Otis Tarda Research Articles

Intraspecific and interspecific competition induces density-dependent habitat niche shifts in an endangered steppe bird.

Interspecific competition is a dominant force in animal communities that induces niche shifts in ecological and evolutionary time. If competition occurs, niche expansion can be expected when the competitor disappears because resources previously inaccessible due to competitive constraints can then be exploited (i.e., ecological release). Here, we aimed to determine the potential effects of interspecific competition between the little bustard (Tetrax tetrax) and the great bustard (Otis tarda) using a multidimensional niche approach with habitat distribution data. We explored whether the degree of niche overlap between the species was a density‐dependent function of interspecific competition. We then looked for evidences of ecological release by comparing measures of niche breadth and position of the little bustard between allopatric and sympatric situations. Furthermore, we evaluated whether niche shifts could depend not only on the presence of great bustard but also on the density of little and great bustards. The habitat niches of these bustard species partially overlapped when co‐occurring, but we found no relationship between degree of overlap and great bustard density. In the presence of the competitor, little bustard's niche was displaced toward increased use of the species' primary habitat. Little bustard's niche breadth decreased proportionally with great bustard density in sympatric sites, in consistence with theory. Overall, our results suggest that density‐dependent variation in little bustard's niche is the outcome of interspecific competition with the great bustard. The use of computational tools like kernel density estimators to obtain multidimensional niches should bring novel insights on how species' ecological niches behave under the effects of interspecific competition in ecological communities.

Scanning Electron Microscopic Observations of the Digestive Canal of the Great Bustard (Otis Tarda)

This study focussed on the microstructure of the digestive canal of the Great Bustard ( Otis tarda). Under scanning electron microscopy (SEM), different morphological plicae (rounded protrusions about 10 μm in height) were observed at different locations along the inner surface of the oesophagus. Concentrated microvilli can be seen on the surface of the protrusions in high-power fields. There are papillae in the mucosal fold on the inner surface of the glandular stomach, with openings of about 250 μm in diameter. In high-power fields, the tops of rod cells could be seen in somewhat circular forms with microvilli on them. Inside the muscular stomach, the scraggly- or wavy-formed surface of the cuticle layer could be seen. Stripping off the cuticle layer, at the tops of mucosal folds row- or rope-like forms could be seen. The mucosa of the small intestine is thrown into ridges running longitudinally in a zigzag pattern along the intestine, rather than the finger-like intestinal villi observed in mammals. There are villi on the inner surface of the caecum with impressions on their domes (the troughs between which have diameters of about 200 μm). Villi on the inner surface of the rectum are even thicker, ranging from 200–500 μm in diameter, and could be seen on the inner surface of the caecum and rectum. Outlines of cell domes are clearer on the inner surface of the caecum than those on the rectum. Studies on the fine structures of the inner surface of the Great Bustard digestive canal will enrich the knowledge of the comparative histology of birds, and provide a reference for raising bustards, as well as preventing and curing its diseases.

Modelling the spatial variation of vital rates: An evaluation of the strengths and weaknesses of correlative species distribution models

AbstractAimSpecies distribution models based on breeding occurrence data allow for identifying both environmental drivers and geographic areas potentially relevant for breeding. However, the interpretation of model predictions in terms of reproductive performance should be further investigated, as this information is crucial for conservation planning. We evaluated the strengths and weaknesses of a correlative modelling approach based on breeding occurrence data (presence–absence) against another approach based on vital rates’ data (breeding success) for gaining insights on species persistence in the case of Great Bustards (Otis tarda).LocationSpain.MethodsBreeding occurrence and breeding success were independently modelled using generalized linear models and multimodel inference analyses. Sensitivities to the way in which the population parameter (breeding success) was defined were explored by building five versions of the dependent variable. We evaluated differences in model performance and identified areas of congruence for breeding occurrence and breeding success.ResultsThe agreement between the spatial predictions achieved by breeding occurrence and breeding success models differed substantially across databases, with the largest differences in occupied breeding areas. The deviance explained by the breeding occurrence model was 64.98% and ranged from 7.83% to 62.27% for the breeding success models. Model performance was higher for models calibrated within potential than within occupied breeding areas.Main conclusionsThe combination of data on both breeding occurrence and breeding success into a species distribution modelling framework showed the limitations of breeding occurrence models for inferring reproductive parameters. The definition of the population parameter as dependent variable was a key factor that strongly affected the inference of vital rates’ models. The approach allowed for discriminating between areas and landscape attributes necessary for the long‐term species persistence from others that may be relevant, but not so much for reproductive performance.

