Dynamics of the shallow-water fish assemblage of the Patos Lagoon estuary (Brazil) during cold and warm ENSO episodes

In southern Brazil, cold ( La Niña ) and warm ( El Niño ) episodes of the El Niño Southern Oscillation (ENSO) phenomenon cause drought and high rainfall, respectively. The low precipitation and freshwater outflow associated with La Niña during 1995–1996 were associated with an increase in the abundance of marine species in the Patos Lagoon estuary. During the 1997–1998 El Niño , high precipitation and river discharge were associated with low abundance of marine species in the estuary. ANOVA results showed a higher abundance during La Niña than El Niño for estuarine resident (RES) and estuarine dependent (DEP) fishes. During La Niña catch per unit of effort (CPUE) of RES increased from the marine to estuarine area, but during El Niño CPUE increased at the marine area and diminished during summer and autumn in some estuarine sites. DEP fishes had an opposite abundance pattern. During La Niña , these fishes were abundant at the coastal marine area and along some estuarine sites, but during El Niño , CPUE remained almost the same at the marine area but dropped along some estuarine sites. These different abundance patterns for dominant fish groups yielded a positive interaction between stations and climatic events. With higher river discharge and the consequent decline of dominant euryhaline fishes, such as Mugil platanus and Atherinella brasiliensis , freshwater species increased in abundance and richness in the shallow waters of the stuary. The ENSO phenomenon influences precipitation and estuarine salinity in southern Brazil and thereby seems to have a strong influence on recruitment, immigration, and emigration dynamics of fish species living within and adjacent to estuarine habitats.     

Avian reproductive failure in response to an extreme climatic event

Recently, climate change research has emphasized the potential increase in the frequency and severity of climatic extremes. We compared the reproductive effort and output among four species of passerine birds in coastal southern California, USA, a semi-arid region, during a normal precipitation year (2001) and the driest year in a 150-year climate record (2002). Both reproductive effort and output differed dramatically between years. Mean reproductive output among the four species was 2.37 fledglings/pair in 2001 and 88.4% of all pairs observed attempted at least one nest. The birds attempted a mean of 1.44 nests per pair and were successful in 47.7% of those attempts. In 2002, only 6.7% of the pairs even attempted a nest and only 1.8% were successful, for a total output of 0.07 fledglings per pair. The abundance of suitable arthropod prey items in the environment was also much lower in 2002, suggesting that low food availability was the proximal cause of the reproductive failure. The data for one of these species, the rufous-crowned sparrow (Aimophila ruficeps), were combined with reproductive and rainfall data from a previous 3-year study (1997–1999) in the same sites. The combined data sets suggest that the response of reproduction to rainfall variation is linear, and that the low end of the precipitation range brings the population near reproductive failure. Any change in climate that would increase the frequency of extreme dry conditions would likely endanger populations of these species.     

Inter-hemispheric synchrony of forest fires and the El Niño-Southern Oscillation

Fire histories were compared between the south-western United States and northern Patagonia, Argentina using both documentary records (1914–87 and 1938–96, respectively) and tree-ring reconstructions over the past several centuries. The two regions share similar fire–climate relationships and similar relationships of climatic anomalies to the El Niño–Southern Oscillation (ENSO). In both regions, El Niño events coincide with above-average cool season precipitation and increased moisture availability to plants during the growing season. Conversely, La Niña events correspond with drought conditions. Monthly patterns of ENSO indicators (southern oscillation indices and tropical Pacific sea surface temperatures) preceding years of exceptionally widespread fires are highly similar in both regions during the 20th century. Major fire years tend to follow the switching from El Niño to La Niña conditions. El Niño conditions enhance the production of fine fuels, which when desiccated by La Niña conditions create conditions for widespread wildfires. Decadal-scale patterns of fire occurrence since the mid-17th century are highly similar in both regions. A period of decreased fire occurrence in both regions from c. 1780–1830 coincides with decreased amplitude and/or frequency of ENSO events. The interhemispheric synchrony of fire regimes in these two distant regions is tentatively interpreted to be a response to decadal-scale changes in ENSO activity. The ENSO–fire relationships of the south-western USA and northern Patagonia document the importance of high-frequency climatic variation to fire hazard. Thus, in addition to long-term trends in mean climatic conditions, multi-decadal scale changes in year-to-year variability need to be considered in assessments of the potential influence of climatic change on fire regimes.     

