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Range contraction in the pampas meadowlark Sturnella defilippii in the southern pampas grasslands of Argentina

Published online by Cambridge University Press:  12 May 2004

Fabián M. Gabelli
Affiliation:
Facultad de Psicología, Universidad de Buenos Aires-Instituto de Biología y Medicina Experimental-CONICET, Vuelta de Obligado 2490, (C1428EHA) Ciudad de Buenos Aires, Argentina
Gustavo J. Fernández
Affiliation:
Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales – Universidad de Buenos Aires, Ciudad Universitaria, Pab. II. (C1428EHA) Ciudad de Buenos Aires, Argentina
Valentina Ferretti
Affiliation:
Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales – Universidad de Buenos Aires, Ciudad Universitaria, Pab. II. (C1428EHA) Ciudad de Buenos Aires, Argentina
Gabriela Posse
Affiliation:
Instituto de Clima y Agua, Instituto Nacional de Tecnología Agropecuaria, Las Cabañas y Los Reseros s/n (1712) Castelar, Provincia de Buenos Aires, Argentina
Eugenio Coconier
Affiliation:
Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales – Universidad de Buenos Aires, Ciudad Universitaria, Pab. II. (C1428EHA) Ciudad de Buenos Aires, Argentina
Hernán J. Gavieiro
Affiliation:
Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales – Universidad de Buenos Aires, Ciudad Universitaria, Pab. II. (C1428EHA) Ciudad de Buenos Aires, Argentina
Paulo E. Llambías
Affiliation:
Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales – Universidad de Buenos Aires, Ciudad Universitaria, Pab. II. (C1428EHA) Ciudad de Buenos Aires, Argentina
Pablo I. Peláez
Affiliation:
Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales – Universidad de Buenos Aires, Ciudad Universitaria, Pab. II. (C1428EHA) Ciudad de Buenos Aires, Argentina
María L. Vallés
Affiliation:
Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales – Universidad de Buenos Aires, Ciudad Universitaria, Pab. II. (C1428EHA) Ciudad de Buenos Aires, Argentina
Pablo L. Tubaro
Affiliation:
División Ornitología, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, Av. A. Gallardo 470. (C1405DJR) Ciudad de Buenos Aires, Argentina
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Abstract

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The Vulnerable Pampas meadowlark Sturnella defilippii (Family Icteridae) is a Neotropical grassland bird that suffered a severe population reduction and range contraction during the 20th century. Formerly distributed across most of the pampas grasslands, it is now confined to the southern tip of its original range. There are small groups of wintering birds in southern Brazil, a small reproductive population in eastern Uruguay, and the main reproductive population occurs on the southern pampas grasslands of Argentina. In this paper we report the results of an extensive field survey of these southern pampas grasslands, carried out to estimate the pampas meadowlark's population size and to identify the factors potentially responsible for its range contraction. During the 1999 breeding season we surveyed a total of 296 sample locations (transects, randomly selected points, and sites checked for nesting site reoccupation). We found 66 reproductive groups of pampas meadowlarks. The minimum population size and extent of occurrence were estimated to be 28,000 individuals and 4,810 km2, respectively. This value represents a range contraction of c. 30% compared to that estimated in a study carried out between 1992 and 1996. Pampas meadowlarks reoccupied natural grassland sites for nesting that were used in previous breeding seasons when these sites remained undisturbed. Habitat transformation appears to be the main factor causing the range contraction of the pampas meadowlark. We suggest that long-term monitoring of this population and its preferred habitat, the natural grasslands, is required in order to ensure the conservation of this species.

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Articles
Copyright
© 2004 Fauna & Flora International