Whooping Crane Migrational Habitat Use Draft (2)

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bank of the river, one down the centerline of the main river channel, and six transects located in the uplands surrounding and parallel to the river. The study area was further divided into two segments: the east segment between Chapman and the Nebraska Highway 10 (Minden) Bridge, and the west segment from the Minden Bridge to the Lexington Bridge. Two planes, each with two surveyors, surveyed two east-west transects within each segment of the study area each survey day. The first flight surveyed the river from the south bank with both observers looking out of the north side of the plane and focused on the river, and the return flight surveyed one of the seven transects parallel to the river corridor. Flights began a half-hour before sunrise and started with the river transect flown in the westward direction. There were changes to the orientation and start locations of the flights during the first years of protocol implementation (Appendix A). The final method used four start locations with alternating chronological order of the two segments for each plane. This method was implemented to allocate the earlier survey times more evenly throughout the study area. The monitoring documented all locations used by crane groups throughout the study area. Crane groups located by the aerial surveys were continuously monitored by ground-based field crews until the cranes left the study area or their location became unknown. This set of observations comprised the systematic sample of observations. Crane groups located in the study area by method other than the aerial survey (the field crew, other biologists, or the public) comprised the opportunistic sample of observations. Activities were sampled every 15 minutes while crane groups were being observed, by documenting the observed activity. Activities were categorized as: 1) alert behavior: crane alert and scanning horizon; 2) courtship behavior: crane performing unison call and/or dancing; 3) agonistic/defensive behavior: defensive or offensive display with other birds (whooping cranes, sandhill cranes, etc.); 4) feeding: any behavior suggesting the bird is in the act of feeding, such as a crane flipping over objects and/or probing for food or slow locomotion interrupted by these activities; 5) preening: crane preening feathers; and 6) resting/loafing: crane standing still in one place. After the crane group departed the study area, habitat characteristics were measured at whooping crane use locations. Habitat measurements included land cover, river profile surveys, estimation of unobstructed view in four directions, and substrate categorization. The river profiles were measured at three transects perpendicular to the flow, with the middle transect traversing through the use area and the endpoints of all transects at obstructions greater than five feet (ft; 1.5 meters [m]) above water level (PRESP 2005). All analyses were conducted separately for crane groups located through the systematic aerial surveys and for crane groups located systematically and opportunistically. Observations of crane groups located by the aerial surveys were included in the systematic sample of locations. Each observation in this sample had known inclusion probabilities based on the flight coverage of the study area and the probability of detection. All observations of a crane group by ground-based observers on a given day were included in the systematic dataset if the crane group had been observed initially from the systematic aerial survey. Crane groups located opportunistically were combined with the systematic locations and analyzed together. All analyses were conducted using crane groups as the sample unit, because of the inherent dependence among cranes migrating as a group. 2