186 The Marquess of Tavistock—Some Problems of Mortality



perfection in the colour and texture of plumage, liveliness, and a readi¬

ness to breed at the appropriate (or inappropriate !) season. If the

“ perfect health 55 theory were free from snags of any kind, the more

perfect a bird’s plumage and the livelier its demeanour, the less liable

that bird should be to sudden attacks of illness. Unfortunately, how¬

ever, I have not the slightest hesitation in saying that it does not

always work out in this way : by good aviary management you can

get a bird into the most perfect show condition in a bad district for its

species and yet at any moment you may find it fatally ill; and not

only that ; your fellow-aviculturalist living in another district favour¬

able to the species may be keeping the same kind of bird and, by reason

of inferior aviary management, his stock may never be a patch on yours

in looks and beauty of plumage, and yet his shabby specimens will

be alive years after the last of yours have gone to a better world—,

which is the most unkindest cut of all, but is nevertheless a fact of

common occurrence ! Lest the reader should think that I may be

unduly prejudiced in favour of my own birds and that a more impartial

observer would not detect inferior condition in the longer-lived

specimens in other collections, I may add that in different districts but

in the same aviaries I have been successful in getting a species of bird

into equally perfect show condition, but in the one place it was always

short-lived and liable to sudden illness and in another gave no trouble

at all.


Occasionally a bird, after years of perfect health in one place, will

start getting ill every time you put it back in the aviary where it has

flourished so long ; yet if sent to another district it may regain its

freedom from illness. Occasionally, too, though much more rarely,

a bird, after a series of illnesses, will enter on a period of immunity in

the very place where it was always going wrong. In all these cases

I am speaking only of acclimatized birds in what appears to be perfect

condition and plumage.


There is an unexplored and probably important field of research

in the direction of finding out whether any system of dieting can

reduce liability to disease. It is said that among domestic poultry

fowls getting an adequate iodine ration are markedly less liable to

disease than those whose diet is deficient in iodine.



