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Phalangeal reduction is a common and widespread phenomenon among tortoises that has been associated with the adaptation to terrestrial life. While reduced manual digit 1 appears characteristic in almost all Testudo species, it is uncertain why the metacarpal I and distal carpal of the same digit are completely missing in some individuals of Hermann's tortoise (Testudo hermanni hermanni). To clarify this issue, we investigated the number of manual claws in six populations of Hermann's tortoise (one from the Ebro Delta in the Iberian Peninsula and five from Minorca Island), their age, sex, genetic lineage, and the substrate type that they inhabit. The number of claws was ascertained based on direct counts (n > 1500 individuals) and by X-rays (n = 32 individuals), obtaining three different phalangeal formulae: (1-2-2-2-1, D-2-2-2-1, 0-2-2-2-1). Thus, claw counts through both methodologies (direct count and X-ray) further confirm that the observed claws serve as a good proxy to assess the actual number of digits. Our results show no loss of phalanges, metacarpal and carpal bones in digit 1 associated with age, sex, or substrate, contrary to some previous authors who hypothesized a relationship between this loss and sexual dimorphism. Therefore, variations in the number of manual digits and the loss of metacarpal I and distal carpal in digit 1 in Hermann's tortoise are related to population and genetic lineage. More detailed comparisons with other Testudo hermanni populations from elsewhere in Europe would be required to understand the evolutionary significance concerning the intrapopulation variability in the number of digits remaining.

Este artículo contiene 9 páginas, 3 figuras, 1 tabla., Social interactions, through infuence on behavioural processes, can play an important role in populations’ resilience (i.e. ability to cope with perturbations). However little is known about the efects of perturbations on the strength of social cohesion in wild populations. Long-term associations between individuals may refect the existence of social cohesion for seizing the evolutionary advantages of social living. We explore the existence of social cohesion and its dynamics under perturbations by analysing long-term social associations, in a colonial seabird, the Audouin’s gull Larus audouinii, living in a site experiencing a shift to a perturbed regime. Our goals were namely (1) to uncover the occurrence of long-term social ties (i.e. associations) between individuals and (2) to examine whether the perturbation regime afected this form of social cohesion. We analysed a dataset of more than 3500 individuals from 25 years of monitoring by means of contingency tables and within the Social Network Analysis framework. We showed that associations between individuals are not only due to philopatry or random gregariousness but that there are social ties between individuals over the years. Furthermore, social cohesion decreased under the perturbation regime. We sustain that perturbations may lead not only to changes in individuals’ behaviour and ftness but also to a change in populations’ social cohesion. The consequences of decreasing social cohesion are still not well understood, but they can be critical for the population dynamics of social species., Funding came from the Spanish Ministry of Science (CGL2017-85210) and Grant PICS INTERACT n°07699 (2016, CSIC-CNRS). MG was partially supported by the European Union (MINOUW Project, H2020-634495).

Este artículo contiene 7 páginas, 3 figuras., Predators are an important ecological and evolutionary force shaping prey population dynamics. Ecologists have extensively assessed the lethal effects of invasive predators on prey populations. However, the role of non-lethal effects, such as physiological stress or behavioural responses like dispersal, has been comparatively overlooked and their potential population effects remain obscure. Over the last 23 years, we developed a mark-recapture program for the Audouin’s gull and an intensive carnivore monitoring program to assess how the appearance and invasion of the study site by carnivores affects population dynamics. We evaluate changes in turnover of discrete breeding patches within the colony, age structure and breeding performance. Once carnivores entered the colony, the number of occupied patches increased, indicating a higher patch turnover. Breeders responded by moving to areas less accessible to carnivores. More importantly, the presence of carnivores caused differential (and density-independent) breeding dispersal: experienced, better-performing breeders were more likely to leave the colony than younger breeders. This differential dispersal modified the age structure and reduced the reproductive performance of the population. Our results confirm the importance experience in the study of populations. The role of differential dispersal for animal population dynamics might be more important than previously thought, especially under scenarios of global change., RESET (ref.CGL2017-85210-P), FPU (ref. FPU2012-000869), IBISES (ref. CGL2013-42203-R) and MINOW (ref. H2020- 634495). ASA and MG are supported by a postdoctoral contract co-funded by the Regional Government of the Balearic Islands and the European Social Fund (ref. PD/003/2016 and PD/023/2015).

