Show Keeping Up 0 Sc n erv e C 0 Science Service Service Crows Arc Are Enemies of the Wild Ducks Ducksin in Breeding Season Control Methods Are I Recommended by by Expert Washington Crows ar are e major enemies of wild ducks duck s in at least a part of the great grea t wild duck breeding grounds ground 9 in Canada a survey by E. E R R. R Kalmbach of the United Unite d States biological survey y shows Of duck nests nest studied 31 SI pei pel pe r cent ISO nests had been ravage ravaged d by crows Other causes cause of tion had accounted for another 2 20 0 per cent of loss so that of all th the tha nests that started the season eason w with hopeful batches of eggs only 49 pe percent per percent t cent turned out outlive live ducklings It is possible however Mr l Kalmbach notes that part of th the egg destruction by crows might t have been wreaked after the parent pares t ducks had abandoned the nests to foi r other causes Furthermore he cautions caution thi survey was made in a part of th the nesting area where th the crow concentration con is fa unusually high and where a large duck population of fers unusually great temptation to raid for eggs Tho The overlap of crow range and nesting duck area does doe not represent more than about a sixth of the whole productive waterfowl water fowl nesting area in Alaska and Canada So crows cannot be counted count ed universal enemies of ot ducks duck low How They Should Be lie Controlled For practical control purposes purpose Mr Kalmbach ch recommends 1 Crow control Crow control operations on on duck duck- breeding grounds should by all aU means be entrusted only to thou who f fully lly recognize the hazards hazard as associated sedated with human intrusion or waterfowl nesting grounds The Tbt work should hould not be carried out hap hazard or by mass action devoid of ol careful supervision The Then Thaws r e should hould in fact be solicitude for the privacy of every nesting duckAt duckAt duckAt duck At winter crow roots roosts where control is possible at a lower cost coat per par bird the benefits bassets wi with respect reaped to waterfowl are in turn less lell di dl direct sect since only a part of the birds bird present at these thee roosts actually cater enter ca In ter the problem of crow waterfowl crow relationships relationshIp on the tha bre breeding grounds For the prevent present and probably for years yean to come such control ma may wisely be restricted to thos those fed ted federal era eral state or privately managed areas area to which crows have been at in unduly large numbers by bythe bythe bythe the presence of nesting waterfowl and on which on-which the consequently delicate deli deU cate cats problem of control may mar be kept in experienced hands |