Effects of Tamarix removal on the community dynamics of riparian birds in a semiarid grassland

Invasion of riparian habitats by non‐native plants is a global problem that requires an understanding of community‐level responses by native plants and animals. In the Great Plains, resource managers have initiated efforts to control the eastward incursion of Tamarix as a non‐native bottomland plant (Tamarix ramosissima) along the Cimarron River in southwestern Kansas, United States. To understand how native avifauna interact with non‐native plants, we studied the effects of Tamarix removal on riparian bird communities. We compared avian site occupancy of three foraging guilds, abundance of four nesting guilds, and assessed community dynamics with dynamic, multiseason occupancy models across three replicated treatments. Community parameters were estimated for Tamarix‐dominated sites (untreated), Tamarix‐removal sites (treated), and reference sites with native cottonwood sites (Populus deltoides). Estimates of initial occupancy (ψ₂₀₀₆) for the ground‐to‐shrub foraging guild tended to be highest at Tamarix‐dominated sites, while initial occupancy of the upper‐canopy foraging and mid‐canopy foraging guilds were highest in the treated and reference sites, respectively. Estimates of relative abundance for four nesting guilds indicated that the reference habitat supported the highest relative abundance of birds overall, although the untreated habitat had higher abundance of shrub‐nesters than treated or reference habitats. Riparian sites where invasive Tamarix is dominant in the Great Plains can provide nesting habitat for some native bird species, with avian abundance and diversity that are comparable to remnant riparian sites with native vegetation. Moreover, presence of some native vegetation in Tamarix‐dominated and Tamarix‐removal sites may increase abundance of riparian birds such as cavity‐nesters. Overall, our study demonstrates that Tamarix may substitute for native flora in providing nesting habitat for riparian birds at the eastern edge of its North American range.     

Land use drivers of species re‐expansion: inferring colonization dynamics in Eurasian otters

Aim Land use intensity has been recognized as one of the major determinants of native species declines. The re‐expansion of species previously constrained by habitat degradation has been rarely investigated. Here, we use site occupancy models incorporating imperfect detection to identify the land use drivers of the re‐expansion of the Eurasian otter (Lutra lutra). Location Czech Republic. Methods We applied multi‐season occupancy models to otter presence–non‐detection data collected in three national surveys (1992, 2000, 2006) at 552 sites (11.2 × 12 km grid cells). Model parameters included site occupancy, colonization and extinction probabilities, and detection probability at a sub‐site level. We modelled changes in occupancy over time as a function of agricultural, urban and industrial land use and change in the extent of agricultural land use. Results Under the best fitting model, occupancy was estimated to be 34.6% in 1992, 51.3% in 2000 and 83.7% in 2006. Detection probability was neither perfect nor constant. Occupancy probability in 1992 was negatively related to land use gradients. Colonization was more likely to occur where a reduction in agricultural land was larger. Variation in extinction and colonization rates along land use gradients resulted in increased occupancy in industrial and especially urban landscapes. Conversely, occupancy remained almost unchanged along agricultural gradients. Main conclusions Dynamics of otter expansion were strongly associated with the two main patterns of the rapid environmental transition that has taken place in the Czech Republic since the early 1990s. Results show that a reduction in intensive agricultural land use led to an increase in otter distribution, providing evidence of the impact of agricultural land use on stream ecosystems. Moreover, otters recolonized urban and industrial landscapes, probably as a result of extensive reduction in water pollution from point sources. Our results suggest that active conservation of otter populations should focus on restoration of freshwater habitat at large scales, especially in agricultural landscapes.     

