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r= <br />Flock Size (Section 2.3): Unlike sandhill cranes which typically migrate in <br />large flocks, whooping cranes migrate as individuals, pai rs, family groups and <br />small fl ocks. Analysi s of conf i rmed si ghti ngs recorded th roughout the flyway <br />indicates an average of approximately 3.2 birds per sighting. Whooping cranes <br />migrati ng si ngly, in pai rs, or i n th reesomes have been observed most <br />f req ue ntl y. <br />Conf i rmed si ghti ngs i n Nebraska f ran 1940 -1984 ref ect a. simil ar average number <br />of birds per sighting in spring (3.2) and fall (3.1) . Overall, most observa- <br />ti ons were of 2 or 3 bi rds, and 92 percent of the si ghti ngs i nvol ved 5 bi rds or <br />1 ess. <br />Flight Distances (Section 2.4): Whooping cranes migrate primarily during <br />daylight hours, but flights sometimes originate before daybreak and /or continue <br />after nightfall. Although daily flight distances are highly variable, <br />migrating birds are capable of making long, sustained flights when weather and <br />wind conditions are favorable. Radio-tracking surveys (fall 1981-spring 1984) <br />I have recorded whooping cranes traveling as many as 504 miles in a single <br />I <br />flight, and approximately 1,140 miles in 2 days. Flight distances are <br />undoubtedly influenced by physiological factors such as hunger or fatigue, and <br />migrating birds tend to curtail their flights or extend their stopovers when <br />strenuous and /or hazardous flight conditions prevail (e.g., storms, fog, or <br />strong headwinds). <br />Travel Time (Section 2.5): Each year whooping cranes spend approximately 5 <br />months on their wintering grounds and 5 months on their breeding grounds. The <br />remaining time is spent migrating between these locations. Based on five <br />radio-tracking efforts in the fall, whooping cranes completed the migration <br />f rcm Wood Buffalo National Park to Aransas NWR in an average of 29 days. In <br />all cases, the birds expended more time traveling the approximately 900-mile <br />segment of their journey through Canada (20.4 days average), than the <br />approximately 1,500 mile segment through the United States (8.6 days average). <br />During two radio-tracking surveys in the spring, monitored birds made the trip <br />I from Aransas NWR to Wood Buffalo National Park in an average of 18.5 days. <br />Time spent travel i ng averaged 11 days in the U.S. portion of the flyway and 7.5 <br />days in the Canadian portion of the flyway. Though these surveys reflected <br />shorter travel times than recorded during the fall, two additional (incomplete) <br />surveys indicated that some spring migrants, particularly immature birds, move <br />north at a sl ower pace. <br />Stopover Duration (Section 2.6): Most migration stopovers during both fall and <br />spring are of the overnight type where the birds arrive one day and leave the <br />next. They represent brief fl ight breaks (of about 12 to 16 hours) to rest and <br />feed. Of the 98 stopovers recorded during radio-tracking surveys, 76.5 percent <br />were of this type. <br />In contrast, only 15.3 percent of the stopovers were for 5 days or longer. <br />During both seasonal migrations, these longer stopovers occurred most <br />frequently in the relatively remote lakes region of Saskatchewan and <br />northeastern Alberta. To some extent this region may serve as a staging area <br />in the fall where adult birds and their new offspring ready themselves <br />ii <br />