Biological effects of El Niño on the Galápagos penguin

Long-term monitoring of physical and biological parameters is essential for understanding the effects of El Niño on bird populations, particularly for small or declining populations. We examined the biological effects of El Niño activity from 1965 to 2004 using instrumental sea-surface temperatures from the Galápagos Islands and 20 years of census counts of the Galápagos penguin. Between 1965 and 2004, nine El Niño events were recorded of which two were strong and seven were weak. The two strong El Niño events of 1982-1983 and 1997-1998 were followed by crashes of 77% and 65% of the penguin population, respectively. The evidence suggests that the increased frequency of weak El Niño events limits population recovery. The 2004 penguin population is estimated to be at less than 50% of that prior to the strong 1982-1983 El Niño event. We discuss the biological effects of increased El Niño intensity and frequency within the context of a 6000-year record of El Niño influence and in the light of increasing anthropogenic threats operating after 1535, when the Archipelago was discovered by Europeans.     

Evaluating effects of deforestation, hunting, and El Niño events on a threatened lemur

Madagascar ranks as one of the world’s top extinction hotspots because of its high endemism and high rate of habitat degradation. Global climate phenomena such as El Niño Southern Oscillations may have confounding impacts on the island’s threatened biota but these effects are less well known. We performed a demographic study of Propithecus edwardsi, a lemur inhabiting the eastern rainforest of Madagascar, to evaluate the impact of deforestation, hunting, and El Niño on its population and to re-evaluate present endangerment categorization under the IUCN. Over 18 years of demographic data, including survival and fecundity rates were used to parameterize a stochastic population model structured with three stage classes (yearlings, juveniles, and adults). Results demonstrate that hunting and deforestation are the most significant threats to the population. Analysis of several plausible scenarios and combinations of threat revealed that a 50% population decline within three generations was very likely, supporting current IUCN classification. However, the analysis also suggested that changing global cycles may pose further threat. The average fecundity of lemurs was over 65% lower during El Niño years. While not as severe as deforestation or hunting, if El Niño events remain at the current high frequency there may be negative consequences for the population. We suggest that it is most critical for this species continued survival to create more protected areas, not only to thwart hunting and deforestation, but also to give this endangered lemur a better chance to recover from and adapt to altered climate cycles in the future.     

Assessing the risks of introduced chickens and their pathogens to native birds in the Galápagos Archipelago

Poultry production is an important economic activity on inhabited islands of the Galápagos archipelago. There has been a recent surge in both small-scale backyard chickens and larger scale broiler production associated with growth in the human population and the tourist industry. With increased poultry production, concerns have been expressed about the increasing risk of transfer of disease from chickens to native Galápagos bird species that may have little resistance to introduced pathogens [Wikelski, M., Foufopoulos, J., Vargas, H., Snell, H., 2004. Galápagos birds and diseases: invasive pathogens as threats for island species. Ecology and Society 9(5). Available from: URL:http://www.ecologyandsociety.org/vol9/iss1/art5]. This study evaluates risks posed by chicken disease to endemic and native Galápagos bird species, based on empirical evidence of pathogens present in chickens on the islands and a literature review of effects of these pathogens in wild species. Pathogens identified in domestic chicken populations of immediate avian conservation concern are Newcastle disease, Mycoplasma gallisepticum, and the proventricular parasite Dispharynx sp. Newcastle disease (avian paramyxovirus-1) poses an imminent threat to Galápagos penguins (Spheniscus mendiculus), flightless cormorants (Phalacrocorax harrisi), and lava gulls (Larus fuliginosus), species with very small population sizes (less than 1500 animals each). Additionally, litter from broiler farms could affect ecological processes in local ecosystems. Improved poultry biosecurity measures are urgently needed on the Galápagos Islands for avian disease management, yet developing these strategies presents political, social, and economic challenges.     

