Gerard Bota

Adverse Effects of Capture and Handling Little Bustard

Abstract Capturing wild animals for research or conservation purposes may cause some adverse effects, which is only acceptable if these are outweighed by conservation benefits. We used information from 3 on-going telemetry studies on the endangered little bustard (Tetrax tetrax) in Western Europe to evaluate the risk factors associated with capture and handling. Of 151 telemetered birds, 23 (15.2%) exhibited impaired mobility and coordination after release, probably related to the occurrence of capture myopathy. Among the 23 impaired birds, 10 (43.5%) died before recovering normal mobility (6.6% of all birds captured). Logistic regression analyses identified longer handling time, longer restraint time, use of cannon nets, and capture of juveniles as inducing factors for these disorders. We conclude that little bustard is fairly susceptible to suffering ataxia and paresia after release as a result of restraint associated with capture and manipulation. Researchers can reduce this risk by keeping handling and restraint time below 10–20 minutes, particularly when using cannon nets or when capturing juveniles.

Capture Myopathy in Little Bustards after Trapping and Marking

Four little bustards (Tetrax tetrax) (one adult and three juvenile males), captured with leg nooses and fitted with a backpack radiotag, died after capture. The first bird was found after 16 days with its left foot caught in the harness and died after 1 day. The other birds showed symptoms of capture myopathy after release, such as the difficulty or inability to fly and/or walk. They died after 5, 6, and 8 days, respectively. At necropsy, muscles affected in all cases were those from the legs, and these were diffusely pale and dull, with a soft friable texture. Microscopically these muscles had multiple foci of myofiber fragmentation, loss of striation, and necrosis; a mononuclear cell infiltrate was observed in muscle from two birds. These findings suggest the little bustard is susceptible to capture myopathy and that caution should be exercised during its capture and handling.

Ranging behaviour of little bustard males, Tetrax tetrax, in the lekking grounds

We investigated the ranging behaviour during the breeding season of 18 radiotracked little bustard (Tetrax tetrax) males, a disperse-lekking species inhabiting the cereal pseudo-steppes. The average kernel 95% home range was 60±50 ha and the average cluster 85% area was 17±17 ha. Range structure was as relevant as home range size for explaining the variation in the ranging behaviour of males, which could be partially explained by age, habitat quality and site. Ranging behaviour varied from males defending small and concentrated home ranges with high habitat quality, to males holding larger home ranges composed by several arenas. Our results suggest that social dominance and resource availability may affect ranging behaviour of males during the breeding season. Also, mating systems constraints may play a role on the use of space of males within the lekking ground. The ranging behaviour of a given male may be determined by a tendency to reduce and concentrate the home range as age and social status increase, and several fine-tuning mechanisms adjusting the ranging behaviour to the prevailing environmental or social factors on a given site and year.

Genetic consequences of interglacial isolation in a steppe bird

In response to climate changes that have occurred during Pleistocene glacial cycles, taxa associated to steppe vegetation might have followed a pattern of historical evolution in which isolation and fragmentation of populations occurred during the short interglacials and expansion events occurred during the long glacial periods, in contrast to the pattern described for temperate species. Here, we use molecular genetic data to evaluate this idea in a steppe bird with Palaearctic distribution, the little bustard (Tetrax tetrax). Overall, extremely low genetic diversity and differentiation was observed among eight little bustard populations distributed in Spain and France. Mismatch distribution analyses showed that most little bustard populations expanded during cooling periods previous to, and just after, the last interglacial period (127,000-111,000 years before present), when steppe habitats were widespread across Europe. Coalescent-based methods suggested that glacial expansions have resulted in substantial admixture in Western Europe due to the existence of different interglacial refugia. Our results are consistent with a model of evolution and genetic consequences of Pleistocene cycles with low between-population genetic differentiation as a result of short-term isolation periods during interglacials and long-term exchange during glacial periods.

A Resource-Based Modelling Framework to Assess Habitat Suitability for Steppe Birds in Semiarid Mediterranean Agricultural Systems

European agriculture is undergoing widespread changes that are likely to have profound impacts on farmland biodiversity. The development of tools that allow an assessment of the potential biodiversity effects of different land-use alternatives before changes occur is fundamental to guiding management decisions. In this study, we develop a resource-based model framework to estimate habitat suitability for target species, according to simple information on species’ key resource requirements (diet, foraging habitat and nesting site), and examine whether it can be used to link land-use and local species’ distribution. We take as a study case four steppe bird species in a lowland area of the north-eastern Iberian Peninsula. We also compare the performance of our resource-based approach to that obtained through habitat-based models relating species’ occurrence and land-cover variables. Further, we use our resource-based approach to predict the effects that change in farming systems can have on farmland bird habitat suitability and compare these predictions with those obtained using the habitat-based models. Habitat suitability estimates generated by our resource-based models performed similarly (and better for one study species) than habitat based-models when predicting current species distribution. Moderate prediction success was achieved for three out of four species considered by resource-based models and for two of four by habitat-based models. Although, there is potential for improving the performance of resource-based models, they provide a structure for using available knowledge of the functional links between agricultural practices, provision of key resources and the response of organisms to predict potential effects of changing land-uses in a variety of context or the impacts of changes such as altered management practices that are not easily incorporated into habitat-based models.

