Migration of wild and captive‐bred Little Bustards Tetrax tetrax: releasing birds from Spain threatens attempts to conserve declining French populations

Populations of the Little Bustard Tetrax tetrax in the farmlands of Europe have declined greatly over the last century. In Western Europe, France now holds the only remaining migratory population, which currently numbers fewer than 300 displaying males. However, the movements of these birds are virtually unknown, in spite of the important implications of this information for the conservation of this species. We identified migratory movements and overwintering areas of French migratory populations, using wild individuals fitted with satellite or radio‐transmitters. Little Bustards completed their migration journey over a relatively short time period (2–5 days), with nocturnal migration flights of 400–600 km per night. All birds overwintered in Iberia. In addition, we tested the consequences of captive rearing on migratory movements. French wild adults and French captive‐bred juveniles behaved similarly with regard to migration, suggesting that hand‐raising does not alter migratory movements. However, birds originating from eggs collected in Spain and reared in western France did not migrate, suggesting a genetic component to migratory behaviour. These results therefore suggest that a conservation strategy involving the release in France of birds hatched from eggs collected in Spain may imperil the expression of migratory movements of the French population. More generally, to maintain the integrity of native populations, the introduced individuals should mimic their migratory movements and behaviour.     

Between‐year variations in Little Bustard Tetrax tetrax population densities are influenced by agricultural intensification and rainfall

The Little Bustard is suffering a widespread population decline mainly due to agricultural intensification. This study evaluates the effects of intensification level, habitat availability and rainfall on the population dynamics of this species. The population density of males was monitored for 7 years (2002–2008) at 184 points located within three sites with contrasting levels of agricultural intensification in southern Portugal. Densities decreased along the intensification gradient from 8.2 to 2.3 males / km². Overall, there was an approximately 50% population decline during the period 2002–2008, driven by a decline observed in one of the less intensive sites, whereas in the other two sites densities remained fairly constant. Yearly variations in male densities were influenced by intensification level, amount of grassland habitat and rainfall patterns. Thus, agricultural intensification is having a negative effect on population densities of this threatened species, particularly through the loss of grasslands (fallow fields and pastures) suitable for displaying males. The results also suggest a positive impact of rainfall on male densities, although this is more likely in grasslands within less intensive agricultural regions of poorer soil quality, where higher breeding male densities occur. Grassland habitat quality, driven by both climate and human management, probably plays a major role in the population dynamics of this threatened steppe bird in its strongholds.     

Testing a novel agri‐environment scheme based on the ecology of the target species,Montagu's Harrier Circus pygargus

Farmland birds are in steep decline and agri‐environment schemes (AES) to counteract these biodiversity losses are expensive and inefficient. Here we test a novel AES, ‘Birdfields’, designed using detailed ecological knowledge of the target species, Montagu's Harrier Circus pygargus. Current AES, such as field margins, that aim to improve foraging conditions (i.e. vole densities) for harriers are inefficient, as prey are difficult to capture in tall set‐aside habitat. ‘Birdfields’ combines strips of set‐aside to boost vole numbers and strips of alfalfa, as voles are accessible after alfalfa has been harvested. We found that vole numbers were generally highest in set‐aside. Montagu's Harriers fitted with GPS‐loggers used ‘Birdfields’ intensively after mowing, preferring mown to unmown strips. Thus, prey availability appeared more important than prey abundance. Thus, ‘Birdfields’, as a targeted AES for Montagu's Harriers, is more effective than previous AES due to increased prey accessibility. An additional advantage of ‘Birdfields’ is that it is considerably cheaper, due to the harvest of alfalfa. We advocate that AES should always include monitoring and research activities, aiming at a more adaptive conservation approach.     