Effective population size in a bottlenecked fur seal population

The census population size (N) is usually the only information available for most threatened species. For evolutionary matters, the effective population size (N_e), not the census number, is a prime concern. Factors such as variation in the sex ratio of breeding individuals, variation of population size in different generations and mating system are important. The South American fur seal, Arctocephalus australis, has been exploited in Peru by humans since ca. 2000 BC and now the original population declined 72%, as a result of low food availability during the severe El Niño in 1997-1998. In this sense A. australis is now classified as in danger of extinction in Peru. We present the first estimate of N_e of the Peruvian population of A. australis that takes into account the effects of mating system and variation in population size caused by the 1997-1998 El Niño. The resulting N_e was 2153 specimens. We believe that the estimated N_e for the Peruvian population is a critical value, because it is significantly lower than the mean minimum viable population for vertebrates (7000 breeding age adults). This estimated N_e is of critical importance because combined with the current El Niño events are reasons of great concern for the survival of the species and should be taken into account in future management plans to ensure the conservation and protection of the species in the Peruvian coast.     

An experimental study on the effects of an introduced parasite in Darwin’s finches

It is widely recognised that the main threats to the biota of the Galápagos Islands stem from newly introduced diseases, plants and animals. Introduced organisms may lead to the rapid extinction of naïve insular populations. Previous research on Galápagos showed that the parasitic larvae of the fly Philornis downsi occurred in virtually all nests of land bird species examined, with high nestling mortality (27% of all broods) in relation to high parasite infestation. In this study, we used an experimental approach to measure the fitness impacts of the fly larvae in two species of Darwin’s finch (Geospizinae). We created parasite-reduced nests by applying a 1% pyrethrin solution to the nest during the early nesting phase, and measured: (1) nestling growth, (2) nestling haemoglobin (Hb) concentration and (3) fledging success. A single insecticide treatment was sufficient to reduce parasite intensity to nearly zero, and revealed reduced mass gain and reduced fledging success in parasitized nests compared to parasite-reduced nests. This is the first experimental study of fitness impacts by Philornis on its host species. The results are discussed in the light of short-term protection measures for nests of rare finch species in the Galápagos archipelago.     

Extinction behind our backs: the possible fate of one of the Darwin’s finch species on Isla Floreana, Galápagos

Without regular monitoring a rare species may slip into extinction unnoticed. We report a possible case from the Galápagos archipelago. The warbler finch (Certhidea fusca) has not been recorded by scientists on Isla Floreana in recent years, and we have been concerned about its status. On a two-day visit to prime habitat in the breeding season of 2004 we used playback of warbler finch song and calls recorded on another island to stimulate an approach of local birds. We failed to find a single warbler finch, whereas we encountered numerous small tree finches (Camarhynchus parvulus), medium tree finches (C. pauper) and yellow warblers (Dendroica petechia). Searches in 1979, 1983, 1997 and 1999 were also unsuccessful. Our continuing failure to find any warbler finches indicates the species must be extremely rare on the island, if not actually extinct. We discuss possible reasons for their demise and draw attention to other species that could be heading in the same direction.     

Plasmodium blood parasite found in endangered Galapagos penguins (Spheniscus mendiculus)

This is the first report of a Plasmodium blood parasite found in the Galapagos Archipelago. Phylogenetic analyses place this parasite, recovered from endangered Galapagos penguins (Spheniscus mendiculus), within the genus Plasmodium, and suggest a close relationship to some of the most dangerous lineages of Plasmodium that have been known to cause severe mortality and morbidity in captive penguin populations. Infectious disease is an increasingly important cause of global species extinctions, and extinctions due to avian pox and avian malaria (Plasmodium relictum) have been well documented in Hawaiian avifauna. Plasmodium blood parasites had not been detected in Galapagos birds until now, despite previous microscopic and molecular screening of many of the species, including the Galapagos penguin. While penguin populations now appear healthy, it is unclear whether this parasite will have an obvious impact on their survival and reproduction, particularly during El Niño events, which cause stress due to reduced food availability. It is possible that this parasite arrived with or shortly after the recent arrival of an introduced mosquito, Culex quinquefasciatus, known elsewhere as a competent vector of Plasmodium blood parasites.     