Translocations to restore populations of endangered species are an important conservation tool, but a reliable diagnosis is needed to assess their success. We used capture-recapture modeling to analyze the adult apparent survival of released and resident tortoises in two translocation projects in Spain monitored for 14 and 29 years. We tested if long-term survival rates differ between released and resident individuals, if survival was lower during the phase of establishment (i.e. release cost), how long acclimation lasts and if increased density due to releases affects survival. We found lower survival of released tortoises during the phase of establishment (1 to 3 years) when residents were already present. After establishment, survival was very high and unaffected by density-dependence. Body condition before release was similar between recaptured and dead/missing tortoises, and did not predict establishment survival. Stochastic population viability analysis showed that success when releasing small numbers of individuals strongly depends upon adult long-term survival. Release of small second batches of tortoises was not sensitive to a growing population, regardless of its release timing. Our results highlight long-term survival as crucial in translocation projects of long-lived species, invalidating short-term (first year) survival assessment, when survival release cost does not match long-term survival. A release cost of different duration should be included in model estimation before modeling predictions. Releasing tortoises (for welfare of captive individuals or for mitigating human negative impacts) in an already established population is not recommended under most circumstances. Acclimation cost is followed by survival approaching wild counterparts. If this milestone is not achieved, the project needs to be carefully assessed to adopt other management options or should be stopped altogether., The regional governments of Catalonia and the Balearic Islands (Generalitat of Catalonia and the Govern de les Illes Balears) and Organismo Autónomo de Parques Nacionales (Ministerio Agricultura, Alimentación y Medio Ambiente, Gobierno de España) authorized our scientific work. Field work in the Ebro Delta and Minorca was partially funded by the Ebro Delta Natural Park, the Generalitat de Catalunya, the Institut Menorquí d'Estudis (IME), the Consell Insular de Menorca and the Spanish Ministry of Science and Technology (CICYT CGL2004-0473/BOS). AB is especially grateful to the Ebro Delta Natural Park staff that recognizes the importance of long-term monitoring programs. We are grateful to Evarist Coll from the GOB Menorca for kindly providing the released tortoises data. We thank several field workers who helped collect the data, especially Marta Massana, for their valuable assistance during several years, and Sam Pons and family for their friendly help and warm hospitality at Minorca. We are grateful to the two anonymous reviewers for improving the manuscript. We are also grateful to Elizabeth Rochon and Jacqueline Donoyan for improving the English on early draft.

Este artículo contiene 7 páginas, 3 figuras, 1 tabla., Studying colonisation is crucial to understand metapopulations, evolutionary ecology and species resilience to global change. Unfortunately, few empirical data are available because field monitoring that includes empty patches at large spatiotemporal scales is required. We examine the colonisation dynamics of a long-lived seabird over 34 years in the western Mediterranean by comparing population and individual data from both source colony and the newly-formed colonies. Since social information is not available, we hypothesize that colonisation should follow particular dispersal dynamics and personal information must be crucial in decision making. We test if adverse breeding conditions trigger colonisation events, if personal information plays a role in colonisation and if colonisers experience greater fitness. Our results show a temporal mismatch between colonisation events and both density-dependence and perturbations at the source colony, probably because colonisers needed a longer prospecting period to compensate for the lack of public information. Colonisers were mostly experienced individuals gaining higher breeding success in the new colony. Our results highlight the demographic value that experienced individuals can have on metapopulation dynamics of social longlived organisms., FPU (ref. FPU2012-000869), IBISES (ref. CGL2013- 42203-R) and MINOW (ref. H2020-634495)

Major landscape transformations have occurred in the northern Mediterranean over the last decades, including urbanization, agricultural intensification and land abandonment, which, in turn, increase the risk of the propagation of fire. We used repeated-count surveys conducted at 369 sites in France and Spain to jointly model the effects of environmental covariates on the abundance, occupancy and detection of Hermann’s tortoise, a long-lived and endangered species, using a novel zero-inflated approach. We also employed a large dataset of presence-only data collected in Provence to model environmental influences on occurrence probability using maximum entropy models. In both France and Spain, sites that experienced wildfires over the last 50 years hosted 31% fewer individuals than unburned sites. In Provence, higher wildfire frequency decreased this species’ occurrence probability, from 50% when 0–1 fire had occurred over the last 50 years, to 7% in areas that had burned at least 3 times. We also showed that abundance required a long recovery time (more than 25 years) after wildfires. In Provence, the highest occurrence probability for this species was found in patchy landscapes and scrub and/or herbaceous vegetation. The lowest species occurrence was found in extensive artificial areas, vineyards and arable lands. These results suggest a high risk of population extinction in the future if these types of habitats continue to expand in plains and coastal areas to the detriment of scrublands. Higher wildfire frequency predicted by climate change scenarios in the Mediterranean is also likely to increase the risk of extinction for some populations.

