Comparison of Breeding and Postbreeding Movements and Habitat Requirements for the Scarlet Tanager {piranga Olivácea) in Virginia

We investigated movements and habitat use during breeding and postbreeding periods in Scarlet Tanagers (Piranga olivácea) during June-September 1998 in northern Virginia deciduous forest. Nine birds (8 males and 1 female) remained on the same home range during both breeding and postbreeding periods, whereas 11 birds (9 males and 2 females) shifted home range (>300 m) between periods. Breeding season home-range size ranged from 2.6 to 5.6 ha (95% kernel), and core area from 0.61 to 0.93 ha (50% kernel). Postbreeding home ranges were similar in size to home range during the breeding period for birds that remained in the vicinity of nesting areas, but were larger for birds that moved away from the nesting area. Scarlet Tanagers occurred in both mature and successional forest during breeding and postbreeding periods, with some indication of increased use of earlier successional stages during the postbreeding period. Needs for Scarlet Tanagers during the postbreeding period (molt, premigratory fattening) differ from those during the breeding period (pair formation, nest placement, rearing of young). Those differences provide a plausible explanation that all tanagers changed focal areas between breeding and postbreeding periods. These findings confirm the need for taking the postbreeding period into account, both for understanding migrant life history and successful conservation. Received 7 December 2001, accepted 28 February 2003. RESUMEN.•De junio a septiembre de 1998 estudiamos los movimientos y el uso del habitat de Piranga olivácea durante los periodos reproductivo y post-reproductivo, en los bosques caducifolios del norte de Virginia. Nueve individuos (ocho machos y una hembra) permanecieron en el mismo ámbito hogareño durante ambos periodos, mientas que 11 individuos (nueve machos y dos hembras) cambiaron de ámbito hogareño (>300 m) entre periodos. El ámbito hogareño durante el periodo reproductivo varió entre 2.6-5.6 ha (95% kernel), y el área núcleo varió de 0.61-0.93 ha (50% kernel). Los ámbitos hogareños durante el periodo reproductivo fueron similares en tamaño a los del periodo post-reproductivo en individuos que permanecieron en la vecindad de los sitios de anidación, pero fueron mayores en aquellos individuos que se movieron fuera de los sitios de anidación. P. olivácea ocurrió en bosques maduros y sucesionales durante ambos periodos reproductivo y post-reproductivo, aunque la tendencia al uso de estadios sucesionales se incrementó en el periodo post-reproductivo. Las necesidades de P. olivácea durante el periodo reproductivo (muda, acumulación pre-migratoria de grasa) difieren de aquellas durante el periodo reproductivo (formación de parejas, localización del nido, cría de los pollos). Estas diferencias proveen de una explicación posible para el hecho que todos los individuos de P. olivácea cambiaran el área focal entre los periodos reproductivo y post-reproductivo. Estos hallazgos confirman la necesidad de considerar el periodo post-reproductivo para mejorar nuestro conocimiento de la historia de vida de especies migratorias e incrementar el éxito de su conservación. POSTBREEDING BEHAVIOR, ECOLOGY, and habitat Lang et al. 2002). Basic questions regarding needs are poorly known for migratory birds behavior, patterns of movements in the landleaving a gap of several months in our underscape, and habitat needs during that part of standing of the migrant life cycle in temperate the life cycle remain unanswered for nearly all regions (Rappole 1995, Faaborg et al. 1996, species, such as minimum area of continuous Chernetsov 1998, Bayne and Hobson 2001, habitat an individual needs to be able to molt, avoid prédation, and prepare for migration. ,• .jj Tri'jD-1'r-i. 1 Postbreeding behavior is difficult to document, 'Present address: Estación de Biología Chamela, '^ Instituto de Biología, UNAM. Apartado Postal yet that mformationis of central importance to 21, San Patricio, Jalisco, 22630, México. E-mail: understanding migrant biology and [email protected] tion, particularly as alteration of the landscape