Assessing the impact of fisheries, climate and disease on the dynamics of the Indian yellow-nosed Albatross

Many seabird populations are currently decreasing, especially albatrosses for which the primary threat is recognised to be mortality in fisheries. Introduced predators, climate change and other factors such as diseases can also have large impacts on seabirds. Here, we assessed the relative effect of three potential threats: climate, fisheries and diseases on the demography of an endangered marine predator and modelled its population dynamics to project its size under different scenarios. We based our study on a long-term monitoring of a colony of individually marked Indian yellow-nosed albatrosses at Amsterdam Island, subtropical Indian Ocean, that has declined during the past twenty years. We found no evidence for an impact of legal tuna longlining on demographic parameters. Hatching success was lower during El Niño years but survival (0.902 ± 0.011) was not affected by climatic factors. Avian cholera caused high chick mortality (0.808 ± 0.181) which in turn probably triggered the high emigration rate (0.038 ± 0.011) through dispersal of failed breeders. This colony has a high risk of extinction. However, the rest of the population at Amsterdam Island seemingly not affected to the same extent, declined but stabilised since 1998. Matrix models indicated that lowered adult survival and the very low breeding success, resulting in low recruitment, have both contributed to the decline of the yellow-nosed albatross colony until the mid-1990s, but that more recent decline was primarily caused by low fledging success. Our results highlight that potential threats such as fisheries, diseases or climate have to be considered simultaneously to disentangle their roles when assessing the conservation status of a marine predator species.     

Effects of the introduced parasite Philornis downsi on nestling growth and mortality in the medium ground finch (Geospiza fortis)

Invasive species have the potential to detrimentally affect native ecosystems by out competing or directly preying upon native organisms, and have been implicated in the extinction of endemic populations. One potentially devastating introduced species in the Galápagos Islands is the parasitic fly Philornis downsi. As larvae, P. downsi parasitize nestling birds and have been associated with high nestling mortality and reduced growth rates. Here I document nestling growth and mortality in a bimodal population of the medium ground finch, Geospiza fortis. Observations were conducted over three years, and under variable ecological conditions. Annual parasite prevalence in nests ranged from 64% to 98%, and nestling mortality in nests with parasites ranged from 16% to 37%. Parasite load and parasite load per nestling follow a skewed distribution with many nests having relatively few parasites, and few nest having many. Parasite load, however, was not correlated with onset of breeding, clutch size, the number of nestlings, nestling survival or fledgling success. Parasite load per nestling, on the other hand, was correlated with clutch initiation date and the proportion of nestlings that died in parasitized nests. Neither nestling size nor growth rate differed between parasitized and unparasitized nests. In addition, male and female beak morphology was not correlated with parasite load, breeding variables or nestling survival. Thus, while overall mortality due to parasitism is high, ecological conditions and possible host defenses may potentially counter some of the detrimental affects of P. downsi on nestling size and growth. These results taken together suggest that parasitism of P. downsi larvae on nestling G. fortis has the potential to lead to large population declines.     

The use of historical collections to estimate population trends: A case study using Swedish longhorn beetles (Coleoptera: Cerambycidae)

Long term data to estimate population trends among species are generally lacking. However, Natural History Collections (NHCs) can provide such information, but may suffer from biases due to varying sampling effort. To analyze population trends and range-abundance dynamics of Swedish longhorn beetles (Coleoptera: Cerambycidae), we used collections of 108 species stretching over 100 years. We controlled for varying sampling effort by using the total number of database records as a reference for non-red-listed species. Because the general frequency of red-listed species increased over time, a separate estimate of sampling effort was used for that group. We observed large interspecific variation in population changes, from declines of 60% to several hundred percent increases. Most species showed stable or increasing ranges, whereas few seemed to decline in range. Among increasing species, rare species seemed to expand their range more than common species did, but this pattern was not observed in declining species. Historically, rare species did not seem to be at larger risk of local extinction, and population declines were mostly due to lower population density and not loss of sub-populations. We also evaluated the species’ declines under IUCN red-list criterion A, and four currently not red-listed species meet the suggested threshold for Near Threatened (NT). The results also suggested that species’ declines may be overlooked if estimated only from changes in species range.     

