Otis Tarda Research Articles

Annual productivity and individual female reproductive success in a Great Bustard Otis tarda population

The reproductive success of Great Bustards Otis tarda in north‐western Spain was studied between 1987 and 1998, both at the population (c. 700 adult females breeding in our study area) and the individual level (sample of 32 marked females). Overall productivity was low, with a population mean of only 0.14 chicks reared per adult female, and an average breeding success of 0.15 chicks per year in the sample of marked females, but interannual variability was high (0.04–0.29). Population productivity was positively correlated with winter (October–March) precipitation prior to each breeding season, and negatively correlated with the number of days of rain during the hatching period. High annual productivity resulted from a high proportion of females rearing two chicks. Reproductive success was higher in females older than 6 years than in younger birds. The proportion of females in the marked sample that failed in breeding after having bred successfully the previous season was significantly higher than the proportion of those that did not. Finally, females with a higher than average breeding success tended to breed successfully in years of both low and high population productivity, whereas those with lower than average breeding success did so only in years of high productivity.

Great bustard population structure in central Spain: concordant results from genetic analysis and dispersal study.

We found significant sex differences in the mtDNA genetic structure and dispersal patterns of great bustards in a population of 11 breeding groups, "leks", in central Spain. The analysis of genetic distances showed that the female population was divided into three groups of leks separated by ca. 50 km, whereas male haplotypes were randomly distributed among leks. Genetic distances among pairs of leks were positively correlated with geographical distances in females but not in males. While female haplotype distributions were homogeneous among leks at close distances, differences in male genetic structure were highly variable even between two close leks. These results from genetic analyses were concordant with those from a radiotracking study on natal dispersal. Natal dispersal distances were higher in males than in females. Also, the frequency of movement of a female between two leks was positively correlated with their genetic affinity and geographical proximity. In males, the frequency of movement was correlated with geographical proximity but not with genetic affinity. Males dispersed among genetically unrelated leks, contributing to keep nuclear genetic diversity in the population, whereas females tended to be philopatric. These results suggest that isolation-by-distance influences the distribution of maternal lineages at a regional level.

SEASONAL MOVEMENTS OF MALE GREAT BUSTARDS IN CENTRAL SPAIN

Abstract A sample of 22 radio-tagged male Great Bustards from central Iberian populations was studied from 1996 to 1998. All birds undertook seasonal movements to postbreeding areas located up to 167 km away from their leks. Departures from leks occurred between May and July, with most birds moving northeast to summering areas. Approximately 47% of the males spent only the summer away from their leks, returning to leks between September and December. Other males overwintered in areas located to the southeast, returning to lek sites between January and March.

Isolation and characterization of microsatellite loci in the great bustard, Otis tarda

AbstractWith the aim to study population genetics of the endangered great bustard, Otis tarda, dinucleotide microsatellite loci were isolated using an adapted hybrid‐capture enrichment protocol. This work reports the characterization of a set of six polymorphic microsatellite markers within the great bustard (n = 52). Results from cross‐species amplifications in several other members of the family Otididae demonstrate that five primer pairs also successfully amplified homologous loci outside the species Otis tarda.

Modelling landscape‐scale habitat use using GIS and remote sensing: a case study with great bustards

Summary Many species are adversely affected by human activities at large spatial scales and their conservation requires detailed information on distributions. Intensive ground surveys cannot keep pace with the rate of land‐use change over large areas and new methods are needed for regional‐scale mapping. We present predictive models for great bustards in central Spain based on readily available advanced very high resolution radiometer (AVHRR) satellite imagery combined with mapped features in the form of geographic information system (GIS) data layers. As AVHRR imagery is coarse‐grained, we used a 12‐month time series to improve the definition of habitat types. The GIS data comprised measures of proximity to features likely to cause disturbance and a digital terrain model to allow for preference for certain topographies. We used logistic regression to model the above data, including an autologistic term to account for spatial autocorrelation. The results from models were combined using Bayesian integration, and model performance was assessed using receiver operating characteristics plots. Sites occupied by bustards had significantly lower densities of roads, buildings, railways and rivers than randomly selected survey points. Bustards also occurred within a narrower range of elevations and at locations with significantly less variable terrain. Logistic regression analysis showed that roads, buildings, rivers and terrain all contributed significantly to the difference between occupied and random sites. The Bayesian integrated probability model showed an excellent agreement with the original census data and predicted suitable areas not presently occupied. The great bustard's distribution is highly fragmented and vacant habitat patches may occur for a variety of reasons, including the species’ very strong fidelity to traditional sites through conspecific attraction. This may limit recolonization of previously occupied sites. We conclude that AVHRR satellite imagery and GIS data sets have potential to map distributions at large spatial scales and could be applied to other species. While models based on imagery alone can provide accurate predictions of bustard habitats at some spatial scales, terrain and human influence are also significant predictors and are needed for finer scale modelling.

