We investigated whether forest-pasture edges affect the distribution of an assemblage of small vertebrate ectotherms in a consistent and predictable manner. We describe the abundance and distribution of two species of anoline lizards ( Norops ) and five species of leaf-litter frogs ( Eleutherodactylus ) along the edges and in the interiors of nine forest fragments near Las Cruces, Costa Rica. Over 4 months, we surveyed 44 pairs of plots by visual encounter. In each pair of plots, one was immediately adjacent to the pasture and the second was within the forest "interior." Both plots of a pair were searched simultaneously. This block design controlled for the effects of weather, topography, and searcher ability. The distribution of all species was highly variable with respect to edges. Only two species of frogs, Eleutherodactylus podiciferus and E. cruentus , were significantly more abundant in interior plots than in edge plots, although not consistently so. Both species of Norops lizards were more abundant along forest edges during the dry season. Both Norops species and several Eleutherodactylus species, however, appeared to become more abundant in the forest interior after the onset of the wet season, suggesting a seasonal edge effect. In Norops polylepis , the most abundant anole, rates of ectoparasitism were lower along edges than in forest interiors. The magnitude of the edge effect on any one species was not influenced by the size of fragments or by the distance of the interior plot from the nearest edge. We believe that edge effects should not be defined by the distance to which they are detected. Rather, they should be viewed as highly dynamic in space and time; taxa appear to respond to different components of edge effects according to their particular biological requirements. Efectos de Borde sobre Lagartijas y Ranas en Fragmentos de Bosque TropicalResumen: Investigamos si los bordes bosque-pastizal afectan la distribución de una comunidad de vertebrados ectotermos pequeños de manera consistente y predecible. Describimos la abundancia y distribución de dos especies de lagartijas anólidas ( Norops ) y cinco especies de ranas habitantes de la hojarasca ( Eleutherodactylus ) a lo largo de los bordes y en el interior de nueve fragmentos de bosque cerca de Las Cruces, Costa Rica. Durante cuatro meses utilizamos la técnica de encuentro visual para muestrear 44 pares de parcelas. En cada par de parcelas una estaba adyacente al pastizal y la segunda estaba en el "interior" del bosque. Ambas parcelas de un par fueron muestreadas simultáneamente. Este diseño de bloques controló los efectos meteorológicos, topográficos y de la habilidad del muestreador. La distribución de todas las especies fue altamente variable con respecto a los bordes. Solo dos especies de ranas Eleutherodactylus podiceferus y E. cruentus , fueron significativamente más abundantes en parcelas del interior que en los bordes, aunque esto no fue consistente. Ambas especies de Norops fueron más abundantes a lo largo de los bordes de bosque en la ép...

To investigate the relationship between reproductive success (RS) and breeding—site fidelity in a transequatorial migrant, we studied two populations of marked Bobolinks (Dolichonyx oryzivorus) in upstate New York during 1982—1985. At these sites, 44% of the males and 25% of the females resident in one year returned in one or more subsequent years. There were more nests built, eggs laid, eggs hatched, and young fledged in territories of returning males in this polygynous species than in territories of males that did not return in subsequent years (P < .04). For females that returned, the number of eggs hatched, young fledged, young fledged on last nest attempt, and young fledged per egg laid were higher than for females that did not return (P < .02). Discriminant function analysis and data from 1982—1984 were used to predict correctly the return behavior of 30 to 42 individuals (sexes combined) in 1985, based on their reproductive success (RS) in 1984 (P < .01). Using data on RS and return rate for all years, the best single—variable model for males based on the number of young fledged from each territory classified correctly 59 of 85 individuals (69%) as returning or not (P < .005). The best single—variable model for females based on the number of yound fledged on their last nest attempt classified correctly 61 of 86 individuals (71%; P < .005). Using all data for 1982—1985, sex—specific models that included only whether an individual fledged one or more young classified correctly the same proportion as the best single—variable models above. However, among males that fledged one or more young, those that returned had fledged significantly more young the previous year than those that did not return (P < 0.5). Not all individuals that failed to return were dead, because five individuals that did not return to our study sites were captured in a subsequent year at another site. We concluded that male and female Bobolinks used information on their breeding success in one year to influence their choice of breeding site in the next year.

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ABSTRACT. In order to determine whether the small‐scale distribution of immature Ixodes dammini Spielman et al. corresponds closely to the activity patterns of white‐tailed deer, Odocoileus virginianus (Zimmerman), these relationships were examined in a site on Long Island, New York, U.S.A. We first determined the extent and temporal pattern of adult ticks feeding on deer by examining twenty‐three resident deer tranquilized during September‐December 1985.1, dammini adults infested deer throughout this fall period, most abundantly during October and November. With radio‐telemetry collars attached to deer we determined the relative frequency that they occupied 0.25 ha quadrats of the study site. During the following summer, we examined white‐footed mice, Peromyscus leucopus (Rafmesque), that inhabited these quadrats and removed immature ticks from each. 8975 larval and 163 nymphal /. dammini were removed from 208 mice trapped in forty‐three such quadrats. The frequency of deer using these quadrats was positively correlated with both the number of larval and of nymphal ticks per mouse. These results suggest that risk of I.dammini‐borne zoonotic disease may be decreased by locally reducing deer density in sites that experience intense human activity.