We used 454-sequencing to identify and characterize 32 microsatellite loci for the Western Hermann's tortoise (Testudo hermanni hermanni) for which primer sequences, characteristics, and multiplexes are provided. These markers have been tested for one continental (Var) and one insular (Corsica) French population as well as for the Eastern Hermann's tortoise (Testudo hermanni boettgeri). For these 3 populations, 24 loci were polymorphic. These microsatellite markers will be particularly useful to assess the genetic diversity and characteristics of the different Hermann's tortoise populations and will have direct applications for its protection, notably with respect to reintroduction and conservation programs.

Assessing population trends is a basic prerequisite to carrying out adequate conservation strategies. Selecting an appropriate method to monitor animal populations can be challenging, particularly for low-detection species such as reptiles. This study compares 3 detection-corrected abundance methods (capture–recapture, distance sampling, and N-mixture) used to assess population size of the threatened Hermann's tortoise. We used a single dataset of 432 adult tortoise observations collected at 118 sampling sites in the Plaine des Maures, southeastern France. We also used a dataset of 520 tortoise observations based on radiotelemetry data collected from 10 adult females to estimate and model the availability (g0) needed for distance sampling. We evaluated bias for N-mixture and capture–recapture, by using simulations based on different values of detection probabilities. Finally, we conducted a power analysis to estimate the ability of the 3 methods to detect changes in Hermann's tortoise abundances. The abundance estimations we obtained using distance sampling and N-mixture models were respectively 1.75 and 2.19 times less than those obtained using the capture–recapture method. Our results indicated that g0 was influenced by temperature variations and can differ for the same temperature on different days. Simulations showed that the N-mixture models provide unstable estimations for species with detection probabilities

International audience; Estimating the genetic variation and demographic trends of species in decline is of major concern in conservation genetics. This study contributes to understanding how historical and anthropogenic factors shape the distribution of current genetic diversity in one of the most endangered reptiles in Western Europe, the Hermann's tortoise Testudo hermanni hermanni. We used 17 microsatellite loci, chosen from a pyrosequencing library specifically developed for the subspecies to genotype eight populations distributed over about 30 sample localities covering almost the entire geographic distribution of the sub-species. The population genetic results reflect a very strong genetic structure and identify three major clusters among the Hermann's tortoise in the occidental Mediterranean basin: a continental cluster (Albera in Spain, Var in France and continental Italy), an insular cluster (Corsica, Sardinia and Sicily) and a cluster of mixed lineage (Minorca). Each of the eight studied populations is characterized by only one lineage except for Minorca, in which two lineages were identified. In contrast to what most empirical studies predict, the genetic diversity of the Hermann's tortoise is greater on islands than on the continent. Islands can therefore be considered as genetic sanctuaries with high conservation potential for this species, particularly in Corsica. Historical demographic patterns inferred with a generalized stepwise-mutation model (GSM) using maximum likelihood showed significant past demographic changes in only two of the eight sampled populations: a demographic bottleneck was detected in the Albera population (Spain) and a demographic expansion in Corsica (France). In contrast to what was argued in previous studies, these results indicate that the Hermann's tortoise lineage found in Corsica is autochthonous. The origin of both lineages found in Minorca remains speculative. Lastly, our study identifies the six most relevant management units (sensu Moritz, 1994) for conservation purposes on the basis that they represent a significant part of the evolutionary legacy of the species. Some conservation recommendations were proposed, in particular for the most threatened population in Albera.