Habitat preferences of great bustard Otistarda flocks in the arable steppes of central Spain: are potentially suitable areas unoccupied?

Summary Great bustards Otistarda are globally endangered and 50% of the world population now occurs in agro‐steppe habitats in Spain. An understanding of the relationship between land use and the species’ habitat requirements is necessary to predict the consequences of land‐use change on this declining species. A 2‐year study of great bustard substrate preferences was conducted in a large region in central Spain where most cereals are still cultivated in a traditional 2‐year rotation. Great bustards showed year‐round selection of stubble fields, but avoided ploughed and uncultivated areas. Other substrate types were variously selected, avoided or used in proportion to availability depending on season. Patterns were consistent over 2 years. Human artefacts such as roads, tracks and powerlines were avoided. Variables correlating with flock locations could not discriminate between occupied and unoccupied but apparently suitable areas of traditionally managed cereal steppe. This suggests that great bustard distribution in central Spain is not limited by inappropriate land use in steppe areas. The evidence suggests that great bustards show fidelity to sites regardless of the availability of suitable habitat elsewhere. Settlement patterns are probably determined by the presence of conspecifics rather than habitat cues. This result demonstrates the value of integrating observations of habitat use with knowledge of species’ behaviour in order to understand distribution more fully. We propose that conservation efforts should be directed towards securing traditional lek sites and we make three recommendations: first all great bustard lek sites should be identified; secondly, existing European Union legislation should be used to protect these and to ensure that compatible land management practices are applied or maintained; and finally, research programmes should be conducted that aim to enhance the conservation value of stubble fields rather than simply demonstrate their selection.

Status and extinction probabilities of great bustard (Otis tarda) leks in Andalucía, southern Spain

Great bustards (Otis tarda) commonly occur in isolated populations consisting of only a few tens of individuals. Knowing where these are, and understanding the factors affecting their persistence, is necessary to save this declining species. A census (Spring 1999) was therefore made of possible great bustard lek sites in Andalucia, southern Spain. Forty-six males and 79 females were observed and a total of 180 conservatively estimated for the areas we visited. These were distributed among five, possibly six, leks, but most (66–72%) were recorded at only two localities. Through interviews with local people we established that at least two, possibly three, leks had become extinct within the last two decades, and also learned of another lek of 50–70 birds in the north of the region. The precarious status of the four largest visited leks was demonstrated through computer simulation (VORTEX). This showed that under status quo conditions their likelihood of extinction within 100 years is 85–99%. Further simulations demonstrated the disastrous consequences of poaching with extinction probabilities of 95% reached in 8–70 years. However when a hypothetical management scheme was modelled the results were encouraging. In these simulations the number of chicks per female per year was increased from 0.14 to 0.18 and annual mortality of females was reduced from 7.5 to 5%. This resulted in extinction probabilities of only 20% within 100 years at the larger leks. Simple, practical conservation actions to enhance annual recruitment and increase female survival are suggested.

Population subdivision in Europe's great bustard inferred from mitochondrial and nuclear DNA sequence variation.

A continent-wide survey of sequence variation in mitochondrial (mt) and nuclear (n) DNA of the endangered great bustard (Otis tarda) was conducted to assess the extent of phylogeographic structure in a morphologically monotypic bird. DNA sequence variation in a combined 809 bp segment of the mtDNA genome from 66 individuals from the last six breeding regions showed relatively low levels of intraspecific sequence diversity (n = 0.32%) but significant differences in the regional distribution of 11 haplotypes (phiST = 0.49). Despite their exceptional potential for dispersal, a complete and long-term historical separation between the populations from the Iberian Peninsula (Spain) and mainland Europe (Hungary, Slovakia, Germany, and Russia) was demonstrated. Divergence between populations based on a 3-bp insertion-deletion polymorphism within the intron region of the nuclear CHD-Z gene was geographically concordant with the primary subdivision identified within the mtDNA sequences. Inferred aspects of phylogeography were used to formulate conservation recommendations for this endangered species.

An approach to sexing young Great Bustards Otis tarda using discriminant analysis and molecular techniques

Adult Great Bustards Otis tarda are sexually dimorphic, males weighing more than twice as much as females. However, there is no practical way to distinguish sex in chicks by their morphology. In this paper we describe a discriminant function, Tail Length/Weight, which correctly sexed 98.2% of 165 Great Bustard chicks at two study areas in Spain, the Wildlife Reserve of Lagunas de Villafáfila and the province of Madrid. The value for Tail Length/Weight separating the sexes was 0.099: Tail Length/Weight for males < 0.099 < Tail Length/Weight for females. We also show that the recently described PCR-based sex determination technique using genomic DNA is valid for the Great Bustard. Both approaches should be useful for sexing young Great Bustards in captive breeding programmes and studies on wild populations.

