Draft Baseline Report - Least Turn and Piping Plover Section

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Productivity (Number of Fledged Young and Fledging Rate) Kirsch (1996) estimated fledglings per nest by defining the number of nesting pairs as the maximum number of active nests and broods present at a colony during a single visit. Kirsch (1996) recognizes that this assumes re- nesting pairs remained at their original colony or that emigration and immigration of pairs must be equal. NPPD, who provides data for the NGPC annual central Platte River census, expresses fledge ratios as fledglings per nest. It is the empirical equation of all chicks documented to fledge divided by the number of nests observed within a colony (Jenniges 2001). Breeding Population Structure Least Tern Breeding Population Structure The least tern breeding population is comprised of metapopulations, which means that breeding subpopulations occurring within local areas are indistinct components of the larger breeding population (Wiens and Rothberry 1981, Pulliam 1988, Hanski and Gilpin 1991 in Kirsch and Sidle 1999). The bare sand areas used for nesting areas are ephemeral, and the quality and amount in any one area can vary from year to year depending on variable conditions that maintain habitat (Sidle et al. 1992). Consequently, the tern breeding population and the reproduction rates on a particular portion of a river system can fluctuate from year to year (Lingle 1993b) Movements of individual breeding birds between nesting areas from year -to -year are common. Least terns banded at central Platte River nesting colonies have been later observed nesting up to 170 miles (273 km) from their banding origin (based on 163 sightings of 109 individuals). Twenty -eight percent of the least terns returned to the colony where they were banded as chicks. Movements have been documented between the central Platte River nesting area and nesting areas at Quivira National Wildlife Refuge (NWR), and the lower Platte River, near Fremont, Nebraska (Lingle 1993c in FWS 1997). Piping Plo ver Breeding Population Structure Piping plovers are semi - colonial, and will nest in or near least tern colonies. Average nesting colonies in Nebraska have 1 to 3 pairs of piping plovers (NGPC 1995). Piping plovers frequently change territories following nest failure and between years. Piping plovers banded at central Platte River nesting colonies have been later observed nesting up to 125 miles (200km) from their banding origin (based on 71 sightings of 57 individuals). Fourteen percent of re- sighted birds were banded as chicks. Thirty -two percent of piping plovers returned to the colony where they were banded (Lingle 1993c in FWS 1997). Draft Baseline Report, July 2002 4 -7