We used multiple and logistic regression analysis to study the breeding-area requirements of 10 species of grassland and early-successional birds at 90 grasslandbarren sites in Maine The incidence of six of the species was clearly sensitive to the area of grasslamt Upland Sandpiper~ the species with the largest area requirement~ umre infrequent at sites of less than 50 ha and reached 50% incidence at those of about 200 ha Grasshopper Sparrows reached 50% incidence at about 100 ha, Vesper Sparrows at about20 I~ and Savannah Sparrows at about 10 hat Incidence for three edge specie~ Brown Thrashe~, Common Yellowthroa~ and Song Sparrow, was negatively correlated with open area~ and incidence for Field Sparrows was not strongly influenced by grassland size These results indicate that grasslands need to be approximately 200 ha in area if they are to be likely to support a diverse grassland bird fauna Ho~, large grasslands or grussland-barrens are rar~ random samples indicated that in Maine only 1% of hayfields and only 8% of grassland-barrens were more than 64 ha in area Conserva. tion efforts seeking to protect habitat for rare grassland birds "Current addres~ Center Los efectos de la superficie del habitat en la distribuci6n de los pfijaros de pastizales en Maine Resumen: En el presente estudio utiltzamos andlisis de re-gresi6n m~lttple y logisttca para estudlar los requerimtentos de las dreas de cria de 10 especies de aves de pastizales y aves comunes durante los estadtos sucecionales tempranos en 90 sitios de pastizales-dridos en Maif*~g EU& La tasa de ocurrencla de 6 especies fue claramente sensitiva al drea del pastizaL Los sandpipers de tierras alta~ la especie con los requerimientos de drea mds grande~ fue poco frecuente en sitios de menos de 50 ha y lleg6 al 50% de incidencia en sitios con unas 200 ha Los Grasshopper sparrows alcanzaron una tasa de ocurrencla de150% en sittos con 100 h~ los Vesper Sparrows 1o hicieron en sitios con 20 ha y los Savannah Sparrows en sittos con 10 h~ La tasa de ocurrencla para ires especies de los borde~ Brown Thrasher;, Common Yellowthroat y Song Sparrow, estuvo negattvamente correlacionada con el drea abierta y la tasa de ocurrencia~ pawa los Field Sparrow~ no estuvo fuertemente influer~iada por el tama~o del pasttzaL Estos resultados indican que los pastizales necesitan cubrir mds de 200 ha para poder man. tenet una fauna de pdjaros divets~ Sin embargo, las grandes extenciones de pastizales o pastizales-dridos son raras; muestras al azar indican queen Maine s61o un 1% de los campos de heno y un 8% de los pasttzales-dridos ocuparon mds de 64 la~ Los esfuerzos de conservaci6n que busquen

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Abstract. Decisions regarding endangered species recovery often face sparse data and multiple sources of uncertainty about the effects of management. Structured decision making (SDM) provides a framework for assembling knowledge and expert opinion and evaluating the tradeoffs between different objectives while formally incorporating uncertainty. The Atlantic Coast piping plover provides an illustrative case for the utility of SDM in endangered species management because its population growth is simple to model, most populations are monitored, decision alternatives are well defined, and many managers are open to recovery recommendations. We built a model to evaluate the decision to use nest exclosures to protect piping plover eggs from predators, where the objective was to maximize λ and the tradeoff was between nest survival and adult survival. The latter can be reduced by exclosures. We used a novel mixed multinomial logistic exposure model to predict daily nest fates and incorporated the results into a stochastic projection matrix that included renesting after nest failure, and adult mortality associated with abandonment. In our test data set (n = 329 nests from 28 sites over four years), the mean nest survival over 34 days was markedly higher for exclosed nests (0.76 ± 0.03 SE) than for unexclosed nests (0.37 ± 0.07). Abandonment rates were also higher for exclosed nests (0.092 ± 0.017) than for unexclosed nests (0.045 ± 0.017), but the difference was not statistically significant and the loss rate to "other sources" (mostly predators) was much lower for exclosed nests (0.15 ± 0.03) than for unexclosed nests (0.58 ± 0.07). Population growth rate (λ) was clearly improved by exclosure use at the sites with high background nest loss rates, but λ was still <1 with exclosure use. Where the background nest loss rates were low, the decision to use exclosures was ambiguous, and λ could benefit from reducing uncertainty in vital rates. Our process demonstrated that geographic and temporal variation in nest mortality determines whether exclosures will be useful in attaining positive population growth rates and that other management options must be considered where the background nest mortality rates are high.

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Piping plovers (Charadrius melodus) that nest and winter along the U.S. Atlantic coast are threatened by cumulative impacts of habitat loss and alteration, human disturbance, and predation. Coastal stabilization activities may degrade plover habitat by altering natural processes of dune and beach erosion and accretion. Dredging and beach nourishment projects may be beneficial or detrimental to plovers, depending on timing and location. Management strategies to reduce disturbance and mortality caused by beachgoers and off-road vehicles include fencing of nesting and brood-rearing areas, partial or complete beach closures to pedestrians or vehicles during the breeding season, restrictions on pets, and public education. Beaches where piping plovers nest are owned and managed by a variety of federal and state agencies, county and municipal governments, private conservation organizations, and individuals. The roles of these and other landowners and managers in plover recovery efforts are discussed. Wildlife biologists must work with coastal managers to implement multiple-use management strategies that include protection for piping plovers and their habitats.