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II Censo Nacional de sisón común: el dramático declive del bastión europeo de la especie
... There, the species is undergoing rapid declines regionally [30][31][32], leading to a global decrease up to 50% of the Spanish population in a decade [33]. Contributing factors to such decline around the world are the loss and degradation of habitat related with agricultural intensification and hunting pressure [34][35][36]. ...
Background
Identifying the factors that affect ranging behavior of animals is a central issue to ecology and an essential tool for designing effective conservation policies. This knowledge provides the information needed to predict the consequences of land-use change on species habitat use, especially in areas subject to major habitat transformations, such as agricultural landscapes. We evaluate inter-individual variation relative to environmental predictors and spatial constraints in limiting ranging behavior of female little bustards (Tetrax tetrax) in the non-breeding season. Our analyses were based on 11 females tracked with GPS during 5 years in northeastern Spain. We conducted deviance partitioning analyses based on different sets of generalized linear mixed models constructed with environmental variables and spatial filters obtained by eigenvector mapping, while controlling for temporal and inter-individual variation.
Results
The occurrence probability of female little bustards in response to environmental variables and spatial filters within the non-breeding range exhibited inter-individual consistency. Pure spatial factors and joint spatial-habitat factors explained most of the variance in the models. Spatial predictors representing aggregation patterns at ~ 18 km and 3–5 km respectively had a high importance in female occurrence. However, pure habitat effects were also identified. Terrain slope, alfalfa, corn stubble and irrigated cereal stubble availability were the variables that most contributed to environmental models. Overall, models revealed a non-linear negative effect of slope and positive effects of intermediate values of alfalfa and corn stubble availability. High levels of cereal stubble in irrigated land and roads had also a positive effect on occurrence at the population level.
Conclusions
Our results provide evidence that female little bustard ranging behavior was spatially constrained beyond environmental variables during the non-breeding season. This pattern may result from different not mutually exclusive processes, such as cost–benefit balances of animal movement, configurational heterogeneity of environment or from high site fidelity and conspecific attraction. Measures aimed at keeping alfalfa availability and habitat heterogeneity in open landscapes and flat terrains, in safe places close to breeding grounds, could contribute to protect little bustard populations during the non-breeding season.
... Recent population trends for Little and Great Bustard in their most important range in south-west Europe. Some examples of regional population trends for both species (more information available inAlonso et al. 2003Alonso et al. , 2005aand Garcia de laMorena et al. 2017).CountryRegionProvince Little Bustard Great Bustard References Trends Period Trends Period Spain Whole country -50% 2005-2016 +25% 1995-2004 García de la Morena et al. 2017; Alonso et al. 2005a Extremadura -75% 1993-2008 -15-20% 1988-2002 De Juana 2009; Alonso et al. 2005a Castilla y León -76% 2005-2016 +34% 1998-2008 García de la Morena et al. 2017; Martin et al. 2012 Madrid -37% 2000-2007 +30% -15% 80s-90s 2000-2015 Morales et al. 2008b; Alonso et al. 2005a; Palacín & Alonso 2018 Cataluña -50% 2002-2014 * * Mañosa et al. 2015 Castilla-La Mancha -46% 2005-2016 1 1 Garcia de la Morena et al. 2017 Albacete 1 1 +40% 1994-2003 Alonso et al. 2005a Ciudad Real 1 1 +329%2001Gosalvez et al. 2002Arredondo- Acero and López-Jamar 2016 Portugal Alentejo -50% 2002 +236% 1995-2002Pinto et al. 2005Silva et al. 2018; Delgado and Moreira 2010 France Western -95% 1978-1996 * * Inchausti and Bretagnolle 2005 1 Data not available for these regions. *Species not present in this region ...