The great bustard reintroduction trial: a response to Ashbrook et al.

The great bustard reintroduction trial: a response to Ashbrook et al.

Genetic structure and population history of wintering Asian Great Bustard (Otis tarda dybowskii) in China: implications for conservation

Wintering areas affect population processes and genetic structuring of many bird species. The Asian Great Bustard (Otis tarda dybowskii) is declining across its range as its breeding and wintering grounds become more fragmented. No genetic information for this vulnerable subspecies in the wild exists. We used noninvasive fecal sampling and mitochondrial sequencing to quantify the level of genetic diversity and the extent of genetic differentiation within and among the wintering populations. Bayesian skyline plot (BSP) analysis was conducted to assess changes in population size over the last several thousand years. Overall, 17 haplotypes were identified in 101 individuals from six wintering grounds, with mean haplotype diversity of 0.90 ± 0.02. Significant population differentiation among wintering grounds was observed [population pairwise test (ΦST) = 0.13, p < 0.001], with genetic differentiation associated with geographical distance (R2 = 0.26, p < 0.05) and pairwise tests consistent with some degree of population admixture. The BSP exhibited a gradual increase in effective population size beginning around 28,000 years ago, but a decrease starting approximately 4000 years ago. Given that China has the most important wintering grounds for the Asian Great Bustard, and that these are becoming increasingly fragmented, it is likely necessary to establish more protected areas to facilitate the protection and monitoring of wintering Great Bustards.

Food Availability But Not Sex Determines Morning Foraging Area Size in the Great Bustard Otis tarda, the Most Sexually Size-Dimorphic Bird Species

Summary. Sexual size dimorphism (SSD) may favour physiological peculiarities in diet, behaviour and home-range size both across species and within species. Sex-specific differences in diet and behaviour have been reported in several bird species but there are fewer studies of foraging area size in sexually dimorphic bird species. Foraging area size should be greater in the bigger sex according to home-range size predictions based on body mass. We tested this prediction in a winter study of foraging area size in the Great Bustard Otis tarda, the most sexually size-dimorphic bird species, which forages in unisexual flocks. In this species the temporal pattern of a flock's feeding intensity; the proportion of birds actively feeding (FI) and the size of the morning foraging area (MFA) of each sex are unknown. We recorded the behaviour and movements of unisexual flocks of Great Bustards during winter mornings and sampled food availability to take into account its effect on FI and MFA. FI increased and then dec...

La explotación de las aves en época romana en la península Ibérica

The scarce published studies on bird bones in the Iberian Peninsula have led to the identification of less than nine hundred remains from 38 roman sites. They correspond to an important number of species, even if most of them are only represented by 1 to 5 specimens. The comparison with the birds mentioned in written sources reveals the absence of Porphyrio porphyrio, Francolinus francolinus and Fulica atra, among others. The predominant species with 77 % of the remains is domestic fowl (Gallus gallus), followed by the red-legged partridge (Alectoris rufa), the grey partridge (Perdix perdix), the greylag goose (Anser anser) and the rock dove (Columba livia). Some finds may indicate the consumption of large species like Otis tarda or Grus grus.