Climate fluctuation effects on breeding of blue penguins (Eudyptula minor)

Abstract

El Niño and La Niña climate perturbations alter sea currents and food availability for seabirds in many areas of the world. This changes their breeding success and mortality. Blue penguin (Eudyptula minor) breeding success is dependent upon whether one or two clutches per season are laid, and the hatching and fledging success of these clutches. This study uses six years of data from five blue penguin breeding colonies, three from Taiaroa Head, Otago Peninsula and two from Oamaru, to examine whether annual variation in breeding success correlates with El Niño/La Niña perturbations. When La Niña conditions prevailed, penguins started breeding later, and there was a lower proportion of double breeders than in El Niño and normal years. The probability of a newly hatched chick surviving to fledging was also dependent on whether large‐scale climatic conditions prevailed, whereas hatching success and overall breeding success (number of fledged chicks per breeding pair) showed no correlation with climate perturbations.     

CHANGES IN THE RELATIVE ABUNDANCE AND DISTRIBUTION OF GRAY WHALES (ESCHRICHTIUS ROBUSTUS) IN MAGDALENA BAY, MEXICO DURING AN EL NIÑO EVENT

The oceanographic changes during the El Niño and La Niña of 1998–1999 have provided an opportunity to document the effects of these events on the migratory patterns of gray whales ( Eschrichtius robustus ). Magdalena Bay is located at the southernmost point of the gray whale's annual breeding migration along the Baja California Peninsula in Mexico. Standardized surveys were conducted for three consecutive seasons (1997–1999) in Magdalena Bay, enabling an assessment of the changes in the relative abundance of gray whales with altered temperature. The average temperature of the bay in 1998 was 4.2°C higher than in 1997 and 5.8°C higher than in 1999. The number of whale sightings during that time period was inversely related to temperature, with nearly 15 times greater relative abundance observed in 1999 than in 1998. It is hypochesized that the decreasing temperatures associated with the La Niña event of 1999 may have induced more whales to travel farther south along their migration route. Alternative hypotheses are also expiored. Comparisons of the three years are discussed with consideration of the importance of environmental conditions versus area fidelity as determining factors in the location of gray whale calving and breeding activities.     

Impact of human activities on the reproduction of Hooded Vultures Necrosyrtes monachus in Burkina Faso

During the last decades, the critically endangered Hooded Vulture Necrosyrtes monachus has strongly declined across its African range. Although direct persecution has been suggested as a major cause of this decline, little is known about the impact of humans on reproductive output in West Africa. We studied the impact of human activities on the reproductive output of Hooded Vultures in the Garango area of Burkina Faso. Twenty and 56 nesting attempts were monitored, respectively, during the breeding season in 2013/14 and 2014/15, to determine reproductive success and identify causes of nest failure. Annual breeding success varied between 0.68 and 0.71 chicks fledged per breeding pair per year and productivity was assessed at 0.57 chicks fledged per territorial pair in 2014/15. The main threats imposed by humans were poaching of eggs, chicks and collection of nest materials, leading to 20% (13 out of 64 breeding attempts) of nest failures over the two years. An additional important reason for nest failure was the pruning and (partial) cutting of nest trees. Despite this high level of human interference, we found that Hooded Vulture nest success increased with proximity to human settlements, probably because breeding vultures benefit from protection by people against persecution and disturbance.     

