Recovery of saltwater crocodiles following unregulated hunting in tidal rivers of the Northern Territory,Australia

Saltwater crocodiles (Crocodylus porosus) in the Northern Territory of Australia were protected in 1971, after a severe population decline resulting from 26 yr of intense commercial hunting. By that time wild saltwater crocodiles were rarely sighted anywhere and they were commercially extinct in areas where they had once been abundant. Standardized monitoring by spotlight surveys started in 1975 and provided relative density indices over time (1975–2009) as a unique record of the post-protection recovery of a wild crocodilian population. We examined the survey data for populations at 12 major tidal rivers, individually and as a single subpopulation. The pattern of recovery in the subpopulation in both abundance and biomass was approximated by logistic curves, predicting 5.26 non-hatchling crocodiles weighing 387.64 kg sighted per kilometer of river in 2010. We predicted potential carrying capacity as 5.58 non-hatchling crocodiles (5.73% higher than 2010) weighing 519.0 kg (25.31% higher than 2010). Individual rivers showed largely different abundance and biomass among rivers. The statistical model that best described the recovery in individual rivers was not always logistic. However, where it was logistic, expected carrying capacity of different rivers showed considerable variation in abundance and biomass. The variation indicates different habitat quality among the rivers. Recovery occurred despite various consumptive uses, particularly a widespread egg-harvest program, which has been an integral part of the incentive-driven conservation program for saltwater crocodiles in the Northern Territory since 1983. We suggest that the saltwater crocodile population of the Northern Territory is achieving full recovery from uncontrolled hunting in 1945–1971. Although saltwater crocodiles are considered an important natural resource, their increase in number, size, and distribution is posing management issues for public safety. Continuation of human–crocodile conflict management through public education and strategic removal of problem crocodiles will be essential. © 2011 The Wildlife Society.     

REBUILDING SEAL STOCKS IN THE KATTEGAT-SKAGERRAK

The harbor seal ( Phoca vitulina ) population in the Kattegat-Skagerrak area has been dwindling for several centuries due to excessive hunting pressure. Corrected hunting statistics during 1890–1976 are used to estimate changes in population size over the past century. After protection was introduced in the 1960s and 1970s the harbor seal population in the area increased at an exponential rate of 0.12 and exceeded 5,000 animals in 1986. The present rate of population growth is used for modelling the influence of fertility and age-specific mortality. It is found that the observed high rate of increase is only realistic if female fertility rate is very high, the range of juvenile mortality rate is 0.33–0.52 and adult mortality is less than 0.15. Commonly cited higher mortality rates are not realistic in the Kattegat-Skagerrak area.     

Long-term dynamics of wild primate populations across forests with contrasting protection in Tanzania

Anthropogenic activities driving tropical forests' loss imperil global biodiversity and provision of ecosystem services. In this context, systematic monitoring programs evaluating wildlife trends are essential. Non-human primates are relevant conservation targets since they represent vital components of tropical forests by serving as pollinators and seed dispersers. Here, we present primate group counts data collected over 19 years in a primate hotspot in Tanzania. We analyzed data with a hierarchical dynamic model accounting for imperfect detection that estimates local group abundance and temporal rates of change, to assess whether habitat protection explained trends of the arboreal and diurnal Peters' Angola colobus (Colobus angolensis palliatus), Udzungwa red colobus (Piliocolobus gordonorum), and Tanzania Sykes' monkey (Cercopithecus mitis subsp. moloneyi). We targeted populations occurring in two forest blocks with contrasting protection regimes, with one block impacted by targeted poaching of the two Colobus species. We found that these latter species were much less abundant in the more human impacted forest, underwent a rapid decline, and subsequently remained at low abundance and without signs of recovery once this forest was granted greater protection. Instead, Sykes' abundance did not differ between forests, and improved protection was associated with a slight increase in abundance. Age class composition for social groups of both Colobus species differed between forests, indicating altered births and survivorship rates in the impacted forest. Results suggest that targeted hunting can prevent recovery for several years and even after increased habitat protection. Our approach appears valuable to monitor population dynamics over the long term, highlighting species-specific variations in both vulnerability to anthropogenic disturbance and recovery patterns in primate populations.     