Nest site selection of the Great Bustard (Otis t. tarda) in Körös-Maros National Park, Eastern Hungary

Abstract In the present study we aimed to identify factors influencing the spatial distribution of Great Bustard (Otis t. tarda) nests found between 1998 and 2015 in Dévaványa-Ecseg area in Körös-Maros National Park. During the study period covering 17 years, we obtained information on 536 nests, which shows that Great Bustards used the following grassland crop types for breeding: wheat (43.07%), grassland (23.3%), fallow land (14.45%) and alfalfa (7.67%). These nests were found during the following activities: chemical weed control (33.63%), hay-cutting (25.37%), disking (8.55%) and harvesting (7.08%) and other 18 types of activities. To identify the effects of disturbance and environmental factors on the spatial distribution of nests, such as distances to lek sites, roads, settlements and altitude, we formulated generalized linear models. As a result, we found that nest sites were significantly closer to lek sites and farther from human settlements than expected by random sampling. Our results may contribute to the understanding of Great Bustard nest distributions, which can be helpful in nest detection prior to the initiation of disturbing agricultural activities, which is a key issue in the conservation of this bird. This study opens the way to analyse the effects of other environmental factors such as anthropogenic linear objects.

Changes in bird-migration patterns associated with human-induced mortality.

Many bird populations have recently changed their migratory behavior in response to alterations of the environment. We collected data over 16 years on male Great Bustards (Otis tarda), a species showing a partial migratory pattern (sedentary and migratory birds coexisting in the same breeding groups). We conducted population counts and radio tracked 180 individuals to examine differences in survival rates between migratory and sedentary individuals and evaluate possible effects of these differences on the migratory pattern of the population. Overall, 65% of individuals migrated and 35% did not. The average distance between breeding and postbreeding areas of migrant individuals was 89.9 km, and the longest average movement of sedentary males was 3.8 km. Breeding group and migration distance had no effect on survival. However, mortality of migrants was 2.4 to 3.5 times higher than mortality of sedentary birds. For marked males, collision with power lines was the main cause of death from unnatural causes (37.6% of all deaths), and migratory birds died in collisions with power lines more frequently than sedentary birds (21.3% vs 6.3%). The percentage of sedentary individuals increased from 17% in 1997 to 45% in 2012. These results were consistent with data collected from radio-tracked individuals: The proportion of migratory individuals decreased from 86% in 1997-1999 to 44% in 2006-2010. The observed decrease in the migratory tendency was not related to climatic changes (temperatures did not change over the study period) or improvements in habitat quality (dry cereal farmland area decreased in the main study area). Our findings suggest that human-induced mortality during migration may be an important factor shaping the migration patterns of species inhabiting humanized landscapes.

On Otis tarda and Marquis de Sade: what motivates male Great Bustards to consume Blister Beetles (Meloidae)?

Blister Beetles (Meloidae), invertebrates that can synthesize high doses of the protein phosphatase inhibitor cantharidin, are ingested preferentially by male Great Bustards (Otis tarda) during their mating season. Previous authors hypothesized that the bustards benefit from antihelminthic and antimicrobial properties of cantharidin. However, given that the ingestion of Blister Beetles is performed particularly in mating season, it may be that the cantharidin has more important direct effects on male behavior, possibly by increasing sexual arousal of males. Thus, we propose that cantharidin consumption by male Great Bustards is a form of self-medication to increase courtship display, willingness to participate in pre-breeding male–male competitions at leks, display intensity, and mating success.

Dietary divergence in the most sexually size-dimorphic bird

ABSTRACT In sexually size-dimorphic species, physiological constraints derived from differences in body size may determine different food requirements and thus a trophic niche divergence between males and females. These relationships between sexual size dimorphism (SSD) and dietary overlap are not well understood in birds. We analyzed differences between the sexes in diet composition, dietary diversity, diet selection, and volume and density of droppings, as well as the dietary overlap between sexes, in the Great Bustard (Otis tarda), the species showing the highest SSD among birds. We discuss the differences that we found in relation to various predictions derived from ecological and physiological differences between the sexes, under the hypothesis that these differences are ultimately determined by the strong SSD of this species. As expected, our best linear mixed-effects food selection models included sex as a main factor explaining differences in diet composition and dietary diversity of Great Bustard...

