I'hree models ot the famous burrow-builder developed 

 by the Denver Wildlife Research Center and Colorado 

 State University, now being manufactured by commer- 

 cial companies. (Top and bottom photos by A. Loren 

 Ward, middle photo by the Colorado District, Predator 

 and Rodent Control) 



lytical method capable of detex^t ing and measuring, 

 in most field samples, 2 micrograms of Sevin in 

 the pure compound. A study of the inetabolites 

 of DDT established the conversion of DDT in the 

 animal body to DDD and other metabolites, some 

 of which are as yet unreported in the literature. 



WILDLIFE DISEASE AND PARASITES 



Investigations in the field of diseases and para- 

 sites, particularly in migratory birds, is an impor- 

 t ant responsibility of the Bureau. Studies involv- 

 ing both birds and mammals at the Disease Lab- 

 oratory at the Patuxent Center, and confined 

 largely to diseases and parasites of waterfowl in 

 the Den\er Center program, were active in 1962. 

 The latter were carried on mainly at the Bear 

 River Station in Utah. 



BotitJism afudi-es at Bear River'. — The Bear 

 River staff undertook a study concerned with tlie 

 role of invertebrates in the transmission of botu- 

 linal toxin and the effects of invertebrate control 

 on the incidence of botulism in waterfowl in 1962. 



Botulism mortality on the Bear River National 

 Wildlife Refuge was somewhat more severe in 

 1962 than in 1961 in spite of the smaller popula- 

 tion of ducks, the peak of which was little more 

 than half of that of the year before. Personnel 

 on the Refuge estimated a loss of 3,240 birds 

 of all species, as compared with 2,0<W in 1961. 



Aquatic invertebrate population studies were 

 continued. Mud and water samples for inverte- 

 brate analyses were collected from the study area 

 once a week at each of 60 collecting stations ran- 

 domly distributed within a 2.9-square-mile plot. 

 Only 747 sick and dead birds were picked up dur- 

 ing the summer. Of these, 455 were collected on 

 the the area proper. Mortality began at a low 

 level in the fifth week of the investigation (July 

 f6), when 5 sick or dead birds were taken. Losses 

 gradually increased in severity until the thirteentl 

 week (September 10), when a peak of KU bird; 

 was reached. Judging from the mortality distri 

 bution, these figures do not represent a general in- 

 crease in loss over the entire area, but ratlier the 

 sum of a series of irregularly distributed miniature 

 outbreaks that increased in frequency from the 

 lift h to the thirteenth week. 



Foi- the second time in the past 4 years, an out- 

 break of lioiulisni Dccui'reil in a flock of mallards 

 maintained for ex])ei'iniental use at the liear River 

 Research Station. Again it appeared (hat the 



48 



