Availability Of High-quality Habitat Research Articles

Do differences in the availability of anthropogenic food resources influence the observed levels of agonistic behaviour in Noisy Miners (Manorina melanocephala)?

ABSTRACT The Noisy Miner (Manorina melanocephala) is a cooperative honeyeater living in social groups throughout south-east Australia that displays high levels of interspecific aggression and reduces avifaunal biodiversity in areas it occupies. Human-induced habitat changes have also potentially increased the availability of high-quality habitat and food resources available for Noisy Miners, which may in turn affect activity budgets and the duration or intensity of aggression displayed by Miners towards other species. To quantify the impact of differences in the potential availability of anthropogenic food resources on Noisy Miner aggression levels, we presented taxidermy models from three different categories of bird species (food competitors, non-food competitors and potential predators) and quantified observed aggression in three separate habitats: natural areas with very limited additional anthropogenic food resources, gardens that provided supplementary resources such as nectar-rich ornamental plants, and cafés that provided access to human food items. As predicted, Noisy Miners exhibited agonistic behaviours for a significantly longer period in the habitats with anthropogenic food resources, namely gardens and cafés in comparison to natural areas. The type of model presented also impacted Miner response, with: (1) greater numbers of Miners mobbing predator rather than competitor models, (2) Miners mobbing predator models for longer periods than competitors, and (3) a greater probability of Miners physically contacting competitor models. These findings demonstrate that additional resources have the ability to impact time budgets of species and, for hyperaggressive birds such as Noisy Miners, can impact biodiversity in more nuanced ways than previously quantified.

Selection of Calf Bedding Sites by Female Elk in the Central Appalachian Mountains

AbstractAcross eastern North America, Rocky Mountain elk Cervus canadensis nelsoni have been reintroduced to 11 states and provinces that were previously occupied by the extinct eastern elk C. canadensis canadensis. Outside of Kentucky, these elk reintroductions have resulted in small populations, typically numbering fewer than 1,000 elk per state. Limited information is available about the demographics and habitat selection within these small eastern populations. The availability of high-quality habitat during the first weeks of life is important for promoting annual recruitment and the identification of these characteristics should aid in management efforts. We characterized habitat at two spatial scales surrounding the bedding sites of 83 elk calves (≤ 7 d old) in the Pennsylvania Elk Management Area during the annual calving seasons of 2005–2008. A concurrent study found that calves in this area experienced high survival (92%) during the first 4 mo of life, despite occupying an area with high predator densities. At a local scale, bedding sites used by calves were closer to ecotones, had less leaf litter, and had greater density of vegetation below 1 m compared to random sites (n = 82). At a landscape scale, calf habitat surrounding bedding sites had greater density of edges between forest and open vegetation and less coniferous forest compared to random areas. The selected habitats appear to balance the high energetic needs of lactating females at the landscape scale and the need for cover to conceal calves and reduce predation risk at a local scale. Conclusions drawn from our models suggest future habitat management include enhancements of transitional vegetation along ecotones between forest and herbaceous openings that address the needs of both lactating females and recently born calves. We recommend that managers periodically evaluate the availability of calf habitat and calf survival rates. These monitoring activities will provide insight necessary to adaptively manage elk and the habitats driving their population growth to maintain their viability in the central Appalachian Mountains.

The impact of personality on the success of prospecting behavior in changing landscapes

Abstract Personality can play a large role in dispersal decisions, influencing how each individual estimates and values expected costs versus benefits of venturing out to explore the unknown. We contrast the impact of persistence on fitness using decision theory models to examine the relative success of prospecting movement (which is a widespread behavior used by animals to explore available breeding habitat before determining where to settle) in different landscapes among individuals with different personalities. While evaluating trends in the costs and benefits of movement we provide a quantifiable measure of the impacts of relative tenacity in prospecting behavior on fitness gains/losses. Our model results predict that, regardless of landscape composition, individuals with greater tenacity in prospecting strategy have reduced fitness gains relative to individuals who are more willing to both initiate novel strategies, but then also abandon the new strategy rapidly if initial search does not seem fruitful. We show that fitness gains from choosing an appropriate prospecting strategy (i.e. abandoning poor habitat or staying in rich habitat) can be very high, indicating a potentially large influence from personality on fitness. Importantly, the model predicts that relative fitness gains are highly dependent on the availability of high quality habitat in the landscape, even if the difference under varying fitness outcomes between poor and rich habitat was substantial.

