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Hoy S.R.,University of Aberdeen | Millon A.,CNRS Mediterranean Institute for Biodiversity and Ecology Marine and Continental | Petty S.J.,University of Aberdeen | Whitfield D.P.,Natural Research Ltd. | Lambin X.,University of Aberdeen
Journal of Animal Ecology | Year: 2016

Deciphering the causes of variation in reproductive success is a fundamental issue in ecology, as the number of offspring produced is an important driver of individual fitness and population dynamics. Little is known, however, about how different factors interact to drive variation in reproduction, such as whether an individual's response to extrinsic conditions (e.g. food availability or predation) varies according to its intrinsic attributes (e.g. age, previous allocation of resources towards reproduction). We used 29 years of reproductive data from marked female tawny owls and natural variation in food availability (field vole) and predator abundance (northern goshawk) to quantify the extent to which extrinsic and intrinsic factors interact to influence owl reproductive traits (breeding propensity, clutch size and nest abandonment). Extrinsic and intrinsic factors appeared to interact to affect breeding propensity (which accounted for 83% of the variation in owl reproductive success). Breeding propensity increased with vole density, although increasing goshawk abundance reduced the strength of this relationship. Owls became slightly more likely to breed as they aged, although this was only apparent for individuals who had fledged chicks the year before. Owls laid larger clutches when food was more abundant. When owls were breeding in territories less exposed to goshawk predation, 99·5% of all breeding attempts reached the fledging stage. In contrast, the probability of breeding attempts reaching the fledging stage in territories more exposed to goshawk predation depended on the amount of resources an owl had already allocated towards reproduction (averaging 87·7% for owls with clutches of 1–2 eggs compared to 97·5% for owls with clutches of 4–6 eggs). Overall, our results suggested that changes in extrinsic conditions (predominantly food availability, but also predator abundance) had the greatest influence on owl reproduction. In response to deteriorating extrinsic conditions (fewer voles and more goshawks), owls appeared to breed more frequently, but allocated fewer resources per breeding attempt. However, intrinsic attributes also appeared to have a relatively small influence on how an individual responded to variation in extrinsic conditions, which indicates that owl reproductive decisions were shaped by a complex series of extrinsic and intrinsic trade-offs. © 2016 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society. Source


Garcia J.T.,Institute Investigacion en Recursos Cinegeticos IREC CSIC UCLM JCCM | Alda F.,Institute Investigacion en Recursos Cinegeticos IREC CSIC UCLM JCCM | Terraube J.,Institute Investigacion en Recursos Cinegeticos IREC CSIC UCLM JCCM | Terraube J.,Natural Research Ltd. | And 5 more authors.
BMC Evolutionary Biology | Year: 2011

Background: Environmental preferences and past climatic changes may determine the length of time during which a species range has contracted or expanded from refugia, thereby influencing levels of genetic diversification. Connectivity among populations of steppe-associated taxa might have been maximal during the long glacial periods, and interrupted only during the shorter interglacial phases, potentially resulting in low levels of genetic differentiation among populations. We investigated this hypothesis by exploring patterns of genetic diversity, past demography and gene flow in a raptor species characteristic of steppes, the Montagu's harrier (Circus pygargus), using mitochondrial DNA data from 13 breeding populations and two wintering populations. Results: Consistent with our hypothesis, Montagu's harrier has relatively low genetic variation at the mitochondrial DNA. The highest levels of genetic diversity were found in coastal Spain, France and central Asia. These areas, which were open landscapes during the Holocene, may have acted as refugia when most of the European continent was covered by forests. We found significant genetic differentiation between two population groups, at the SW and NE parts of the species' range. Two events of past population growth were detected, and occurred ca. 7500-5500 and ca. 3500-1000 years BP in the SW and NE part of the range respectively. These events were likely associated with vegetation shifts caused by climate and human-induced changes during the Holocene. Conclusions: The relative genetic homogeneity observed across populations of this steppe raptor may be explained by a short isolation time, relatively recent population expansions and a relaxed philopatry. We highlight the importance of considering the consequence of isolation and colonization processes in order to better understand the evolutionary history of steppe species. © 2011Garcia et al; licensee BioMed Central Ltd. Source


Christie D.,Kessels Ecology | Urquhart B.,Natural Research Ltd.
New Zealand Journal of Zoology | Year: 2015