Habitat and introduced predators influence the occupancy of small threatened macropods in subtropical Australia

Australia has had the highest rate of mammal extinctions in the past two centuries when compared to other continents. Frequently cited threats include habitat loss and fragmentation, changed fire regimes and the impact of introduced predators, namely the red fox (Vulpes vulpes) and the feral cat (Felis catus). Recent studies suggest that Australia's top predator, the dingo (Canis dingo), may have a suppressive effect on fox populations but not on cat populations. The landscape of fear hypothesis proposes that habitat used by prey species comprises high to low risk patches for foraging as determined by the presence and ubiquity of predators within the ecosystem. This results in a landscape of risky versus safe areas for prey species. We investigated the influence of habitat and its interaction with predatory mammals on the occupancy of medium‐sized mammals with a focus on threatened macropodid marsupials (the long‐nosed potoroo [Potorous tridactylous] and red‐legged pademelon [Thylogale stigmatica]). We assumed that differential use of habitats would reflect trade‐offs between food and safety. We predicted that medium‐sized mammals would prefer habitats for foraging that reduce the risk of predation but that predators would have a positive relationship with medium‐sized mammals. We variously used data from 298 camera trap sites across nine conservation reserves in subtropical Australia. Both dingoes and feral cats were broadly distributed, whilst the red fox was rare. Long‐nosed potoroos had a strong positive association with dense ground cover, consistent with using habitat complexity to escape predation. Red‐legged pademelons showed a preference for open ground cover, consistent with a reliance on rapid bounding to escape predation. Dingoes preferred areas of open ground cover whereas feral cats showed no specific habitat preference. Dingoes were positively associated with long‐nosed potoroos whilst feral cats were positively associated with red‐legged pademelons. Our study highlights the importance of habitat structure to these threatened mammals and also the need for more detailed study of their interactions with their predators.     

Assessing the conservation value of secondary savanna for large mammals in the Brazilian Cerrado

Debate about the conservation value of secondary habitats has tended to focus on tropical forests, increasingly recognizing the role of secondary forests for biodiversity conservation. However, there remains a lack of information about the conservation value of secondary savannas. Here, we conducted a camera trap survey to assess the effect of secondary vegetation on large mammals in a Brazilian Cerrado protected area, using a single‐season occupancy framework to investigate the response of individual species (species‐level models) and of all species combined (community‐level models). In addition, we investigated the cost effectiveness of different sampling designs to monitor globally threatened species in the study area. At the community level, savanna that regenerated from eucalyptus plantation had similar occupancy estimate as old growth areas. At the species level, none of the ten species individually assessed seemed to respond to succession stage, with greater support for the effect of other covariates on occupancy, such as distance from water and vegetation physiognomy. These results demonstrate that secondary vegetation does not appear to negatively impact large mammals in the study area and suggest that, given a favorable context, Cerrado mammals can recolonize and use secondary savannas that regenerated from clearcut. However, our study area should be considered a best‐case scenario, as it retained key ecological attributes of high‐value secondary habitats. Our simulations showed that a sampling design with 60 camera trap sites surveyed during nine occasions is appropriate to monitor most globally threatened species in the study area, and could be a useful starting point for new monitoring initiatives in other Cerrado areas.     

Distribution and Habitat Use of King Rails in the Illinois and Upper Mississippi River Valleys

ABSTRACT The migratory population of the king rail (Rallus elegans) has declined dramatically during the past 40 years, emphasizing the need to identify habitat requirements of this species to help guide conservation efforts. To assess distribution and habitat use of king rails along the Illinois and Upper Mississippi valleys, USA, we conducted repeated call-broadcast surveys at 83 locations in 2006 and 114 locations in 2007 distributed among 21 study sites. We detected king rails at 12 survey locations in 2006 and 14 locations in 2007, illustrating the limited distribution of king rails in this region. We found king rails concentrated at Clarence Cannon National Wildlife Refuge, an adjacent private Wetlands Reserve program site, and B. K. Leach Conservation Area, which were located in the Mississippi River floodplain in northeast Missouri. Using Program PRESENCE, we estimated detection probabilities and built models to identify habitat covariates that were important in king rail site occupancy. Habitat covariates included percentage of cover by tall (>1 m) and short (>1 m) emergent vegetation, percentage of cover of woody vegetation, and interspersion of water and vegetation (2007 only) within 50 m of the survey location. Detection probability was 0.43 (SE = 0.12) in 2006 and 0.35 (SE = 0.03) in 2007 and was influenced by observer identity and percentage of cover by tall herbaceous vegetation. Site occupancy was 0.11 (SE = 0.04) in 2006 and 0.14 (SE = 0.04) in 2007 and was negatively influenced most by percentage of cover by woody vegetation. In addition, we found that interspersion of vegetation and water was positively related to occupancy in 2007. Thus, nesting king rails used wetlands that were characterized by high water-vegetation interspersion and little or no cover by woody vegetation. Our results suggest that biologists can improve king rail habitat by implementing management techniques that reduce woody cover and increase vegetation-water interspersion in wetlands.     

