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The Llanos is a significant waterbird site in the Western Hemisphere, but abundance and distribution of waterbirds across this vast region are poorly known, which hampers conservation initiatives. We used point counts along road routes in the Llanos region of Venezuela to examine abundance and distribution of waterbirds during 2000-2002 within five ecoregions across the Llanos. We detected 69 species of waterbirds and recorded 283,566 individuals, of which 10 species accounted for 80% of our observations. Wading birds (Ciconiiformes) represented the largest guild both in numbers of species (26) and individuals (55%), followed by waterfowl (26%), and shorebirds (11%). Five species comprised 62% of all individuals: Cattle Egret (Bubulcus ibis), White-faced Whistling Duck (Dendrocygna viduata), Black-bellied Whistling Duck (D. autumnalis), Great Egret (Ardea alba), and Wattled Jacana (Jacana jacana). Wading birds were particularly ubiquitous with at least 21 of 26 species recorded in each of the ecoregions. Species richness (66), proportion of waterbirds detected (54%), and mean number of birds per route (1,459) were highest in the Banco-Bajio-Estero savanna ecoregion. Our study provides the most comprehensive data set available on waterbirds in the Llanos of Venezuela and highlights regions of special conservation concern. Received 20 April 2009. Accepted 7 October 2009., Erratum The second author's name was inadvertently left off of the article published in the March 2010 Issue (Volume 122: 102-115). We apologize for this error. The corrected author sequence [...]

Fire and grazing can interact to affect the structure and composition of vegetation com-munities in a manner that may differ from the effects of fire or grazing that occurs in isolation of the other. In order to better understand the effects of a fire-grazing interaction at the level of an individual plant species, we studied the response of a perennial tallgrass prairie forb, Arnoglossum plantagineum Raf., to the interaction of spring and summer fires with grazing by bison (Bison bison L.). During one field season (2006), we collected data in areas that had been treated with summer fires while in a subsequent field season (2007) we collected data in areas that had been treated with spring fires. Many measures of plant growth (plant height, vegetative biomass, and total biomass) and reproductive effort (reproductive biomass, indices of flowering plant density) suggested greater resource availability for individuals of A. plantagineum growing in areas that had been recently burned and were being heavily grazed by bison. However, the response of these variables to the fire-grazing interaction often varied among differing topographical positions. Our results demonstrate that the interaction of fire and bison grazing can further interact with topographical position in tallgrass prairie to affect the growth and reproductive effort of the perennial forb A. plantagineum. [ABSTRACT FROM AUTHOR]

Temporal changes in land use, vegetation cover types, and landscape structure were examined in a hardwood forest-tall-grass prairie ecotone in northern Oklahoma using a Geographic Information System. Our objective was to examine relationships between human activity, changes in land use and vegetation cover type, and landscape structure in rural landscapes between 1966 and 1990. Cover types in most of the high density rural population landscape in this study require more intensive inputs and management, which resulted in a landscape with lower diversity, higher homogeneity, and greater patch fragmentation comparedto the low density rural population landscape. Both native grasslands and forests were less fragmented in the low density rural population landscape whereas forests were increasingly fragmented in the high density rural population landscape. Native grasslands were less fragmented than forests for all years in both the low density rural population and high density rural population landscapes. Our study suggestsconservationists should focus their concerns on fragmentation and losses in biological diversity that accompany increased human activity in densely populated rural landscapes that surround urban centers. Extensively managed landscapes dominated by native vegetation that are under less pressure from expanding human influence are in less peril. [ABSTRACT FROM AUTHOR]