青海省海北地区高寒草甸雀形目鸟类的繁殖生产力

通过对高寒草甸１０种雀形目鸟类繁殖生产力研究表明,高寒草甸鸟类的繁殖生产与鸟类栖息地所处的地理环境、营巢类型和繁殖方式密切相关。其中繁殖季节长度和窝卵数是影响高寒草甸鸟类繁殖生产力的两个最重要的因子（Ｐ〈０．０５）。鸟类平均繁殖生产力为２．８０（只／对．年）。     

Primary production dynamics and climate variability: ecological consequences in semiarid Chile

Increase in rainfall variability has important consequences for organisms in arid and semiarid regions around the world. In South American and Australian deserts, the El Niño/Southern Oscillation (ENSO) phenomenon greatly influences rainfall patterns, and therefore the dynamics of plant communities. However, the field data needed to assess the effect of climate change on vegetational patterns is difficult to obtain because of the large spatial scale required for such studies. Normalized Difference Vegetation Index (NDVI) characteristics allow the use of several indexes related to vegetational structure. Due to its direct relationship with primary productivity, it is possible to obtain several measures of annual productivity. These include annual plant yield, annual maximum yield, onset of 'greening-up' and senescence phases, length of the 'green' season, vegetation peak, and therefore, the periods when more or less food is available for herbivores. After verification with ground-truth measures, we used NDVI data from two semiarid localities in north-central Chile (Fray Jorge and Aucó) to determine the relationship between rainfall patterns and vegetation cover and productivity related to El Niño phenomenon. With this information we gauge the influence of climatic processes on primary productivity in western South America, an area subject to strong climate variability. We predict significant variation in Chilean semiarid regions due to climate change, affecting mainly the extent and timing of annual growth season of vegetation, and also including a shorter and delayed greening-up season. Also, we predict that important decreases in rainfall levels will not have strong effects on primary production in these semiarid ecosystems.     

VARIATION IN TOXIN PRODUCTION OF SYNCHRONIZED CULTURES OF CHRYSOCHROMULINA POLYLEPIS (PRYMNESIOPHYTA)

We studied spatial variability in giant kelp ( Macrocystis pyrifera ) forests at 84 sites along the west coast of North America in order to assess the impacts of the 1997–98 El Niño. Our sites spanned the geographic range of giant kelp in the Northern Hemisphere and were surveyed just before, immediately following, several months after, more than one year after, and nearly two years after the El Niño. Interspersion of sample units allowed us to compare the effects of this disturbance among spatial scales ranging from a few meters to more than a thousand kilometers. Variance components analyses revealed that El Niño shifted the relative importance of factors that regulate giant kelp communities from factors acting at the scale of a few meters (local control) to factors operating at hundreds of kilometers (regional control). Moreover, El Niño resulted in a near-to-complete loss of giant kelp populations throughout nearly two-thirds of the species' range. Evaluation of these effects along with oceanographic data (at the "appropriate" spatial scales), along with closer examination of giant kelp populations in the most severely impacted region (Baja) suggested that the among-region differences in giant kelp survival was due, at least in part, to El Niño-induced differences in ocean climate. Giant kelp recovery following El Niño was also scale-dependent, but driven by factors different from those of the disturbance. Here, we present results for several species of macroalgae in an attempt to relate the importance of El Niño to that of other processes in creating scale-dependent patterns of variability.     

Environmental conditions but not nest composition affect reproductive success in an urban bird

Adjusting the composition of their nests, breeding birds can influence the environmental conditions that eggs and offspring experience. Birds often use feathers to build nests, presumably due to their insulating properties. The amount of feathers in nests is often associated with increased nestling survival and body condition. However, it is unclear whether these putative beneficial effects of adding feathers to nests are relevant in a wide range of environmental conditions. Here, we combine data on weather conditions and feathers in nests (i.e., nest composition) to investigate their relative contribution to reproductive success in the Eurasian tree sparrow (Passer montanus). Specifically, we investigate whether the effect of weather conditions on breeding success is modulated by the amount of feathers added to the nest. We found a strong negative effect of rainfall on the number of nestlings that successfully fledged per breeding attempt, but this negative effect was not mitigated by the amount of feathers in nests. We also found that the amount of feathers in nests varied along the breeding season, with nests containing more feathers early in the breeding season, when temperatures were lower. Despite considerable variation in nest composition, our results do not suggest an important role of feathers in nests protecting eggs or nestling tree sparrows against fluctuations in environmental conditions.     

