Red-legged Partridge Alectoris Rufa Research Articles

Prioritising Research in Steppe Bird Conservation: A Literature Survey

With the aim to identify priorities in conservation-oriented research, this paper reviews the level of scientific attention given to steppe birds in Spain during the last 50 years. We surveyed scientific literature using Thomson Reuters Web of Science and the journal Ardeola, using the English names of 28 species of steppe birds and the word “Spain” as search terms. Every species was assigned a Scientific Attention Index (SAI), based on the number of articles published on each of them. In addition, a vulnerability measure (Vulnerability Score; VS) was calculated for each species on the basis of the trend estimate provided by the Sacre or Noctua monitoring programmes, or according to expert criteria. The sample gathered (432 articles) was a significant and thus representative proportion of WOS and Ardeola contents on the species considered. The most studied species was the red-legged partridge Alectoris rufa, with 83 papers (20.15%); while the least studied was the short-eared owl Asio flammeus (1 paper; 0.24%). The most studied knowledge area was Habitat Selection (92 papers; 22.17%), while the least was Niche/Climate, with nine papers (2.17%). Preferred habitat (grass steppe, shrub steppe or mixed) was not a significant factor in the level of scientific attention given to the different species. However, large-sized species (non-Passerines) were significantly more studied than small-sized ones (Passerines), indicating a research bias for the former group. Finally, no significant relationship was found between SAI and VS, which suggests that research effort has been allocated irrespective of the species' conservation status. These results highlight the scarce scientific attention given to most steppe birds in Spain in spite of their overall high vulnerability, and for most of the knowledge areas considered. On the other hand, they also show the high relative importance of research carried out in Spain, in both the Mediterranean and world contexts. This work underscores the need to focus scientific effort on certain species, especially those that currently show more regressive trends or higher levels of vulnerability, and in most areas of knowledge.

Gender-related amino acid intake of adult wild Red-legged Partridge (Alectoris rufa)

The Red-legged Partridge (Alectoris rufa) is under an enormous hunting pressure. It is bred intensively in game farms. The hunting season is during the non-reproductive resting period when partridges are at maintenance conditions.There is a lack of information about the amino acid (AA) composition of the natural diet of the adult birds in their habitat or differences in dietary AA composition related to gender. The objective of this work was to establish a first approach to the AA composition of the natural diet of adult wild Red-legged Partridge.Food content in crops and gizzards of female and male birds hunted in the same hunting season and area was analysed for AA composition.Females food had higher concentrations of individual essential AA (EAA) and non-essential AA (NEAA) than males.There are important differences in the concentration of AA in the natural diet of wild females and males. It may be advisable to use diets differing in the proportion of individual AA in the game farms during the non-reproductive resting period.

Anti-predator behaviour of adult red-legged partridge (Alectoris rufa) tutors improves the defensive responses of farm-reared broods

The aim of this work was to improve natural anti-predator behaviour of farm-reared gamebirds.We evaluated the anti-predator behaviour of reared red-legged partridge Alectoris rufa chicks kept in brooder houses in large groups (>350 chicks), trained and not trained by parent red-legged partridges acting as experienced tutors.The experiment consisted of two conditioned tests (a raptor model and a human) and two control tests, which were conducted during three consecutive phases of life (1–4, 15–17 and 30–32 d after hatching). The motor anti-predator behaviour, its duration, the intensity of response in chicks and alarm calls elicited by adults were recorded.Tutors elicited aerial alarm calls (76% of tests) and showed prolonged crouching (59% of tests) in response to the raptor model whereas uttering the ground alarm call (73% of tests) and showing vigilance behaviour (78% of tests) was the main pattern during the human test.Trained and not trained chicks showed similar motor behaviour in response to the raptor model (crouching) and the human test (escaping), but frequency of strong responses (all chicks responding) from chicks trained with tutors was double that of chicks trained without them, and chicks trained with tutors showed a higher frequency of long responses (41–60 s).This study indicates that anti-predator training programmes before release may improve behaviour of farm-reared partridges which may confer benefits to survival of birds.