Effects of fire regime on plant species richness and composition differ among forest,woodland and heath vegetation

Question

Do the effects of fire regimes on plant species richness and composition differ among floristically similar vegetation types?

Location

Booderee National Park, south‐eastern Australia.

Methods

We completed floristic surveys of 87 sites in Sydney Coastal dry sclerophyll vegetation, where fire history records have been maintained for over 55 years. We tested for associations between different aspects of the recent fire history and plant species richness and composition, and whether these relationships were consistent among structurally defined forest, woodland and heath vegetation types.

Results

The relationship between fire regime variables and plant species richness and composition differed among vegetation types, despite the three vegetation types having similar species pools. Fire frequency was positively related to species richness in woodland, negatively related to species richness in heath, and unrelated to species richness in forest. These different relationships were explained by differences in the associations between fire history and species traits among vegetation types. The negative relationship between fire frequency and species richness in heath vegetation was underpinned by reduced occurrence of resprouting species at high fire frequency sites (more than four fires in 55 years). However, in forest and woodland vegetation, resprouting species were not negatively associated with fire frequency.

Conclusions

We hypothesize that differing relationships among vegetation types were underpinned by differences in fire behaviour, and/or biotic and abiotic conditions, leading to differences in plant species mortality and post‐fire recovery among vegetation types. Our findings suggest that even when there is a high proportion of shared species between vegetation types, fires can have very different effects on vegetation communities, depending on the structural vegetation type. Both research and management of fire regimes may therefore benefit from considering vegetation types as separate management units.     

The impact of a fox‐ and cat‐free safe haven on the bird fauna of remnant vegetation in southwestern Australia

Introduced predators are a serious threat to Australian vertebrates. However, the consequences of predation for an area's avifauna have rarely been quantified. We took advantage of the establishment of a 7,832 ha fox‐ and cat‐free safe haven at Mt Gibson, in Western Australia, to assess the consequences of excluding introduced mammal predators on the bird fauna. Bird surveys were conducted over 6 years, before and after the establishment of the introduced predator‐free safe haven. After 3 years, half the sites were enclosed by the fence that excluded introduced predators, while the remainder of sites remained outside the fence and were exposed to fox and cat activity. The sites were stratified by four major vegetation types. A total of 91 bird species were variously detectable with the survey approach, but were typically more detectable during morning surveys. Site occupancy varied considerably among species, but overall, occupancy by all species was most likely to be either not impacted or positively impacted by the safe haven. The most notable change was that avifaunal richness appeared to increase in woodland and shrubland habitats within, as compared to outside, the safe haven. We conclude that: (1) the safe haven had an overall positive impact on bird occupancy; and (2) there were no consistent trends with respect to the kinds of species whose occupancy was positively impacted, beyond them all being small‐ to medium‐sized birds and mostly insectivorous. However, these conclusions must be tempered by the poor detection probability of many species.     

Habitat‐dependent population regulation in an irrupting population of long‐nosed bandicoots (Perameles nasuta)