Evaluating the protection of wildlife in parks: the case of African buffalo in Serengeti

Human population growth rates on the borders of protected areas in Africa are nearly double the average rural growth, suggesting that protected areas attract human settlement. Increasing human populations could be a threat to biodiversity through increases in illegal hunting. In the Serengeti ecosystem, Tanzania, there have been marked declines in black rhino (Diceros bicornis), elephant (Loxodonta africana) and African buffalo (Syncerus caffer) inside the protected area during a period when there was a reduction of protection through anti-poaching effort (1976–1996). Subsequently, protection effort has increased and has remained stable. During both periods there were major differences in population decline and recovery in different areas. The purpose of this paper is to analyse the possible causes of the spatial differences. We used a spatially structured population model to analyze the impacts of three factors—(i) hunting, (ii) food shortage and (iii) natural predation. Population changes were best explained by illegal hunting but model fit improved with the addition of predation mortality and the effect of food supply in areas where hunting was least. We used a GIS analysis to determine variation in human settlement rates and related those rates to intrinsic population changes in buffalo. Buffalo populations in close proximity to areas with higher rates of human settlement had low or negative rates of increase and were slowest to recover or failed to recover at all. The increase in human populations along the western boundary of the Serengeti ecosystem has led to negative consequences for wildlife populations, pointing to the need for enforcement of wildlife laws to mitigate these effects.     

Hunting behavior of Florida largemouth bass, Micropterus salmoides floridanus, in a channelized river

The distribution and behavior of Florida largemouth bass, Micropterus salmoides floridanus, and their main prey (sunfish, genus Lepomis, and the cichlid Tilapia mariae) were studied in southern Florida to determine how fish behave in the simplified habitats found in channelized rivers. Time budgets were constructed from focal animal observations on 69 bass. Patterns of behavior associated with hunting were performed during a significantly higher proportion of the time when bass were in vegetated habitats. Scan samples of the behavior of 236 observed bass revealed that hunting was more common in areas of high structural complexity. Only 38% of observed bass were solitary, with the majority occurring in groups with either conspecifics or in mixed-species groups with similar sized bluegill sunfish, Lepomis macrochirus. Largemouth bass (n=1014) and sunfish (n=1372) were significantly more abundant in areas with vegetation and were almost entirely absent from the water column in the center of the canal. All species of fish avoided the water column, where currents were swift and no cover was available. The structure of the habitat appears to be important in the way largemouth bass organize their activity patterns. This suggests that habitat availability in channelized rivers significantly influences important behaviors such as hunting, thus potentially altering energy budgets and population dynamics of both predator and prey.     

Unregulated hunting and genetic recovery from a severe population decline: the cautionary case of Bulgarian wolves

European wolf (Canis lupus) populations have suffered extensive decline and range contraction due to anthropogenic culling. In Bulgaria, although wolves are still recovering from a severe demographic bottleneck in the 1970s, hunting is allowed with few constraints. A recent increase in hunting pressure has raised concerns regarding long-term viability. We thus carried out a comprehensive conservation genetic analysis using microsatellite and mtDNA markers. Our results showed high heterozygosity levels (0.654, SE 0.031) and weak genetic bottleneck signals, suggesting good recovery since the 1970s decline. However, we found high levels of inbreeding (F _IS  = 0.113, SE 0.019) and a N _e/N ratio lower than expected for an undisturbed wolf population (0.11, 95 % CI 0.08–0.29). We also found evidence for hybridisation and introgression from feral dogs (C. familiaris) in 10 out of 92 wolves (9.8 %). Our results also suggest admixture between wolves and local populations of golden jackals (C. aureus), but less extensive as compared with the admixture with dogs. We detected local population structure that may be explained by fragmentation patterns during the 1970s decline and differences in local ecological characteristics, with more extensive sampling needed to assess further population substructure. We conclude that high levels of inbreeding and hybridisation with other canid species, which likely result from unregulated hunting, may compromise long-term viability of this population despite its current high genetic diversity. The existence of population subdivision warrants an assessment of whether separate management units are needed for different subpopulations. Our study highlights conservation threats for populations with growing numbers but subject to unregulated hunting.     

Hunting impact on waders in Spain: effects of species protection measures

The hunting impact on waders in Spain was studied to test the efficiency of species protection measures. Using information on ringed bird recoveries in Spain of 28 species a hunting impact index was calculated. The results show a high hunting pressure similar to that of other groups of birds. The hunting impact on quarry species was higher than on protected species. The change of protection level in a group of species from quarry to protected species resulted in a decrease in hunting impact. A negative trend in the hunting impact was found during a 15-year period. This result could be due to under-reporting or falsification of death causes in the recovery report. However, recoveries of shot and dead birds showed a positive relationship in contrast with expected if found dead reports increased by falsification, suggesting that there has not been a falsification of the ring recovery reports. Nevertheless, in spite of the decrease in the hunting pressure when protection measures were applied, hunting impact remains very high on protected species for a long time and studies evaluating the impact of hunting on the population dynamics of waders needs further study.     

