Denver C«iter biologists checting respiration and heart- 

 beat of male deer used in iiesticide sradies. (Photo 

 by ilichael J. Stephen) 



been obtained from robins collected tremoring or 

 dead after DDT treatments for Dutcli ebn disease. 



In 196i. residue levels were determined in the 

 brains and certaLa other tissues of 11 cowbirds 

 that died during a period of 12 days on a diet 

 of 5<X> pans per million DDT: 3 that were re- 

 moved from a toxic diet after 8 days, but died 

 after 2. 9, and 40 days mi clean diet : and 3 that 

 survived S days on toxic diet plus 112 days of 

 clean diet and then were killed. 



DDT and DDD in the brains of these birds 

 showed no time-related trends, being similar in 

 birds that died on dosage for the various lengths 

 of time and in those dying after long periods on 

 clean food. DDT plus DDD averaged 66 = 6 ppm 

 wet weight, with a range of 35-99 ppm. DDE, 

 however, appeared not to be critical in this series. 

 for more was present in survivors than in those 

 that died. 



Quantities of DDT residues were remarkably 

 similar to those reported for the other species 

 listed above, when expressed comparably and 

 with allowance for differences in chemical meth- 

 odology. Thus, it appears that similar brain lev- 

 els of DDT-^ DDD are diagnostic of DDT-induced 



mortality over a wide range of species, mainma.1.g! 

 as well as birds. 



Xeic techniques facilitate pesticide studies. — 

 New and improved techniques developed at the 

 Denver :ind Patuxent Laboratories in 196i facili- 

 tated Bureau pesticide research. 



Cholinesterase-level determinations were given 

 greater accuracy and meaning through the use of 

 colorimetric and pH cliange measurements. DDT 

 and its metabolite recovery from eggs was sig- 

 nificantly higher with thin-layer chromatography 

 than with gas chromatc^raphy. but there was no 

 significant difference between levels recovered by 

 use of two separate cleanup procedures. Dieldrin 

 recover}" from animal tissues, however, was many 

 times greater with a recently developed cleanup 

 procedure, regardless of detection method — color- 

 imetric indication, thin-layer plate, or gas 

 chromatography. 



A sensitive method of extraction, isolation, and 

 estimation of DRC-1339 was developed and in- 

 volved a titrimetric technique, the titration end- 

 point being detected with a pH meter. DRC- 

 1339 is a highly promisiug bird avicide. 



A modified method was developed for deter- 

 mining microamounts of thallium in urine, in- 

 direct identification of this compoimd being ac- 

 complished by reading the iodine color in a 

 Spectronic-20 colorimeter. Tests showed oolori- 



The Cotumis qnaii is a desirable species for studying the 

 effects of pesticides on birds. Females lay eggs at 5 

 weeks of age. breed year around in captivity, and pro- 

 duce a large number of eggs annually. The 29 eggs 

 shown, produced in 1 month, are twice the weight of the 

 adult. The very rapid rate of maturity permits, in a 

 year's time, study of pesticide effects through several 

 generations. (Photo by Bex G. Schmidt) 



50 