Softening the agricultural matrix: a novel agri‐environment scheme that balances habitat restoration and livestock grazing

The loss and degradation of woody vegetation in the agricultural matrix represents a key threat to biodiversity. Strategies for habitat restoration in these landscapes should maximize the biodiversity benefit for each dollar spent in order to achieve the greatest conservation outcomes with scarce funding. To be effective at scale, such strategies also need to account for the opportunity cost of restoration to the farmer. Here, we critique the Whole‐of‐Paddock Rehabilitation program, a novel agri‐environment scheme which seeks to provide a cost‐effective strategy for balancing habitat restoration and livestock grazing. The scheme involves the revegetation of large (minimum 10 ha) fields, designed to maximize biodiversity benefits and minimize costs while allowing for continued agricultural production. The objectives and design of the scheme are outlined, biodiversity and production benefits are discussed, and we contrast its cost‐effectiveness with alternative habitat restoration strategies. Our analysis indicates that this scheme achieves greater restoration outcomes at approximately half the cost of windbreak‐style plantings, the prevailing planting configuration in southeastern Australia, largely due to a focus on larger fields, and the avoidance of fencing costs through the use of existing farm configuration and infrastructure. This emphasis on cost‐effectiveness, the offsetting of opportunity costs through incentive payments, and the use of a planting design that seeks to maximize biodiversity benefits while achieving production benefits to the farmer, has the potential to achieve conservation in productive parts of the agricultural landscape that have traditionally been “off limits” to conservation.     

Sex‐dependent habitat selection in a high‐density Little Bustard Tetrax tetrax population in southern France,and the implications for conservation

Conservation measures often rely on habitat management, so knowledge about a species’ habitat use is a prerequisite for effective conservation planning. The Little Bustard Tetrax tetrax, a medium‐sized bird native to the Palaearctic steppes and today found in extensively farmed habitats, is a threatened species. Its population experienced a 94% decline in farmland habitats in France between 1982 and 1996, and populations all over Europe have suffered equally sharp declines. Due to this steep negative trend, this species has been the subject of a number of habitat selection studies in order to develop relevant conservation measures based on its habitat requirements. In this study, we investigated the habitat selection of a range of habitat types by both sexes and at two nested spatial scales: plot scale and landscape scale. In addition, we analysed intra‐specific social interactions by incorporating conspecific density in the statistical models of habitat use. The study was conducted on a very high‐density population, perhaps the highest ever recorded for this species at around 50 Bustards per 100 ha of suitable habitat. Our methodology combined two field approaches (point counts and quadrat counts). The findings showed rather limited sexual dimorphism in terms of habitat selection at a local scale, with only vegetation height differing between sexes at a micro‐habitat scale, no selection at landscape scale, and a prevailing role of social factors at both scales. The implications for future conservation strategies in relation to population density and landscape composition are discussed.     

Identifying Core Areas in a Species’ Range Using Temporal Suitability Analysis: an Example Using Little Bustards <Emphasis Type="Italic">Tetrax Tetrax</Emphasis> L. in Spain

Variations in habitat quality impact on breeding success, leading to strong selection pressure for the best sites to be occupied first during a population increase and last during a decline. Coupled with dispersal and metapopulation processes, the result is that snapshot surveys of wildlife distributions may fail to reveal core areas that conservation seeks to protect. At a local scale, territory occupancy is a good indicator of quality but data are not readily available to assess occupancy for rarer species, in remote areas, and over large spatial extents. We introduce temporal suitability analysis as a way to generate an analogue of occupancy from a single survey and illustrate it using data on the little bustard in Spain. We first used Generalised Additive Modelling (GAM) to build a predictive distribution model using Geographic Information System (GIS) coverages and satellite imagery, and then applied the model retrospectively to a time series of satellite images to produce one distribution map for each year. These annual maps differed in the extent of Spain predicted as suitable for little bustards. By overlaying the maps, we identified areas predicted as suitable in one to n years. We show that this temporal suitability map correlates with a conventional habitat suitability map based on a single year but contains extra information on hierarchical use of habitats and the lag between suitability and use. The technique may be applied at a variety of spatial scales to reveal changes in expected occupancy as land use or external factors determining land cover types vary over time.     