Comparison of Three Temperatures for the Hatching Phase in the Artificial Incubation of Red-legged Partridge (Alectoris rufa) Eggs

This study aimed at investigating the effects of three incubation temperatures during the hatching period on egg weight loss, hatchability, chick weight at hatching and length of the incubation period of red-legged partridge (Alectoris rufa) under artificial incubation. One hundred and fifty eggs obtained from a red-legged partridge game farm were randomly allocated to three batches of 50 eggs each. Eggs were incubated at 37.8oC during the first 20 days, and subsequently at 37.0, 37.4 or 37.8oC until hatching. Fertility was 74.7% and a good hatching performance was obtained, characterized by 85.7% hatchability, 9.1% egg weight loss after 20 days of incubation, 13.8±0.1 g chick weight at hatching, and 23.2±0.1 days incubation length. Hatchability, egg weight loss after 20 days of incubation, and length of the incubation period were not affected by incubation temperature during the hatching period. However, hatching synchrony improved when the incubation temperature was increased from 37.0 to 37.8°C (p<0.05). Thus, hatching distribution became very leptokurtic and very positively skewed with the increase in incubation temperature during the hatching phase. In conclusion, higher hatching synchrony can be achieved in A. rufa when setting temperatures within the range 37.0 to 37.8oC to incubate eggs during the hatching period. Consequently, incubation temperature management during the hatching phase may have a direct impact on hatching synchrony and hatchling management.

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.

Factors Affecting Red-Legged PartridgeAlectoris rufaAbundance on Big-Game Hunting Estates: Implications for Management and Conservation

The red-legged partridge Alectoris rufa is not only the most important bird game species but also an important prey species for many predators in Iberia. However, its populations have significantly declined in recent decades, principally as the result of agricultural intensification on arable land. Its abundance has also undergone a significant decline in forested areas over the last few decades, where wild ungulate management and abundance have increased. In this scenario, we aimed to test the factors that affect red-legged partridge abundance in relation to high wild ungulate (wild boar and red deer) abundance in south-central Spain. The factors included as predictors were carnivore, wild boar and red deer abundances, vegetation features, nest predation rate and invertebrate availability. Red deer abundance showed a negative relationship with partridge abundance in spring (non-significant negative trends were also evident for carnivore and wild boar), whereas variables related to food availability (grass biomass, Hemipteran abundance and total invertebrate mass) had a positive effect in the same season. Moreover, deer and carnivore abundances and spring nest predation rate were negatively associated with partridge abundance in autumn. Plant biomass and Hemipteran abundance were negatively correlated with wild boar abundance, whereas maximum pasture height was negatively related to red deer and wild boar abundance. Overall, our results show that high ungulate densities may negatively affect partridge abundance, which may be mediated by (i) a reduction in food availability (invertebrate and herbaceous plant biomass) and (ii) nest predation by wild boar. This research has shown that current intensive big-game hunting management schemes in south-central Spain are often incompatible with red-legged partridge conservation, and that these effects should be taken into account when defining big-game management and conservation policies.

Successful use of artificial insemination in the production of red-legged partridges (Alectoris rufa)

This paper reports the first successful artificial insemination (AI) of red-legged partridges (Alectoris rufa), the fertility rate achieved, and the length of time sperm cells can survive inside the oviduct (i.e., the post-AI fertile period). Semen from 20 mature males was collected by massage and pooled for use in single intravaginal inseminations (20 μL of fresh, undiluted semen) of eight females (15 × 106 sperm/female). The latter’s eggs were then collected for 4 weeks, and the fertilizing capacity of the sperm used in the preceding AIs was determined by observing the development of the blastoderm. The duration of the post-AI fertile period was determined by subjecting fertilized eggs to the SP-holes assay. A second experiment was then performed to measure the percentage of viable embryos at 20 days of incubation (30 %) and hatchability (40 %). The mean fertility rate was 34.5 ± 11.7 % and the SP-holes value 17.3 ± 4.3. The mean duration of the post-AI fertile period was 3 weeks. In conclusion, the present work reports the first ever birth of partridge chicks following AI and shows that this procedure may be of use in the conservation of this species.