Determining productivity of Maui Parrotbills,an endangered Hawaiian honeycreeper

ABSTRACT Maui Parrotbills (Pseudonestor xanthophrys), critically endangered Hawaiian honeycreepers endemic to the island of Maui, are restricted to a single population of ～500 individuals located in remote, mountainous terrain. From January to June 2006–2011, we located nests and fledglings in the Hanawi Natural Area Reserve (NAR) in east Maui, Hawaii, to document nest success and annual reproductive success. Nest success is a commonly used measure of productivity and is a central component of many demographic studies. Annual reproductive success is less frequently documented because greater effort is required to monitor the reproductive success of breeding pairs through time. However, for species whose nests are difficult to locate or access, such as Maui Parrotbills, the presence or absence of fledged young may provide a more accurate measure of breeding success than monitoring nests. During our study, we located and determined the outcome of 30 nests to document nest success, and monitored 106 territories for the presence or absence of fledglings to calculate annual reproductive success. Nest success probability was 19% (N= 30) and seasonal nest success was 46%. During our monitoring efforts, 49 of 106 breeding pairs produced a single fledged young. Because parrotbills typically have single egg clutches and only re‐nest after nests fail, the presence or absence of a fledgling is an indication of a pair's overall reproductive success for a breeding season. Based on the number of fledglings per pair, our estimate of annual reproductive success was 46%, confirming our initial productivity estimate from nests. Thus, our results indicate that the two methods, determining annual reproductive success by monitoring fledglings and calculating nest success, provide similar estimates of annual productivity for Maui Parrotbills. Based on our estimates, the parrotbill population appears to be demographically stable. However, our productivity estimate was based only on the population at Hanawi, an area representing just 3% of the total range of parrotbills. Thus, our results may not accurately reflect the status of parrotbills over their entire range.     

Factors affecting the breeding success of the south polar skua Catharacta maccormicki at Edmonson Point, Victoria Land, Antarctica

A south polar skua (Catharacta maccormicki) population was studied at Edmonson Point (74°20'S-165°08'E), Victoria Land, Antarctica, in 1998/1999. The local population consisted of 101 pairs, 89 of which were located within a large, loose colony associated with a rookery of about 2,000 pairs of Adélie penguin (Pygoscelis adeliae). Skua nests were clumped around penguin subcolonies. Mean skua Nearest Neighbour Distance (NND) was 21ᆣ m (n=89). NND was positively correlated with the distance from the nearest penguin subcolony. Mean laying date was 24Lj December (n=89). Mean clutch size was 1.9ǂ.2 eggs (n=89). Hatching success was 77% (n=174 eggs laid), and 20.2% of the breeding pairs successfully raised chicks to fledging. Mean number of fledged young was 0.2ǂ.4 per breeding pair (n=89), and 1 per successful pair (n=18). Main causes of breeding failure were intraspecific predation and sibling aggression. Breeding success was negatively related to distance from the nearest penguin nest and to laying date. Because of the extensive and persistent sea-ice cover, penguins represented an important source of food for the skua population.     

Annual and seasonal reproductive trends in the Lesser Spotted Woodpecker Dendrocopos minor

Annual and seasonal variation in reproductive timing and performance were studied in a population of the Lesser Spotted Woodpecker Dendrocopos minor over 10 years in southern Sweden. The median laying date of the first egg varied by up to 17 days between years, being generally larger than the variation of laying dates within years. Neither clutch size, brood size in successful nests, fledging success in successful nests nor mean nestling weight differed significantly between years. There was no trend for mean clutch size to vary between early and late years. In spite of a more than threefold variation in population size, no reproductive variable demonstrated an apparent density-dependence. Within the season, clutch size declined steeply with increasing clutch initiation date, whereas fledging success and nesting success did not, leading to a trend in brood size almost identical to the trend in clutch size. The survival prospects of fledged young declined with increasing clutch initiation date, and it is argued that the clutch size laid is a strategic adjustment to laying date. Out of 124 breeding attempts, 34% did not produce fledged young. In 9% of the breeding attempts, pairs laid no eggs. At least 20% of the breeding attempts failed after egg-laying. The most common cause of breeding failure was loss of the breeding partner followed by nest abandonment (40% of the failures). Only 16–28% of the failures were due to predation on the nest. Most complete failures, and also partial losses from nests, occurred at the early breeding stages. It is argued that the early nestling phase may be a critical stage, which the woodpeckers adjust to coincide with the seasonal food peak, explaining the strikingly late breeding season compared with other non-migrant species.     

