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Historical Patterns of Vagrancy by Blue-Gray Gnatcatchers in New England (Patrones Históricos de Movimientos Errantes de Individuos de Polioptila caerulea en New England)

Walter G. Ellison
Journal of Field Ornithology
Vol. 64, No. 3 (Summer, 1993), pp. 358-366
Published by: Wiley on behalf of Association of Field Ornithologists
Stable URL: http://www.jstor.org/stable/4513834
Page Count: 9
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Historical Patterns of Vagrancy by Blue-Gray Gnatcatchers in New England (Patrones Históricos de Movimientos Errantes de Individuos de Polioptila caerulea en New England)
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Abstract

The pattern of occurrence of the Blue-gray Gnatcatcher (Polioptila caerulea) during its recent range expansion into New England is examined. Prior to widespread nesting in New England beginning in the 1970s the species was a rare vagrant in spring and autumn. Significant differences were observed between seasons in the frequency of occurrence of vagrants at coastal and inland sites from 1937 to 1960. Coastal reports predominated in both seasons but inland reports were more frequent in spring. It is proposed that spring vagrants overshot the breeding range on a broader front than autumn reverse migrants. Autumn vagrancy does not presage range expansion whereas an increase in spring vagrancy does. /// Se examina en este trabajo, los patrones de aparición de Polioptila caerulea en New England, durante su reciente extención territorial. Previo al inicio del 1970, cuando el ave comenzó a anidar en grandes números en New England, éste se consideraba como un raro errante durante la primavera y el verano. Entre el 1937 y 1960, se observaron diferencias significativas estacionales en la frecuencia de aparición de estos errantes en localidades de la costa del interior del estado. Los informes en la costa predominaron tanto en la primavera como en el verano, pero los informes de tierra adentro resultaron más frecuentes en la primavera. Se propone que los errantes primaverales excedieron en número y en forma más amplia a las posibles áreas reproductivas que los migrantes otoñales. Los movimientos errantes durante el otoño no presagian la extención territorial de una especie, contrario a los movimientos errantes durante el período primaveral.

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