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r The Condor 93:;66-278 ` C rhe Cooper Ornahok cal S.nct;• 1941 i t DISTRIBUTION AND ABUNDANCE OF LARGE SANDHILL CRANES, GRUS CANADENSIS, WINTERING IN 3 CALIFORNIA'S CENTRAL VALLEY' ! t THomAs H. 130GSON2 Department of Biology and Wildlife. University of Alaska, Fairbanks. AK 9975-1780 SUSAN M. LINDSTEDT3 Malheur Field Station, HC72, Boz 260, Princeton, OR 97721 t Abstract. Distribution and abundance of large Sandhill cranes(Grus canadensis tabida, Greater Sandhill Crane,and Grus canadensis rowant,Canadian Sandhill Crane)were studied in California's Central Valley during October—February 1983-1984 and 1984-1985. We estimated that the pt>pulation contained h.000-6800 cranes which were concentrated at cigf geographic ei ographic locattons from Chico to Pixley Natwna Wildlife Refuge (NWR) near ` De!ano. Ninety-five Lvrccnt of the population occurred in the Sacramento Valley and the northeastern&-icramento-San Joaquin Deltic(S-SJ Delta);portions of the winter range varied seasonally in their inipariance to the population in bout winters. More than half the pop- ulation used the Butte Sink region in the Sacramento Valley during October—November. From Decenilx;r through January the Thontton and Cosumnes r4uns on the S-SJ Delta L hosted 56-7x%of the population.Sightings and locations of 157 color-marked and 10 radio- tagged Greater Sandhill Cranes confirmed the movements of the population among different portions of the winter range.Most wintering sites were in private ownership,and the majority of the nocturnal roosting sites were privately owned waterfowl hurting areas. Present pop- ulation estimates range tiorn 2.5 to 2.9 times the estimates of the late 1960s and mid-1970s; differences are largely explained by variation in the effort between this and earfier studies,, and the increased concentration ofeTartes at vintexing sites in the 1980s. More than half of the wintering popuLetio:a rna•; uriginatc in coastal and interior British Columbia. Cranes originating in Canada stay belong to didereat bleeding populations than thou originating in Oregon and California, although they are sympatric during the winter. Studies of the cranes from British Columbia are needed to clarify the status of the large sandhill cranes wintering in California's Central Valley. Key words: Greater Sandhill Crane;Gets canadensis tabida; Canadian Sandhill Crane: G. c. rowani; ►vinterin; distribution. abundant.; California's Central Valley; population status. INTRODUCTION Thompson 1979, U.S. Fish and Wildlife Service Four populations of Greater Sandhill Cranes are [U.S.F.W.S.] 1983). The segment of the popu- i recognized:the Eastern,Rocky Mountain,Lower lation spending the summer in Oregon and Cal- 1 Colorado River, and Central Valley Populations ifornia has been estimated at 3,200-3,400 indi- (Braun et al. 1975,Lewis et al. 1977).The Central vlduals (Stern et al. 1987, Littlefield 1989), and Valley Population winters in agricultural areas the number spending the summer in British Co- on the floor of California's Central Valley-and lumbia has been stated to be 600 (U.S.F.W.S. nests in northeastern California,eastern Oregon, 1983)• i and in British Columbia west of the Continental The U.S.F.W.S. included the Central Valley Divide of the Rtxicy Mountains (Littlefield and Population on its Sensitive Species List (U.S.F.W.S. 1982a) because of low productivity of Sandhill Cranes nesting at Malheur NWR, in Received 2 May 1990. Final acceptance 20 No- southeastern Oregon(Littlefield 1976),threats to velrttxr 1990, nesting habitat in Oregon and California(Little- = Present address:Alaska Fish and Wildlife Research field and Thompson 1979, Littlefield 1982), and Center, U.S. Fish and wildlife Service, 1011 F."Cudor destruction of wetland habitat at wintering Rd., Anchorage, AIC 99775.1780. g areas ' Present address: 3204 N. Spruce, La Grande, OR itt California's Central Valley(Gilmer et al. 1982). 9?850. In 1983 the California Game Commission listed VI-126