Status, distribution and long-term changes in the waterbird community wintering in Doñana, south-west Spain

The Guadalquivir Marshes or Doñana wetland complex is the most important wintering site for migratory waterbirds in the Mediterranean region. However, there is a lack of previous information on the status of different species in this area. Using monthly aerial counts conducted from 1978 to 2005, we analysed the size of wintering populations of 21 waterbird species, their distribution within the Guadalquivir Marshes, and their long-term population trends. We used Underhill indices to replace missing values and to correct for flocks of unidentified ducks. Based on long-term means, we identified 16 species whose populations at Doñana exceed 1% of the biogeographical flyway population. For at least 1 month of the year, mean counts were around 10% of the flyway population for six species. The natural, temporary marshes of Doñana National Park were particularly important for Anatidae, ricefields for gulls, white storks and grey herons, fish ponds for flamingos, cormorants and avocets, and salt pans for shelduck. Four Anatidae species have undergone long-term declines and eight non-Anatidae have undergone long-term increases. Population trends were related with trophic guild, migratory status and habitat use. Winter visitors and herbivorous species showed more negative trends than resident, omnivorous-carnivorous species. Those species concentrated in strictly-protected natural marshes have tended to decline. The surface area of ricefields and fish ponds has increased over the study period, and bird species concentrated in these artificial wetlands have tended to increase. This raises questions about the value of waterbirds as flagship or umbrella species for wetland conservation.     

The proportion of immature breeders as a reliable early warning signal of population decline: evidence from the Spanish imperial eagle in Doñana

Methods to evaluate population trends have recently received particular attention because of perceived declines in several species during the 20th century. We investigated whether age at first breeding could be used as an “early warning signal” to detect possible changes in population trends in long-lived species with deferred maturity using data from the Spanish imperial eagle (Aquila adalberti) population in Doñana National Park (Spain). This bird of prey is an endangered species that has suffered a rapid decline in this population during the last 10 years. As a result of our 27-year monitoring (1976-2002) study, we detected that an increase in immature breeding birds occurred before population decline became evident. The proportion of immature-plumaged breeders in the population was significantly higher during the period of decline than during the period of stability. In our case, more than 10% of immature breeders can be considered as an “early warning signal” that anticipates population decline. Owing to the ignorance of this warning signal, urgent actions for the recovery of this eagle population started 10 years later than necessary, and when population size had been reduced.     

Hazard,risk and agrarian adaptations in a hyperarid watershed: El Niño floods,streambank erosion,and the cultural bounds of vulnerability in the Andean Middle Horizon

Peru's Osmore drainage, also known as the Moquegua Valley, is one of the driest regions on Earth, yet agricultural development has supported complex societies in the basin for almost 4000 yrs because of canal construction and irrigation. We compare the distinct agrarian and settlement systems of three coeval archaeological cultures in this arid region, Huaracane, Wari and Tiwanaku, and how each adapted—or failed to adapt—to geomorphic and climatic hazards. Systematic settlement pattern survey and radiocarbon dating along with geomorphological analysis of flood history and riverine processes permit detailed discussion of agrarian strategies during the Formative (1800 BC–AD 500) and Middle Horizon (AD 500–1000) periods, with distinct settlement “niches” in terms of agricultural practices and longitudinal position in the drainage, and lateral location relative to the floodplain. These adaptive strategies each manifest distinct “bounds of adaptability” to natural hazard, climate events and social stressors, and thus varying risk profiles. Besides the continual risk associated with sustained droughts, the Atacama and Peruvian Coastal Desert and culturally connected highland Altiplano are also vulnerable to the vagaries of the El Niño-Southern Oscillation (ENSO) leading to catastrophic floods in the mid-valley during warm phase ENSOs, in tandem with simultaneous hazards in other regions inhabited by these transregional cultures. By comparing the archaeological record of Wari, Huaracane, and Tiwanaku culture settlements with geomorphic signatures of catastrophic El Niños, we show that the viability of each cultural sequence depended on specific relationships to floodplain streambank erosion, construction and reworking over multiple time scales.     

