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Capture Site (capture + site)
Selected AbstractsPrey size and ingestion rate in raptors: importance for sex roles and reversed sexual size dimorphismJOURNAL OF AVIAN BIOLOGY, Issue 6 2007Tore Slagsvold Compared to other birds, most raptors take large prey for their size, and feeding bouts are extended. However, ingestion rate has largely been overlooked as a constraint in raptors, foraging and breeding ecology. We measured ingestion rate by offering avian and mammalian prey to eighteen wild raptors temporarily kept in captivity, representing seven species and three orders. Ingestion rate was higher for small than for large prey, higher for mammalian than for avian prey, higher for large than for small raptors, and higher for wide-gaped than for narrow-gaped raptors. Mammalian prey were ingested faster by raptors belonging to species with mainly mammals in their diet than by raptors with mainly birds in their diet, but the drop in ingestion rate with increasing prey size was more rapid for the former than for the latter. We argue that the separate sex roles found in raptors, i.e. the male hunting and the female feeding the young, is a solution of the conflict between the prolonged feeding bouts at the nest, and the benefit of rapid resumption of hunting in general, and rapid return to the previous capture site in particular (the prey size hypothesis). Thus, the sex roles differ more when prey takes longer to feed, i.e. from insects to mammals to birds. We then argue that the reversed sexual size dimorphism in raptors, i.e. smaller males than females, results from a conflict between the benefit of being small during breeding to capture the smallest items with the highest ingestion rate among these agile prey types (mammals and bird), and the benefit of being large outside the breeding season to ensure survival by being able to include large items in the diet when small items are scarce (the ingestion rate hypothesis). This hypothesis explains the observed variation in reversed sexual size dimorphism among raptors in relation to size and type of prey, i.e. increasing RSD from insects to mammals to birds as prey. [source] On cognitive conservation biology: why chickadees leave a patch of woodlandJOURNAL OF AVIAN BIOLOGY, Issue 4 2001Thomas C. Grubb Although not previously emphasized, colonization of habitat patches by cognitive animals involves both decisions bringing an animal to a particular patch and decisions causing the animal to remain in the patch. We focus on the latter form of decision by examining the habitat and landscape correlates of persistence in chickadees (Poecile spp.) that we introduced into small woodlots previously cleared of conspecifics. The birds' decisions to remain were associated importantly with the presence of a canopy layer of large trees, and less so with area of the woodland patch and distance they had been transported from the capture site. The decision to persist was little related to landscape features near the focal habitat patch. The future holds promise for application of principles of cognition to landscape biology. [source] Quaternary landscape evolution: a framework for understanding contemporary erosion, southeast SpainLAND DEGRADATION AND DEVELOPMENT, Issue 2 2002A. E. Mather Abstract Recent research into the long-term landscape development of a tectonically active terrain in arid SE Spain has revealed the significance of river capture in understanding current landscape instabilities (badlands and landslides). The river capture was initiated at c.100,ka,BP and effected a 90,m base-level change at the point of capture. This stimulated a wave of incision to propagate through the landscape to 20,km upstream of the capture site. The net effect of the associated increase in erosion has been to change valley shapes from broad and shallow to narrow and deep. The associated unloading and steepening of valley sides has led to a focus of landslide activity in lithologies with more unconfined compressive strength (limestones) and a dominance of gullying, piping and badland development in the lithologies with lower unconfined compressive strengths (marls and sands). Post-capture rapid valley widening was initially achieved through landslide development. This form of slope degradation was sustained in the more resistant, joint-controlled lithologies. In weaker lithologies it was superseded by badland development. The elevated sediment fluxes associated with the c.100,ka,BP base-level perturbation will continue into the near future, but are expected to decay, assuming that no additional environmental disturbances occur. The patterns of landscape instability witnessed today are controlled by (1) proximity to the areas affected by the base-level change and (2) the robustness of the local geology. Understanding of this long-term temporal context of the landscape provides a valuable spatial and temporal framework for land system management, facilitating the prediction of future natural trends in landscape stability. Copyright © 2002 John Wiley & Sons, Ltd. [source] What happens to translocated game birds that ,disappear'?ANIMAL CONSERVATION, Issue 5 2009M. J. Dickens Abstract The ultimate goal of most translocation efforts is to create a self-sustaining wild population of a species deliberately moved from one part of their range to another. As follow-up of a translocation attempt is often difficult, causes for failure are relatively unknown. Dispersal away from the release site is one potential source of failure because it decreases the likelihood of the released population establishing itself post-translocation. In this study, we used chukar Alectoris chukar as a surrogate for translocated game birds in order to conduct a large-scale experimental study. We observed that these desert-adapted birds demonstrate a strong fidelity for specific water sources. We also report the propensity for the translocated individuals to either disperse and return to their original water source site or remain at the release site. During two field seasons, we observed opposing behaviors such that the proportion of individuals returning to the capture site, versus those remaining at the release site, shifted