Species Recovery Objectives for Four Target Species in the Central and Lower Platte River

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estimates of survivorship and dispersal. They found that a mean productivity of 2.0 fledglings per pair was required to maintain the current population size. Their analysis suggests that a fledge rate on the Platte River should be 1.7 to have an 88 percent chance of surviving 100 years and 2.0 to have a 99.8 chance of surviving 100 years. This report acknowledges that the recent paper by Plissner and Haig suggests a higher fledge rate than recommended in this report. However, based on other existing references and the discussion at the September workshop, 1.13 fledglings per pair is recommended as the fledge rate for piping plovers on the central Platte River at this time. This report recommends that managers consider reviewing the fledge rate for piping plovers for the central Platte River in a few years, especially as new research and studies become available. If a preponderance of evidence suggests that this fledge rate should be significantly different, it should be reviewed and changed as appropriate. A.5.2. Interior Least Tern A.5.2.a. Numbers Objectives for the central Platte River (Lexington to Columbus) should be 300 least terns as a 10 -year running average, which is 40 percent of the Recovery Plan goal for the entire Platte River. The central Platte River supported about 1/3 of the birds (147 terns out of 549 or 27 percent) on the Platte River over the recent 10 year period (Table 1). Twenty -seven percent of 750 birds (the Recovery Plan goal for the Platte River) is 202 individual birds for the central Platte River. However, 202 terns does not appear to be enough to support a viable population on the central Platte River. This is because of the same factors as discussed under the piping plover (A.5.1.a.). This recommended numbers objective for least terns on the central Platte River is based on professional judgements in view of existing scientific data. However, no analyses of population viability has been done for the central Platte River. A more thorough analysis of such parameters such as habitat quantity and quality, productivity, movements and survival may be needed in order to better determine the minimum viable population needed and specific population objectives. Therefore, based on current information available, it is reasonable to expect that 40 percent of 750 adult least terns (the Recovery Plan goal for the Platte River), or 300 birds, should be attained on the central Platte River as a 10 -year running average. A.5.2.b. Distribution The distribution objective for the central Platte River should be that no fewer than 25 percent and no greater than 75 percent of the birds occur above Kearney, Nebraska over a 10 year average. Nesting habitat can occur at both sand pits and instream sites. 13