Great bustards Otis tarda in Morocco: status in spring 1999 and evidence of a decline in recent decades

AbstractA spring (1999) census was conducted of great bustards Otis tarda in north-western Morocco, where a poorly known population of this species occurs. Sixty-four birds were seen in four distinct areas. Adult males were seen displaying at three of these areas, indicating that they are probably traditional lek sites. No adult males were observed in the fourth area and its status as a lek site is uncertain. Two further sites were visited but no birds were seen. Two lst-year males were seen with their mothers, demonstrating successful breeding in 1998. We argue that the small number of birds, a population sex ratio of 1:3.3 in favour of females, evidence for a range contraction, and probable isolation from other great bustard populations mean that this population is now extremely endangered and will decline to extinction unless conservation measures are implemented immediately.

Great bustards Otis tarda in Morocco: status in spring 1999 and evidence of a decline in recent decades

Great bustards Otis tarda in Morocco: status in spring 1999 and evidence of a decline in recent decades

Partial Migration, and Lek and Nesting Area Fidelity in Female Great Bustards

AbstractWe examined the seasonal movements of wing-tagged and radio-marked adult female Great Bustards Otis tarda in a population in northwestern Spain. Four different movement patterns were found: females that migrated between breeding and wintering areas (20%), females that only left their year-round home range area to mate (32%), females that migrated from a wintering-mating area to a nesting-summering area (16%), and females that stayed all year round within a relatively small home range area (32%). All females displayed fidelity to their nesting and wintering areas, and most also showed fidelity to their leks. Migration patterns were not affected either in timing or distance by breeding success. The maximum distance between natal and dispersal locations during their first year of life was significantly higher in migratory females than in sedentary ones. These patterns explained the seasonal variations in population numbers observed in the study area. Surveys showed that the number of females increased from 600–700 breeding birds, with 1,000–1,100 birds present from October to March.

Partial Migration, and Lek and Nesting Area Fidelity in Female Great Bustards

Partial Migration, and Lek and Nesting Area Fidelity in Female Great Bustards

Migration Patterns in Male Great Bustards (Otis tarda)

The Great Bustard (Otis tarda) is distributed from Iberia and Morocco in the west to China in the east and has been considered sedentary in all but the northern and eastern parts of its range (Gewalt 1959, Glutz et al. 1973, Cramp and Simmons 1980). However, some studies have reported seasonal changes in population numbers in different areas in the Iberian Peninsula (Hidalgo and Carranza 1990, Alonso et al. 1995), suggesting that the species is a partial migrant (sensu Terrill and Able 1988) in this region. We describe seasonal movements of marked adult male Great Bustards and discuss observed patterns in relation to the following questions: (1) Do migratory males display interannual fidelity to breeding and postbreeding areas? (2) Do males travel significantly farther than females in their seasonal movements? We also suggest several hypotheses that could explain patterns of partial and differential migration in male Great Bustards. Methods.—Our study was carried out in the Wildlife Reserve of Villafafila (41 50 N, 5 35 W; ca. 700 m elevation), which extends over 32,682 ha of dry, treeless and gently undulating farmland in the Province of Zamora, northwestern Spain. The land is almost entirely cultivated with wheat and barley. The remaining surface (ca. 9%) is occupied by natural grassland used for sheep grazing. The Reserve holds the world’s densest population of Great Bustards (Alonso et al. 1995), which are ground-dwelling lekking birds that inhabit natural and cultivated grasslands. The Great Bustard is endangered in most of its range except for the Iberian Peninsula, which is the main stronghold for the species (Alonso and Alonso 1996). It exhibits one of the highest amounts of sexual size dimorphism of all vertebrates, and males and females generally occur in separate flocks. Between late winter and early spring, males concentrate at traditional arenas where they fight to establish rank and display in an exploded-lek mating system (see Hoglund and Alatalo 1995). Juvenile males usually disperse after independence. From their third year on, they begin to establish territories at

PARTIAL MIGRATION, AND LEK AND NESTING AREA FIDELITY IN FEMALE GREAT BUSTARDS

We examined the seasonal movements of wing-tagged and radio-marked adult female Great Bustards Otis tarda in a population in northwestern Spain. Four different movement patterns were found: females that migrated between breeding and wintering areas (20%), females that only left their year-round home range area to mate (32%), females that migrated from a wintering-mating area to a nesting-summering area (16%), and females that stayed all year round within a relatively small home range area (32%). All females displayed fidelity to their nesting and wintering areas, and most also showed fidelity to their leks. Migration patterns were not affected either in timing or distance by breeding success. The maximum distance between natal and dispersal locations during their first year of life was significantly higher in migratory females than in sedentary ones. These patterns explained the seasonal variations in population numbers observed in the study area. Surveys showed that the number of females increased from 600–700 breeding birds, with 1,000–1,100 birds present from October to March.