Targeted agri‐environment schemes significantly improve the population size of common farmland bumblebee species

Changes in agricultural practice across Europe and North America have been associated with range contractions and local extinction of bumblebees (Bombus spp.). A number of agri‐environment schemes have been implemented to halt and reverse these declines, predominantly revolving around the provision of additional forage plants. Although it has been demonstrated that these schemes can attract substantial numbers of foraging bumblebees, it remains unclear to what extent they actually increase bumblebee populations. We used standardized transect walks and molecular techniques to compare the size of bumblebee populations between Higher Level Stewardship (HLS) farms implementing pollinator‐friendly schemes and Entry Level Stewardship (ELS) control farms. Bumblebee abundance on the transect walks was significantly higher on HLS farms than ELS farms. Molecular analysis suggested maximum foraging ranges of 566 m for Bombus hortorum, 714 m for B. lapidarius, 363 m for B. pascuorum and 799 m for B. terrestris. Substantial differences in maximum foraging range were found within bumblebee species between farm types. Accounting for foraging range differences, B. hortorum (47 vs 13 nests/km²) and B. lapidarius (45 vs 22 nests/km²) were found to nest at significantly greater densities on HLS farms than ELS farms. There were no significant differences between farm type for B. terrestris (88 vs 38 nests/km²) and B. pascuorum (32 vs 39 nests/km²). Across all bumblebee species, HLS management had a significantly positive effect on bumblebee nest density. These results show that targeted agri‐environment schemes that increase the availability of suitable forage can significantly increase the size of wild bumblebee populations.     

Rapid recovery of a population of the cryptic and evolutionarily distinct Hochstetter's Frog,Leiopelma hochstetteri,in a pest‐free environment

New Zealand's native frogs (genus Leiopelma) display a very high degree of endemism and belong to a distinctive and ancient evolutionary lineage. All four extant species are considered to be threatened or endangered, but the mechanisms behind their decline are poorly understood. Many of the potential factors causing population declines are confounded for the two species living on the mainland; in particular, habitat degradation and the presence of introduced mammalian pests have been difficult to disentangle in the past. Here we present data on a population of Hochstetter's Frog (Leiopelma hochstetteri) living in a pest‐free mainland sanctuary, the 3363‐ha Maungatautari Ecological Island. Survey data from this population shows a fourfold increase in numbers between 2009 and 2012 from a very low initial density. Our results suggest that for Hochstetter's Frog at least, and possibly the other mainland species of Leiopelma, introduced mammals are a major driving factor in population declines. Given that the frog population at Maungatautari was discovered by serendipity when planning for the pest‐free sanctuary was already well underway, this also highlights the conservation value of large pest‐free areas and ecosystem‐level management.     

Rapid commencement of ecosystem recovery following aerial baiting on sub‐Antarctic Macquarie Island

Introduced rabbits have severely impacted the terrestrial ecosystem of sub‐Antarctic Macquarie Island. Here we describe first observations of rapid recovery of an important plant species following the commencement of a vertebrate pest eradication plan. The tussock grass Poa foliosa, a major component of the Macquarie Island landscape, has been severely impacted by rabbit grazing with large‐scale reductions in cover across the island observed at times over the last 50 years. Preliminary aerial baiting for rabbits and rodents commenced in winter 2010, and within 6 months, we observed substantial regrowth of tussock grass. The rapid re‐emergence of this grass over such a short time period following localised removal of rabbits has positive implications for the island’s recovery and provides insight for restoration monitoring.     

