Annual Population Size Research Articles

Increased health service use for asthma, but decreased for COPD: Northumbrian hospital episodes, 2013-2014.

The burden of respiratory disease has persisted over the years, for both men and women. The aim of the present study was to investigate the hospital episode rates in respiratory disease and to understand whether and how the use of the health service for respiratory disease might have changed in recent years in the North-East of England. Hospital episode data covering two full calendar years (in 2013–2014) was extracted from the Northumbria Healthcare NHS Foundation Trust, which serves a population of nearly half a million. Hospital episode rates were calculated from admissions divided by annual and small area-specific population size by sex and across age groups, presented with per 100,000 person-years. The use of the health service for influenza and pneumonia, acute lower respiratory infections and chronic obstructive pulmonary disease (COPD) increased with an advancing age, except for acute upper respiratory infections and asthma. Overall, the use of the health service for common respiratory diseases has seemed to be unchanged, except for asthma. There were large increases in young adults aged 20–50 for both men and women and the very old aged 90+ in women. Of note, there were large increases in acute lower respiratory infections for both men and women aged 90+, whereas there was also a large decrease in COPD in women aged 80–90. This is the first study to examine health service use for respiratory diseases by calculating the detailed population size as denominator. Re-diverting funding to improve population health on a yearly basis may serve the changing need in local areas.

Health service use for cardiovascular disease

Background: The aim of the present study was to investigate the hospital episode rates in cardiovascular disease by sex and across age groups in order to understand whether and how the use of health services for cardiovascular disease might have changed in recent years in the north-east of England. Methods: Hospital episode data in 2010–2014 covering 5 full calendar years was extracted from Northumbria Healthcare NHS Foundation Trust, which is serving a population of nearly half a million. Hospital episode rates were calculated from all admissions divided by annual and areaspecific population size for each sex and age group, presented per 100 000 person-years using Microsoft Excel. Results: The overall use for each subtype of cardiovascular disease seemed to decrease from 2010 to 2013, but increase from 2013 to 2014. This is particularly apparent in the very old, aged 80 and above, such as in the case of diagnoses owing to essential primary hypertension and angina. For atrial fibrillation and haemorrhagic strokes, a similar situation was observed in the oldest old-aged, 90 and above. For myocardial infarction, heart failure, and cerebral infarction, however, service use seemed to have remained constant over the last 5 years. Of note, there was a huge sex difference in health-service use for cerebral infarction in those aged 90 and above, where there were more women than men admitted. Conclusion: Examining local health-service use owing to the burden of cardiovascular disease annually might help indicate which of its subtypes might require more attention.

Increased health service use for allergy in adults: Northumbrian hospital episodes, 2010-2015.

Little is known on the health service use for allergy. Therefore, the aim of this study was to investigate the hospital episode rates in allergy by sex and across age groups in order to understand whether and how the health service use for allergy might have changed in recent years in north-east of England. Hospital episode data in mid-2010 to mid-2015 covering five full calendar years were extracted from Northumbria Healthcare NHS Foundation Trust, which is serving nearly half of a million population and free from central government control. Hospital episode rates were calculated from all admissions divided by annual and area-specific population size for each sex and age group, presented with per 100 000 person-years using Microsoft Excel. Health service use for allergy in adults for both men and women has increased, with large increases in young adults aged 40-49 (both male and female), 50-59 (female) and 60-69 (male). In children, there were decreases in those aged 0-9, but increases in those aged 10-19. Emergency admissions due to allergy were only minimal. Higher admissions were observed in spring and autumn than in summer and winter. Allergy admissions have increased in adults. For future research, local health policy could benefit from annual clinical records on health service use due to allergy. For clinical practice, in addition to increasing and improving the role of health and nursing professionals to reduce burden and rehabilitation, public awareness, attitude and knowledge should be continuously raised and improved as well.

Increasing Dengue Incidence in Singapore over the Past 40 Years: Population Growth, Climate and Mobility.

