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272 THOMAS H. POGSON AND SUSAN M. LINDSTEDT TABLE 2. Seasonal distribution ofcolor-marked and cranes known to be alive each season (based on radio-tagged Greater Sandhlll Cranes, in California's sightings at nesting, staging, and wintering areas Central Valley during the winters of 1983-1984 and through December 1988), respectively. Marked e8 1985. Missing values indicate no data were col- cranes were observed at all important regions used by the population, although the number in No.of marked cranes each region varied among months(Table 2). The Locations Oct Nov Dec tan Fch seasonal pattern of sightings paralleled the sea- Chico 4 6 5 12 14 sonal pattern of abundance estimated by popu- Afton 0 10 6 0 0 -latiorrcounts (Tables I and 2). In the Butte Sink Butte Sink 8 38 21 5 5 the largest numbers of marked cranes were ob- Thornton 99 116 135 152 117 served during November and December, the only Cosumnes I - 8 3 20 months when marked birds were present at Af- •Marked at Malheur NWR and Sycan Marsh in southeastern and ton. The largest number of marked cranes at Chi- southcentral Oregon,rpecttvely,and Modoc NWR in northeastern Cal- ifornia. aco occurred in January and.February. At Thorn- ton, the number of marked cranes increased from October through January, while on the adjacent Numbers of large cranes using the Chico region floodplain of the Cosumnes River. peak numbers increased from October to January, and use of of marked birds occurred in February. The num- the Modesto region increased from October at ber of marked cranes observed at Modesto in- least until December. Use of the Afton region creased in December and most of these remained was short-lived; cranes began using the area in until February. late November, but declined after December. In Marked cranes moved among regions in both both winters, small flocks of cranes (containing years (Table 3). Forty-five percent of the marked <30 individuals) only occurred west of the Sac- cranes observed in the Butte Sink(from October- ramento River on Colusa, Delevan, and Sutter December)were resighted at other locations(be- NWRs in October and November (fall migra- tween November-February). Fifteen percent tion) (Sacramento NWR, unpubl. data). Four which were observed in the Butte Sink moved monthly estimates indicated the population of north and were relighted at Afton and Chico. large cranes numbered between 6,012-6,8 10 in- Thirty-six percent of the marked cranes first ob- dividuals (Table 1). served in the Butte Sink were later relighted at the Thornton and Cosumnes regions on the S-SJ SIGHTINGS OF MARKED CRANES Delta. Twelve percent of the marked cranes ob- We observed 157 color-marked and 10 radio- served at Thornton were later relighted in the tagged cranes during 1983-1984 and 1984-1985, Cosumnes region. This pattern of movement representing at least 86 and 82% of the marked confirmed that the seasonal changes in the abun- TABLE 3. Winter movements of color-marked and radio-tagged,Greater Sandhill Cranes in California's Central Valley during the winters of 1983-1984 and 1984-1985. CHI = Chico, AFT = Afton, BSK = Butte Sink, THR = Thornton, COS = Cosumnes, MOD = Modesto. First sighting No.marked Locations of resighting Locations tunes CHI AFT BSK THR COS MOD ' Chico 20 1 1 e Afton 1 I I 1 2 Butte Sink 53 3° 5 19° 4' Thornton 146 16 Cosumnes 5 2 Modesto 12 Pixley NWR I Marked at Malheur NWR and Symn Marsh in southeastern and southcentral Oregon,respectively,and Modoc NWR to northeastern Cabrorrua. Previously resighted at Afton. 'One individual previously rrsighted at Afton and Thornton. j Two individuals prrnously restghted at Afton. All previously relighted at Thornton. VI-132