THE GAME BREEDER 



141 



the West. By actual experiment it has 

 been found that the duck sickness may 

 be caused by the chlorides of calcium 

 and magnesium. Experiments have in- 

 dicated that other salts may be incrim- 

 inated in Utah and elsewhere, but this 

 statement is made with reserve, as it has 

 not yet been definitely established. 



The Salt Lake Valley is well culti- 

 vated and owes its fertility almost en- 

 tirely to irrigation. The irrigation has 

 decreased the amount of water supply- 

 ing the marshes and the resulting slow 

 drainages induces stagnation over large 

 areas. Surface evaporation and capil- 

 lary attraction rapidly draw the salts held 

 in solution in the mud to the surface and 

 there concentrate them. 



Fresh water is the only agency that 

 has been found of value in combatting 

 the duck sickness. Birds slightly af- 

 fected, and even many entirely helpless, 

 recover in almost all cases when given 

 plenty of moderately fresh water to 

 drink. With an abundance of good 

 water in the marshes sick ducks are in- 

 frequent, as when the bays are well filled 

 and well drained many birds that become 

 affected recover in a few days. 



For remedial agencies, therefore, 

 measures must be adopted that tend to 

 supply fresh water or to drive ducks out 

 from areas where they are liable to ob- 

 tain alkalis in harmful quantity. Three 

 methods of treatment that promise suc- 

 cess in dealing with the trouble are : ( 1) 

 Increasing summer water in streams ; 

 (2) draining affected areas, and (3) 

 collecting sick birds for treatment. 



Since more water is constantly needed 

 for irrigation, the first method is said 

 to be impractical. The drainage of the 

 areas where the birds may become poi- 

 soned can be done with little effort and 

 in this way it is said opportunity for in- 

 fection may be removed. In the marshes 

 controlled by the New State Gun Club 

 this means of meeting the situation is 

 particularly applicable. 



Serious objection has been offered to 

 this plan on the ground that it kills off 

 the duck foods in the marsh and that 

 shooting in the fall is poor in conse- 

 quence. 



Birds with the duck sickness recover 



in a short time (unless too far gone) 

 when placed on water that is moderately 

 fresh. A large number of ducks were 

 cured by this means at the field labor- 

 atory on Bear river, and it has been 

 proved that recovery is permanent. In 

 past years men have been employed to 

 gather and bury the dead birds on the 

 marshes. If they were set< to work 

 gathering the sick birds and bringing 

 them in, a large number of ducks could 

 be saved at comparatively small expense- 

 In the course of the investigation, 

 1,211 individuals belonging to the seven 

 species of ducks most severely affected 

 were treated in this manner. Of these 

 284 died and 927 recovered. Among 

 the ducks treated were a large number 

 of very weak birds that were so far 

 along that ordinarily they would have- 

 been disregarded. Eliminating these, the 

 ratio of recovery was about 90 per cent 

 of those brought in. 



Among mallards and pintails many in- 

 dividuals are killed by lead poison due to 

 eating shot. These have been eliminated 

 from the table showing the number 

 treated and the percentage of each spe- 

 cies which recovered. 



Release of Banded Birds. 



Aluminum bands were placed on the 

 legs of about 1,000 ducks that were cured 

 and released at the mouth of Bear river. 

 From these banded birds data have been 

 obtained upon the permanency of the 

 cure and the subsequent longevity of in- 

 dividuals that have recovered. The 

 bands used thus are of two types : 

 Each bears a number stamped upon one 

 side ; on the reverse, one is marked, 

 "Notify U. S. Dept. Agr., Wash., D. C. ;" 

 the other, "Notify Biological Survey, 

 Washington, D. C." These bands are 

 light and in addition are little affected by 

 salt or alkaline waters. Returns have 

 come in at the present time from about 

 170 of these ducks. Many of these were 

 killed locally, but nearly always under 

 circumstances that indicated that they 

 had fully recovered. Others have come 

 from greater distances. Individual rec- 

 ords range west to the Pacific Ocean in 

 California, south to the Mexican border 