In Singapore, the frequency and magnitude of dengue epidemics have increased significantly over the past 40 years. It is important to understand the main drivers for the rapid increase in dengue incidence. We studied the relative contributions of putative drivers for the rise of dengue in Singapore: population growth, climate parameters and international air passenger arrivals from dengue endemic countries, for the time period of 1974 until 2011. We used multivariable Poisson regression models with the following predictors: Annual Population Size; Aedes Premises Index; Mean Annual Temperature; Minimum and Maximum Temperature Recorded in each year; Annual Precipitation and Annual Number of Air Passengers arriving from dengue-endemic South-East Asia to Singapore. The relative risk (RR) of the increase in dengue incidence due to population growth over the study period was 42.7, while the climate variables (mean and minimum temperature) together explained an RR of 7.1 (RR defined as risk at the end of the time period relative to the beginning and goodness of fit associated with the model leading to these estimates assessed by pseudo-R2 equal to 0.83). Estimating the extent of the contribution of these individual factors on the increasing dengue incidence, we found that population growth contributed to 86% while the residual 14% was explained by increase in temperature. We found no correlation with incoming air passenger arrivals into Singapore from dengue endemic countries. Our findings have significant implications for predicting future trends of the dengue epidemics given the rapid urbanization with population growth in many dengue endemic countries. It is time for policy-makers and the scientific community alike to pay more attention to the negative impact of urbanization and urban climate on diseases such as dengue.

Annual plant functional traits explain shrub facilitation in a desert community

AbstractQuestionFor a desert where winter is the driest, harshest season we asked: does the effect of dominant shrubs (Bulnesia retama) on annual species depend on (1) the functional traits of the latter, (2) the season of the year, or (3) the activity of livestock?LocationA low‐density goat farm in central‐northern Monte Desert, Argentina.MethodsWe estimated the effect of shrubs using a log response ratio based on annual species population sizes underneath shrub canopies and in open spaces. We collected density data of annual species in 18 visits between Aug 2010 and Apr 2013 in permanent 50‐cm square areas laid out according to a split‐plot design, in which the activity of livestock (fenced and unfenced; plots were 10‐m squares) was the main factor, and microsite type (shrub and open) was the subordinate factor, with 20 replicates for each combination. We also gathered data on eight functional traits (characterizing whole plants, leaves, roots and seeds) from annual plants collected in the study site following standardized protocols.ResultsAnnual species with acquisitive attributes (high specific leaf area, intermediate‐to‐low leaf dry matter content, large leaves and high specific root volume) were more benefited by shrubs compared to species with the opposite, relatively conservative attributes. Facilitative influences of shrubs were pervasive during winter, while competitive influences increased in frequency during summer, when total plant density was higher. This pattern was not affected by livestock.ConclusionsThe outcome of species interactions depended on the interplay between plant strategies and abiotic stress: facilitated species were mostly acquisitive, and shrub facilitation was more important during the harshest season (winter). Specific root volume, along with widely used functional traits (specific leaf area, leaf dry matter content, leaf size) delineated such strategies. This underlines the importance of considering below‐ground traits when studying plant–plant interactions. Single traits achieved superior explanatory power of shrub effects than composite ones (i.e. principal component axes based on single traits), reinforcing the idea that single functional traits are themselves meaningful indicators of complex physiological trade‐offs that ultimately affect community structure and dynamics.

Forage fish abundance is a predictor of timing of breeding and hatching brood size in a coastal seabird

Current and future climate alterations might impact ecological processes like timing of breeding. We used multivariate linear models to assess the importance of food availability and climate on timing of breeding and hatching brood size of European shags Phalacrocorax aristotelis in 2 colonies, Sklinna (65° N) and Rost (67° N), in the Norwegian Sea over 21 yr (1989 to 2009). Pre- dictor variables were ICES abundance estimates of young saithe Pollachius virens, the staple food of shags in these colonies, the previous winter's North Atlantic Oscillation index (wNAO), and sea surface and air temperatures. Annual population size was included to control for density-depen- dent effects. The best model for hatching date explained 15% (Sklinna) and 70% (Rost) of the variation and showed that shags bred earlier when 1 yr old saithe were more abundant. The model for Rost also included 2 yr old saithe and wNAO. The best model for hatching brood size explained 40% (Sklinna) and 48% (Rost) and included a positive effect of population size at both sites. The model for Rost also included a positive effect of 1 yr old saithe. Our study demonstrates that abundance of 1 yr old saithe is a key factor for the breeding performance of shags in both colonies, whereas the climate variables were of less importance. Delayed breeding and low brood size were not associated with a high population of breeders, indicating breeding performance was density-independent and that the positive relationship between breeding numbers and saithe abundance mainly reflected variation in non-breeding among established breeders.