We used isodars to analyse habitat‐dependent population regulation by long‐nosed bandicoots Perameles nasuta during an irruption and subsequent population crash in three habitats (heath, woodland and forest) at Booderee National Park, south‐eastern Australia. Specifically, we aimed to see whether patterns of habitat‐dependent population regulation matched a priori estimates of quantitative and qualitative differences between habitats. We also tested if habitat preference changed between the increasing and decreasing phase of the irruption as predicted by the reciprocating dispersal theory. Quantitative differences in habitat quality were indexed by the relative abundance of the main food of long‐nosed bandicoots (terrestrial invertebrates), while qualitative differences were indexed by the availability of refuge from predation (vegetation understorey density). One index of fitness, body weight, was highest in forest, and lowest in heath, suggesting an ideal despotic model of habitat selection. Over the entire course of the irruption, there was density‐dependent habitat selection with forest and woodland both quantitatively superior to heath. This reflected the overall abundance of invertebrates with highest abundance in woodland and forest and less in heath. Isodar analysis also revealed that although forest was quantitatively better than heath and equivalent to woodland it was qualitatively poorer than either habitat. Heath had a higher density of understorey than woodland and woodland having a higher density of understorey than forest giving crossover population regulation. When the increasing and declining phase of the irruption were analysed separately, no habitat was quantitatively superior to any other during either phase. The lack of switching in preference between habitats from the increasing to the declining phase of the irruption and the virtual absence of any dispersal by adults, does not support the reciprocating dispersal hypothesis.     

Reference conditions for restoration of heterogeneous Mediterranean wetland are best defined by multiple,hydrologically diverse sites

In a Mediterranean climate, the vegetation of embanked salt marshes can vary considerably in time and space to obscure the definition of reference condition for restoration purposes. The aim of our study was to find a basis for defining reference vegetation for the reinstatement of a wetland hydrological regime on abandoned agricultural land. We investigated five reference sites surrounding a 2,668 ha restoration site in the Doñana National Park (southwest Spain). Environmental conditions were monitored on a sampling grid for 7 years: surface elevation and hydroperiod were mapped (using Light Detection and Ranging [LIDAR] and satellite imagery, respectively) and rainfall, soil salinity, and soil pH were recorded. The reference sites collectively encompassed the range of elevation and environmental conditions at the restoration site, although none individually was representative. The vegetation at the reference sites was sampled annually at fixed grid points. Hierarchical cluster analyses identified assemblages of perennial and annual species that were differently distributed among the reference sites. BIO‐ENV analysis showed that the distribution of perennial assemblages was determined by elevation, annual hydroperiod, and salinity. More labile annual assemblages were loosely associated with particular perennial ones. Species composition fluctuated over 7 years, in concert with rainfall and hydroperiod, but showed no directional change. Understanding the hydrochemical drivers of spatiotemporal variation in vegetation across multiple sites has established a rationale for defining reference conditions for large, heterogeneous wetland restoration sites.     

Species richness and abundance among macromoths: A comparison of taxonomic,temporal and spatial patterns in Oregon and South Korea

The present study aims to establish a long‐term intercontinental collaboration based on a sampling protocol using standardized repeated measures at permanent sites to document macromoth species richness and abundance through time and across the landscape. We pooled the data from two continental regions providing a total of 12 trap sites: Mt. Jirisan National Park in South Korea (2005–2007) and HJ Andrews Experimental Forest in Oregon, USA. (2004–2006). A synthesis of our data indicated that: (i) noctuids (43–52%) and geometrids (33–39%) dominated the measures of species richness; (ii) using our sampling protocols more than three years would be needed to obtain a value of 90% of empirical species richness relative to Chao‐1 estimated species richness; (iii) temperature alone could not explain the peak pattern in moth abundance and species richness; (iv) the highest/lowest proportion of species richness and abundance were present in similar elevation and forest sites. These observations established a foundation for developing a network‐oriented database for assessing biotic impact of environmental and contributed to identifying species at high risk to environmental change based on empirical measures of temporal and spatial breadth.     

Relationship Between Avifaunal Occupancy and Riparian Vegetation in the Central Great Basin (Nevada, U.S.A.)