First finding of spontaneous infections with Cryptosporidium baileyi and C. meleagridis in the red-legged partridge Alectoris rufa from an aviary in the Czech Republic

This paper represents the first report of spontaneous infection with Cryptosporidium baileyi and Cryptosporidium meleagridis in the red-legged partridge (Alectoris rufa), as well as the percentage of positive samples and age-associated dynamics of cryptosporidial infections in an aviary in the Czech Republic. The entire infection process was monitored over two semesters (July–December 2012 and 2013) until release of birds for hunting purposes. Coprological examination of 663 pooled fecal samples and 89 post-mortem examinations of red-legged partridges were carried out. Our results indicated that infections with C. baileyi only occurred in 5–7 week-old birds during 2013 (percentage of positivity, 1%) and those with C. meleagridis in 18–22 week (17%) and 17–21 week-old birds (24%) during 2012 and 2013, respectively. Molecular characterization of isolates of C. baileyi and C. meleagridis heat shock protein 70 and actin genes were analyzed in order to support our coprological results. DNA sequence analysis of the 60kDa glycoprotein gene was used to subtype C. meleagridis. Our findings extend the host range for C. baileyi.

Evaluation of some theoretical Habitat improvement actions in a Mediterranean area through observation of pheasant and red-legged partridge land uses

Red-legged partridge (Alectoris rufa) and Pheasant (Phasianus colchicus) have suffered population declines in the last decades. Several researches have suggested that the decline is related to the habitat alterations in agricultural ecosystems caused by intensification of agricultural techniques and land abandonment. We evaluated habitat use and distribution of red-legged partridges pairs and cock pheasants in an estate that can be representative of most of the agricultural Mediterranean areas from 2007 to 2012 with particular attention to the effect of artificial Habitat Improvement Actions (HIAs) and other management options as supplemental feeding and hedgerows maintenance. We compared the habitat use with its availability and we analyzed the spatial distribution by comparing points with pheasant cocks and partridge pairs with random ones. HIAs were used more then their availability by both species and resulted to have an important role in their distribution as well as hedgerows. Feeders resulted to have a strong effect on pheasant distribution, but not on partridges pairs. Our results showed that habitat management could be a fundamental tool for game-birds conservation, however the effectiveness of the employment of artificial feeders need to be better clarified for red-legged partridges.

Audience effect on aerial alarm calls in the monogamous red-legged partridge

The presence of conspecifics can affect alarm calls and in particular the signaller's behaviour. This study investigated the anti-predator response in males of a monogamous species, the red-legged partridge (Alectoris rufa), in relation to the audience. Aerial alarm calls and nonvocal behaviour were analyzed, in order to assess whether they were affected by the presence of an audience, and in particular by the audience's composition: unfamiliar males, unfamiliar females and signallers’ mates. Rate and spectrographic characteristics of the alarm calls, as well as behavioural responses to a dummy avian raptor, were analyzed in a sample of 18 farm-reared males. Our findings show that the presence of conspecifics was able to alter the number and structure of male alarm calls. In addition, the number of alarm calls drastically decreased when no audience was present: when the male was alone, it might even not vocalize, thus reducing predation risk. The audience composition was also important; the presence of the signaller's mate elicited more calls than that of an unfamiliar male. The spectrographic structure of alarm calls was affected by the audience, mainly in terms of peak frequency. This study shows that alarm calls of red-legged partridge males are influenced by the audience, and in particular by the presence of the signaller's mate: red-legged partridge males in presence of their mates not only warn them by increasing alarm calling rate, but also produce less detectable calls.

Density and habitat requirements of red-legged partridge on Elba Island (Tuscan Archipelago, Italy)

The red-legged partridge (Alectoris rufa, Linnaeus 1758, Phasianidae) is a common game bird in Europe and it is classified as SPEC 2 (Species of European Conservation Concern), that is, a species with unfavorable conservation status due to a marked population decline. Loss of suitable habitat and hunting management are considered among the major causes of its decline. Such a decline can be also related to agriculture intensification, changes in agricultural practices and the abandonment of less productive lands. Habitat suitability models are an important management tool to define the potential distribution range of a given species, design a protected area network, and plan appropriate management actions and evaluate their effects. This study was conducted on Elba Island (Tuscany) in spring 2011 to define the habitat factors that affect the A. rufa distribution in a typical Mediterranean landscape. On this island the species is declining, as it is in other areas of Europe. We carried out point counts in a survey stratified according to vegetation. We formulated Resource Probability Selection Functions following a presence vs. availability design by Binary Logistic Regression Analysis to obtain a map of potential distribution of the species. We observed that the red-legged partridge distribution was mainly linked to the natural habitat with garrigue and perennial meadows, whereas woody landscape had a negative effect. To stop the species decline on the island habitat improvement actions are needed, such as the cutting of dense vegetation to create open areas.

