Naveda-Rodriguez A.,Acopian Center for Conservation Learning
Journal of Raptor Research | Year: 2015
I here evaluate the conservation status of 64 species of diurnal raptors in Venezuela based on extent of occurrence (EOO) and area of occupancy (AOO) derived from geomatic-based geographic distribution modeling and gap analysis. I modeled the geographic distribution of raptor species to quantify distribution areas using the maximum entropy modeling techniques with nine environmental variables that were believed to influence the geographic distribution of raptors. The EOO and AOO were used to reevaluate the conservation status of diurnal raptors in Venezuela, applying Criteria B of the IUCN Red List. Furthermore, a gap analysis was performed to evaluate the effectiveness of strictly protected areas (SPA) in the conservation of birds of prey. EOO ranged from 10,423 km2 to 907,223 km2 and AOO values ranged from 6566 km2 to 903,193 km2; four species met the B1 criterion and are qualified to be reclassified. The gap analysis revealed that, on average, 20% and 24% of species' EOO and AOO, respectively, were protected within SPA. In theory, SPA are assuming an effective role in the protection of species' geographic distribution. Raptor conservation in Venezuela must be thoroughly planned; an update in land-use planning (territorial ordering) to enhance the connectivity among SPA would improve the protection of raptors. © 2015 The Raptor Research Foundation, Inc.
Rexer-Huber K.,PO Box 598 |
Bildstein K.L.,Acopian Center for Conservation Learning
Polar Biology | Year: 2013
Striated caracaras occur only on the Falkland Islands and the outer islands of southern Chile and Argentina. In summer, the species associates with seabirds and seals and depends heavily upon them for food. The winter diet is less well understood. We studied the diet of 90-130 mainly juvenile and sub-adult striated caracaras overwintering at a farm on Saunders Island, Falkland Islands, in mid-winter (July-August) 2011. Direct observations of feeding and regurgitation pellets collected at a roost indicate that the winter diet of the striated caracaras at the site is mainly native geese, beetles and other invertebrates, and the carcasses of domestic sheep. This study illustrates seasonal shifts in the diet of this near-threatened South Atlantic endemic and suggests an important nutritional link between juvenile and subadult caracara survival in winter and traditional human activities at sheep farms. © 2012 Springer-Verlag Berlin Heidelberg.
Ferrer M.,CSIC - Donana Biological Station |
Bildstein K.,Acopian Center for Conservation Learning |
Penteriani V.,CSIC - Donana Biological Station |
Casado E.,Fundacion Migres |
de Lucas M.,CSIC - Donana Biological Station
PLoS ONE | Year: 2011
Background: Island faunas have played central roles in the development of evolutionary biology and ecology. Birds are among the most studied organisms on islands, in part because of their dispersal powers linked to migration. Even so, we lack of information about differences in the movement ecology of island versus mainland populations of birds. Methodology/Principal Findings: Here we present a new general pattern indicating that large birds with deferred sexual maturity are sedentary on islands, and that they become so even when they are migratory on the mainland. Density-dependent variation in the age at first breeding affects the survivorship of insular populations and this, in turn, affects the movement ecology of large birds. Because density-dependent variation in the age of first breeding is critical to the long-term survival of small isolated populations of long-lived species, migratory forms can successfully colonize islands only if they become sedentary once there. Analyses of the movement ecology of continental and insular populations of 314 species of raptors, 113 species of Ciconiiformes and 136 species of passerines, along with individual-based population simulations confirm this prediction. Conclusions: This finding has several consequences for speciation, colonization and survival of small isolated population of species with deferred sexual maturity. © 2011 Ferrer et al.
Bohrer G.,Ohio State University |
Brandes D.,Lafayette College |
Mandel J.T.,Advanced Conservation Strategies |
Bildstein K.L.,Acopian Center for Conservation Learning |
And 5 more authors.
Ecology Letters | Year: 2012
Soaring birds migrate in massive numbers worldwide. These migrations are complex and dynamic phenomena, strongly influenced by meteorological conditions that produce thermal and orographic uplift as the birds traverse the landscape. Herein we report on how methods were developed to estimate the strength of thermal and orographic uplift using publicly available digital weather and topography datasets at continental scale. We apply these methods to contrast flight strategies of two morphologically similar but behaviourally different species: golden eagle, Aquila chrysaetos, and turkey vulture, Cathartes aura, during autumn migration across eastern North America tracked using GPS tags. We show that turkey vultures nearly exclusively used thermal lift, whereas golden eagles primarily use orographic lift during migration. It has not been shown previously that migration tracks are affected by species-specific specialisation to a particular uplift mode. The methods introduced herein to estimate uplift components and test for differences in weather use can be applied to study movement of any soaring species. © 2011 Blackwell Publishing Ltd/CNRS.
Farmer C.J.,Acopian Center for Conservation Learning |
Smith J.P.,HawkWatch International Inc.
Journal of Raptor Research | Year: 2010
Long-term monitoring is important for ensuring effective conservation of raptor populations. Raptors also can serve as indicators of biodiversity and ecosystem condition. Therefore, effective monitoring of raptor populations yields the added benefit of helping to evaluate the status of ecosystems. Spring counts of migrating raptors at concentration points may contribute to these goals, particularly by providing insight into the vital demographic rates underlying population trends. Although much is known about the monitoring value of autumn migration counts in North America, little research has addressed the value of spring counts. We compared counts at seven spring watchsites to those at seven autumn watchsites matched by region (Southwest, Great Lakes, and Northeast) to assess the value of spring counts for population monitoring. Our analyses suggested that population indexes derived from spring migration counts provided estimates of population change that differed overall from autumn migration counts in the same region. The concordance of spring and autumn trends was higher in the Southwest and Northeast than in the Great Lakes region, suggesting greater variation in the seasonal representation of populations in the latter region. The average precision of spring trend estimates was better than for autumn estimates in the same region in two of three regions, and the estimated rates of change often were lower in spring. Spring counts enhanced the ability to estimate population trends for species that are less common in autumn counts, including the Rough-legged Hawk (Buteo lagopus) and Red-shouldered Hawk (B. lineatus). To realize fully the value of spring counts, we recommend the establishment of additional spring watchsites in areas that concentrate migrants in autumn, but do so to a lesser extent in spring, as well as additional research to define the populations sampled by autumn and spring counts. © 2010 The Raptor Research Foundation, Inc.