Not Only Habitat But Also Sex: Factors Affecting Spatial Distribution of Little Bustard Tetrax tetrax Families

Abstract Species distribution patterns are determined not only by habitat preferences but also by biotic factors. Particularly, the presence of conspecifics may yield different types of benefits and costs for the individuals involved. This study analyses the spatial distribution of Little Bustard families during the breeding season in relation to the distribution of male core areas in three Spanish populations of the species. A compositional analysis is used to evaluate habitat selection and the habitat types most preferred by females with offspring. Spatial analyses were performed to evaluate the proximity of Little Bustard families to male core areas and male displaying sites. The habitat selection pattern was similar between regions, with semi-permanent vegetation and stubbles as most preferred habitats while others, such as ploughed land, were avoided. Families were located closer to male core areas than expected by chance and were spatially associated to male displaying sites. Little Bustard females may obtain different benefits from this spatial association such as access to more food resources and chances for second matings after a clutch loss. Also in stubbles, the capture of prey by chicks would be easier and semi-permanent habitats would serve as shelter. These results highlight the importance of intraspecific interactions in the definition of the habitat selection pattern of females and families. This study shows how spatial point pattern analysis may be a useful tool for integrating landscape and behavioural ecology.

Identifying set-aside features for bird conservation and management in northeast Iberian pseudo-steppes

Capsule Set‐aside (land temporally removed from agricultural production) features and their regional locations influence steppe‐bird species of conservation concern in Catalonia. Aims To identify set‐aside features important to the ecology of four ground nesting species, namely Little Bustard Tetrax tetrax, Stone‐curlew Burhinus oedicnemus, Greater Short‐toed Lark Calandrella brachydactyla and Calandra Lark Melanocorypha calandra. Methods Set‐aside fields were surveyed in four regions of Catalonia (northeast of Spain) for the selected species during the 2004 and 2005 breeding seasons. Set‐aside habitat descriptors (e.g. size, vegetation structure) were collected. Ordination plots and information theoretic methods were used to assess the relationship between the selected bird species, set‐aside features and the regions. Results The region where the set‐aside was located had a strong effect on the abundance of the selected species. In addition, vegetation coverage, field shape of set‐aside and surrounding natural habitats were critical features, but with contrasting effects on the different species. Conclusion Populations of the selected species of conservation concern could be improved by effective management of set‐aside. As selected species responded differently, we recommend that management at local level should take into account the conservation value at a regional level of the protected area for each of the selected species.

Trapping techniques for Little Bustards Tetrax tetrax according to age, sex and season

Capsule We describe four techniques for the capture of Little Bustards according to their age, sex and season, and discuss their adequacy for different research objectives.

Migration Patterns of Iberian Little Bustards Tetrax tetrax

Summary. The term “migratory” refers to animals performing yearly round-trips between breeding grounds and post-breeding areas, whereas the term “sedentary” refers to those remaining the whole year in their breeding grounds. However, migration is a complex and varying phenomenon governed by genetic and environmental factors, particularly in species with wide distribution ranges. Here we describe and classify the seasonal movement patterns of 71 little bustards Tetrax tetrax, an endangered Palearctic steppe bird, radio- and satellite-tracked in the Iberian Peninsula. Four major movement patterns were identified, with 89% of little bustards behaving as migrants, among which 75% (summer migrants and summer-winter migrants) performed their first movement after breeding during the summer (mainly between May and July), whereas 14% (winter migrants) left their breeding sites in autumn (mainly between September and November). The remaining 11% were strictly sedentary. On average, summer migration started on June 14th, and winter migration on October 3rd, while pre-breeding migration started on March 23rd. Summer migration occurred in most Iberian regions, although it was mainly found in semiarid Mesomediterranean areas. Winter migration occurred only in the northern half of the Peninsula, being the only pattern found in Subatlantic and highland areas. All winter migrants wintered in Thermomediterranean localities of southern Iberia. The sedentary pattern was found only in the Semiarid Mesomediterranean and Thermomediterranean sectors. This is a good example of complex intraspecific variation in the migratory behaviour of a species that occupies a diverse range of environments. The variability of movement patterns of Iberian little bustards is much greater than previously thought and should be taken into account in conservation programmes for the species.

Fallow management for steppe bird conservation: the impact of cultural practices on vegetation structure and food resources

The potential of fallow lands to favor farmland bird conservation is widely recognized. Since fallows provide key resources for birds within the agricultural matrix, such as nesting sites, shelter and forage, complete understanding of the effect of field-management strategies on vegetation structure and food is essential to fulfill bird requirements and improve habitat management. In this study we experimentally compare the most common field practices (ploughing, shredding, herbicide application and cover cropping) on fallow lands by assessing the resources they provide for birds in terms of vegetation structure and food resources (leaf and seed availability), as well as the economic costs of their implementation. Fallow management treatments are ranked for six target species in a lowland area of the north-eastern Iberian Peninsula, according to the available information on their requirements. The different agronomic practices offer various quantities and types of resources, highlighting the importance of fallow management in bird conservation. Shredding and early herbicide application (February) are estimated to be good practices for Little Bustard (Tetrax tetrax) and Calandra Lark (Melanocorypha calandra), providing both favorable habitat and foraging conditions, while being economical. Meanwhile, superficial tillage in spring is found to be optimum for the rest of the species tested, despite being among the poorest food providers. Alternating patches of the best treatments would improve the effectiveness of agri-environmental schemes by maximizing the harboring habitat for the endangered species.