Conservation action in the Galàpagos: feral pig (Sus scrofa) eradication from Santiago Island

Introduced mammals are major drivers of extinction and ecosystem change. As omnivores, feral pigs (Sus scrofa) are responsible for wholesale adverse effects on islands. Here, we report on the eradication of feral pigs from Santiago Island in the Galápagos Archipelago, Ecuador, which is the largest insular pig removal to date. Using a combination of ground hunting and poisoning, over 18,000 pigs were removed during this 30-year eradication campaign. A sustained effort, an effective poisoning campaign concurrent with the hunting program, access to animals by cutting more trails, and an intensive monitoring program all proved critical to the successful eradication. While low and fluctuating control efforts may help protect select native species, current eradication methods, limited conservation funds, and the potential negative non-target impacts of sustained control efforts all favor an intense eradication effort, rather than a sustained control program. The successful removal of pigs from Santiago Island sets a new precedent, nearly doubling the current size of a successful eradication, and is leading to more ambitious projects. However, now we must turn toward increasing eradication efficiency. Given limited conservation funds, we can no longer afford to spend decades removing introduced mammals from islands.     

The ecology of extinction: population fluctuation and decline in amphibians

Even among widespread species with high reproductive potentials and significant dispersal abilities, the probability of extinctions should be correlated both with population size variance and with the extent of population isolation. To address how variation in demographic characteristics and habitat requirements may reflect on the comparative risk of species decline, I examined 617 time series of population census data derived from 89 amphibian species using the normalized estimate of the realized rate of increase, ΔN, and its variance. Amphibians are demonstrably in general decline and exhibit a great range of dispersal abilities, demographic characteristics, and population sizes. I compared species according to life-history characteristics and habitat use. Among the populations examined, census declines outnumbered increases yet the average magnitudes for both declines and increases were not demonstrably different, substantiating findings of amphibian decline. This gives no support for the idea that amphibian population sizes are dictated by regimes featuring relatively rare years of high recruitment offset by intervening years of gradual decline such that declines may outnumber increases without negative effect. For any given population size, those populations living in large streams or in ponds had significantly higher variance than did populations of completely terrestrial or other stream-dwelling amphibians. This could not be related to life-history complexity as all the stream-breeding species examined have larvae and all of the wholly terrestrial species have direct development without a larval stage. Variance in ΔN was highest amongst the smallest populations in each comparison group. Estimated local extinction rates averaged 3.1% among pond-breeding frogs, 2.2% for pond-breeding salamanders, and negligible for both stream-breeding and terrestrial direct-developing species. Recoveries slightly exceeded extinctions among European pond-breeding frogs but not among North American pond-breeding frogs. Less common species had greater negative disparities between extinctions and recoveries. Species with highly fluctuating populations and high frequencies of local extinctions living in changeable environments, such pond- and torrent-breeding amphibians, may be especially susceptible to curtailment of dispersal and restriction of habitat.     

An evaluation of the status of five threatened plant species in the Pyrenees

In this paper we assess the conservation status of five of the most threatened species in the Pyrenean range (listed in the European Habitats Directive), and present updates of their distribution, reliable censuses to estimate population sizes, population growth rate, population structure, longevity, reproductive success and frequency of herbivory. Recent surveys and careful censuses revealed that the four taxa exclusively restricted to rocky habitats (Borderea chouardii, Androsace pyrenaica, Petrocoptis pseudoviscosa, Petrocoptis montsicciana) have more populations and/or individuals than previously thought. The remaining species, an orchid (Cypripedium calceolus), showed an important decline in population number. So while the rupicolous taxa might be considered naturally rare, the orchid is becoming rare. We failed to find evidence of current poor performance within populations, as recruitment was detected, population growth rate was quite stable in recent years, fruit and seed set was apparently adequate, and herbivory and predation were absent or very low. Additionally, most of the species show a long life span, which might buffer them against demographic and environmental stochasticity in absence of human disturbance.     

Exposure to tourism reduces stress-induced corticosterone levels in Galápagos marine iguanas

Unstressed and stress-induced plasma corticosterone levels in Galápagos marine iguanas (Amblyrhynchus cristatus) were compared in animals from a site heavily exposed to tourism to animals from a site undisturbed by humans. Initial corticosterone levels not only did not differ between the two groups, but they were 50% of levels in iguanas known to be chronically stressed. These data suggest that iguanas in tourist areas are not chronically stressed. Both groups of iguanas exhibited elevated corticosterone levels after 30 min of capture and restraint, indicating that they can physiologically respond to stressful stimuli. The stress response was lower, however, at the tourist site. This result indicates that iguanas are physiologically affected by tourism, although it is presently unknown whether these changes are ultimately beneficial or harmful.     