气候变化对鄱阳湖白鹤越冬种群数量变化的影响

分析了1983-2011年鄱阳湖国家级自然保护区越冬白鹤种群数量的年际变化趋势，检验了白鹤种群动态与繁殖地和越冬地气候变化的相关性，气候变量包括月平均气温、月平均最高气温、月平均最低气温和月降水量。研究结果表明，鄱阳湖国家级自然保护区内的白鹤年最大数量平均为（2 130±153）只，呈显著地线性增长趋势（<em>R</em>²=0.454，<em>F</em>=22.441，d<em>f</em>=28，<em>P</em>=0.000），但年际波动较大。在越冬地，越冬当年10月、11月、12月的气候变量与白鹤种群数量没有显著的相关性，但越冬初期10月份和越冬后期翌年3月份的气温变量与第4年、第5年、第6年及第7年的白鹤种群数量存在显著的正相关，表明越冬地气候对白鹤种群大小的影响存在时滞效应。越冬初期和末期可能是白鹤补充能量的关键阶段，而且越冬初期的气候可能也与冬季食物的数量或质量相关，因此这两个阶段的适宜气温可能有利于个体尤其是幼鹤的存活，使更多的个体参加繁殖，由于白鹤的性成熟年龄在3-5a，因此其对白鹤种群增长的有利影响会在3a以后表现出来。白鹤种群数量变化与繁殖地繁殖期的降水量没有显著的相关性，而与7月份的气温变量存在显著的正相关。多元线性回归分析结果表明，6a前的10月份平均最低温度、2a前的10月最高温度及5a前的10月平均气温是白鹤种群数量变化的显著预测因子，共同解释了鄱阳湖国家级自然保护区白鹤种群数量变化的74.8%（<em>F</em>=23.807，d<em>f</em>=27，<em>P</em>=0.000）。;Siberian crane (<em>Grus leucogeranus</em>) is a critically endangered species and has been a bird species under second class protection. In recent years, almost the entire population winters at or very near Poyang Lake, China. Based on the annual maximum population size of Siberian crane wintering in the Poyang Lake National Nature Reserve during 1983 and 2011, we tested the correlation between population size and the climate variables of its wintering and breeding areas. The climate variables included monthly average air temperature, monthly average maximum air temperature, monthly average minimum air temperature and monthly precipitation. The results showed that the annual maximum population size of Siberian crane in the Poyang Lake National Nature Reserve was 2130±153, with a significant linear increase (<em>R</em>²=0.454, <em>F</em>=22.441, d<em>f</em>=28, <em>P</em>=0.000) and drastic annual fluctuation. The Pearson correlation analysis results indicated that there were no significant correlations between the population size and the climate variables in the same year. However, the air temperature variables of October and March of the following year during a wintering period showed a significant positive correlation with the population size of the Siberian crane after 3, 4, 5 and 6 years, which indicated that the influence of the wintering area climate on the Siberian crane population size has a time-lag effect. October and March were the early and late periods of winter when the Siberian crane finishes and starts its long-distance migration, respectively. We speculated that early and late winter may be key stages for the crane to replenish energy. The climate in these two months may be correlated with the quantity or quality of winter food, therefore, presumably a suitable temperature in these periods could improve individuals, especially encouraging young crane's survival, allowing more individuals to participate in breeding. Furthermore, the age of sexual maturity of the Siberian crane is usually 3-5 years, therefore, the increase in population numbers caused by the suitable temperature during wintering periods becomes obvious after 3-5 years. As for the climate in breeding areas, there was no significant correlation between Siberian crane population size and precipitation during the breeding period. However, the population size of Siberian crane in the Poyang Lake National Nature Reserve was significantly positively correlated with the air temperature variables in July in its breeding area during the same year. The air temperature in July in breeding areas may be correlated with the food availability for Siberian crane, which is especially important for bringing up young cranes. The stepwise linear regression result showed that the average minimum air temperature in October before the 6th year, the average maximum air temperature in October before the 2nd year, and the average air temperature in October before the 5th year were significant predictive factors for the population size fluctuation of the Siberian crane and accounted for 74.8% of the total population size change (<em>R</em>²=0.748, <em>F</em>=23.807, d<em>f</em>=27, <em>P</em>=0.000). The climate-related prediction model for the Siberian crane population size was <em>Y</em>=-18 101+53.150<em>X</em>₁+29.610<em>X</em>₂+22.363<em>X</em>₃, where <em>Y</em> was the annual maximum population size of the Siberian crane in the Poyang Lake National Nature Reserve, <em>X</em>₁ was the average minimum air temperature in October before the 6th year, <em>X</em>₂ was the average maximum air temperature in October before the 2nd year, and <em>X</em>₃ was the average air temperature in October before the 5th year. Only considering the climate factor, the model predicted that the population size of Siberian crane will show an obvious decrease in 2016.

