BUREAU OF BIOLOGICAL. SURVEY. 439 



Manuscript for a revised bulletin on bird houses also lias been 

 largely completed, along with a series of sketches illustrative of prin- 

 ciples in bird-house construction. A circular on the various names 

 b}' which migratory game birds are known locally is in press. 



WAR GASES AS BIRD-CONTROL AGENCIES. 



Through a cooperative arrangement with the Chemical Warfare 

 Service, experiments were conducted at the Edge wood Arsenal, Md., 

 to determine whether some of the common war gases might be 

 of use in the control of certain injurious birds, which for one rea- 

 son or another do not lend themselves to poisoning operations. Use 

 was made of the ample facilities for such work at the toxicological 

 laboratory at the arsenal, and through the cooperative help of the 

 laboratory staff extensive series of asphyxiation tests were made for 

 the purpose of discovering a gas that would be lethal to birds, yet 

 safe to use in agricultural sections. 



English sparrows and domestic pigeons were used in the tests and 

 were subjected, in varying concentrations and exposures, to the action 

 of phosgene, " mustard," methyldichloroarsine, chloropicrin, chlorine, 

 and bromocyanogen. A comparison of the results here obtained with 

 the lethal dose for a dog (considered to approximate that for a human 

 being) indicated that consistent results could not be expected against 

 the birds in doses less than one-third of the lethal dose for man. In 

 some instances birds survived after being subjected to a full lethal 

 dose for a human being. Owing to the fact that such high concen- 

 trations are required, as well as to the factors of cost and the diffi- 

 culty of handling, it is apparent that, with the possible exception of 

 a limited use of chlorine or chloropicrin, the common war gases have 

 no utility as bird-control agents. Chlorine and chloropicrin, as well 

 as the others, can be released only in sections where their effect on 

 vegetation would not be objectionable. 



FOOD HABITS OF REPTILES AND AMPHIBIANS. 



Progress has been made in the study of the food habits of reptiles 

 and amphibians, including the critical examination of 642 stomachs 

 of toads, representing 19 species, from North and Central America 

 .and the West Indies. Important additions were made to the card- 

 index files on subjects relating to food habits, behavior, life histories, 

 and other general information regarding reptiles and amphibians. 

 A mimeographed account of the common toad, including information 

 on its range, life history, and economic status, was prepared. About 

 550 stomachs of amphibians were added to the collection, including 

 300 presented by Cornell University. 



EXAMINATION OF STOMACHS OF MAMMALS. 



An examination of 85 stomachs of grasshopper mice was made and 

 a report prepared on the food habits of these beneficial rodents. Ap- 

 proximately 380 stomachs have been added to the collection during 

 the fiscal year. 



7S0OT— AGR 1923 29 