Assessing the extinction risk of the great bustard Otis tarda in Africa

We studied the dynamics and trend of the last extant population of great bustards Otis tarda in Africa. Moroccan great bustards are the southernmost population of this species, and thus show the characteristics of a peripheral population: small size, isolation and low gene flow. Available counts indicate a severe population decline (62% in the last 15 yr), as well as a contrac- tion of the species' distribution. We used a population viability analysis (PVA) to evaluate the quasi-extinction risk and to identify the most important threats. The estimated geometric growth rate of the more realistic of a set of possible scenarios was 0.87 (95% CI: 0.85, 0.89). This implies a 13% annual decline over 50 yr. However, projections derived from these results should be inter- preted with caution, because models have a great deal of uncertainty and vital rates from Iberian populations may be different from those of the Moroccan population. PVA showed the negative consequence of human-induced mortality. According to the model that best fits our census data and if present threats remain in the coming years, this peripheral population could go extinct in ca. 20 yr. Agricultural intensification, infrastructure developments and new power lines in rural areas where the species occurs are causing habitat destruction and fragmentation and increasing artifi- cial mortality. Urgent conservation measures, especially to reduce human-induced mortality, are needed to save African great bustards from extinction. We suggest that these findings can be gen- eralized to other peripheral great bustard populations living in highly humanized landscapes.

Genetic structure of the threatened West-Pannonian population of Great Bustard (Otis tarda).

The genetic diversity, population structure and gene flow of the Great Bustards (Otis tarda) living in Austria-Slovakia-West Hungary (West-Pannonian region), one of the few populations of this globally threatened species that survives across the Palaearctic, has been assessed for the first time in this study. Fourteen recently developed microsatellite loci identified one single population in the study area, with high values of genetic diversity and gene flow between two different genetic subunits. One of these subunits (Heideboden) was recognized as a priority for conservation, as it could be crucial to maintain connectivity with the central Hungarian population and thus contribute to keeping contemporary genetic diversity. Current conservation efforts have been successful in saving this threatened population from extinction two decades ago, and should continue to guarantee its future survival.

Forecasting Large-Scale Habitat Suitability of European Bustards under Climate Change: The Role of Environmental and Geographic Variables.

We modelled the distribution of two vulnerable steppe birds, Otis tarda and Tetrax tetrax, in the Western Palearctic and projected their suitability up to the year 2080. We performed two types of models for each species: one that included environmental and geographic variables (space-included model) and a second one that only included environmental variables (space-excluded model). Our assumption was that ignoring geographic variables in the modelling procedure may result in inaccurate forecasting of species distributions. On the other hand, the inclusion of geographic variables may generate an artificial constraint on future projections. Our results show that space-included models performed better than space-excluded models. While distribution of suitable areas for T. tetrax in the future was approximately the same as at present in the space-included model, the space-excluded model predicted a pronounced geographic change of suitable areas for this species. In the case of O. tarda, the space-included model showed that many areas of current presence shifted to low or medium suitability in the future, whereas a northward expansion of intermediate suitable areas was predicted by the space-excluded one. According to the best models, current distribution of these species can restrict future distribution, probably due to dispersal constraints and site fidelity. Species ranges would be expected to shift gradually over the studied time period and, therefore, we consider it unlikely that most of the current distribution of these species in southern Europe will disappear in less than one hundred years. Therefore, populations currently occupying suitable areas should be a priority for conservation policies. Our results also show that climate-only models may have low explanatory power, and could benefit from adjustments using information on other environmental variables and biological traits; if the latter are not available, including the geographic predictor may improve the reliability of predicted results.

AVIAN POXVIRUS INFECTION IN A FLAMINGO (PHOENICOPTERUS RUBER) OF THE LISBON ZOO.

