346 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



ness of climatic agencies and the time interval required for these to 

 destroy the eggs and larvae of parasites present in the pen soil. Re- 

 sults indicate that little reliance can be placed upon time to overcome 

 infestation. 



BREEDING SEASON OF THE MARTEN. 



The discovery at the experimental fur farm that martens breed the 

 last of July and in August has solved the problem which has here- 

 tofore prevented the successful rearing of these animals in captivity. 

 The belief has been that these animals mate late in fall or in winter 

 and that they could not be kept together during the summer sea- 

 son, and following this theory efforts to breed these animals in cap- 

 tivity have been unsuccessfid. Martens have been bred on the 

 experimental fur farm in August during the last three seasons and 

 the period of gestation has proved to be about eight months. This 

 discovery, together with the determination made regarding feeding 

 and management, has made practicable the rearing of another of 

 our valuable fur bearers in captivity. 



FOOD HABITS RESEARCH. 



The work of this division has centered about the relations of birds 

 to agriculture, but progress w^as made also on an economic study of 

 toads, and numerous stomachs of mammals were examined. During 

 the year arrangements were made with three States for preserving 

 the stomachs of animals killed as vermin by game wardens and 

 (employees of game farms. By means of this cooperation it is hoped 

 to get a good basis of fact for discussion of the vexed vermin prob-' 

 lem, consideration of wiiich in the past has been based largely on 

 conjecture and speculation. 



A small auto truck and two motor cycles procured for field use 

 have proved highly economical and effective aids to the work. The 

 cost of operation has been surprisingly low, and the results show not 

 only a very great economy over the use of common carriers but 

 nuich more work accomplished, owing to the attendant freedom 

 of action and elimination of delay. 



CONTROL OF PINYON JAYS DAMAGING GRAIN IN COLORADO. 



Pinyon jays, inhabiting the Kocky Mountain States, are birds of 

 the same family as crows and about half their size. Between nest- 

 ing seasons they rove in large flocks, sometimes containing thou- 

 sands of birds, and wreak havoc on grain crops. Experiments in 

 methods of control of these birds when attacking corn were entirely 

 successful in west-central Colorado, and a leaflet containing direc- 

 tions for using a simple but effective poison formula has been dis- 

 tributed in that territory. Plans are being laid for studying the 

 Milations of the birds to wheat during the coming fiscal year. 



liLACKBIRDS AND DUCKS IN RKLATION TO GRAIN IN THE IMPERIAL VALLEY, 



CALIF. 



Milo maize and barley, grain crops of the fertile Imperial Valley. 

 Calif., attract immense flocks of blackbirds, which feed upon them 

 throughout the fall and winter months. Investigation by a repre- 

 sentative of the Biological Survey revealed an average destruction 



