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I ;I • 'ill � i I LARGE SANDHILL CRANES WINTERING IN CALIFORNIA 273 dance of cranes within regions resulted from the than two other recent estimates of the number i l movement of cranes among regions. of cranes in the Central Valley Population. Si- multaneous counts of cranes in eastern Oregon IMPORTANT WINTERING SITES and northeastern California during fall migration The most important sites used during October in 1985 estimated a total of 5,292 Greater Sand- and November were the Bean Patch, Brady hill Cranes (C. D. Littlefield, pers. comm.). A Ranch, and Gray Lodge Wildlife Management second and independent estimate of thepopu- Area (WMA) in the Butte Sink region, each of lation's size suggested a population of at least which supported 12-37% of the entire popula- 5313 individuals (Littlefield 1986, Stern et al. tion (Table 1). In the Thornton region, the El 1987, C. D. Littlefield, pers. comm.). Both of Dorado Gun Club and Staten Island Ranch each these probably represent underestimates because supported 8-15% of the population during Oc- they assumed that all cranes in the population tober and November (Table 1). During Decem- were counted at fall staging areas in eastern Or- ber, approximately 80% of the cranes were dis- egon and northeastern California, which is un- ` persed at numerous nocturnal roosting sites in likely. the Chico, Afton, and Thornton regions, none of Littlefield and Thompson (1979) counted be- which supported more than 4-11% of the pop- tween 2,359-2,553 large cranes of the Central ulation.The roosting sites provided by waterfowl Valley Population at wintering areas during the 1 hunting clubs at Thornton were drained at the winters of 1969-1970, 1970-1971, and 1976— end of the hunting season in mid-January. Dur- 1977. Three factors may have contributed to the ing the last week of January more than half of greater than two-fold increase between these i the population, 3,829 cranes, concentrated in 295 counts and ours: I) an increased concentration ha in two roosting sites at Thornton: Staten Is- of the population on winter areas, 2) differences land Ranch(235 ha)and the El Dorado Gun Club in the geographic coverage between the two stud- (60 ha), and supported 25 and 41% of the total, ies, and 3) increases in the size of certain seg- i respectively(Table 1).These roost sites were wa- ments of the population (see Status of the pop- terfowl hunting areas that were drained,and they ulation). dried out at the end of January. In late January Probably because of changes ir. 'Aint=r raD1::a-, 3=A tar�i ;'cbvi ariq yet nLaL`bcr�. of cr•.lnc�, 1c1t in the last trJa deczdg,t�e pop-"n Was con- trrc T:.crnton region and mo,-cd to the a.ij.&:ent ccniratcd at few'r;itt ::. :}80s ccmpxYr4 doodplain of the Cosumnes River, Ahcre 24% to the late 19001 ax)'Z m�J :y'�rs, Ir, of the population concentrated in the flooded 1983, we counted 4,51X1 Grc3rcr Jandrtr:l Cr"cs riparian woodlands, meadows and pastures near in the same areas of the Central Valley where the river(Table 1). This movement to the flood- Littlefield and Thompson (1979) found 2,359— plain occurred in both winters. 2,553 Greater Sandhill Cranes in December of 1969, 1970, and 1976, suggesting that the pop- DISCUSSION ulation could have be=en almost twice as concen- trated on its winter range in the 1980s. On the ABUNDANCE S-SJ Delta, the area of harvested corn increased 'l The consistency of our estimates of the size of from an average of 16,300 ha in 1969-1971 to the Central Valley Population(Table 1)indicated 28,100 ha in 1980-1982, replacing dairy pas- that at least 6,000 Greater and Canadian Sandhill tures, meadows, and asparagus as the dominant :1 Cranes winter in California's Central Valley.The land use (San Joaquin Co. Agric. Commission, two lowest estimates occurred in October and unpubl.). Waste corn is an important food for , November, when fall migration was still under- sandhill cranes during the non-breeding season way and not all large cranes had arrived at their (Reinecke and Krapu 1979, Iverson and Tacha wintering areas (Littlefield 1986; M. Stern, pers. 1982,Walker and Schemnitz 1987)and contains comm.). Higher population estimates during De- higher levels of lipids, protein, and energy than cember and January occurred after the arrival of rice, and higher levels of lipids and energy than cranes on the winter grounds, and after cranes wheat, sorghum, and barley (National Research had concentrated on the S-SJ Delta when cen- Council et al. 1971). The increased area of har- susing conditions improved.Our estimates of the vested corn likely attracted a higher proportion population size were approximately 30% higher of the population to the S-SJ Delta causing an t i VI-133