Infestations of Atlantic salmon, Salmo salar, by Gyrodactylus salaris in Norwegian rivers

Over the 6 years 1980–85, 212 Norwegian rivers have been examined for occurrence of Gyrodactylus salaris: it was found in 26 rivers and six salmon hatcheries scattered throughout the country from Troms county in the north to Sogn og Fjordane in western Norway. The distribution of G. salaris is connected with the stocking of fish from infected salmon hatcheries. The populations of salmon parr have been drastically reduced in the infected rivers. In later years catches of ascending salmon in these rivers have also sharply declined: in 1984 salmon fishery losses were estimated at 250–500 t.
Gyrodactylus salaris is most probably a recent introduction to Norwegian rivers. A primary aim is to exterminate this parasite from all infected rivers and hatcheries: so far this has been accomplished in one river and one hatchery.     

The decline of the otter Lutra lutra L. in Britain: an analysis of hunting records and discussion of causes

The records of one pack of Otter Hounds hunting in southwest England are examined for the period 1907 to 1971 as well as the records of all packs active in Britain between 1950 and 1976. The hunting success per unit effort varies from year to year depending on changes in hunting conditions but longer term changes can also be identified. The hunting success of the Culmstock Otter Hounds (hunting in parts of south-west England) increased steadily from 1907 to 1956 but in most of England and south Wales the success rate of the hunts declined rapidly after 1957. There was also a decline in success in northern England and southern Scotland but to a lesser extent, while in north Wales and Eire, there is no evidence for a decline.
These changes are considered to reflect changes in otter populations but the extent of the decline in hunting success (to between 37% and 55% of previous levels in the southern hunts) is probably less than the actual decline in otter numbers. There are no signs of a recovery in the population but indications of a continuing decline up to 1976.
The reason for the increasing population in the first half of the century in south-west England is probably the decrease in persecution since the nineteenth century. A variety of causes for the crash in the late 1950s are considered and the factor most likely to be responsible is the introduction of the dieldrin group of insecticides in 1956. Use of these compounds has been increasingly restricted since 1963 and the possible reasons for the failufe of the otter population to recover are listed but no firm conclusions can be drawn as yet.     

Could Have Gone Wrong: Effects of Abrupt Changes in Migratory Behaviour on Harvest in a Waterbird Population

To sustainably exploit a population, it is crucial to understand and reduce uncertainties about population processes and effects of harvest. In migratory species, management is challenged by geographically separated changing environmental conditions, which may cause unexpected changes in species distribution and harvest. We describe the development in the harvest of Svalbard-breeding pink-footed geese (Anser brachyrhynchus) in relation to the observed trajectory and migratory behaviour of the population. In autumn, geese migrate via stopover sites in Norway and Denmark (where they are hunted) to wintering grounds in the Netherlands and Belgium (where they are protected). In Denmark and Norway harvesting increased stepwise during the 2000s. The increase in the population size only partly explained the change. The change corresponded to a simultaneous stepwise increase in numbers of geese staging in Denmark throughout autumn and winter; geese also moved further inland to feed which collectively increased their exposure to hunting. In Norway the increase in harvest reflected greater utilisation of lowland farmland areas by geese, increasing their hunting exposure. The study demonstrates how changes in migratory behaviour can abruptly affect exposure to hunting, which showed a functional response to increased temporal and spatial availability of geese. The harvest has now reached a level likely to cause a population decline. It highlights the need for flexible, internationally coordinated hunting regulations and reliable up-to-date population estimates and hunting bag statistics, which are rare in European management of migratory waterbirds. Without such information decisions are left with judgments based on population estimates, which often have time lags of several years between recording and reporting, hampering possibilities for the timely adjustment of management actions.     

