The Marquess of Tavistock—Some Problems of Mortality 185


SOME PROBLEMS OF MORTALITY


By The Marquess of Tavistock


This article, in spite of its title, is neither religious nor philosophical;

it merely attempts to delve further into the question of why birds

die and why they don’t !


It is the belief of some students of human disease and also of certain

livestock breeders whose wide experience entitles their opinions to

respect that a 'perfectly healthy creature cannot succumb to an attack

by internal parasites or bacteria ; something must have happened to

lower its vitality before these enemies can gain a foothold. That there

is a considerable amount of truth in this theory may be conceded

straight away. Anyone with experience in keeping the larger herbivora

on pasture learns that many animals will become infested with parasitic

worms and soon sicken and die if fed only on hay and grass, but will

remain perfectly healthy and free from parasites it they receive an

ample and well balanced corn ration in addition. Even an inexperienced

beginner in aviculture, moreover, is well aware that certain foreign

birds, when acclimatized, can stand our severest winters, but it would

nevertheless be folly to turn a newly imported example of the same

species into the open during inclement weather.


But the “ perfect health ” idea, attractive as it is in theory, has

certain limitations in practice, for a bird may have all the recognizable

symptoms of perfect health and yet be in a condition at any moment

to be attacked by fatal illness.


I have already in previous articles called attention to the fact

that, with identical feeding, housing, and general management, birds

of a certain species—sometimes even the same individuals—will do well

in one district and badly in another. It would, indeed, be helpful to

aviculturalists if some kind of geographical chart could gradually be

drawn up showing the districts suitable and unsuitable for different

species, information being derived only from the experience of people

who, if they met with failure in one district, had proved, by their

success in another, that their aviary management was not the cause

of their losses.


Eor the most reliable indications of good health in birds we look to



