Eladio L. García de la Morena

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.

Foraging activity and use of space by Lesser Kestrel Falco naumanni in relation to agrarian management in central Spain

Summary Arthropod abundance in most places across Europe has suffered a dramatic decline induced by modifications in agricultural practices, and this could induce changes in the selection of breeding habitat and foraging behaviour of several endangered raptor species. We studied a 6,500 ha Special Protection Area (SPA) in Spain created for the benefit of its important steppe bird populations and examined the patterns of land-use selection and use of vegetation structure by the Lesser Kestrel Falco naumanni in relation to prey-capture success. We also studied the spatial relationship between foraging sites and the location of colonies in that breeding area. The type of land-use most frequently used by foraging Lesser Kestrels was unploughed fallow (positively selected) while kestrels significantly avoided areas with cereal crops. The relationship between foraging sites and colonies (kestrels forage preferentially in areas close to the colonies) indicates that not only is farmland management important, but also the spatial relationships between foraging areas and breeding sites. Maintaining the Spanish traditional rotation of cultivation (called barbechos) may improve the correct habitat management for Lesser Kestrels in agricultural areas in Spain.

Habitat selection and density-dependent relationships in spatial occupancy by male Little Bustards Tetrax tetrax.

This study analyses habitat selection by male Little Bustards Tetrax tetrax of a central Spanish population within their display sites during two consecutive breeding seasons. The areas of sexual display sites were determined by applying minimum convex polygons (MCP) to locations of individual males throughout the 2001 and 2002 breeding seasons. Habitat selection was addressed by means of a compositional analysis. The effects of variables related to phenology and to the density of conspecifics were examined, assuming an ideal free distribution of organisms. The spatial distribution of display areas was also analysed. During both years male Little Bustards showed a significant preference for old and same-year fallows, these offering both shelter and food. Contrary to what was expected, individuals did not select lower quality habitats when conspecific density increased or when areas were occupied earlier, suggesting that the population was not saturated. Display sites were not clumped, showing that in this population the Little Bustard may not employ a lek mating system, even though certain requirements of an exploded lek system — the inclusion in territories of particular habitat types that females could potentially use — were met. Our results emphasise the importance of agrarian substrates in determining occupation by this species, a finding with direct implications for the conservation of populations given that the agrarian landscape is on a sufficiently large scale for management measures to be introduced.

Surveys of wintering Little Bustards Tetrax tetrax in central Spain: distribution and population estimates at a regional scale

Developing a standardized survey methodology to census and estimate the size of wintering populations is a main conservation priority for the endangered Little Bustard. We present a standard and repeatable methodology to census wintering Little Bustard populations at a regional scale, and the first statistically reliable population estimate of a Little Bustard wintering population in Spain. We carried out two surveys, in 2003 and 2004, using UTM 10 km 6 10 km squares as census units, which were subjected to stratified sampling over the species’ potential distribution range in the region of Madrid (Central Spain). Only the areas of potentially suitable habitat within squares of known winter presence of the species were considered. The species’ winter distribution in Madrid was fairly constant between years, showing a fragmented pattern in three main nuclei. The number of Little Bustards observed was consistent between surveys (752 and 786 birds, respectively), with birds grouped in an average of 32 flocks (1 to 350 birds, mean 5 27.9 birds). No between-winter differences in flock size were observed, although differences between sectors were significant. The highest densities were observed in the Tagus valley (mean density 5 2.9 birds km, 293 birds), followed by north-eastern farmland (mean density 5 0.6 bird km, 269 birds). The estimated size of the Little Bustard population wintering in the Madrid region was 1,051 (95% CI 5 1,043–1,231). This calculation was based on recorded population density, measured as the number of birds per square kilometre, and considers the potential habitats available in each sector. We propose this methodology as adequate for surveying any Little Bustard wintering area, at both regional and smaller spatial scales. Survey results are consistent with previous tentative estimates for the region of Madrid, and with available information on Little Bustard movements. Sixty-five per cent of squares with Little Bustard presence were outside any protected area, which makes the wintering Little Bustard population of Madrid highly vulnerable to habitat disappearance and may affect the viability of breeding nuclei whose individuals winter in the region.