Geographic patterns of genetic variation in four Neotropical rodents: conservation implications for small game mammals in French Guiana

The Neotropics contributes significantly to global biodiversity yet little is known about its mammalian fauna. Given our limited knowledge, concerns are that extinctions at the local level may cause a decline in genetic diversity through the loss of unique alleles. Here we report the geographical population structure of four rodent species from French Guiana: Dasyprocta leporina , Agouti paca , Proechimys cayennensis and P. cuvieri . Two of them ( Dasyprocta and Agouti ) are commonly harvested throughout the country for subsistence and/or game hunting. Cytochrome b and control region sequences revealed the presence of a number of maternal lineages occurring in sympatry throughout French Guiana. We applied two cytochrome b rodent clock calibrations (7.5% and 12% per million years) to our data, and placed the divergence of the maternal lineages to between 160 000 and 260 000 years ago for the more diverse D. leporina and P. cuvieri , and between 66 000 and 46 000 years ago for the more recent A. paca and P. cayennensis . The clades appear to be widespread throughout South America as indicated by specimens sampled in Brazil, Peru, and Venezuela. At the population level, AMOVA revealed little or no geographical structure within French Guiana. However, this conclusion is based on a single genetic marker and relatively few specimens.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 203–218.     

Molecular assessment of the genetic integrity,distinctiveness and phylogeographic context of the Saltwater crocodile (<Emphasis Type="Italic">Crocodylus porosus</Emphasis>) on Palau

The saltwater crocodile (Crocodylus porosus) is the largest and most broadly distributed crocodilian species, and thus is of special conservation and economic interest. Similar to other parts of its range throughout the Indo-Pacific, C. porosus distributed in the Republic of Palau have experienced a severe population decline over the past century primarily due to commercial hunting and eradication campaigns. In addition, several thousand crocodiles of undocumented species and origin were imported into Palau during the 1930’s for commercial farming purposes, potentially polluting the gene pool of the endemic saltwater crocodiles. Analysis of 39 individuals collected throughout the Republic of Palau revealed a single mitochondrial DNA control region haplotype shared by populations sampled in Sulawesi, Borneo and Australia. The mtDNA results, in combination with microsatellite genotypic data at six loci, detected no evidence for inter-specific hybridization between endemic Palauan C. porosus and potentially introduced Crocodylus species. There was no evidence for a genetic bottleneck in the Palauan population, however an excess of rare alleles was identified, indirectly suggesting a recent history of admixture potentially linked to introductions of non-native C. porosus. Following from these findings, Palauan C. porosus should be included in the single ESU previously established for all saltwater crocodiles given the recovery of a fixed, but geographically widespread haplotype. Although Palauan C. porosus exhibited significant genetic differentiation relative to all other sampled populations, it’s delineation as a distinct management unit is precluded at the present time by evidence that the genetic integrity of the population may have been compromised by the introduction of non-native saltwater crocodiles.     

Anthropogenic causes of the western Steller sea lion Eumetopias jubatus population decline and their threat to recovery

• 1 The western Steller sea lion Eumetopias jubatus population has experienced a chronic decline since the 1960s. The causes are likely multifactorial and a combination of anthropogenic and natural factors. A draft revised recovery plan for the Steller sea lion has been published by the US National Marine Fisheries Service, listing both anthropogenic and natural factors that may have contributed to the observed decline or which may be a threat to the recovery of the western Steller sea lion population. The purpose of this review is to consider the anthropogenic threats to this stock.
• 2 Anthropogenic sources of mortality include fisheries competition resulting in nutritional stress, mortality incidental to commercial fisheries (i.e. fisheries by‐catch), subsistence hunts, legal and illegal shooting, commercial hunts, anthropogenic‐related contamination, and research‐induced mortalities.
• 3 We present evidence that the following anthropogenic factors likely contributed to the decline of the western Steller sea lion population over the last 40 years: (i) mortality incidental to commercial fisheries (i.e. by‐catch); (ii) commercial hunting of western Steller sea lions; and (iii) legal and illegal shooting; whereas the subsistence hunts for western Steller sea lions and mortality incidental to research were not likely to be contributors to the observed decline.
• 4 Further, we present evidence that the following can be excluded as significant anthropogenic threats to the recovery of the western Steller sea lion population: (i) mortality incidental to commercial fishing; (ii) legal and illegal shooting; (iii) commercial hunts of Steller sea lions; (iv) subsistence hunting; and (v) mortality incidental to research.
• 5 Competition with fisheries resulting in nutritional stress, and the potential impacts of contaminants, are two anthropogenic factors that should continue to be a priority for the various organizations currently doing research on this population.

