Laserfiche WebLink
i -t <br />3) Whooping cranes depart on migration in a staggered fashion and proceed along <br />the flyway in small groups usually consisting of 1 to 3 birds. This pattern <br />of migration effectively increases the stopover options available to migrant <br />birds in that it facilitates the use of wetlands that are too small to <br />accommodate large flocks. As documented during radio - tracking surveys, <br />stopover sites commonly included small natural and manmade waterbodi es of 5 <br />acres or less, as well as some wetlands that were intermittent or ephemeral <br />(e. g. , 1/4 acre flooded grain fields). Based on a review of aerial <br />photographs and topographic maps, such small -sized wetlands appear to be <br />well distributed throughout the Nebraska portion of the migration corridor <br />and elsewhere along the flyway. <br />4) A more than a five -fold increase in the Wood Buffalo-Aransas population has <br />been steadily achieved si nce 1941, an unlikely accompl ishment 1f the <br />avail ability of stopover habi tat al ong the flyway was truly l imiti ng the <br />survival and recovery of the species. <br />Rather, it seems apparent that the whooping crane's opportunistic stopover use <br />of a wide variety of different types of wetlands (including marinade reservoirs, <br />farm ponds and stockponds) serves to the species' survival advantage, providing <br />resit iency in adj Usti ng to year -to -year changes i n flyway habitat. <br />Regulatory opinion that wetlands along the Platte River provide food items <br />necessary to the species' nutritional well -being and reproductive preparedness <br />is inconsistent with the fact that most whooping cranes do not use this habitat <br />during seasonal migrations. As stated previously, of the 27 migration passes <br />by individual bi rds monitored across Nebraska during the 1981 -1984 radio- <br />tracking surveys, no stopovers occurred along the Platte River. Moreover, <br />despite considerable survey emphasis over the past 20 years (1965 -1984) the <br />number of whooping cranes sighted on the Platte River (20 birds) represents <br />only 1 percent of the potential stopovers; i.e., 99 percent of the whooping <br />cranes that migrated across the Platte during these 20 years chose not to use <br />habitat associated with the river (98 percent if it is assumed that twice as <br />many birds stopped on the river as were sighted). Nonetheless, the size of the <br />Wood Buffalo-Aransas population doubled during this period. <br />The contribution of food items consumed at locations al ong the U.S. portion of <br />the flyway to the annual nutritional requirements of individual whooping cranes <br />is obviously limited by the short (overnight) duration of most stopovers. If a <br />specific stopover site is not used during a given year (in accordance with the <br />species' opportunistic strategy for selecting stopover habitat), then food <br />sources at that site play no role at all in satisfying annual dietary needs. <br />Conversely, because whooping cranes in the Wood Buff al o- Aransas popul ati on make <br />more extended stopovers in the lakes region of Saskatchewan and northeastern <br />Alberta, which may indicate staging use to some extent, the food and habitat <br />resources of this region warrant close management attention. <br />viii <br />