between years. We analyzed this change between the years as well as within the years to assess the potential underlying causes such as translocated distance, differences in rainfall between seasons and water source type. We concluded that homing behavior was strong in this non-migratory bird species and that strength of this homing behavior varied, potentially due to conditions surrounding the limiting resource, water availability. The large-scale, original data presented here may help to explain why some releases result in a successfully established population while other releases result in widely dispersed individuals. [source] Migration, Diet, or Molt?BIOTROPICA, Issue 4 2010Interpreting Stable-Hydrogen Isotope Values in Neotropical Bats ABSTRACT Migratory behavior in bats is poorly described, particularly in the Neotropics. Stable-hydrogen isotope (,D) analysis may allow tracking of altitudinal movements of bats but has not been explored. ,D values in rainwater (,Dp) deplete linearly with altitude and are reflected in the keratinous tissues of animals through diet. A mismatch between keratin ,D (,Dk) and that expected at the capture site based on ,Dp can indicate prior migration. We collected rainwater, claws and hair from eight bat species at two lower-montane forest sites in Nicaragua. Claw ,D for Carollia brevicauda and hair and claws for Desmodus rotundus (known to be non-migratory) fell within the predicted range based on rainwater (,17 to ,60,) suggesting these tissues were synthesized at the study site. ,D tissue values for Artibeus toltecus, Sturnira lilium, Glossophaga soricina, Anoura geoffroyi, and hair for C. brevicauda were more negative than predicted for the capture site (,60,) suggesting tissue synthesis at higher elevation and migration downslope to the capture site. However, our study area represents the highest elevation in the region; the nearest appropriate higher elevations are 350,500 km away and seasonal migration is expected to be<200 km. Thus we consider that seasonal shifts in ,Dp (9 to ,45,) may result in differences in species which molt at different times, and that diet may have driven differences in ,D. Our results suggest that the effects of molt timing and diet may first need to be understood before ,D may be successfully used to track bat movements. [source] Post-juvenile dispersal of Hazel Grouse Bonasa bonasia in an expanding population of the southeastern French AlpsIBIS, Issue 1 2006MARC MONTADERT We studied the post-juvenile dispersal of 18 radiotagged juvenile Hazel Grouse Bonasa bonasia (14 males, four females) in an expanding population in the southeastern French Alps between 1998 and 2001. The mean dispersal distances between the capture sites of juveniles in September,October and the centre of the home range in the following spring was 4 km for males (range 0.1,24.9 km) and 2 km for females (range 0.2,5.6 km). The distances recorded for two long-dispersing males (15 and 24.9 km) are greater than those reported to date for Hazel Grouse. Using our radiotracking data, we interpret the pattern of range expansion that has been occurring since the 1950s around our study area. Barriers to dispersal included rocky ground and other alpine habitats above 2000 m and over 1 km wide, but Hazel Grouse did cross open agricultural land at lower elevation. Two patterns of dispersal movements were recognized in juveniles: erratic movements that led to settlement on or near the natal site, and direct movements to a new range relatively far from the natal area. We discuss the adaptive consequences of these different behaviour patterns. [source] The distribution of South American galaxiid fishes: the role of biological traits and post-glacial historyJOURNAL OF BIOGEOGRAPHY, Issue 1 2004Víctor Cussac Abstract Aim, The aim of this work is to update the distribution data of Galaxiidae in South America, relating extant distribution to physiological and reproductive characteristics of the species, latitude, temperature, and post-glacial opportunities for colonization. Location, Lakes and rivers of Patagonia. Methods, We compared, and eventually reconsidered, general data about distribution based on the original literature about capture sites, incorporating several published and unpublished data to the analysis of the biological traits and distribution of Galaxiidae. Results, The more consistent issue in the comprehension of galaxiid biogeography in South America is the ability to establish landlocked populations. Different founding events in landlocked populations of Galaxias maculatus suggest the possible existence of older and younger landlocked populations. This difference in the time since the establishment of lacustrine populations could have been expressed in their ability for colonization of post-glacial areas. Galaxias maculatus, Aplochiton and Brachygalaxias are more clearly excluded from the post-glacial area than G. platei. For all the species we could note a more abundant record of lake populations at the area of glacial refuges. It could be noted that the most successful species, Galaxias platei, is a specialized deep bottom dweller. Deep bottom dwelling helps to endure winter constraints and it appears to be an alternative to the colonization of the littoral and limnetic zones of post-glacial lakes, the prefered habitat of the other Patagonian fish species. Main conclusions, At the end of this process of post-glacial colonization, in the beginning of twentieth century, man introduced several salmonid species in Patagonia. In addition, antropogenic actions had its more recent consequences in global warming. Nowadays we were able to observe new localities for Brazilian fishes into the Austral Subregion and expect some changes in the distribution of Galaxiidae. Northern limits for all species and southern limits for landlocked G. maculatus, Brachigalaxias bullocki and Aplochiton zebra, could be displaced southward. Probably, the species less affected by the changes will be G. platei. These predictions could be accurately formulated using the model of B.J. Shuter & J.R. Post (1990) Transactions of the American Fisheries Society119, 314,336, when biological database on these species are completed. [source] | ||||||||||