     

Is nest‐site availability limiting Lesser Kestrel populations? A multiple scale approach

The Lesser Kestrel, a colonial migratory falcon, is one of the most endangered birds in Europe and, due to a sharp population decline across much of the breeding range, is globally threatened. The reasons for this decline are unclear, but reduced nest-site availability might be a major cause. To test this hypothesis we looked at nest-site availability within Portuguese colonies in rural and urban buildings. Nest holes were larger, longer, higher and older than unoccupied cavities. A typical nest cavity was approximately 29–30 cm long, 300–340 cm high and had an inner chamber 16.5–18 cm wide. Large-scale surveys of existing buildings in Portuguese villages suggested that 85% of sites lacked suitable nest cavities. The model for selection of buildings indicated that Lesser Kestrels prefer buildings with many roof and wall cavities, and that are surrounded by extensive cereal and fallow fields. The villages selected had many old buildings and monuments, were located in areas with few rivers, and a low percentage cover of cereal, olive groves and forest. The conservation implications of these results are discussed.     

Size and trends of the House Sparrow Passer domesticus population in Great Britain

House Sparrow Passer domesticus populations have declined throughout Europe over the last two to three decades; this is of particular concern in urban areas. We analysed data from extensive census schemes organized by the British Trust for Ornithology to determine the current population size of the House Sparrow in Britain, and to assess long-term patterns of change, both in the wider countryside and in urban environments. The national breeding population of House Sparrows was estimated at approximately 13 million individuals (95% confidence interval, 11.9–14.8 million), or about six million pairs. Most of these occur in southeast England and densities are greatest in suburban and rural garden habitats. Overall, populations in rural areas have declined by 47% since the mid 1970s, whereas those in urban and suburban areas have declined by about 60%. Changes in farming practices are likely to account for at least some of the decline in the wider countryside, probably related to changes in food resources, with a loss of grain in fields and more secure storage of harvested grain, though these changes are unquantified. In urban areas, there was an earlier period of decline in the first half of the 20th century due to the loss of horse-drawn transport and generally cleaner streets. The overall national decline since the 1970s masks much heterogeneity in trend among regional populations, and evidence suggests that population processes in the House Sparrow may be relatively fine-grained.     

Two centuries of the Scandinavian wolf population: patterns of genetic variability and migration during an era of dramatic decline

The grey wolf (Canis lupus) was numerous on the Scandinavian peninsula in the early 19th century. However, as a result of intense persecution, the population declined dramatically and was virtually extinct from the peninsula by the 1960s. We examined historical patterns of genetic variability throughout the period of decline, from 1829 to 1979. Contemporary Finnish wolves, considered to be representative of a large eastern wolf population, were used for comparison. Mitochondrial DNA (mtDNA) variability among historical Scandinavian wolves was significantly lower than in Finland while Y chromosome variability was comparable between the two populations. This may suggest that long-distance migration from the east has been male-biased. Importantly though, as the historical population was significantly differentiated from contemporary Finnish wolves, the overall immigration rate to the Scandinavian peninsula appears to have been low. Levels of variability at autosomal microsatellite loci were high by the early 1800s but declined considerably towards the mid-20th century. At this time, approximately 40% of the allelic diversity and 30% of the heterozygosity had been lost. After 1940, however, there is evidence of several immigration events, coinciding with episodes of marked population increase in Russian Karelia and subsequent westwards migration.     

Meta-analysis of status and trends in breeding populations of black-fronted terns (

Black-fronted tern (Chlidonias albostriatus) breeding populations on braided rivers in the South Island, New?Zealand, are assumed to be in decline as their habitat comes under increasing pressure from exotic pests, hydroelectric power development and water abstraction. We collated 326 index counts of black-fronted terns from 2313?km of surveys on 84 rivers throughout their breeding range to test this assumption. Black-fronted terns were observed on 73% (n = 61) of rivers surveyed, and the sum of the most recent counts was 8325 birds. However, >200 black-fronted terns were counted on only 14% of rivers. We used generalised linear modelling to assess whether population trends could be detected using data from 29 rivers where counts were repeated 4?18 times between 1962 and 2008. We detected significant declines on eight rivers (range 5.5?15.8% p.a.), a significant increase on one river (Eglinton; 16.3% p.a.) and no trends on the remaining 20 rivers. The Eglinton River is the only site at which sustained predator control (aimed at mustelids) occurred throughout the monitoring period. Rivers on which declines have occurred are characterised by having relatively low flows (<30 m³ s^?1). At such rates, populations on low-flow rivers (64% of rivers surveyed, representing 51.4% of black-fronted terns counted on the oldest counts) would decline by a further c. 90% within 25 years. Based on these results we predict that if flows were reduced significantly on higher-flow rivers, rates of population decline would accelerate. We conclude that the IUCN status of ?Endangered? is appropriate for black-fronted terns, based on a predicted population reduction of around 50% over the next three generations (c. 30 years). This conclusion is supported by previous studies that described significant loss of habitat, low breeding success and vulnerability to predation by introduced mammals, and population models that predict continued declines towards extinction if management aimed at recovering populations is not instigated with some urgency.     

