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and Wildlife Service, Ecological Services Field Office, at Grand Island, Nebraska. (W. <br />Jobman pers. comm.). <br />A Sighting is the observation of a whooping crane group (single or multiple birds) that is <br />migrating together through an area. Reported sightings are classified by the Service database <br />managers, per their professional judgment, as confirmed, probable, or unconfirmed, based <br />on the definitions given in the Whooping Crane Recovery Plan. <br />A Confirmed Sighting is an observation made by a State or Federal biologist or officer or by <br />other known qualified observer (trained ornithologist or birder with experience in <br />identification of whooping cranes). A photograph may also be used to confirm sightings. In <br />the USFWS database, confirmed sightings in the same general area (within a reasonable <br />distance of daily crane activities) along the Platte and within one to several days of another <br />sighting are assumed to be the same crane group (and thus given the same USFWS number), <br />unless: 1) the number of birds differs, 2) the bird(s) constitute a bird/bird group in addition to <br />those already known to be in the general area, or 3) the original birds were observed to <br />migrate from the valley or are known to have moved to a different area of the valley. This <br />assumption is necessary because individual cranes cannot be distinguished; very few birds <br />are marked, and continuous surveillance of a crane or crane group using the study area is not <br />possible. Confirmed sightings of whooping cranes from 1940 -2000 are presented in Table 3. <br />A Probable Sighting is defined by USFWS as no confirmation made by State or Federal <br />biologist or officer or by other known qualified observer, yet details of the sighting seem to <br />identify the birds as whooping cranes. To be classified as a probable sighting each of the <br />following factors must be met: (1) location of sighting is within normal migration corridor <br />and is an appropriate site for whooping cranes, (2) date of sighting is within period of <br />migration, (3) accurate physical description, (4) number of birds is reasonable, (5) behavior <br />of the birds does not eliminate whooping cranes, and (6) good probability that the observer <br />would provide a reliable report. Probable sightings of whooping cranes from 1980 -2000 are <br />presented in Table 4. <br />An Unconfirmed Sighting classification is assigned when details of the sighting meet some, <br />but not all of the six factors listed for a probable sighting. <br />Attempts have been made, either by USFWS biologists or others, to investigate all reports in <br />the Platte River study area that appear to have accurate whooping crane descriptions. <br />However, a large proportion of the sightings that are reported are not confirmed due to late <br />reporting after the birds have left, inability to find reported birds, unavailability of personnel <br />to investigate sighting reports, or misidentified birds. It is also probable that not all <br />whooping cranes are observed, or that all observed birds are reported. Therefore, confirmed <br />stopovers represent a subset of total whooping crane use of the study area, and it is not <br />known how many stopovers actually occur. <br />Austin and Richert (2001) summarized the confirmed sightings of fall and spring migrating <br />whooping cranes throughout their flyway within the United States between 1943 -1999. The <br />data was derived from two databases maintained by the USFWS: Observational sightings; <br />(1943 -1999, 1,352 confirmed sightings) and Site evaluation data (1977 -1999, 1,060 <br />Draft Baseline Report — Whooping Crane Section 6 <br />