Free and Esterified Carotenoids in Ornaments of an Avian Species: The Relationship to Color Expression and Sources of Variability

Many animal species show ornaments with yellow-orange-red colors produced by carotenoid pigments. Such traits have evolved as reliable signals of individual quality because of the costs inherent to their production or maintenance. In animal tissues, carotenoids are often found combined with free fatty acids, as carotenoid esters, which may confer more stability to coloration than free carotenoids. Surprisingly, the potential relevance of carotenoid esterification in the expression of animal sexual signals has been virtually ignored. Moreover, the sources of variability of esterified carotenoid levels are barely known, because most studies have not quantified their concentrations. Here, carotenoids in the ornaments (bill, eye rings, and legs) of red-legged partridges Alectoris rufa were quantified in their free and esterified forms. Carotenoid ester levels were the best predictors of leg color, whereas the redness of the other traits was better explained by free carotenoids. Nonetheless, total carotenoid levels (the sum of free and esterified forms) were always significantly correlated to redness. Young partridges had lower levels of free and esterified carotenids in the legs than did older individuals. Also, wild animals had higher ester levels and a higher proportion of carotenoids in esterified forms in all traits than did captive partridges. Probable physiological mechanisms explaining these patterns are discussed.

Use of an AG Microsatellite to Characterise Alectoris Species

The red-legged partridge ( Alectoris rufa) is normally found in the Iberian Peninsula, southern France and some points of northern Italy and southern England. A number of factors have drastically reduced the number of wild red-legged partridges in these areas. It is necessary to know their genetic situation and to identify different populations and species. Microsatellite markers are very effective genetic markers. In order to identify microsatellite markers in this species to gain genetic knowledge of their populations, DNA was cleaved partially with AluI and ligated in plasmid pSMART; this was inserted in Escherichia coli to obtain a whole genome library. This library was screened by amplifying with the polymerase chain reaction and then sequencing the A. rufa DNA in plasmids isolated from colonies selected at random. Some of the sequenced PCR products were found to contain possible microsatellite sequences and two of these were used to characterise four different species of Alectoris. One of these sequences (GTTTT) was always found to be repeated three times but the number of repeats of the second one (AG) was found to vary between species. Therefore, the (AG)n microsatellite may be a good candidate to distinguish between species of the genre Alectoris.

Effect of Game Management on Wild Red-Legged Partridge Abundance

The reduction of game and fish populations has increased investment in management practices. Hunting and fishing managers use several tools to maximize harvest. Managers need to know the impact their management has on wild populations. This issue is especially important to improve management efficacy and biodiversity conservation. We used questionnaires and field bird surveys in 48 hunting estates to assess whether red-legged partridge Alectoris rufa young/adult ratio and summer abundance were related to the intensity of management (provision of supplementary food and water, predator control and releases of farm-bred partridges), harvest intensity or habitat in Central Spain. We hypothesized that partridge abundance would be higher where management practices were applied more intensively. Variation in young/adult ratio among estates was best explained by habitat, year and some management practices. Density of feeders and water points had a positive relationship with this ratio, while the density of partridges released and magpies controlled were negatively related to it. The variables with greatest relative importance were feeders, releases and year. Variations in post-breeding red-legged partridge abundance among estates were best explained by habitat, year, the same management variables that influenced young/adult ratio, and harvest intensity. Harvest intensity was negatively related to partridge abundance. The other management variables had the same type of relationship with abundance as with young/adult ratio, except magpie control. Variables with greatest relative importance were habitat, feeders, water points, releases and harvest intensity. Our study suggests that management had an overall important effect on post-breeding partridge abundance. However, this effect varied among tools, as some had the desired effect (increase in partridge abundance), whereas others did not or even had a negative relationship (such as release of farm-reared birds) and can be thus considered inefficient or even detrimental. We advise reconsidering their use from both ecological and economical points of view.