Potential factors controlling the population viability of newly introduced endangered marble trout populations

While several population viability analyses (PVAs) have been performed on anadromous salmonids, less attention has been given to stream-living salmonids. In this work, we explore the role of PVA as a tool in the recovery of threatened stream-living salmonid species. The analysis has been performed with reference to marble trout Salmo marmoratus, a salmonid with a limited geographic distribution and at risk of extinction due to hybridization with the non-native introduced brown trout. Demographic parameters, such as survival, fecundity and density-dependent patterns were estimated from an eight year on-going monitoring program of two translocated marble trout populations in pristine, previously fishless streams (Zakojska and Gorska) in the Soca and Idrijca river basins (Slovenia). To explore the importance of disturbance events such as floods on marble trout population dynamics, we performed a PVA under three scenarios: (1) occurrence of both severe and moderate floods; (2) occurrence of only moderate floods; (3) no flood events. Our analysis shows that population viability is threatened only by severe flood events, otherwise the two populations prove to be fairly stable with population abundance fluctuating around stream carrying capacity. A sensitivity analysis performed on model parameters highlighted that density-dependence in first-year survival and the magnitude of reduction in population size after a severe flood are the two most crucial parameters affecting population abundance and quasi-extinction probability, respectively. While only extreme floods can drive the population to extinction, the increase in juvenile survival when population abundance collapses after a major flood may allow the populations to quickly recover from few reproductive individuals back to stream carrying capacity.     

Predation by New Zealand sea lions (Phocarctos hookeri) as a threat to the viability of yellow-eyed penguins (Megadyptes antipodes) at Otago Peninsula, New Zealand

This study presented evidence that creates a quandary for conservation management: predation by one threatened species, New Zealand sea lion (Phocarctos hookeri), threatens the viability of another threatened species, yellow-eyed penguin (Megadyptes antipodes), at Otago Peninsula, South Island, New Zealand. Otago Peninsula holds the largest population of yellow-eyed penguins on South Island and the only breeding population of New Zealand sea lions on the New Zealand mainland. New Zealand sea lions here represent the vanguard of re-colonisation within their prehistoric range, with nine females and 50-70 males resident in 2005. The initial indication of a potential problem was an attack on a yellow-eyed penguin by a New Zealand sea lion witnessed in 1996. The majority of 20 records for attacks were at two neighbouring sites, where they coincided with decreases in penguin nest numbers and adult annual survival. In contrast, penguin nest numbers increased at a third site, the main base for male sea lions at Otago Peninsula. Evidence from prey remains indicated that male sea lions did not eat yellow-eyed penguins but that females ate 20-30 annually, with one individual possibly responsible for most kills. Modelling indicated that the penguin population at any one site could not remain viable if it was the sole source of penguins killed. The dilemma is either to do nothing, and risk collapse of the Otago Peninsula population of yellow-eyed penguins, or to take action against known culprits, and risk failure in re-colonisation of the New Zealand mainland by New Zealand sea lions.     

Effects of the 1982–1983 El Nino on Humboldt penguin colonies in Peru

The Humboldt penguin Spheniscus humboldti is endemic to the Peruvian Current which flows northward along the coast of Chile and Peru. This species has greatly diminished from its former abundance.The coast of Peru is characterised by high biological productivity which concentrates fish such as the anchovy Engraulis ringens, the main prey item of marine predators including seabirds. In years of the abnormal oceanographic conditions of El Nino, the schools of anchovies become unavailable to the seabirds and they disperse in search of food. Massive mortality, especially of juveniles, results and there is nest desertation and lack of reproduction.This paper describes the effects of the 1982–1983 El Nino on Humboldt penguin colonies in Peru. There has been an overall population decline of 65% and the surviving population in 1984 was estimated to be between 2100 and 3000 adults. Although El Nino is a periodic event and the Humboldt penguin has evolved to adapt to such unpredictable changes, the environment has now been altered by man. Under these circumstances, the 1982–1983 El Nino has contributed to placing this species in a critical position.