鄱阳湖区灰鹤越冬种群数量与分布动态及其影响因素

1998-2011年，采用地面同步调查法开展了鄱阳湖越冬灰鹤种群监测，并整合1984-2011年鄱阳湖国家级自然保护区历年的越冬灰鹤最大种群数量，分析了鄱阳湖灰鹤越冬种群动态以及影响其数量变化与空间分布的环境因素。结果表明，近13年来鄱阳湖区越冬灰鹤种群平均数量为（2 335±651）只，种群数量呈增长趋势，2011年冬季记录到最大种群数量7 640只。灰鹤越冬种群数量与10月平均最低气温以及10月平均气温存在显著正相关，与10月平均最大风速存在显著负相关，与各月的平均水位没有显著的相关性。每年冬季灰鹤在鄱阳湖呈聚集型分布。大湖池、大莲子湖、三湖、汉池湖、企湖、珠湖、南湖（共青）、大汊湖等8个湖泊是灰鹤的重点活动区，（74.9±5.6）%的越冬灰鹤分布在保护区之外。灰鹤的空间分布与滩地面积存在显著的正相关，与农田面积、人口密度、村庄数量、8月份初级生产力、11月份初级生产力等环境因子存在显著负相关。滩地面积是影响灰鹤空间分布的重要因子，对灰鹤利用频次空间变化的解释率为15.0%，与11月份初级生产力共同解释了灰鹤年平均群体数量空间变化的24.6%。如竞争、小生境结构、干扰等局地尺度的环境要素对灰鹤空间分布的影响研究将有助于更全面地认识鄱阳湖越冬灰鹤种群动态的影响机制。;Poyang Lake has been an important wintering site for Common Cranes. In this paper we monitored the dynamics of population size and spatial distribution of Common Cranes wintering in Poyang Lake during 1998-2011 and analyzed the potential determinants of its population dynamics. This was combined with the monitoring record of the annual maximum number of Common Cranes wintering in the Poyang Lake National Nature Reserve during 1984-2011. We illustrated the changing trend of this Common Crane population over a long time scale, and analyzed the impact of climate variation and water level change on the population size dynamics.<br>The results showed that the Common Crane population wintering in Poyang Lake significantly increased from 1998 to 2011, with an average population size of 2335±651 and a maximum of 7640 in the winter of 2011. The exponential curve fit well with the population growth trend (<em>R</em>²=0.808, <em>F</em>=46.234, d<em>f</em>=12, <em>P</em>=0.000). The wintering Common Cranes clustered in the Poyang lakes, with the lakes of Dahuchi, Dalianzihu, Sanhu, Hanchihu, Qihu, Zhuhu, Nanhu (gongqing), and Dachahu being the hotspots used by them. On average, (74.9±5.6)% of Common Cranes wintered outside nature reserves.<br>The spatial distribution of the common crane was significantly positively correlated with the areas of mudflat habitat, and was negatively correlated with areas of agricultural land, human density, village areas, and areas of net primary productivity (NPP) in August and November. The mudflat area was an important factor determining the spatial distribution of Common Cranes, which accounted for 15% of the spatial change in occurrence frequency, and when combined with the NPP factor in November, accounted for 24.6% of the spatial change in the average number of Common Cranes. The results mean that there are still factors which may affect the spatial distribution of Common Crane in Poyang lakes which were not assessed, such as competition, the structure of the microhabitat, and human interference, which maybe contribute to a more comprehensive understanding of the impact mechanisms of crane population dynamics wintering in the Poyang Lake.<br>In the Poyang Lake National Nature Reserve, the average annual maximum number of Common Cranes was 276±51 (<em>n</em>=28), which showed a significant linear increase (<em>R</em>²=0.176, <em>F</em>=5.537, d<em>f</em>=27, <em>P</em>=0.026), but there was a drastic annual fluctuation. The results of Pearson correlation analysis indicated that the annual maximum population number of Common Cranes wintering in the Poyang Lake National Nature Reserve was significantly positively correlated with the average air temperature in October (<em>r</em>=0.480, <em>P</em>=0.010, <em>n</em>=28) and the average minimum air temperature in October (<em>r</em>=0.480, <em>P</em>=0.010, <em>n</em>=28), and significantly negatively correlated with the average maximum wind speed in October (<em>r</em>=-0.450, <em>P</em>=0.016, <em>n</em>=28).<br>As for the water level of Poyang Lake, no significant correlation was found between the annual maximum population size of Common Cranes in the Poyang Lake National Nature Reserve and the annual minimum water level (<em>r</em>=-0.259, <em>P</em>=0.192, <em>n</em>=27), or the annual maximum water level (<em>r</em>=-0.373, <em>P</em>=0.051, <em>n</em>=28). There was also no significant correlation between the population size and the monthly average water level in the wintering period. Although the water level of Poyang Lake in winter was tested and found to significantly change the structural landscape of Poyang Lake wetland, influencing the availability of habitat and food, the water level of those lakes in the nature reserve was largely determined by the artificial aquaculture discharge time and velocity of the lake, which eliminated the influence of water level in Poyang Lake.