Model-based design for restoration of a small urban river

A model-based design is presented for restoring the small urban river Panke located in Berlin, Germany. This new design process combines high resolution 2D hydraulic modeling with habitat modeling and river-ecological expert knowledge in a highly iterative way. Advances have been made for the habitat modeling: habitat suitability maps have been developed for fish and the habitat suitability for benthos has been assessed by including groups with different hydraulic preferences.Using the model-based design we have developed preference variants for the Panke which include structures such as pools, riffles, river banks, dead wood as well as aquatic vegetation. To account for the very detailed geometry of some structures such as dead wood, high resolution grids with edge length up to one decimeter have been generated. Furthermore flood protection has been assured. The variants should be constructed in the Panke in 2015. We expect that the ecological conditions for fish and benthos will improve, however this has to be evaluated by further measurements. The model-based approach for the design of enhancement measures delivered valuable hints on current shortcomings in the river morphology, priorities for the creation of new habitats and quantitative information on the increase of suitable areas to be expected. In addition, relating the habitat changes to different flow rates helped to estimate the temporal availability of high quality habitats after the implementation of the measures.

Relative roles of grey squirrels, supplementary feeding, and habitat in shaping urban bird assemblages.

Non-native species are frequently considered to influence urban assemblages. The grey squirrel Sciurus carolinensis is one such species that is widespread in the UK and is starting to spread across Europe; it predates birds’ nests and can compete with birds for supplementary food. Using distance sampling across the urbanisation intensity gradient in Sheffield (UK) we test whether urban grey squirrels influence avian species richness and density through nest predation and competition for supplementary food sources. We also assess how urban bird assemblages respond to supplementary feeding. We find that grey squirrels slightly reduced the abundance of breeding bird species most sensitive to squirrel nest predation by reducing the beneficial impact of woodland cover. There was no evidence that grey squirrel presence altered relationships between supplementary feeding and avian assemblage structure. This may be because, somewhat surprisingly, supplementary feeding was not associated with the richness or density of wintering bird assemblages. These associations were positive during the summer, supporting advocacy to feed birds during the breeding season and not just winter, but explanatory capacity was limited. The amount of green space and its quality, assessed as canopy cover, had a stronger influence on avian species richness and population size than the presence of grey squirrels and supplementary feeding stations. Urban bird populations are thus more likely to benefit from investment in improving the availability of high quality habitats than controlling squirrel populations or increased investment in supplementary feeding.

Mechanistic modelling of animal dispersal offers new insights into range expansion dynamics across fragmented landscapes

Understanding and predicting the dynamics of range expansion is a major topic in ecology both for invasive species extending their ranges into non‐native regions and for species shifting their natural distributions as a consequence of climate change. In an increasingly modified landscape, a key question is ‘how do populations spread across patchy landscapes?‘ Dispersal is a central process in range expansion and while there is a considerable theory on how the shape of a dispersal kernel influences the rate of spread, we know much less about the relationships between emigration, movement and settlement rules, and invasion rates. Here, we use a simple, single species individual‐based model that explicitly simulates animal dispersal to establish how density‐dependent emigration and settlement rules interact with landscape characteristics to determine spread rates. We show that depending on the dispersal behaviour and on the risk of mortality in the matrix, increasing the number of patches does not necessarily maximise the spread rate. This is due to two effects: first, individuals dispersing at the expanding front are likely to exhibit lower net‐displacement as they typically do not travel far before finding a patch; secondly, with increasing availability of high quality habitat, density‐dependence in emigration and settlement can decrease the number of emigrants and their net‐displacement. The rate of spread is ultimately determined by the balance between net travelled distance, the dispersal mortality and the number of dispersing individuals, which in turn depend on the interaction between the landscape and the species’ dispersal behaviour. These results highlight that predicting spread rates in heterogeneous landscapes is a complex task and requires better understanding of the rules that individuals use in emigration, transfer and settlement decisions.

