José F. Calvo

Factors influencing the decline of a Bonelli's eagle Hieraaetus fasciatus population in southeastern Spain: demography, habitat or competition?

We investigated three possible causes of territory desertion among Bonellis eagles Hieraaetus fasciatus in Murcia (southeastern Spain): low demographic parameters, low habitat quality and competition with Golden eagles Aquila chrysaetos. From 1983 to 1997, we surveyed a Bonellis eagle population. Abandoned and occupied territories were compared to find differences in demographic parameters (flight rate, productivity and mortality) or habitat characteristics. Mortality was significantly higher in abandoned territories. Abandoned territories also had larger areas of forest and extensive agriculture, while occupied territories had more shrublands. Competition with Golden eagles was not a determinant of territorial abandonement but interacted with human persecution of the species. Management implications are discussed.

SEED GERMINATION, GROWTH, AND OSMOTIC ADJUSTMENT IN RESPONSE TO NaCl IN A RARE SUCCULENT HALOPHYTE FROM SOUTHEASTERN SPAIN

In this paper, some issues of the autoecology of Halocnemum strobilaceum (a rare succulent halophyte that occurs in southeastern Spain) are examined, particularly the germination process and the first stages of plant development. In regards to germination, this species shows the general pattern of halophytes under increased salt stress (reduced germination and germination rate). What stands out is the extreme salt tolerance of H. strobilaceum seeds. The stimulation of root length by the presence of salt probably plays an important role in avoiding salt stress at surface-level soils, within salt concentrations where germination still occurs. Halocnemum strobilaceum typically accumulates Na+ ions, which, combined with Cl−, contributes to the internal osmotic potential. The accumulation of both ions clearly increases with an increase in salinity stress. In contrast, accumulation of K+, Mg2+, and Ca2+ decreases with an increase in salinity stress. Glycinebetaine contents are approximately 100 times greater than proline contents, although their contribution was significant only if cell compartmentalization was considered. The accumulation of ions along with the osmoprotective compounds glycinebetaine and proline allows seedlings to mantain a lower internal osmotic potential than that of the growth medium, which is necessary for water uptake in saline soils.

Raptor Ecotoxicology in Spain: A Review on Persistent Environmental Contaminants

Abstract Initial studies on the pressure from environmental contaminants on raptor populations in Spain date back to the 1980s, and they have been carried out from a range of viewpoints using a range of sentinel raptor species. However, there is no national monitoring scheme, and therefore the research carried out has been sporadic both spatially and temporally. The exposure to metals has not varied over time, except in the case of lead, whose concentration in eggs and tissues has diminished. In general, the concentrations of metals detected in raptor samples from Spain are generally low and not sufficient to produce toxic effects. Excepting DDT and DDE, most organochlorine-based pesticides in raptors from Spain have diminished over the last 2 decades. The concentrations of DDE found in the eggs of various species could in part explain problems in the reproductive success of raptors in Spain.

Habitat Use of Booted Eagles (Hieraaetus pennatus) in a Special Protection Area: Implications for Conservation

We examined the patterns of habitat use of six radio-tagged booted eagles (Hieraaetus pennatus) in a Special Protection Area (SPA) in southeastern Spain. Variable percentages of radio locations (20.8–72.0 %) and home range areas (45.2–81.3 %) lay outside the SPA limits. A model selection procedure showed that habitat use was mainly influenced by habitat type and the distance to the nest. Edges and open lands were the most selected habitat types at long distances, while the probability of forest use strongly decreased with the distance. We conclude that effective conservation strategies for this species should encourage not only the protection of the forest nesting habitats, but also the traditional agricultural practices of the surrounding agroecosystems.

How to manage human-induced mortality in the Eagle Owl Bubo bubo

Summary The Eagle Owl Bubo bubo, which feeds mainly on rabbits and partridges, has been persecuted widely for causing damage to game interests. Although it is a protected species throughout Europe, there is a noteworthy gap in the scientific literature on the causes of mortality in this top predator. Here, we assess the relative importance and the geographical and temporal variation of human-related causes of death by reviewing 1,576 files of individuals admitted to wildlife rescue centres in Spain, a stronghold for Eagle Owls. The main known cause of death was interaction with powerlines followed by persecution and collisions with game fences and cars. There were within-year variations in the distribution of persecution, electrocution and collisions with game fences. Some man-induced causes of mortality were seen to depend on both the geographical region and the period of the year; moreover, mortality within each region was also yeardependent. Since there are strong socio-economic and ethical components involved, management guidelines are discussed bearing in mind such points of view.