Variation in platypus (Ornithorhynchus anatinus) life-history attributes and population trajectories in urban streams

An understanding of animal population dynamics relies on identifying life-history attributes associated with population growth and determining how these are affected by environmental variables. We analysed platypus population processes over a 10-year period through mark–recapture studies conducted in three spatially independent stream systems located in the suburbs of Melbourne, Australia. The three populations were collectively characterised by a slightly male-biased adult sex ratio (1.15 : 1) and relatively low reproductive success (&lt;0.5 juvenile captured annually per adult female). An estimated 16% of core residents disappeared annually and 18% of marked juveniles were recaptured as adults. However, some demographic parameters (reproductive success, frequency of non-core adult captures) varied significantly among populations. Estimates of annual core population size in the three systems varied asynchronously, with different trajectories in population size potentially reflecting habitat differences (amount of urban development, reliability of surface flow) as well as variation in spatial isolation and catchment history (implementation of stream rehabilitation programs, occurrence of severe floods). Across all three populations, significant variability in annual reproductive success was explained by linear relationships with the amount of rainfall recorded in the five months before breeding (positive) and after juveniles emerge from nesting burrows (negative).

Corrigendum to: Effectiveness of commercial harvesting in controlling feral-pig populations

Context The feral pig (Sus scrofa) is a widespread pest species in Australia and its populations are commonly controlled to reduce damage to agriculture and the environment. Feral pigs are also a resource and harvested for commercial export as game meat. Although many other control techniques are used, commercial harvesting of feral pigs is often encouraged by land managers, because it carries little or no cost and is widely perceived to control populations. Aims To use feral-pig harvesting records, density data and simple harvest models to examine the effectiveness of commercial harvesting to reduce feral-pig populations. Methods The present study examined commercial harvest off-take on six sites (246–657km2) in southern Queensland, and 20 large blocks (~2–6000km2) throughout Queensland. The harvest off-take for each site was divided by monthly or average annual population size, determined by aerial survey, to calculate monthly and annual harvest rates. A simple harvest model assuming logistic population growth was used to determine the likely effectiveness of harvesting. Key results Commercial harvest rates were generally low (50%) in long-term population size were isolated occurrences and not maintained across sites and years. High harvest rates were observed only at low densities. Although these harvest rates may be sufficiently high to hold populations at low densities, the population is likely to escape this entrapment following a flush in food supply or a reduction in harvest effort. Implications Our results demonstrated that, at current harvest rates, commercial harvesting is ineffective for the landscape-scale control of feral-pig populations. Unless harvest rates can be significantly increased, commercial harvesting should be used as a supplement to, rather than as a substitute for, other damage-control techniques.

