
Pygmy Goose. It had a most comical appearance as its legs and 
feet were even more out of proportion to the size of its body than 
in the adult birds, reminding me of a small boy wearing his 
father’s boots. I liberated this bizarre specimen to see how it would 
thread its way across the water-lily leaves and other aquatic vege- 
tation to the reed-beds, but to my surprise it instantly dived like 