Conditions during early life, including maternal cohort effects, can influence the future fitness of individuals. This may be particularly true for longdistance migrating birds, because, apart from conditions experienced by cohorts during rearing, conditions during early life in regions far from breeding grounds may also influence their population dynamics. Very little is known about the fitness consequences of those conditions experienced by juveniles after independence, especially in wild populations and for longlived birds. We used multi-event capture-recapture-recovery models and a unique 26-year dataset for the Audouin’s gull (Larus audouinii) to assess for the first time whether survival was influenced by early conditions, both during the rearing period (i.e. a maternal cohort effect potentially affected by density dependence) and the first winter (i.e. a cohort effect driven by climate when birds disperse to wintering grounds). Our results show that juvenile survivalwas highly sensitive to early-life conditions and that survival decreased with stronger density dependence and harsh climate. The two consecutive cohort effects were of similar magnitude and they may represent a selection filter. Thus, early-life conditions had a strong impact on survival, and neglecting this complexity may hinder our understanding on how populations of long-lived animals fluctuate and respond to perturbations.

Climatic shifts may increase the extinction risk of populations, especially when they are already suffering from other anthropogenic impacts. Our ability to predict the consequences of climate change on endangered species is limited by our scarce knowledge of the effects of climate variability on the population dynamics of most organisms and by the uncertainty of climate projections, which depend strongly on the region of the earth being considered. In this study, we analysed a long-term monitoring programme (1988–2009) of Hermann's tortoise (Testudo hermanni) aimed at evaluating the consequences of the drastic changes in temperature and precipitation patterns predicted for the Mediterranean region on the demography of a long-lived species with low dispersal capability and already suffering a large number of threats. Capture–recapture modelling of a population in the Ebro Delta (NESpain) allowed us to assess the effect of climate variability on the survival of tortoises. Winter rainfall was found to be the major driver of juvenile and immature survival, whereas that of adults remained high and constant across the study. Furthermore, local climate series obtained ad hoc from regional climate simulations, for this and 10 additional Mediterranean locations where tortoises occurred, provided us with reliable future climate forecasts, which were used to simulate the fate of these populations under three precipitation scenarios (mean, wet and dry) using stochastic population modelling. We show that a shift to a more arid climate would have negative consequences for population persistence, enhancing juvenile mortality and increasing quasiextinction risk because of a decrease in recruitment. These processes varied depending on the population and the climate scenario we considered, but our results suggest that unless other human-induced causes of mortality are suppressed (e.g. poaching, fire, habitat fragmentation), climate variability will increase extinction risk within most of the species’ current range., We also wish to thank the Ensembles project, funded by the European Commission's 6th Framework Programme, through contract GOCE-CT-2003-505539, for supplying us with the multimodel data sets and the GIS service at the IMEDEA for their support. We are also grateful to Xavier Rodó for his advice on the sources of climatic information, and Meritxell Genovart and three anonymous referees, whose comments helped to improve the earliest versions of the manuscript. The Servei de Protecció i Gestió de la Fauna (Environmental Department of the Catalan government) and the Ebro Delta Natural Park authorised our scientific study. The study was funded by the Ebro Delta Natural Park (Generalitat de Catalunya), grants from CIRIT (2000BEAI200029), the Spanish Ministry of Science (postdoctoral EX2003-0769, grant ref. CGL2009-08298) and the MEDICANES project (CGL2008-01271/CLI). Albert Fernandez-Chacon was supported by a FPU grant (AP2008-04476) from the Spanish Ministry of Education.

Studies of ranging behaviour can provide valuable information on the ecological requirements of a species. They may be an essential tool in designing conservation policies (Sutherland 1998, Tella et al. 1998) as they provide the information needed to predict the consequences of land-use change on species’ habitat use, especially in regions subject to major habitat transformations. In particular, knowledge of the temporal and spatial variation in ranging behaviour is needed to understand space-use patterns over species’ complete annual cycles and over a range of habitats (Blanco et al. 1998, Tella & Forero 2000, Peterjohn 2003). However, this sort of information is available for only a few species, and even then does not usually cover the non-breeding season (Suarez et al. 1997). Marsh Harriers Circus aeruginosus occur within a wide range of open habitats, including agricultural landscapes. After a dramatic population decline during 1960–80, mainly due to drainage of wetlands, contamination and direct persecution, the European population has recovered in recent decades and is currently classified as ‘Secure’ (Cramp & Simmons 1994, BirdLife International 2004). Within the Iberian Peninsula, the increase and spread of the Marsh Harrier population has been noticeable in some agricultural regions, including those dominated by intensified farmlands. This is the case in the Catalan Ebro Basin (Spain), where the breeding population increased from eight breeding pairs in 1997 to 51 in 2008 (Departament de Medi Ambient i Habitage de la Generalitat de Catalunya unpubl. data). However, little is known about the ranging behaviour of the Marsh Harrier in these agricultural areas. The objective of our study was to investigate the ranging behaviour and foraging-area requirements of the Marsh Harrier throughout the complete annual cycle in a representative agricultural area within the Iberian Peninsula.