Conservation insights from changing associations between habitat,territory distribution and mating system of Corn Buntings Emberiza calandra over a 20‐year population decline

Associations between habitat and animal distributions are widely used to make conservation recommendations. However, short‐term studies do not allow investigation of temporal variation in associations as habitats change or populations decline. Here we quantify changes in the habitat attributes and distribution of breeding territories in a multiple‐brooded, crop‐nesting farmland bird, the Corn Bunting Emberiza calandra, over a 20‐year period during which the study population declined by 91%. Corn Buntings were positively associated with weedy fields, overhead wires, spring cereals and, in early summer, with winter barley and forage grass. Territory associations with wires (positive) and fallow (positive in early summer, negative in late summer) were stronger in later years when the population was smaller. Trends in the proportions of males holding territories into late summer (decline), and mated polygynously or not at all (increases), suggested that habitat quality declined and became more spatially variable in later years. Field size increased and weed abundance within fields declined, reducing the availability of field‐boundary song‐posts, invertebrate‐rich foraging habitats and physical cover for nests within crops. Conservation recommendations are for weed‐rich or under‐sown spring cereals and winter barley combined with late‐cut hay and fallow, especially when offered close to song‐posts such as overhead wires. We also demonstrate the value of long‐term studies by comparing our 20‐year analysis with 3‐year periods at the start, middle and end of this period, and expose some risks of conservation recommendations derived from short studies.     

Multiple estimates of effective population size for monitoring a long‐lived vertebrate: an application to Yellowstone grizzly bears

Effective population size (N_e) is a key parameter for monitoring the genetic health of threatened populations because it reflects a population's evolutionary potential and risk of extinction due to genetic stochasticity. However, its application to wildlife monitoring has been limited because it is difficult to measure in natural populations. The isolated and well‐studied population of grizzly bears (Ursus arctos) in the Greater Yellowstone Ecosystem provides a rare opportunity to examine the usefulness of different N_e estimators for monitoring. We genotyped 729 Yellowstone grizzly bears using 20 microsatellites and applied three single‐sample estimators to examine contemporary trends in generation interval (GI), effective number of breeders (N_b) and N_e during 1982–2007. We also used multisample methods to estimate variance (N_eV) and inbreeding N_e (N_eI). Single‐sample estimates revealed positive trajectories, with over a fourfold increase in N_e (≈100 to 450) and near doubling of the GI (≈8 to 14) from the 1980s to 2000s. N_eV (240–319) and N_eI (256) were comparable with the harmonic mean single‐sample N_e (213) over the time period. Reanalysing historical data, we found N_eV increased from ≈80 in the 1910s–1960s to ≈280 in the contemporary population. The estimated ratio of effective to total census size (N_e/N_c) was stable and high (0.42–0.66) compared to previous brown bear studies. These results support independent demographic evidence for Yellowstone grizzly bear population growth since the 1980s. They further demonstrate how genetic monitoring of N_e can complement demographic‐based monitoring of N_c and vital rates, providing a valuable tool for wildlife managers.     

Growth,development, and life‐history strategies in an unpredictable environment: case study of a rare hoverfly Blera fallax (Diptera,Syrphidae)

1. Development in organisms can vary in response to fluctuating environments. In holometabolous insects, variation in adult phenotypic traits is strongly influenced by growth conditions experienced by larvae. The main aim of this study was to assess how much environmental insight can be gained from analysis of the phenotypic changes in an insect's life history parameters in response to realistic food limitations. 2. This investigation was motivated by a need for more information about the developmental requirements of the endangered pine hoverfly Blera fallax (Linnaeus) (Diptera, Syrphidae) in Scotland. Blera fallax depends on a scarce and often ephemeral habitat, rot holes of Scots pine Pinus sylvestris L. stumps. We studied how rearing conditions affected growth in captive larvae, and compared these responses with a wild population. 3. The growth curve observed in the field was similar to that in resource‐limited, lab conditions, suggesting that resources are limiting in nature. The effects of resource availability on development time and body size depended on sex. Adult females were larger but had more variable size at maturity compared with males. In contrast, males typically were not smaller in resource‐limited conditions, but rather continued to develop for another year. Between 2% and 20% of larvae extended development over 2 years regardless of growth conditions, perhaps indicating a semivoltine strategy to circumvent extinction during years with a low breeding success. 4. These results identify life history traits that may be important for other saproxylic Diptera in rot holes, and organisms that experience food restrictions during growth.