In conservation biology, population monitoring is a critical step, particularly for endangered groups, such as steppe birds in European agrosystems. Long-term population monitoring allows for determination of species population trends and also provides insights into the relative roles that environmental variability and human activities have on priority species. Here, we compare the population trends of two sympatric, closely related farmland bird species, the little and great bustards, in a protected area of Central Spain, which is their main stronghold in Europe. Over 12 years of monitoring, the abundance of little and great bustards shifted in opposite directions in our study area. Little bustard abundance decreased significantly (both males [-56%], and harder-to-detect females [-55%]), while great bustard abundance increased significantly (1800%). Future surveys should be more precise and frequent for little bustards to facilitate evaluating their population status and trends. We recommend annual surveys in 2-3 important locations by region throughout the breeding range for little bustards, while for great bustard the current regional monitoring programs would be sufficient.
... The Little bustard Tetrax tetrax is an endangered palearctic steppe bird, currently listed as 'Near Threatened' globally and 'vulnerable' in Europe (IUCN, 2012;birdLife International, 2016). It is declining rapidly despite of the abundant research attention it has recently received (Morales & Traba, 2016;García de la Morena et al., 2017). It occupies extensive cereal farmland, pastureland and natural steppes (Cramp & Simmons, 1980;Morales et al., 2005;Faria et al., 2012). ...
Traffic noise is an associated effect of roads, potentially impacting wildlife. In the case of birds, it may alter spatial distribution, behavioural responses and physiological status, frequently masking acoustic signals of conspecifics and predators. We analyse how road traffic noise affects habitat selection of Little Bustard males during the breeding season, when they produce brief territorial snort calls. The study site is framed in a typical agrarian area in central Spain, markedly affected by traffic noise. A noise map was built using specific environmental noise modelling software. Habitat in the territories of 26 individualized males (62% of the male population in the study year) was characterized in relation to noise levels, agrarian substrate composition and distance to nearest males. Habitat selection models were performed using MaxEnt, and an averaged model of the first 20 significant ones was generated. The noise map revealed high noise pollution levels for the whole study area (range: 50.13-62.35 dB). Distance to the nearest male was the most important variable in habitat selection models, so that as distance increased suitability decreased, while the effect of traffic noise was nearly negligible. This lack of effect of traffic noise on the habitat selection of Little Bustard males might be explained by the small overlap of their snort call frequency range with that of traffic noise, but it also suggests poor capacity in this bird to cope with recent, anthropogenic disturbance. In this sense, noisy but otherwise suitable habitats could be functioning as ecological traps for this rapidly declining species.
Collision with power lines is a major cause of mortality for many bird species. Understanding the biotic and abiotic factors that increase collision risk is therefore important for implementing mitigation measures to minimize mortality, such as power line rerouting or wire marking. Here, we used collision events registered during - along km of transmission power lines in southern Portugal to analyse spatio-temporal patterns and collision risk factors in two sympatric, threatened, and collision-prone species: the great bustard Otis tarda and the little bustard Tetrax tetrax. The occurrence of collisions was not uniform across space and time, and variations could be explained by the species' ecological requirements, distribution patterns and behaviour. Although both species fly considerable distances between areas of suitable habitat, collisions were far more likely in power line sections with. % (for the little bustard) or. % (for the great bus-tard) of open farmland habitat in the surroundings. Power line configuration was also important: taller pylons and those with a higher number of wire levels posed a higher risk for both species. Wire marking had a small but significant effect for the little bustard, reducing collisions risk. There was, however, no similar effect for the great bustard, possibly a result of limited data. Mitigation measures should be implemented to prevent bustard collisions, including adequate route planning, ideally avoiding areas with. % of open habitat. Line configuration and wire marking are particularly important where such localities cannot be avoided and power lines cross areas with a high proportion of bus-tard habitat, including outside protected areas.