The presence of the Mediterranean pond turtle Mauremys leprosa in the Ebre Delta (Catalonia, north-east Spain) is well documented after the late 1970s, when the first reptile distribution lists were published. Owing to the fact that the species was considered scarce, a reintroduction programme based on the release of individuals at sites with potential habitat suitability was launched. From 1999 to 2001, 234 turtles of different ages were released and subsequently monitored until 2007, in order to make a conservation diagnosis using five assessment criteria. These criteria were body condition, individual growth, reproduction, survival and population growth rate. Despite the relatively large number of turtles released, no viable population resulted from the programme. Assessment criteria suggested that: (1) released individuals showed good physical condition and satisfactory growth (the only positive results); (2) reproduction was almost absent; (3) local survival was reduced compared with that of Spanish wild populations of the species; (4) temporary emigration was high; (5) the growth rate of the population was negative. In conclusion, the results suggested that the habitat at the Ebre Delta marshes may not be favourable to the species, and that the scarce historical data record may indicate a relatively low-quality habitat; the few records may correspond to individuals dispersing from the river, a more suitable habitat. Thus, we conclude that historically scarce records may be the result of natural patchiness and heterogeneous distributions, and they are not necessarily a good indicator of relict, decimated populations. Good assessment criteria, as those proposed and used here, are necessary tools to assess results in reintroduction projects to recover endangered chelonian populations.

Abstract Over a period of two years we used radiology to investigate breeding traits in females of two western populations of the threatened Hermann's tortoise Testudo hermanni hermanni. The main purpose of the study was to see if reproductive traits – clutch size, clutch frequency, annual egg production and egg width – varied between populations in Corsica (France) and the Ebro Delta (Spain), and if these traits were affected by female body size and amounts of spring rainfall. All the breeding traits analysed were greater in the Corsican population than in the Ebro Delta population. These differences were also significant when we used female body size as a covariable. In both populations the amount of spring rainfall affected breeding traits but not clutch size. Nevertheless, only in the Corsican population did clutch frequency, annual egg production and egg width increase significantly in the year with a wet spring. Contrary to the predictions of Optimal Propagule Size theory, we found that egg size and clutch size increased with female size, and that both variables were independent. On the other hand, clutch frequency was not related to female body size. Thus, in the Hermann's tortoise, as clutch size did not change between years and clutch frequency was independent of female size, all females are able to increase their reproductive output in years with favourable conditions by increasing their clutch frequency. Nevertheless, other factors besides female size and rainfall may influence in a highly complex way variability in breeding traits among populations.

The ability to control infections is a key trait for migrants that must be balanced against other costly features of the migratory life. In this study we explored the links between migration and disease ecology by examining natural variation in parasite exposure and immunity in several populations of Lesser Black-backed Gulls (Larus fuscus) with different migratory strategies. We found higher activity of natural antibodies in long distance migrants from the nominate subspecies L.f.fuscus. Circulating levels of IgY showed large variation at the population level, while immune parameters associated with antimicrobial activity showed extensive variation at the individual level irrespective of population or migratory strategy. Pathogen prevalence showed large geographical variation. However, the seroprevalence of one of the gull-specific subtypes of avian influenza (H16) was associated to the migratory strategy, with lower prevalence among the long-distance migrants, suggesting that migration may play a role in disease dynamics of certain pathogens at the population level.

Growth ring counts on the shell have been widely used for age estimation in Chelonians. However, as stated by Wilson et al. (2003), most studies have applied this method without assessing its reliability by proving that 1 : 1 ratio between number of rings and real age exists. In the present study, the reliability of this method is analysed for a population of Hermann's Tortoise, Testudo hermanni introduced in the Ebro Delta (NE Spain). Age estimations were obtained from direct observations of tortoises in the field in 2000 (n = 82) together with those from photographs of the same and other individuals of the population taken between 1991 and 2001 (n= 356). A second photograph was taken at one or more years after the first one for 101 individuals. Results of Model II linear regression analysis indicated that the method was reliable only for tortoises between 0 and 7 years old, whereas tended to underestimate age for those between 8 and 11 years. Since, sexual maturity in this population is attained around 8 years (mean for both sexes), ring counts are only reliable for juveniles and subadults. Finally, it is noteworthy that the results coming for photographs were equivalent to those coming from direct observations in the field.