Does the use of playback affect the estimated numbers of red–legged partridge Alectoris rufa?

The red–legged partridge Alectoris rufa lives in a situation of potential conservation risk for its long–term preservation in Italy as its habitat is increasingly threatened by the disappearance of traditional agriculture–related environments. In such a situation, it is important to use effective and appropriate monitoring methods to assess population changes over time and to identify potential conservation threats. The objective of this study was to evaluate the effectiveness of the playback method to estimate the density of calling males. We compared playback method with spontaneous calling of males at dawn and direct observations along transects. The results on raw count data of playback counts revealed a strong underestimation rate compared to the method that gave the best results: count of spontaneous calls at dawn. Our study provides a critical evaluation of a method that is widely used even though data about its effectiveness are scarce. Our data do not evaluate detection probability of the three methods. Our aim was only to evaluate which methods give the best results in term of population size estimation under the same field condition (same population density, same period, same monitoring area). The results raise some doubts about the ability of the playback method to monitor red–legged partridge populations. The implications of our results for red–legged population management are discussed.

Water-site selection and behaviour of red-legged partridge Alectoris rufa evaluated using camera trapping

This paper explores watering patterns of wild red-legged partridges at water troughs (WT) during three consecutive summers on a farm-land area of Spain where drought periods are frequent. Camera trapping was used in order to assess climatic effects on weekly and daily watering patterns, investigate the influence of shrub cover on water-site selection, evaluate behavioural patterns displayed when using WT, and describe age and number of birds observed at WT. Red-legged partridges used WT throughout the study period, but significant use did not occur until August, decreasing dramatically in mid September, and ending in October. A circadian watering pattern was observed during daylight hours with most photographs taken from 08:00hours to 11:00hours (54.8%). Partridges displayed different behaviours (drinking, feeding/dusting, vigilance, moving/unknown), but patterns did not vary significantly throughout the day. WT were used mostly by adult birds with only 26.5% of photographs also depicting young partridges. WT selection was strongly influenced by the presence of surrounding vegetation as partridges preferred troughs with shrub cover. We also found a significant negative relationship (P<0.05) between the percentage of vigilant birds and covey size at water sources with shrub cover. Given the high predation rates observed in this species, security risk is likely an important factor involved in water-site selection.

Contrasted effects of an oxidative challenge and α-melanocyte-stimulating hormone on cellular immune responsiveness: an experiment with red-legged partridges Alectoris rufa

Oxidative stress is increasingly recognized as a key selective force shaping evolutionary trade-offs. One such trade-off involves investing in immunity versus combating oxidative stress. While there is broad evidence that mounting an immune response causes increased oxidative stress, the effect that increased oxidative stress during development has at a later stage on immune responsiveness remains little known. The production of melanin-based coloration in vertebrates is influenced by oxidative stress and by hormones, such as the alpha-melanocyte-stimulating hormone (α-MSH). Oxidative stress could impair immunity, and this might be a cost associated with the production of melanin traits. α-MSH has immunomodulatory effects, with most evidence pointing towards an improvement of immunity (improved pro-inflammatory activity). Here, we investigated the effects of an oxidative challenge (exposure to a pro-oxidant compound, diquat) and of experimentally elevated α-MSH on the cell-mediated immune responses (CMIR) of growing young (1 month old) red-legged partridges Alectoris rufa in captivity. CMIR were assessed in response to primary and secondary challenges with phytohemagglutinin (PHA). We specifically tested whether an oxidative challenge during growth and development had a delayed effect (4 months after exposure) on immunity. We found that the diquat treatment did not affect primary CMIR, but significantly reduced secondary CMIR. Elevated α-MSH increased primary CMIR in males, but not in females. Our experimental results are consistent with a trade-off between investing in activities that generate oxidative stress (e.g., growth, reproduction, production of ornaments) versus investing in immunity, and shed new lights onto the inter-relationships between immunity, oxidative stress and the expression of melanin-based coloration in vertebrates, revealing a novel, delayed physiological cost that can contribute to ensuring honest signaling.

