AUTUMN SANDHILL CRANE MIGRATION INSOUTHEASTERN OREGON

Each autumn, from 2,000 to 3,000 greater sandhill cranes (Grus canadensis tabi~) of the ~en­ tral Valley Population congregate on Malheur National Wildlife Refuge. Migratory behavIor, flock SIzes and arrivals and departures from this important autumn use area were observed for 13 years (1970-1986). Average size of flocks arriving from the north was 15.7, with those arriving from the southwest averaging 7.4. Flocks departing for California wintering areas averaged 9.2, but as ~maller groups merged, fl?ck , sizes increased to 24.8 (35 km southwest from the departure area). Most flIghts were at speeds ra~?mg from 56 to 88 kmh-l, at altitudes ranging from 150 to 900 m. If favorable habitat and ~eather condItions occurred in September and October, en masse migrations generally did not occur untII.Nov~mb~r. Most southward departures occurred when winds aloft were from a northerly quadrat but wmd dIrection was less important for birds arriving onto the refuge. Malheur National Wildlife Refuge (NWR), Harney County, Oregon is the most important autumn use area for the Central Valley Population of greater sandhill cranes. In July and August, cranes begin congregating on refuge grain fields and by mid-October, 2,000 to 3,000 are often present (Littlefield 1986). Depending on food supplies, roost site availability, weather conditions and human disturbance, cranes have lingelied into midNovember and on rare occasions into December. If inclement weather grounds cranes for periods in late October or early November, a spectacular migration frequently occurs once favorable migratory conditions return. On days after these periods, a major percentage of these birds often migrate en masse for their California wintering areas. Williams (1970) and Nesbitt (1975) reported on the spring departures of sandhill cranes in Florida, while Walkinshaw (1960), DeVore (1972) and Patterson (1978) discussed spring and autumn flock sizes in the midwest and eastern United States. But little information has been available on migratory behavior, flock size and arrivals and departures of sandhill cranes from autumn staging and traditional use areas. The U.s. Fish and Wildlife Service has provided financial support for sandhill crane studies on Malheur NWR for the past 21 years, and I am extremely grateful. In addition, staff and students at Malheur Field Station helped in various ways during the study. I would like to express my appre1 Present address: HeR 4 Box 212, Muleshoe, TX 79347 47 Proc. 1988 N. Am. Crane Workshop ciation to these, in particular Caylin Holloway and Susan Lindstedt.