Spatial, temporal, and habitat-related variation in abundance of pelagic fishes in the Gulf of Mexico: potential implications of the deepwater horizon oil spill.

Time-series data collected over a four-year period were used to characterize patterns of abundance for pelagic fishes in the northern Gulf of Mexico (GoM) before (2007–2009) and after (2010) the Deepwater Horizon oil spill. Four numerically dominant pelagic species (blackfin tuna, blue marlin, dolphinfish, and sailfish) were included in our assessment, and larval density of each species was lower in 2010 than any of the three years prior to the oil spill, although larval abundance in 2010 was often statistically similar to other years surveyed. To assess potential overlap between suitable habitat of pelagic fish larvae and surface oil, generalized additive models (GAMs) were developed to evaluate the influence of ocean conditions on the abundance of larvae from 2007–2009. Explanatory variables from GAMs were then linked to environmental data from 2010 to predict the probability of occurrence for each species. The spatial extent of surface oil overlapped with early life habitat of each species, possibly indicating that the availability of high quality habitat was affected by the DH oil spill. Shifts in the distribution of spawning adults is another factor known to influence the abundance of larvae, and the spatial occurrence of a model pelagic predator (blue marlin) was characterized over the same four-year period using electronic tags. The spatial extent of oil coincided with areas used by adult blue marlin from 2007–2009, and the occurrence of blue marlin in areas impacted by the DH oil spill was lower in 2010 relative to pre-spill years.

Survival and cause‐specific mortality of elk Cervus canadensis calves in a predator rich environment

AbstractQuantification of basic demographic parameters such as survival rates and cause‐specific mortality is important for effective species management. We conducted a 4‐year study (during May 2005‐June 2009) of elk Cervus canadensis calf survival and cause‐specific mortality in Pennsylvania, USA. We captured and radio‐collared 93 elk calves ≤ 7 days old and monitored them weekly to detect mortality and cause of death. Of the 93 radio‐collared elk calves, 15 (16%) died during our study. Despite high black bear Ursus americanus and coyote Canis latrans densities, none of the mortalities were the result of predation. Causes of death included poaching (N = 3), legal harvest (N = 2), road kill (N = 2), pneumonia (N = 1) and rumen acidosis (N = 1). We were unable to determine the cause of mortality for six of the elk calves; however, predation was eliminated as a possible source of mortality in all unknown cases. Survival probabilities were similar between sexes and among years. Summer survival (birth‐31 October) was 0.92 (SE = 0.03, N = 93) and winter survival (1 November ‐ 1 April) was 0.90 (SE = 0.04, N = 79). Annual estimated elk calf survival was 0.82 (SE = 0.04, N = 93). Our findings suggest that Pennsylvania elk calves have a > 80% chance of survival to one‐year of age, despite high densities of predators known to influence elk calf survival elsewhere. The high calf survival rates that we observed indicate the availability of high quality habitat leading to excellent physical condition of elk.

Moisture as a determinant of habitat quality for a nonbreeding Neotropical migratory songbird

Identifying the determinants of habitat quality for a species is essential for understanding how populations are limited and regulated. Spatiotemporal variation in moisture and its influence on food availability may drive patterns of habitat occupancy and demographic outcomes. Nonbreeding migratory birds in the neotropics occupy a range of habitat types that vary with respect to moisture. Using carbon isotopes and a satellite-derived measure of habitat moisture, we identified a moisture gradient across home ranges of radio-tracked Northern Waterthrush (Seiurus noveboracensis). We used this gradient to classify habitat types and to examine whether habitat moisture correlates with overwinter mass change and spring departure schedules of Northern Waterthrush over the late-winter dry season in the tropics. The two independent indicators of moisture revealed similar gradients that were directly proportional to body mass change as the dry season progressed. Birds occupying drier habitats declined in body mass over the study period, while those occupying wetter habitats increased in body mass. Regardless of habitat, birds lost an average of 7.6% of their mass at night, and mass recovery during the day trended lower in dry compared with wet habitats. This suggests that daily incremental shortfalls in mass recovery can lead to considerable season-long declines in body mass. These patterns resulted in consequences for the premigratory period, with birds occupying drier habitats having a delayed rate of fat deposition compared with those in wet habitats. Taken together with the finding that males, which are significantly larger than females, are also in better condition than females regardless of habitat suggests that high-quality habitats may be limited and that there may be competition for them. The habitat-linked variation in performance we observed suggests that habitat limitation could impact individual and population-level processes both during and in subsequent periods of the annual cycle. The linkage between moisture and habitat quality for a migratory bird indicates that the availability of high-quality habitats is dynamic due to variation in precipitation among seasons and years. Understanding this link is critical for ascertaining the impact of future climate change, particularly in the Caribbean basin, where a much drier future is predicted.