Small and peripheral populations are typically vulnerable to local extinction processes but important for the metapopulation dynamics of species. The Slender-billed gull (Chroicocephalus genei ) is a long-lived species breeding in unstable ephemeral coastal habitats. Their Western Mediterranean populations are relatively small and represent the edge of their global geographical distribution. At a local scale, using long-term data (14 years) on annual breeding success and capture-resights of marked individuals, we estimated and compared the vital rates and evaluated the connectivity of two Spanish populations (Ebro Delta and Doñana) varying in their local environmental conditions. At a metapopulation scale, we analyzed 22 years of data on breeding numbers to predict their future prospects by means of population demographic models. Local survival and breeding success of gulls from the Ebro Delta was lower than those from Doñana, which is likely the result of higher permanent emigration and/or winter mortality in the former. Gulls from the Ebro Delta wintered mostly in Mediterranean areas whereas those from Doñana did so in Atlantic coasts, where food availability is higher. Whereas adult local survival was constant, juvenile local survival showed temporal parallel variations between colonies, probably related to natal dispersal to other breeding colonies. Our results suggested that dispersal was higher at the Ebro Delta and gulls emigrating from their natal colonies settled preferentially in close patches. We found large fluctuations in breeding numbers among local populations probably related to the fact that the Slender-billed gull is a species adapted to unstable and unpredictable habitats with high abilities to disperse between suitable patches depending on environmental stochastic conditions during breeding. © 2014 Sanz-Aguilar et al.

Dispersal is a key process for the population dynamics of spatially structured populations (at local and metapopulation levels), so the understanding of the mechanisms underlying the movement of individuals in space and time is important for evolutionary and ecological studies. Here we analyzed, for the first time, a long-term (1992–2009) multi-site capture– recapture database collected at four local populations of a long-lived seabird, the Audouin’s gull Larus audouinii, covering 90% of its total world population. Those local populations show different ecological and demographic features that allow us to assess the influence of several key factors involved in breeding dispersal patterns at large spatio-temporal scales. A recently developed analytical tool in mark–recapture modelling, the multi-event approach, allowed us to obtain separate departure and settlement probabilities and test different biological hypotheses for each step of the dispersal process. Our results revealed that site fidelity was the most common strategy among breeders, and dispersal was only high from the site with the lowest population size and habitat quality. However, departures from the two largest local populations increased over the study period in response to severe ecological perturbations. Dispersers chose different settlement patches depending on their site of origin, with settlement choices determined by the population size of the destination colony rather than by the local reproductive performance, foraging area (a proxy of food availability) or distance to the destination site. Our results indicate that a breeding site is not abandoned by breeders unless a series of cumulative perturbations occur; once dispersing, settlement is directed towards densely populated sites, with dispersers using population size to rapidly assess the quality of the breeding patch.

Lead poisoning in waterfowl was investigated during 1991/92 at the Ebro Delta Natural Park. Sediment examination showed a lead shot concentration available to waterfowl ranging from 60,149 to 544,748 shot pellets/ha in some zones. Examination of gizzards from 108 bird carcasses confirmed that four different species had ingested lead shot. To establish prevalence values for waterfowl, 50 ducks, mainly mallards (Anas platyrhynchos) (n=40), were captured. Examination of the gizzard contents revealed that 25% of the mallards had ingested lead pellets. Lead concentration in liver and kidneys was determined by atomic absorption spectrometry, and the diagnostic concentration values for both of the organs were studied. The mallard population was divided into two groups, based on the presence or absence of lead shots in their gizzards. After a probit transformation of data, threshold values were 1.5 μg/g WW in liver and 3.0 μg/g WW in kidneys. The results derived from lead concentrations and gizzard examination showed that 27% of the mallards in the winter period were poisoned, which represents about 10,000 individuals of a population of 36,500 mallards in the Ebro Delta.