The inherent defencelessness against natural predators of bustards, which have relatively small bills and can neither perch in trees nor take
refuge in water at night, renders them warier than other large-bodied birds. They are therefore dependent on large areas of little-disturbed,
little-developed open country within which they can see and keep danger at a good distance. In Asia (here including Central Asia and Asian
Russia), six species—Little Bustard Tetrax tetrax (IUCN global category Near Threatened), Great Bustard Otis tarda (Vulnerable), Asian Houbara
Chlamydotis macqueenii (Vulnerable), Great Indian Bustard Ardeotis nigriceps (Critically Endangered), Bengal Florican Houbaropsis bengalensis
(Critically Endangered) and Lesser Florican Sypheotides indicus (Endangered)—are already at serious risk of extinction. Great Bustard (of the
nominate race) is struggling to survive in Asian Russia (<200 individuals), Kazakhstan (100–1,000) and China (maximum 52 seen in extensive
surveys, 2014–2016), while in Asian Russia the eastern race dybowskii numbers just 380–430 (with only 5% in protected areas), fewer than 1,000
in Mongolia and 600 in China. Little Bustard is now largely restricted to Kazakhstan and westernmost Asian Russia and, although its status
evidently improved in the 1990s with the post-Soviet abandonment of agriculture in Central Asia, re-intensification of farming is poised to
cause new declines. Asian Houbara has a population claimed to be between 50,000–100,000 individuals, but is certainly declining despite largescale
captive breeding programmes, with one study suggesting an offtake of 27.1% in the years 1994–2008 when the maximum sustainable
level was 7.2%, and another indicating a current annual population decline in Uzbekistan of 9.4%. Great Indian Bustard (<200 birds in the
most recent assessments, some in unviable habitat fragments), Bengal Florican (225–249 males estimated for South Asia; several hundred in
Cambodia) and Lesser Florican (270 males estimated in 2017 compared with 1,103–1,765 in 1994–1999) are all in extreme trouble. Habitat
change, chiefly in the form of rapid and widespread agricultural intensification (mechanisation, chemical applications, overgrazing, increased
fencing and new choices of crop), but also involving infrastructure developments and disturbance, is probably the single biggest threat; only
the semi-desert-dwelling Asian Houbara remains relatively unaffected. Hunting and poaching is a particularly serious threat to Great and Little
Bustards and Asian Houbara, as well as Great Indian Bustard. Powerlines are known to have killed and injured birds of five of the six species
and currently are the most serious cause of mortality to Great Indian Bustards, and problems caused by powerlines are anticipated to intensify
for all species. Predation, most seriously by uncontrolled dogs, has been registered as a strong negative influence on Great Bustard and seems
likely also to affect Little Bustard, Great Indian Bustard and both floricans. The long-term prospects of all six species are extremely bleak unless
their conservation is prioritised and significantly strengthened. Adult survival and productivity are key to the health and recovery of bustard
populations and both need to be improved through well-managed nature reserves (organised along flyways for long-distance migrants),
plus: special protection of areas where males display and around which females are known or expected to breed; continuous unfragmented
landscapes subsidised for low-impact farming with reduced grazing pressure within which the birds’ social dynamics are unconstrained;
the strategic planting of crops favoured by all species; strict and strong regulation of both powerlines and fencing within and beyond those
landscapes; equally strict and strong control of hunting, poaching, dog predation and inappropriate grass-fires; and sustained campaigns of
public awareness and engagement. The model of Castro Verde Special Protection Area in Portugal, where Great and Little Bustard numbers have
multiplied and the livelihoods of communities have been supported through subsidy, provides evidence that practical solutions are possible.
Detailed cataloguing of records and intensive biological research programmes are also needed for all species, together with support for local
conservation groups and scrupulous review of all landscape-related plans to prevent adverse developments. Hunting of Asian Houbara must
come under national systems of control based on an internationally agreed strategy. Governments must now prioritise the conservation of
bustards as the burden of responsibilities is too great for NGOs to bear alone. International coordination and collaboration will, with high levels
of communication, be crucial to success. The setting of time-bound targets is required to spur key staff into rapid action.
ResearchGate has not been able to resolve any references for this publication.