Predator–prey relationships in a Mediterranean vertebrate system: Bonelli’s eagles, rabbits and partridges

How predators impact on prey population dynamics is still an unsolved issue for most wild predator-prey communities. When considering vertebrates, important concerns constrain a comprehensive understanding of the functioning of predator-prey relationships worldwide; e.g. studies simultaneously quantifying 'functional' and 'numerical responses' (i.e., the 'total response') are rare. The functional, the numerical, and the resulting total response (i.e., how the predator per capita intake, the population of predators and the total of prey eaten by the total predators vary with prey densities) are fundamental as they reveal the predator's ability to regulate prey population dynamics. Here, we used a multi-spatio-temporal scale approach to simultaneously explore the functional and numerical responses of a territorial predator (Bonelli's eagle Hieraaetus fasciatus) to its two main prey species (the rabbit Oryctolagus cuniculus and the red-legged partridge Alectoris rufa) during the breeding period in a Mediterranean system of south Spain. Bonelli's eagle responded functionally, but not numerically, to rabbit/partridge density changes. Type II, non-regulatory, functional responses (typical of specialist predators) offered the best fitting models for both prey. In the absence of a numerical response, Bonelli's eagle role as a regulating factor of rabbit and partridge populations seems to be weak in our study area. Simple (prey density-dependent) functional response models may well describe the short-term variation in a territorial predator's consumption rate in complex ecosystems.

Laying the Foundations for a Human-Predator Conflict Solution: Assessing the Impact of Bonelli's Eagle on Rabbits and Partridges

BackgroundPredation may potentially lead to negative effects on both prey (directly via predators) and predators (indirectly via human persecution). Predation pressure studies are, therefore, of major interest in the fields of theoretical knowledge and conservation of prey or predator species, with wide ramifications and profound implications in human-wildlife conflicts. However, detailed works on this issue in highly valuable –in conservation terms– Mediterranean ecosystems are virtually absent. This paper explores the predator-hunting conflict by examining a paradigmatic, Mediterranean-wide (endangered) predator-two prey (small game) system.Methodology/Principal FindingsWe estimated the predation impact (‘kill rate’ and ‘predation rate’, i.e., number of prey and proportion of the prey population eaten, respectively) of Bonelli's eagle Aquila fasciata on rabbit Oryctolagus cuniculus and red-legged partridge Alectoris rufa populations in two seasons (the eagle's breeding and non-breeding periods, 100 days each) in SE Spain. The mean estimated kill rate by the seven eagle reproductive units in the study area was c. 304 rabbits and c. 262 partridges in the breeding season, and c. 237 rabbits and c. 121 partridges in the non-breeding period. This resulted in very low predation rates (range: 0.3–2.5%) for both prey and seasons.Conclusions/SignificanceThe potential role of Bonelli's eagles as a limiting factor for rabbits and partridges at the population scale was very poor. The conflict between game profitability and conservation interest of either prey or predators is apparently very localised, and eagles, quarry species and game interests seem compatible in most of the study area. Currently, both the persecution and negative perception of Bonelli's eagle (the ‘partridge-eating eagle’ in Spanish) have a null theoretical basis in most of this area.

Isolation from predators: a key factor in the failed release of farmed red-legged partridges (Alectoris rufa) to the wild?

1. The effects of predation isolation were studied in two lines of 10 month-old farmed red-legged partridges (Alectoris rufa). Birds came from bred generations in captivity (F) and directly from wild parents (W). 2. Releases were carried out in March for two consecutive years on private farmland with a stable population of wild red-legged partridge using 68 tagged birds (36 F, 32 W). 3. No statistical differences were found in survival time (mean 18 d) or home range values (mean 7·38 ha); 49% of mortality was attributable to raptors, 36% to wild canids and 15% had doubtful causes of death. F birds suffered more predation by raptors and W partridges more by mammalian carnivores. 4. A statistical difference was found in post-release dispersion: the means were 243·4 m in F and 593·3 m in W. 5. The result of predation isolation was similar in both groups, which confirms the adverse effects of current production systems on anti-predator behaviour. Farmers should consider the introduction of new rearing techniques with the aim of improving survival after release.