Avian poxviruses (APV) are very large viruses spread worldwide in a variety of hosts. They are responsible for a disease usually referred to as pox, mainly characterized by nodular lesions on feather-free regions of the body. On May 2010, a young American flamingo (Phoenicopterus ruber) of the Lisbon Zoo (Portugal) developed a nodular lesion suggestive of poxvirus infection on its right foot. Avipoxvirus was isolated from the lesion and a fragment of the P4b-encoding gene was amplified by polymerase chain reaction. The nucleotide sequence of the amplicon was determined and analyzed. A close relationship (100% identity) was observed between the flamingo poxvirus and isolates from great bustard (Hungary 2005), house sparrow (Morocco 2009), MacQueen's bustard (Morocco 2011), and Houbara bustard (Morocco 2010 and 2011), suggesting interspecies transmission as a possible source of infection. To strengthen the investigation, the 5' and 3' ends of genes cnpv186 and cnpv 187, respectively, were also analyzed. The cnpv186-187 fragment exhibited 100% identity with MacQueen's bustard and Houbara bustard isolates, both from Morocco 2011. Phylogenetic analyses based in both fragments grouped the flamingo isolate consistently within clade B2 of canarypox. However, the phylogenetic relationships among the different representatives of avian poxviruses were more comprehensive in the tree based on the concatenated coding sequences of the cnpv186-187 fragment, rather than on the P4b-coding gene. The clearer displacement and distribution of the isolates regarding their host species in this last tree suggests the potential usefulness of this genomic region to refine avian poxvirus classification.

Effects of Land Use and Wildfires on the Habitat Selection of Great Bustard (Otis tarda l.)—Implications for Species Conservation

AbstractIncreasing agricultural activities have been shown to affect soil and vegetation changes leading to serious biodiversity declines throughout the world. These effects are amplified in dry grassland areas, where resulting changes in habitat structure affect threatened animals on long temporal scales. Great bustards (Otis tarda) inhabit open landscapes where fire and grazing have been a part of the natural disturbance regime since historical times. Even fire and grazing are hypothesized to be important factors in the lifecycle of the species, studies are still missing on disturbance‐related lekking distribution patterns of great bustards. We analyzed the importance of fires and grazing on the spatial distribution of lekking bustards controlling for habitat types, habitat diversity, distance from roads and social effects. Our standardized dataset spanned 31 years, being one of the largest datasets on bustard lekking. During the 31 years we observed 10 118 individuals at 639 observation points in Hortobágy National Park, East‐Hungary. One of the most important predictors for total number of birds and number of males was the area burnt in previous years. We found that increased habitat diversity had a positive effect on female numbers. Models fit on second‐ and third‐year burn data detected no substantial role of burning on lekking distribution. Our results suggest that introduction of a patch‐burning management system in lekking areas could increase the availability of optimal lek sites for bustards. As an effective management tool, we suggest applying patch‐burning annually in a spatially mosaic structure inside the area occupied by each sub‐population unit. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Climate envelope predictions indicate an enlarged suitable wintering distribution for Great Bustards (Otis tarda dybowskii) in China for the 21st century.

The rapidly changing climate makes humans realize that there is a critical need to incorporate climate change adaptation into conservation planning. Whether the wintering habitats of Great Bustards (Otis tarda dybowskii), a globally endangered migratory subspecies whose population is approximately 1,500–2,200 individuals in China, would be still suitable in a changing climate environment, and where this could be found, is an important protection issue. In this study, we selected the most suitable species distribution model for bustards using climate envelopes from four machine learning models, combining two modelling approaches (TreeNet and Random Forest) with two sets of variables (correlated variables removed or not). We used common evaluation methods area under the receiver operating characteristic curves (AUC) and the True Skill Statistic (TSS) as well as independent test data to identify the most suitable model. As often found elsewhere, we found Random Forest with all environmental variables outperformed in all assessment methods. When we projected the best model to the latest IPCC-CMIP5 climate scenarios (Representative Concentration Pathways (RCPs) 2.6, 4.5 and 8.5 in three Global Circulation Models (GCMs)), and averaged the project results of the three models, we found that suitable wintering habitats in the current bustard distribution would increase during the 21st century. The Northeast Plain and the south of North China were projected to become two major wintering areas for bustards. However, the models suggest that some currently suitable habitats will experience a reduction, such as Dongting Lake and Poyang Lake in the Middle and Lower Yangtze River Basin. Although our results suggested that suitable habitats in China would widen with climate change, greater efforts should be undertaken to assess and mitigate unstudied human disturbance, such as pollution, hunting, agricultural development, infrastructure construction, habitat fragmentation, and oil and mine exploitation. All of these are negatively and intensely linked with global change.