In western North America, riparian vegetation is being lost in response to changes in land use and climate. We examined the relationship between obligate riparian species of songbirds and environmental and riparian habitat factors in three mountain ranges in the central Great Basin (Nevada, U.S.A.). We estimated patterns of occupancy, colonization, and local extinction for three species detected during the breeding seasons of 2001–2006: MacGillivray's Warbler ( Oporornis tolmiei ), Broad-tailed Hummingbird ( Selasphorus platycercus ), and Song Sparrow ( Melospiza melodia ). We used model selection and multimodel inference to identify functional relationships between the occupancy of each species and multiple habitat variables, including the structure and composition of riparian vegetation. Among all years and species, we observed considerable variation in estimates of detection probability. For MacGillivray's Warbler, annual occupancy rates were relatively constant. Occupancy rates for Broad-tailed Hummingbird and Song Sparrow increased during the first 3–4 years of our study and then decreased. Each species experienced its highest rate of local extinction during 2005. Different components of riparian vegetation were good predictors of occupancy, colonization, and local extinction for each species. Typically, elevation and latitude also were strong predictors. Establishing functional relationships between avifauna and vegetation is essential to predicting how land-cover change may affect the occupancy of riparian areas and other habitats for birds. The conservation of breeding birds in riparian areas in the central Great Basin is more likely to succeed if the quality of their understory habitat as well as the canopy is maintained and restored.     

A dynamic multi‐scale occupancy model to estimate temporal dynamics and hierarchical habitat use for nomadic species

Distribution models are increasingly being used to understand how landscape and climatic changes are affecting the processes driving spatial and temporal distributions of plants and animals. However, many modeling efforts ignore the dynamic processes that drive distributional patterns at different scales, which may result in misleading inference about the factors influencing species distributions. Current occupancy models allow estimation of occupancy at different scales and, separately, estimation of immigration and emigration. However, joint estimation of local extinction, colonization, and occupancy within a multi‐scale model is currently unpublished. We extended multi‐scale models to account for the dynamic processes governing species distributions, while concurrently modeling local‐scale availability. We fit the model to data for lark buntings and chestnut‐collared longspurs in the Great Plains, USA, collected under the Integrated Monitoring in Bird Conservation Regions program. We investigate how the amount of grassland and shrubland and annual vegetation conditions affect bird occupancy dynamics and local vegetation structure affects fine‐scale occupancy. Buntings were prevalent and longspurs rare in our study area, but both species were locally prevalent when present. Buntings colonized sites with preferred habitat configurations, longspurs colonized a wider range of landscape conditions, and site persistence of both was higher at sites with greener vegetation. Turnover rates were high for both species, quantifying the nomadic behavior of the species. Our model allows researchers to jointly investigate temporal dynamics of species distributions and hierarchical habitat use. Our results indicate that grassland birds respond to different covariates at landscape and local scales suggesting different conservation goals at each scale. High turnover rates of these species highlight the need to account for the dynamics of nomadic species, and our model can help inform how to coordinate management efforts to provide appropriate habitat configurations at the landscape scale and provide habitat targets for local managers.     

The importance of incorporating imperfect detection in biodiversity assessments: a case study of small mammals in an Australian region

Aim Assessments of biodiversity are an essential requirement of conservation management planning. Species distributional modelling is a popular approach to quantifying biodiversity whereby occurrence data are related to environmental covariates. An important confounding factor that is often overlooked in the development of such models is uncertainty due to imperfect detection. Here, I demonstrate how an analytical approach that accounts for the bias due to imperfect detection can be applied retrospectively to an existing biodiversity survey data set to produce more realistic estimates of species distributions and unbiased covariate relationships. Location Pilbara biogeographic region, Australia. Methods As a component of the Pilbara survey, presence/absence (i.e. undetected) data on small ground‐dwelling mammals were collected. I applied a multiseason occupancy modelling approach to six of the most common species encountered during this survey. Detection and occupancy rates, as well as extinction and colonization probabilities, were determined, and the influence of covariates on these parameters was examined using the multi‐model inference approach. Results Detection probabilities for all six species were considerably lower than 1.0 and varied across time and species. Naïve estimates of occupancy underestimated occupancy rates corrected for species detectability by up to 45%. Seasonal variation in occupancy status was attributed to changes in detection for two of the focal species, while reproductive events explained variation in occupancy in three others. Covariates describing the substrate strongly influenced site occupancy for most of the species modelled. A comparison of the occupancy model with a generalized linear model, assuming perfect detection, showed that the effects of the covariates were underestimated in the latter model. Main conclusions The application of the multiseason occupancy modelling approach to the Pilbara mammal data set demonstrated a powerful framework for examining changes in site occupancy, as well as local colonization and extinction rates of species which are not confounded by variable species detection rates.     