The effects of seasonal and interannual variability of oceanic structure in the western Pacific North Equatorial Current on larval transport of the Japanese eel Anguilla japonica

As the North Equatorial Current (NEC)–bifurcation is known to be related to El Niño-Southern Oscillation (ENSO) events, the influence of the position of the NEC bifurcation on transport success of the larval Japanese eel Anguilla japonica was investigated. Using a Lagrangian modelling approach, larval transport was simulated and the relative influence of El Niño and La Niña events and the NEC-bifurcation position on the success of particle transport analysed. The number of particles transported from the NEC to the Kuroshio tended to be lowest during El Niño years, and differences between La Niña and regular years were small. The transport success observed in simulations showed some relationships to annual A. japonica glass eel recruitment to Tanegashima Island over 1993 to 2001, but not in 2002. The study shows that particle tracking simulations can be used to improve knowledge of the oceanic migration of A. japonica but further studies are required, including comparisons with the effects on larval survival of fluctuations in temperature and food availability.     

Preliminary Evidence of the Importance of ENSO in Modifying Food Availability for White‐tailed Deer in a Mexican Tropical Dry Forest1

The influence of El Niño/Southern Oscillation (ENSO) on rainfall and its possible effect on availability of food for white‐tailed deer (Odocoileus virginianus) in a tropical dry forest in the Pacific coast of Mexico was studied. From 1977 to 2003 there were three significant El Niño and La Niña events. During El Niño years rainfall decreased during the wet season ( June to October) and increased during the dry season (November to May), with the opposite effect during La Niña years. Plant diversity was monitored in permanent plots during the wet and dry seasons of 1989–1993. The results provide evidence that ENSO events affect deer food availability, particularly in the dry season.     

IMPROVED BODY CONDITION OF WEANED HAWAIIAN MONK SEAL PUPS ASSOCIATED WITH EL Niño EVENTS: POTENTIAL BENEFITS TO AN ENDANGERED SPECIES

Efforts to enhance recovery of endangered Hawaiian monk seals ( Monachus schauinslandi ) require an understanding of factors influencing population dynamics. This study examines relationships between body condition and survival of monk seal pups at French Frigate Shoals and Laysan Island and El Niño events. Girth measurements and mass estimates were used as indicators of pup body condition, and survival was evaluated from weaning to age 2. Linear models and logistic regression analysis were used to evaluate El Niño effects. Temporal trends in mean girth, mass, and survival were identified at both study sites. After accounting for temporal trends, girths were 3.7 cm and 2.7 cm greater during El Niño years at French Frigate Shoals and Laysan Island, respectively. Average mass estimates were significantly greater during El Niño years at French Frigate Shoals (2.6 kg increase), but were not significantly different at Laysan Island (1.8 kg increase). Weaned pups born at French Frigate Shoals during El Niño years survived significantly better, but this effect was not detected at Laysan Island. El Niño events probably affect pup condition and survival, but these parameters need to be monitored during future El Niño events to clarify these relationships.     

Effects of large-scale climatic fluctuations on survival and production of young in a Neotropical migrant songbird, the yellow warbler Dendroica petechia

Migrant songbirds are vulnerable to changes in climatic conditions on both the breeding and wintering grounds. For North American Neotropical migrants, the El Niño/Southern Oscillation (ENSO), via its effects on global precipitation and temperature, modulates the productivity of their temperate and tropical terrestrial ecosystems used during the course of their annual cycle. We evaluated how a densely nesting population of yellow warblers Dendroica petechia in a riparian forest in southern Manitoba, Canada, responded to the El Niño/Southern Oscillation (ENSO) between 1992 and 2001. Standardized mist netting was used to estimate apparent annual survival of adults and production of young. Both adult survival and the production of young were positively correlated with the Southern Oscillation Index (SOI). More specifically, values of both these demographic parameters were lowest during El Niño years and highest during La Niña years. These findings demonstrate the influence of climate on populations of Neotropical migrants in North America. The more frequent El Niños predicted to result from future global climate change could negatively affect populations of yellow warblers and other Neotropical migrants breeding in this region.     