Seasonal changes in diet and diet selection of great bustards (Otis t. tarda) in north‐west Spain

AbstractFaecal analysis was used to study the diet of great bustards in north‐west Spain on a monthly basis for 1 year. After correction for differential digestibility, the diet composition by dry weight varied from 48.4% green plant material, 40.9% invertebrates and 10.6% seeds in August, to consisting almost completely of green plant material between December and March. At least 65 plant species were represented in the green plant material, but most occurred rarely and the bulk of this portion of the diet consisted of alfalfa. Eight invertebrate orders were detected in the faeces, of which Coleoptera, Hymenoptera and Orthoptera were most important by numbers. From August to November when seeds were important by dry weight, wheat and barley seeds were found in more faecal pellets than other species. Estimates of use and abundance were obtained to evaluate diet selection in the green plant material and invertebrate components. Alfalfa was strongly selected throughout the year, but grasses were used less often than expected. Coleoptera were always eaten in greater numbers than expected, Orthoptera were used either in proportion to abundance or less often than expected, and Hymenoptera less often in May, more often in September and November, and as expected at other times. The results support the suggestion that increasing alfalfa cultivation would be a useful management tool for maintaining endangered great bustard populations, but further work on the cost‐effectiveness of this option is needed.

Seasonal changes in diet and diet selection of great bustards (Otis t. tarda) in north-west Spain

Faecal analysis was used to study the diet of great bustards in north-west Spain on a monthly basis for 1 year. After correction for differential digestibility, the diet composition by dry weight varied from 48.4% green plant material, 40.9% invertebrates and 10.6% seeds in August, to consisting almost completely of green plant material between December and March. At least 65 plant species were represented in the green plant material, but most occurred rarely and the bulk of this portion of the diet consisted of alfalfa. Eight invertebrate orders were detected in the faeces, of which Coleoptera, Hymenoptera and Orthoptera were most important by numbers. From August to November when seeds were important by dry weight, wheat and barley seeds were found in more faecal pellets than other species. Estimates of use and abundance were obtained to evaluate diet selection in the green plant material and invertebrate components. Alfalfa was strongly selected throughout the year, but grasses were used less often than expected. Coleoptera were always eaten in greater numbers than expected, Orthoptera were used either in proportion to abundance or less often than expected, and Hymenoptera less often in May, more often in September and November, and as expected at other times. The results support the suggestion that increasing alfalfa cultivation would be a useful management tool for maintaining endangered great bustard populations, but further work on the cost-effectiveness of this option is needed.

Artificial incubation of Great bustard (Otis tarda) eggs

A trial of artificial incubation to great bustard (Otis tarda) egg was conducted from 1995 to 1997. Among the 45 collected eggs, 28 eggs were fertilized and 26 hatched, with fertilizing rate 62.2% and incubation rate 92.85%. The mean incubation-days for great bustard egg was confirmed as 24.4 (21–28 days) with the formula for caculating fresh egg weight (W=KwLB2) and that for counting the incubated days by parents birds in field (Id=24(w−y)/0.144y). The proper incubation temperature and relative humidity were 36–37.8°C and 50–65%, respectively. The egg weights and egg size average 130.45 g and 77.4±1.42×55.5±0.65 mm respectively. The total weight loss of egg was 18.38±0.646 g, daily weight loss 0.748±0.071 g in the incubation time, with a weight loss rate of 13.6±1.02%. A linear regression equation to discribe the relationship between the egg weight and incubation days, was built,y=130.73−0.619x (x-incubation day,y-egg weight) r=−0.978. Twenty-eight hours were nassassary for great bustard embryo to complete the fledging when the were put in gas room. The mean weight of fledglings was 86.3±3.29 g(n=26).

Observation on ultra-micro structure of eggshell and analysis of composition of eggshell and feather in great bustard

Ultra-micro structure of eggshell was observed and compositions of eggshell and feather were analyzed. The results showed that the structure of eggshell has special characters besides common structure. The content of poisonous elements in wild great bustard(Otis tarda) eggshell and feather is significant lower than that in eggshell of crested ibes(Nipponia nippon) and in feather of red crown crane(Grus japonesis) because of less disturbance by people. The contents of 14 elements of female's feather all are higher than those of male's.

Status of distribution of Great Bustard in Northeast area of China

Great bustard is one of the enelangered species in China. It breeds in China. The breeding area is not complete, but scattered, which is from the northeast of Neimenggu grassland to the sand land of Hulunbeier. This breeding areas are isolated by Daxing’an Mountain, which are Neimeng, Songnen Plain and Kerqin sand land. The total area is about 7810 km2. The estimated total number of Great Bustands in the Northeast area of China is 377 birds.