Competition and specialization in an African forest carnivore community

Globally, human activities have led to the impoverishment of species assemblages and the disruption of ecosystem function. Determining whether this poses a threat to future ecosystem stability necessitates a thorough understanding of mechanisms underpinning community assembly and niche selection. Here, we tested for niche segregation within an African small carnivore community in Kibale National Park, Uganda. We used occupancy modeling based on systematic camera trap surveys and fine‐scale habitat measures, to identify opposing preferences between closely related species (cats, genets, and mongooses). We modeled diel activity patterns using kernel density functions and calculated the overlap of activity periods between related species. We also used co‐occupancy modeling and activity overlap analyses to test whether African golden cats Caracal aurata influenced the smaller carnivores along the spatial and/or temporal axes. There was some evidence that related species segregated habitat and activity patterns. Specialization was particularly strong among forest species. The cats and genets partitioned habitat, while the mongooses partitioned both habitat and activity period. We found little evidence for interference competition between African golden cats and other small carnivores, although weak interference competition was suggested by lower detection probabilities of some species at stations where African golden cats were present. This suggests that community assembly and coexistence in this ecosystem are primarily driven by more complex processes. The studied carnivore community contains several forest specialists, which are typically more prone to localized extinction. Preserving the observed community assemblage will therefore require the maintenance of a large variety of habitats, with a particular focus on those required by the more specialized carnivores.     

Assessing the effectiveness of long-term monitoring of the Broad-toothed Rat in the Barrington Tops National Park,Australia

Biodiversity monitoring is crucial for effective conservation efforts. Effective monitoring allows managers to determine the status and trends of biodiversity, as well as the success of conservation actions. The population of the Broad-toothed Rats (Mastacomys fuscus) in the Barrington Tops National Park New South Wales, Australia has been monitored since 1999 via scat and live-trapping surveys. We reviewed the methods used and analysed the data produced with the aim of describing patterns of population change over time using a range of outcome variables and identifying different climate correlates. A secondary aim was to explore the use of population statistics that account for imperfect detection by comparing naïve occupancy, with an index of relative abundance based on trap effort, the latency to find scats during scat surveys and an occupancy model based on trapping surveys. Neither of these three methods accounts for detectability variation. Naïve occupancy decreased slightly over time, while the relative abundance based on trap effort revealed no evidence of change. Additionally, naïve occupancy decreased with increasing temperature while temperature had no clear impact on relative abundance. Finally, precipitation had no impact on either naïve occupancy or relative abundance. We found no evidence of a relationship between the latency to find scats and the index of relative abundance, suggesting that one or neither is related to actual abundance. Finally, a multi-season occupancy model found occupancy probability to be 0.78 ± 0.23 (standard error); detection probability as 0.51 ± 0.06; seasonal colonisation rate as 0.36 ± 0.13 and seasonal extinction rate at 0.44 ± 0.13. We conclude that despite significant investment in monitoring, this historical data set does not allow managers to ascertain whether population change has occurred and to identify potential drivers of change. Careful consideration of future methods, in particular, whether there is imperfect detection in scat surveys, will help to inform future monitoring.     

Discrepancies in occupancy and abundance approaches to identifying and protecting habitat for an at‐risk species

Predicting how environmental factors affect the distribution of species is a fundamental goal of conservation biology. Conservation biologists rely on species distribution and abundance models to identify key habitat characteristics for species. Occupancy modeling is frequently promoted as a practical alternative to use of abundance in identifying habitat quality. While occupancy and abundance are potentially governed by different limiting factors operating at different scales, few studies have directly compared predictive models for these approaches in the same system. We evaluated how much occupancy and abundance are driven by the same environmental factors for a species of conservation concern, the greater short‐horned lizard (Phrynosoma hernandesi). Occupancy was most strongly dictated by precipitation, temperature, and density of ant mounds. While these factors were also in the best‐supported predictive models for lizard abundance, the magnitude of the effects varied, with the sign of the effect changing for temperature and precipitation. These discrepancies show that while occupancy modeling can be an efficient approach for conservation planning, predictors of occupancy probability should not automatically be equated with predictors of population abundance. Understanding the differences in factors that control occupancy versus abundance can help us to identify habitat requirements and mitigate the loss of threatened species.     