Organochlorine residues in booted eagle (Hieraaetus pennatus) and goshawk (Accipiter gentilis) eggs from southeastern Spain

Most organochlorine (OC) use has been banned in Spain, but these compounds are persistent and may still adversely affect predatory birds. Data generally are lacking, however. Residues of hexachlorobenzene, alpha-hexachlorocyclohexane, lindane, hexachloro-octahydro-epoxy-dimethanonaphthalene, DDT, dichlorodiphenyldichloroethane, dichlorodiphenyldichloroethylene (DDE), and polychlorinated biphenyls (PCBs) were measured in 22 failed eggs of booted eagles (Hieraaetus pennatus) and goshawks (Accipiter gentilis) from southeastern Spain; both species are declining in this region. Hexachloro-octahydro-epoxy-dimethanonaphthalene, DDE, and sum PCB congener concentrations were significantly higher in booted eagle than in goshawk eggs, and an inverse relationship was found between shell thickness and DDE concentrations in booted eagles. Organochlorides may have been associated with the failure of some booted eagle eggs, but concentrations in booted eagle and goshawk eggs decreased over the period during which populations have dwindled. Thus, although OCs may be a contributory factor, they are unlikely to be the primary cause of the recent population declines in southeastern Spain.

Factors that influence mercury concentrations in nestling Eagle Owls (Bubo bubo)

Mercury (Hg) is a global pollutant that bioaccumulates and biomagnifies in food chains, and is associated with adverse effects in both humans and wildlife. The Hg levels detected in blood obtained from Eagle Owl (Bubo bubo) chicks in Southeast Spain (Murcia) can be considered low (mean Hg concentration in blood from 2006 to 2012 was 36.83 ± 145.58 μg/l wet weigh, n=600), and it is therefore unlikely that Hg pollution can negatively affect their breeding. Positive correlation (r=0.339, p<0.001, n=229) was found to exist between the Hg concentrations in the blood and back feathers of the chicks. We provide a regression equation that could be helpful to estimate blood Hg levels when analyzing Hg concentrations in back feathers. Blood Hg concentrations in Eagle Owls have shown positive correlations with Hg levels in rabbit muscles, more evident in nests from the Northern area (r=0.600, p=0.014, n=16), where rabbits are the main prey of Eagle Owls. The best Linear Mixed Model to explain variations in blood Hg concentrations in nestling Eagle Owls includes year and location within the mining area as variables. The variable year is assigned the largest value of relative importance, followed by the location in the ancient mining sites and then the zone. Rainfalls may have an effect on the temporal differences in the blood Hg concentrations of nestling Eagle Owls. Although the studied region is not considered Hg polluted, the Hg levels were higher in Eagle Owls and European Rabbits from areas within the ancient mining sites as compared to those in the entire region. This result shows that spatial differences in Hg concentrations in Eagle Owls may be affected by local contamination, and that the role of diet composition may be less significant.

Changes in blood pesticide levels in booted eagle (Hieraaetus pennatus) associated with agricultural land practices.

We estimated the degree of exposure to lindane and endosulfan in the blood of booted eagle nestlings (Hieraaetus pennatus) (1999-2003), in order to assess the usefulness of these samples as a unit for monitoring changes in exposure as a result of shifts in agricultural practices and the implementation of legal measures. The highest blood lindane concentrations were obtained 1 year prior to its prohibition by the European Union. Subsequent to that year, the drop in blood concentrations was dramatic. Furthermore, endosulfan blood concentrations follow a progression coinciding with an increase in olive, grape and plum-tree crops. We conclude that concentrations of organochlorine pesticides in the blood of booted eagle nestlings may be used to monitor the use of those pesticides over a particular agricultural region and alert the authorities of possible environmental or health risks.

Are species listed in the Annex II of the Habitats Directive better represented in Natura 2000 network than the remaining species? A test using Spanish bats

One of the main aims of protected areas is to be effective in the conservation of target species, i.e. those of the highest conservation concern. The Natura 2000 network (N2000) of protected areas is the main pillar of European action to halt biodiversity loss. Within N2000, special areas of conservation (SACs) are designated to protect habitats and species of the highest conservation interest, i.e. habitats from Annex I and species (other than birds) listed in Annex II of the Habitat Directive. Thus, a critical and urgent task is to assess the effectiveness of N2000 in the protection of these species. Here, we used distribution data for Spanish bats to test whether the species included in Annex II are better represented in N2000 than the remaining bats found in Spain, since SAC sites were specifically designated to protect the former species. In general, we found significantly high overlapping values between species distribution and N2000 sites (both groups of species are in general over-represented in N2000). However, contrary to our expectations, N2000 (even when only SACs were considered) did not offer higher representation values for the species listed in Annex II than for other species. We found that N2000 performed well even for non-target species, and that species from Annex II could have acted as effective umbrella species for the remaining bat species. Finally, the usefulness of including a species in Annex II is discussed, and guidelines to improve the efficiency of the N2000 for bat conservation are offered.

Potential impact of wind farms on territories of large eagles in southeastern Spain

Although wind farms in Spain have increased in numbers in recent years, their impact on birds, particularly large raptors, has received relatively little attention in the scientific literature. We study the potential impact of 72 wind energy developments planned for the south-east of Spain covering 128 golden eagle and 152 Bonelli’s eagle territories using nearest neighbour distances (NND) as an indicator of potential future interactions (abandonment, displacement and collision risk). Our analyses indicate low levels of potential interactions between wind farms and large eagles, and suggest that, of the two species studied, golden eagles will be the more affected because a greater proportion of wind farms will be constructed close to the breeding territories of this species. In the light of these findings, we discuss various management strategies in order to improve the compatibility of harvesting wind energy with the conservation of both species.