MOISTURE AS A DETERMINANT OF HABITAT QUALITY FOR A NON-BREEDING NEOTROPICAL MIGRATORY SONGBIRD.

Identifying the determinants of habitat quality for a species is essential for understanding how populations are limited and regulated. Spatiotemporal variation in moisture and its influence on food availability may drive patterns of habitat occupancy and demographic outcomes. Nonbreeding migratory birds in the neotropics occupy a range of habitat types that vary with respect to moisture. Using carbon isotopes and a satellite-derived measure of habitat moisture, we identified a moisture gradient across home ranges of radio-tracked Northern Waterthrush (Seiurus noveboracensis). We used this gradient to classify habitat types and to examine whether habitat moisture correlates with overwinter mass change and spring departure schedules of Northern Waterthrush over the late-winter dry season in the tropics. The two independent indicators of moisture revealed similar gradients that were directly proportional to body mass change as the dry season progressed. Birds occupying drier habitats declined in body mass over the study period, while those occupying wetter habitats increased in body mass. Regardless of habitat, birds lost an average of 7.6% of their mass at night, and mass recovery during the day trended lower in dry compared with wet habitats. This suggests that daily incremental shortfalls in mass recovery can lead to considerable season-long declines in body mass. These patterns resulted in consequences for the premigratory period, with birds occupying drier habitats having a delayed rate of fat deposition compared with those in wet habitats. Taken together with the finding that males, which are significantly larger than females, are also in better condition than females regardless of habitat suggests that high-quality habitats may be limited and that there may be competition for them. The habitat-linked variation in performance we observed suggests that habitat limitation could impact individual and population-level processes both during and in subsequent periods of the annual cycle. The linkage between moisture and habitat quality for a migratory bird indicates that the availability of high-quality habitats is dynamic due to variation in precipitation among seasons and years. Understanding this link is critical for ascertaining the impact of future climate change, particularly in the Caribbean basin, where a much drier future is predicted.

Predicting grey squirrel expansion in North Italy : a spatially explicit modelling approach

There is growing concern about the spread of the North American grey squirrel (Sciurus carolinensis) in northern Italy which were introduced into Piedmont in 1948. They have since spread across the Po-plain covering an area of approximately 450 km 2 and continue to expand their range. In parallel to what has been observed in Britain and Ireland, grey squirrels replace the native red squirrel (S. vulgaris) and damage poplar (Populus) plantations through bark-stripping. Spatially explicit population dynamics models have been successfully used to predict the spread of grey squirrels in East Anglia, England. We extended a previous approach employing a sensitivity analysis where life history and other demographic inputs are generated using Latin Hypercube Sampling from the known ranges of each input parameter, and applied it to Italy using field data collected in Piedmont. The analysis indicated that reproductive output was the most important factor determining total population size present in Piedmont. The structure and composition of woodland habitats around the introduction site suggested that initial grey squirrel expansion would have been slow and subject to emigration rates from the available habitat blocks. A comparison of the 1996 survey results with model predictions indicated that a mean litter size of three young gave the best fit with the observed distribution and we use this to predict future grey squirrel spread. We also present a ‘worst case’ scenario in which grey squirrels experience improved reproductive success due to the availability of high quality habitats beyond the Po plain. In both cases they could disperse along existing continuous woodland corridors into France between 2039–2048. The case of the grey squirrel highlights the problems of implementing conservation conventions and the resulting conflicts between wildlife management, public perception and local political support and the narrow time frame that is available to control alien species effectively before it is too late. If allowed to spread, grey squirrels have the potential of becoming a European forest pest species and are likely to replace the native red squirrel in large parts of its range.