Booderee National Park Management: Connecting science and management

A 10‐year science–management partnership has focussed on three key issues within Booderee National Park in eastern Australia: the impacts of fire on native biota, the response of vertebrates to feral animal control and the control of Bitou Bush. What has been achieved to date and what are the partnership's key ingredients?     

Habitat use by five sympatric Australian freshwater crayfish species (Parastacidae)

1. The Grampians National Park in Victoria is a ‘hot spot’ for freshwater crayfish diversity, with seven species from six genera occurring in sympatry. Few studies have examined how multiple species of freshwater crayfish co‐exist across landscapes consisting of a mosaic of perennial and seasonal habitats. Despite their endemicity and likely key role in freshwaters, the ecology and biology of these crayfish remains unknown. 2. This study determined the distribution and habitat use of five crayfish species (Euastacus bispinosus, Cherax destructor, Geocharax falcata, Gramastacus insolitus and Engaeus lyelli). Seasonal sampling surveys ascertained whether crayfish distribution was related to habitat type, environmental or physicochemical variables, catchment or season. 3. Distribution was directly related to habitat type and the environmental and physicochemical variables that characterised habitats. Engaeus lyelli, G. falcata and G. insolitus occurred predominantly in floodplain wetlands and flooded vegetation habitats, E. bispinosus occurred only in flowing soft‐sediment channels and C. destructor was found in all catchments and habitat types studied. Gramastacus insolitus co‐occurred with G. falcata at all sites except two, so no distinct habitat separations were apparent for these two species. 4. A high percentage cover of boulders was the best indicator of crayfish absence, and discriminated between habitat types and crayfish species: it was probably a surrogate for a larger range of environmental and physicochemical variables. Catchment and season did not affect crayfish distribution. 5. These crayfish species varied in their degree of habitat specialisation from strongly generalist (C. destructor) to occupying only a specific habitat type (E. bispinosus). Some species appeared specialised for seasonal wetlands (G. insolitus and G. falcata). Overlap in site occupancy also varied: G. insolitus and G. falcata distributions were strongly associated, whereas C. destructor appeared to occur opportunistically across habitats, both alone and co‐occurring with all the other species. 6. Management strategies to conserve multiple species of crayfish co‐existing within landscapes will need to incorporate a range of perennial and seasonal habitat types to ensure sufficient space is available for species to maintain different occupancy patterns. Given that water resources are under increasing pressure and are strongly regulated within the Grampians National Park, this may present a conservation challenge to water managers in this location.     

Rapid deterioration of Aquatic Warbler Acrocephalus paludicola habitats at the western margin of the breeding range

In the last German breeding area of the rapidly declining “Pomeranian” population of the Aquatic Warbler (Acrocephalus paludicola), the Lower Oder Valley National Park, we investigated changes in habitat suitability between 1993 and 2006 by combining monitoring results with repeated assessments of vegetation structure and composition, site conditions, and land use. Sites with recent Aquatic Warbler records showed shorter and sparser vegetation, a thinner litter layer, and a higher total plant species richness and cover of small and least competitive (CSR) species than abandoned or unoccupied sites. On a long-term study plot, during a period of late mowing and subsequent cessation of land use, vegetation height increased, the cover of CSR species decreased, and the site became abandoned by Aquatic Warblers. The probability of Aquatic Warbler occurrence was dependent on elevation and increased with the proportion of early mown or grazed area in the preceding year, with early use being most important on slightly higher elevated sites. This rapid deterioration of eutrophic habitats by delayed or discontinued land use is atypical for the majority of Aquatic Warbler breeding habitats. We conclude that both late or no land use and land use during the breeding season negatively affect the Pomeranian breeding sites and that a more sophisticated and flexible land management is urgently needed.