Declining trends in the majority of Greenland’s thick-billed murre (Uria lomvia) colonies 1981–2011

Large population declines were reported for the thick-billed murre (Uria lomvia) in Greenland for the period 1930s–1980s, but no national status has been published for the past 20 years. Meanwhile, the murres have gained more protection and several human-induced mortality factors have been markedly reduced. Here, we give an updated status based on the past 30 years of murre count data. The total Greenland population in 2011 was estimated to 468,300 birds (95 % CI 430,700–505,900) or around 342,000 breeding pairs, distributed within 19 colonies. This represents an overall reduction of 13 % since the mid-/late 1980s. In the same period, five colonies went extinct. Large and apparently stable colonies in Qaanaaq (Northwest Greenland) account for more than half the population (68 %), but most other colonies declined heavily, with up to 6 % p.a. in the most critical areas. So far, nothing indicates that food is a limiting factor in Greenland during the breeding season, although rather few colonies have been studied in details. In contrast, illegal hunting and disturbances during the breeding season are still a problem in Greenland, despite more restrictive hunting regulations, and may explain much of the continued population decline. In addition, recent studies from Svalbard indicate that a large-scale deterioration of the marine environment in the North Atlantic, due to oceanographic changes, may impact recruitment to some of the Greenland colonies. Murre colonies in southern Upernavik, Disko Bay, South Greenland and East Greenland are in urgent need of additional conservation initiatives to avoid further declines and local extinctions.     

The role of forest maturation in causing the decline of Black Grouse Tetrao tetrix

Black Grouse Tetrao tetrix in Britain have declined through the 20th century, and most birds are now in Scotland. Many causes for this decline have been suggested, notably agricultural intensification, increased grazing levels and moorland afforestation. We examine habitat correlates of Black Grouse distribution and population change from a 700-km² area in the core of the Scottish range, where the numbers of lekking male Black Grouse declined by an estimated 70% to 270 between 1990 and 2002. Habitat data were derived from satellite imagery, in combination with map and field-collected data. Lek occurrence, lek size and changes in lek size were all correlated with forest structure, either positively with the amount of pre-thicket forest cover, or negatively with closed canopy cover. Additional effects of the cover of grass moor and dry heath suggest that Black Grouse are most likely to occur where moorland comprises Heather Calluna vulgaris and grass mosaics. Analysis of the change in Black Grouse abundance within 1.5 km of discrete forest blocks suggests that forest maturation, which has been the dominant habitat change during the course of the study, alone accounts for 58–78% of the decline. Given the close association of Black Grouse and the occurrence of woodland (and particularly conifer plantation) throughout much of their British range, these findings can be used to inform the design of management schemes for the recovery of Black Grouse.     

Natural and human-mediated factors in the recovery and subsequent expansion of the Purple swamphen Porphyrio porphyrio L. (Rallidae) in the Iberian Peninsula

Instances of range contraction and population decline in bird species in Europe are more common than cases of recovery following decline. Here we report on the recovery and expansion processes of an endangered bird species in Europe, the purple swamphen (Porphyrio porphyrio L., Rallidae), with special reference to the Iberian Peninsula, its main distribution area in Western Europe. After a drastic decline during the first half of the 20th century, which restricted its range to a few areas in southern Spain, the Iberian population has recovered. Currently, the species occurs in a range similar to the one it had at the beginning of the 20th century, and has even colonized new areas. These processes seem to be the result of both human-mediated (effective protection of the species and suitable habitats; success of reintroduction programs as expansion focuses of birds colonizing nearby and distant regions [>300 km] wetlands) and natural factors (inter- and intra-seasonal cycles of wet and dry years). Thus, we found a significant relationship between rainfall and bird abundance and productivity, suggesting that such inter- and intra-seasonal cycles may have significant effects on demographic parameters that could be related to the expansion process. Finally the species shows remarkable adaptability, as proven by data on breeding success in recently colonized areas and the ability to breed shortly after reintroduction. We hypothesize that saturation of breeding habitats in established areas, a reasonable habitat continuity and favorable environmental conditions, and protection have facilitated the dispersion of birds.