A new spreadsheet is presented, to be used as part of the Band model for estimating potential avian mortality due to wind turbine strike. The spreadsheet extends the Band collision risk spreadsheet by allowing for oblique approach angles and wind speed. The differences in the results between this new spreadsheet and the standard Band spreadsheet are given for two species, the white-tailed eagle Haliaeetus albicilla and the South Island pied oystercatcher Haematopus finschi, chosen for their contrasting sizes and flight characteristics. Under more representative conditions, the true risk for large birds is shown to be substantially greater than that calculated by the Band spreadsheet. Examples of how to use the new spreadsheet with bird survey and wind data are given. © 2015 The Royal Society of New Zealand Source


Separation of animals and humans using a protective set-back distance (Minimum Approaching Distance) is a popular tool for conservation managers to promote wildlife-human coexistence. In several cases, Minimum Approaching Distance is based on how animals respond to an approaching human, using Flight InitiationDistance orAlert Distance. Alert Distance, when animals first show increased vigilance to an approaching human, is considered the best basis for Minimum ApproachingDistance because animals have time to adapt their response. Alert Distance is frequently difficult or impossible to measure in practice, however, especially in breeding birds.Using a study of breedingWood Sandpipers Tringa glareola, in which Alert Distance could not be measured directly, we tested three possible solutions to this dilemma. Alarm Call Distance did not appear to provide a useful substitute for Alert Distance because sandpipers probably alarm called after they had first detected a human. Published predictions of Alert Distance using bodymass also failed to provide realistic estimates of disturbance distances in Wood Sandpipers. The "fixed-slope rule", which predicts that Alert Distance is about double Flight Initiation Distance, was not supported by relationships between AlarmCallDistance and Flight InitiationDistance, but was supported by a relationship between an estimated AlertDistance surrogate and Flight InitiationDistance. This suggests that this rulemay have general utility in predicting Alert Distance when only the more readily measured Flight Initiation Distancemetric is known.AMinimum ApproachingDistance (protective buffer zone) of 160 m is recommended for breedingWood Sandpipers. Source


Terraube J.,Natural Research Ltd. | Terraube J.,Institute Investigacion en Recursos Cinegeticos | Terraube J.,French National Institute for Agricultural Research | Arroyo B.E.,Institute Investigacion en Recursos Cinegeticos | And 3 more authors.
Biodiversity and Conservation | Year: 2012

Ecological specialization can explain the declining status of many species in the face of current global changes. Amongst specialists, nomadic predators present conservation biologists with many challenges, mainly because of the difficulty of studying highly mobile individuals over time and across very large areas. For these species, the relative influence of prey abundance, habitat heterogeneity and arrival time at the breeding grounds on breeding parameters remains poorly understood. We studied the factors influencing variation in breeding numbers and performance of a declining nomadic specialist raptor, the Pallid Harrier Circus macrourus, in north-central Kazakhstan. During a 5-year period, we recorded large inter-annual variation in vole abundance in the main study area, and differences between habitats. We also recorded a strong numerical response of breeding Pallid Harriers to inter-annual changes in local vole abundance. From a 13-year dataset on breeding harriers in the same area, harrier numbers appeared to vary cyclically, with an interval between peaks of approximately 6 years. At a broader, regional scale, variations in Pallid Harrier abundance appeared asynchronous, suggesting a regional redistribution of harriers between years. Reproductive success depended on local vole abundance, but also on timing of breeding and nesting habitat. Clutch size, nest success and fledged brood size increased with vole abundance. Late breeders had smaller clutches and apparently lower hatching rates than early ones, possibly as a result of the interplay between their probable poorer body condition and habitat-specific variation in predation rates. In true nomadic specialist predators, such as Pallid Harriers, breeding success may therefore depend on a complex interplay between spatial variation in prey abundance, habitat composition and timing of breeding attempts. One of the factors influencing the start of breeding is the length of time taken to prospect between different breeding sites, which in turn may depend on the predictability of spatial and temporal variation in vole abundance. These results have important conservation implications, as changes in climate and habitat could affect spatial and temporal variations in vole abundance, with possible consequences for timing of breeding, food availability and, ultimately, the reproductive success of this declining nomadic predator. © 2012 Springer Science+Business Media B.V. Source

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