ОБИЛИЕ ЧЛЕНИСТОНОГИХ НА УЧАСТКАХ ГНЕЗДОВАНИЯ ДРОФЫ В САРАТОВСКОМ ЗАВОЛЖЬЕ

The results of our study of the quantitative and qualitative arthropod composition at potential nesting areas of Otis tarda in the Saratov Trans-Volga region are presented. Specific information obtained at 7 areas (2 fallow fields, two fields of winter and spring wheat, two natural fallow lands of different ages, and virgin land) in 2012 is given. A comparative analysis of some indicators of the arthropod abundance and biomass on winter fields treated with chemicals and untreated is conducted. The obtained results are compared with those of previous years. In the Saratov Trans-Volga region in the nesting period O. tarda currently has favorable conditions for rearing nestlings on natural fallow lands of different ages and on early-spring crop fields. In winter fields after their complex treatments with chemicals the abundance and composition of arthropods cannot meet the needs of O. tarda during rearing nestlings.

СТАТИСТИЧЕСКИЙ АНАЛИЗ ВЛИЯНИЯ ФАКТОРА БЕСПОКОЙСТВА НА ФОРМИРОВАНИЕ ПРОСТРАНСТВЕННОЙ СТРУКТУРЫ ЗАВОЛЖСКОЙ ПОПУЛЯЦИИ ДРОФЫ (OTIS TARDA L.) (OTIDIDAE, AVES)

The paper examines the influence of the location of settlements, railroads and highways on the spatial structure of the Otis tarda population in the Trans-Volga region studied on a model area of 12,000 km2, located in the southern part of the Saratov Trans-Volga region in 1998 - 2016. The zone of influence of our estimated disturbance factor caused by the movement of people and a variety of ground vehicles along roads of various purposes, on the territorial distribution of bustards in the autumn can be located as a 300 - 500 m width band on both sides of the transport communications. Shelter belts created along transport communications render a beneficial effect on the distribution of O. tarda and the disturbance influence reduction. Besides, crop rotation fields with the side sizes more than 1 km can be considered a factor to compensate for the birds’ anxiety. We have found that in the Saratov Trans-Volga region, because of the large size of crop rotation fields and the significant development of roadside and shelter belts, no special measures are required to protect O. tarda as to restrict the movement of people and vehicles on the territory where this species lives.

Resource partitioning and niche segregation in a steppe bird assemblage

Niche theory predicts that coexisting species will partition resources to limit the effects of interspecific competition. We examined microhabitat partitioning in six sets of steppe birds associated to agroecosystems in central Spain (female and male Great Bustards Otis tarda, female and male Little Bustards Tetrax tetrax, Red-legged Partridges Alectoris rufa and Eurasian Stone-curlews Burhinus oedicnemus) to estimate realized niche breadth, overlap and segregation. Principal Components Analysis on data from used and random microhabitat locations produced two axes we retained for analysis related with two key factors: cover-visibility and food availability. Non-parametric kernel density functions were calculated for each of the PCA axes and species (or sexes), and niche overlap estimated as the area shared between species’ density functions. Null models were run to evaluate overlap significance. In analyses of microhabitat selection by the six sets of birds, 13 out of 15 pairs had significant resource partitioning and niche segregation, except for the pairs partridge and female Great Bustard and the two sexes of Great Bustard. Eurasian Stone-curlew showed wider trophic niche breadth, although segregated from the other species, probably because of its higher invertebrate requirements. Great and Little Bustards segregated in both niche axes, selecting microhabitat according to their body size. Accessibility to food resources and shelter seems to be similar for partridges and female Great Bustards, overlapping in their selection, which may indicate the existence of segregation in other niche factors (e.g., feeding habits). Great Bustard males showed niche overlap with females. Little Bustard males showed feeding microhabitat selection patterns similar to those of females, although they preferred more open microhabitats to meet their sexual display requirements. The entire assemblage had significantly less overlap than expected by chance, suggesting that differential microhabitat selection and realized niche partitioning may explain coexistence in steppe bird communities. Our results suggest that the maintenance of different microhabitat structure should be a priority in the management of agricultural environments.