EXCLUDING BIRDS FROM RESERVOIRS 
AND FISHPONDS 
By W. L. McAtTex, technical adviser and research specialist, Office of Chief of 
Bureau, and S. E. Pirer, formerly associate biologist, Division of Wildlife 
Research, Bureau of Biological Survey 
Fish-eating birds are undesirable visitors to hatchery and other 
fish-rearing ponds, as are any birds to reservoirs directly ‘drawn upon 
for drinking water. The reason for objection in the former case 
is economic; in the latter it is a matter of public health, for pollution 
causes a rise in the count of colon bacilli—the ordinary test of the 
suitability of water for human consumption. Troubles of these 
sorts, In some instances serious, have been experienced in various 
parts of the country and steps to remedy them have not always 
been wisely taken. 
Some of the remedies applied have involved, and some still involve, 
destroying the birds. Since certain of these birds are protected by 
law, it has been necessary in special cases to maintain a system of 
issuing permits authorizing their killing. Objectionable features 
of this system are the correspondence, investigation, and delay in- 
volved, in addition to the destruction of birds “that under other cir- 
cumstances have an economic or esthetic worth that fully entitles 
them to protection. From the conservation standpoint it is cer- 
. tainly better to adopt measures that will prevent damage rather 
than at first to countenance conditions that invite trouble and then 
carry on some degree of warfare against the birds. It is the pur- 
pose of this leaflet to show that preventive devices can be installed 
at moderate cost, in some cases for less than the cost of patrolling 
property and killing the birds. 
Water-supply Reservoirs 
Birds as small as swallows, nesting about the outlet tower of 
reservoir, have been known to add colon bacilli to such an extent 
as to make it necessary to chlorinate water otherwise perfect. When 
gulls, cormorants, coots, wild ducks, and other large species frequent 
reservoirs of purified water, pollution may rapidly assume dangerous 
proportions and be difficult and expensive to correct. Increase in 
colon bacilli, however, is not the only objectionable feature connected 
with the presence of birds. The oxygen content of the water is 
reduced by oxidation of the fecal matter and as a result there develop 
in it anaerobic bacteria that give the water a bad taste. 
The fecal defacement of structures connected with reservoirs, while 
less serious, is another objection to bird occupation. Such disfigur- 
ing, however, should be controllable by preventive measures. Struc- 
tures can be built in the first place so as to afford few or no perches 
for birds and no nesting sites. This requires a smooth exterior, 
without cavities or ledges, and with summits ending in sharp points 
74300°—36 1 
