an infeftioii, deteriuiuiiig tlie extent of occurrence 

 of specific infections in wildlife populations, trac- 

 iufT the cycle of infection and the mode of trans- 

 mission to wildlife species, and appraising the 

 effect of the infection on an individual animal or 

 populations of animals are the long-range goals of 

 the wildlife pathologists at tlie (^enter. 



To reach these- goals, Center pathologists inves- 

 tigate outhreaks of disease reported to tlie station. 

 They bring sick animals back to the laboratory for 

 detailed study. They .survey latent disease in wild 

 animals by blood studies and autopsies and by 

 laboratory examination of tissues. For example, 

 they are now conducting studies on trichomonas 

 infection in doves and i)igeons, a protozoan disease 



that kills thousands of doves each year in the 

 southern States. They are also working on dis- 

 temper, a virus disease that atfects wild carnivores 

 and has symptoms like those of rabies. Surveys of 

 the parasites and diseases of the Canada goose and 

 the raccoon are largely completed, and detailed 

 surveys of the ailments of blackbirds are underway 

 in a search for biological methods for control of 

 these birds where they do excessive damage to 

 agricultural crops. 



For mutual benefit, the stat!' woiks closely with 

 governmental and other research agencies conduct- 

 ing studies on diseases and parasites of man and 

 domestic animals. 



^The blackbird problem 



Corn and rice growers have complained in re- 

 cent years of increasing crop losses due to damage 

 by blackbirds. As a result, (^ongress appropriated 

 funds for research to find ways to reduce the 

 damage. 



Biologists assigned to the problem made plans 

 for both basic and applied research on this group 

 of birds, which in the P^ast includes primarily 

 red-wings, grackles, and cowbirds. The first step 

 was to establish dependable methods of measuring 

 blackbird damage to corn in the field. Ways are 

 being sought to scai-e the birds away from standing 

 crops. The rope firecracker and other frightening- 

 devices have been developed ; these are often 

 effective in reducing damage locally, but they are 

 not a final solution. Some biologists are ex])loring 

 methods of reducing i)opulations of the iiirds that 

 cause the damage. Others ai-e testing chemicals 

 that repel birds and deter lliciii from pulling seed 

 corn or eating maturing ears. Since some varieties 

 of corn are more heavily attacked than others, agri- 

 cultural scientists are being tMicoinagcd to develop 

 damage-resistant variet ies. 



One group of biologists has been making surveys 



to find where blackbirds live at differeiit times of 

 the year, how numy young they produce, and what 

 habitat favors their breeding and increase. In 

 winter, blackbirds roost in flocks of several million 

 bii'ds in remote parts of isolated swamps along the 

 Coastal Plain from Vii'ginia southward; in sum- 

 mer, they spread out into marshes and surrounding 

 fields. In 1958, it was estimated that red-wings 

 produced ^40,()(K) j-oung on 2()(),()()() acres of marsh- 

 land in the Lower Chesapeake Bay region. 



Biologists at the Center have begun a blackbird- 

 banding program to help spot the winter (•on<'en- 

 ti-ations of the birds that do the damage next 

 sununei'. With a new-type light trap developed 

 at the Centei', they can capture thousands of 

 starlings, grackle.s, and cowbirds in an evening at 

 loosting sites. ,Ta])anese silk nets, often I'eferred 

 to as mist nets, ai-e mounted on poles and used to 

 ca])! ure birds during the day. Blackbird research 

 is going on at the Center's headquarters and at 

 substations at (Jainesville, Fla., and Newark, Del. 

 Etrcclisc nu'thodsof (lei)re(lat ion I'onlrol ac('e|)t- 

 able both to the fai'mei' and to the public are the 

 goal toward whicji the biologists are working. 



16 