Cross-scale Changes in Bird Behavior Around a High Speed Railway: From Landscape Occupation to Infrastructure Use and Collision Risk

Large-scale transportation infrastructures, such as high-speed railway (HSR) systems, cause changes in surrounding ecosystems, thus generating direct and indirect impacts on bird communities. Such impacts are rooted in the individual responses of birds to infrastructure components, such as habitat occupancy of railway proximities, the use of structural elements (e.g., perching or nesting sites), flights over the railway, and behavior towards approaching trains. In this chapter, we present the most important results of several studies that were carried out on bird communities, between 2011 and 2015 on a 22-km stretch of HSR built on an agrarian landscape in central Spain. Available data describe the abundance and spatial distribution of birds up to 1000 m from the railway, bird infrastructure use (e.g., embankments, catenaries), cross-flights of the railway obtained through focal sampling, and animal responses to approaching trains recorded from train cockpits. These data depict how bird species respond at various scales to the presence of the HSR, and show how the infrastructure impacts bird communities, due to both habitat changes and increases in mortality risk.

On-Board Video Recording Unravels Bird Behavior and Mortality Produced by High-Speed Trains

Large high-speed railway (HSR) networks are planned for the near future to accomplish increased transport demand with low energy consumption. However, high-speed trains produce unknown avian mortality due to birds using the railway and being unable to avoid approaching trains. Safety and logistic difficulties have precluded until now mortality estimation in railways through carcass removal, but information technologies can overcome such problems. We present the results obtained with an experimental on-board system to record bird-train collisions composed by a frontal recording camera, a GPS navigation system and a data storage unit. An observer standing in the cabin behind the driver controlled the system and filled out a form with data of collisions and bird observations in front of the train. Photographs of the train front taken before and after each journey were used to improve the record of killed birds. Trains running the 321.7 km line between Madrid and Albacete (Spain) at speeds up to 250-300 km/h were equipped with the system during 66 journeys along a year, totaling approximately 14,700 km of effective recording. The review of videos produced 1,090 bird observations, 29.4% of them corresponding to birds crossing the infrastructure under the catenary and thus facing collision risk. Recordings also showed that 37.7% bird crossings were of animals resting on some element of the infrastructure moments before the train arrival, and that the flight initiation distance of birds (mean ± SD) was between 60±33 m (passerines) and 136±49 m (raptors). Mortality in the railway was estimated to be 60.5 birds/km year on a line section with 53 runs per day and 26.1 birds/km year in a section with 25 runs per day. Our results are the first published estimation of bird mortality in a HSR and show the potential of information technologies to yield useful data for monitoring the impact of trains on birds via on-board recording systems. Moreover, recordings point to the use of the infrastructure by birds as a key issue leading to bird train-kill.

Tracking data of the Little Bustard Tetrax tetrax in Iberia shows high anthropogenic mortality

The Little Bustard Tetrax tetrax (Linnaeus, 1758) is a medium-sized, ‘Near Threatened’ steppe bird, whose Iberian population has been alarmingly declining over recent decades. Although this population loss has been mainly attributed to agricultural intensification, there is no information on Little Bustard adult mortality levels and their drivers. Based on a joint effort combining all the tracking data on adult Little Bustards collected over a period of 12 years by all research teams working with the species in Iberia, we found that annual anthropogenic mortality is likely to have a critical impact on the species, with values almost as high as the mortality attributed to predation. Collision with power lines was found to be the main anthropogenic threat to the adult population (3.4–3.8%/year), followed by illegal killing (2.4–3%/year), which had a higher impact than initially foreseen. Our work shows how poorly understood and previously unknown threats are affecting the survival of the most important Little Bustard population in Europe.