Food web structure and climate effects on the dynamics of small mammals and owls in semi-arid Chile

Population dynamics of small mammals and predators in semi-arid Chile is positively correlated with rainfall associated with incursions of El Niño (El Niño Southern Oscillation: ENSO). However, the causal relationships between small mammal fluctuations, predator oscillations, and climatic disturbances are poorly understood. Here, we report time series models for three species of small mammal prey and two species of owl predators. The large differences in population fluctuations between the three small mammal species are related to differences in their respective feedback structures. The analyses reveal that per capita growth rate of the leaf-eared mouse is a decreasing function of log density and of log barn owl abundance together with a positive rainfall effect. In turn, per capita population growth rate ( R -function) of the barn owl is a negative function of log barn owl abundance and a positive function of leaf-eared mouse abundance, suggesting a predator–prey interaction. The dramatic population fluctuations exhibited by leaf-eared mouse ( Phyllotis darwini ) are caused by climate effects coupled with a complex food web architecture.     

Group structure,within-group conflict and reproductive tactics in cooperatively breeding Galápagos mockingbirds,Nesomimus parvulus

Reproductive conflict within groups can be an important feature of cooperative breeding systems, especially when more than one individual of a sex breeds within a social group. Relationships between group structure, dominance, within-group conflict and reproductive tactics of cooperatively breeding Galápagos mockingbirds were examined on Isla Genovesa. Territorial groups of 2–24 adults included up to three breeding females, with 42% of the groups containing more than one (plural groups); females in most plural groups nested separately. Territory size increased with group size, but the area available per pair in plural groups was smaller than in singular groups (groups with only one breeding pair). Most pairings were monogamous, and males usually outnumbered females; high-ranking males obtained mates more frequently than subordinate males. In 3 relatively dry years, but not in a wet El Niño year, subordinate pairs in plural groups fledged fewer young than dominant pairs or pairs breeding in singular groups. Interference by dominant breeders, often leading to abandonment of nests by subordinate pairs, appears to account for these differences: through nest disruption in drier years, dominant individuals may reduce the cost of sharing their territories and increase the chances of recruiting helpers. Dominant males in plural groups may also father young through extra-pair copulations with subordinate females. Despite costs imposed by within-group conflict, subordinate breeders have higher long-term reproductive success than birds that defer breeding. Plural group structure is maintained because unpredictable climatic variation favours opportunistic breeding by subordinates.     

Effects of El Niño-related Drought on Freshwater and Brackish-water Fishes in Suriname, South America

Droughts associated with the El Niño-Southern Oscillation (ENSO) affected fishes of brackish-water lagoons, freshwater swamps and a rainforest creek in Suriname, South America. The mean rainfall in the period August to February in 22 El Niño years was 76.6% of the mean rainfall in the same months of non-El Niño years. In the period 1900–1999, three out of four years in which an extreme drought (rainfall less then 60% of the mean value) occurred were El Niño years. The recent 1997/1998 ENSO event caused the second most severe drought in a 100-year record. Drying up of brackish-water lagoons, freshwater swamps and rainforest creeks was observed during El Niño-related droughts. In the lagoons ariid catfish died first, followed by snook, tilapia, mullet and tarpon, respectively. Landings of lagoon fish were positively correlated with rainfall in the period August–February. During the El Niño-related drought we observed failure of reproduction in three species of callichthyid armoured catfish in both coastal freshwater swamps and a rainforest creek in the interior. In the El Niño year 1997/1998, the no flow period of the rainforest creek was extended by four months beyond the long dry season and the dissolved oxygen levels in the dry-season pools dropped to 1.27mg O₂l^–1 (as compared to 4.53mg O₂l^–1 under running water conditions). Other fish species of the rainforest creek also showed decreased reproductive success in the El Niño year. We suggest that the stochastic effects of El Niño-related drought may be an important non-equilibrium component in the ecology of neotropical inland fish communities.