On the Fast Track to Recovery: Island Foxes on the Northern Channel Islands

The island fox (Urocyon littoralis) represents an unusual case of a species that achieved virtual recovery a mere 15 years after population declines were first discovered. Island fox subspecies on San Miguel, Santa Rosa, and Santa Cruz islands declined precipitously in the mid-1990s due to predation by Golden Eagles (Aquila chrysaetos), which had not historically bred on the islands. In 2008, a 10-year period of recovery action implementation ended. The recovery program had included captive breeding and reintroduction of island foxes and capture and relocation of Golden Eagles. Free-ranging fox populations have been monitored to assess recovery of each subspecies and to detect potential threats of disease and predation. Monitoring included (1) annual grid trapping to allow estimation of annual population size via capture-mark-recapture methods and (2) systematic surveillance of radio-collared foxes to allow estimation of mortality rates and causes. A comprehensive demographic modeling effort produced a population recovery tool that uses adult mortality and population size estimates from the monitoring programs to estimate extinction risks for each fox population. The tool allows managers to assess when threats are sufficiently mitigated to consider populations acceptably safe from extinction. Population monitoring indicates that island foxes on the northern Channel Islands have increased up to 30-fold from population lows and that annual survival has been 90% or better in most years. The San Miguel and Santa Cruz subspecies have approached or reached predecline population levels, and application of the recovery tool indicates they will be biologically recovered by 2013. Biological recovery of the Santa Rosa subspecies, hindered by predation which caused lower survival in 2010, will occur by 2017.

Bottlenose dolphin Tursiops truncatus at São Tomé Island (São Tomé and Príncipe) — relative abundance, site fidelity and social structure

Although the bottlenose dolphin Tursiops truncatus is one of the most common cetacean species around São Tomé Island, Gulf of Guinea, little research has focused on this species in this region. This study investigated the population of bottlenose dolphins around São Tomé Island by estimating the minimum population size, site fidelity and social structure. During a total of 226 surveys between 2002 and 2006, and in 2012, 51 sightings were recorded but only 33 had photographic data suitable for rigorous analysis. The minimum annual total population size, based on permanently marked dolphins, was 37 individuals, and the discovery curve indicated that a large part of the population remained undiscovered. The annual sighting rate for 76 highly distinctive adult animals ranged from 0.20 (seen in one year only) to 1.0 (seen every year of the study period). Resighted individuals demonstrated low association values; the dolphins seemed to form a single group with a fluid structure.

Spatial and temporal unpredictability of colony size in Cliff Swallows across 30 years

Most colonially breeding animals occupy colonies that range in size from a few pairs to thousands of individuals, but the causes of colony size variation are largely unknown. Three general hypotheses are: (1) that variation in colony size is maintained by fluctuating selection via spatial and temporal changes in fitness associated with different colony sizes; (2) that colony formation reflects heterogeneity in habitat, with some sites having resources to support more individuals than others; and (3) that individuals assess the presence or annual reproductive success of current colony residents at each site and aggregate preferentially at high‐quality sites. These hypotheses make predictions about how consistent colony size should be across sites and among years. We examined temporal and spatial variability of colony size for &gt;200 Cliff Swallow (Petrochelidon pyrrhonota) colony sites in western Nebraska across a 30‐year period. A colony's substrate type, annual population size in the study area, and whether the nesting season was relatively warm or cool, influenced average annual colony size. While some Cliff Swallow colony sites hosted perennially large colonies and others perennially small ones, between‐year variability in colony size at most sites was high. Annual colony size distributions were relatively stable over 30 years and provided no evidence for long‐term directional changes in colony size. The only ecological characteristic that was strongly associated with Cliff Swallow colony size at a site was the type of nesting substrate, with bridges tending to have larger colonies and being more frequently occupied than other substrates. Some sites showed annual changes in colony size consistent with the birds' basing their choice of colony on the presence or success of conspecifics, but many sites did not conform to a pattern expected if coloniality is a by‐product of traditional aggregation. Colony size in Cliff Swallows was temporally and spatially unpredictable when viewed across the 30 years of this study. Each of the three hypotheses to explain size variation may have applied at certain sites, but the pattern of colony size variability leant the most support to the hypothesis that fluctuating selection on group size maintains colonies of widely different sizes.

Are habitat loss, predation risk and climate related to the drastic decline in a Siberian flying squirrel population? A 15‐year study

AbstractTo devise effective conservation actions, it is important to know which factors are associated with the population parameters of a declining population. Using mark–recapture methods, we estimated the annual population size, growth rate and survival probability of an ear‐tagged flying squirrel population over a 15‐year period in a 4,500 ha study area in western Finland. The species is considered vulnerable, but detailed knowledge concerning population sizes or trends is lacking. The population parameters and changes therein were regressed against habitat availability, an indicator of predation pressure, and mean winter temperature (an indicator of climate change), to reveal potential reasons for trends in the population. The best‐fit models suggested the annual growth rate to be below one, and on average it was 0.93 (±0.06; SE) across the 15‐year period. The survival probability was about 0.22 (±0.03) for juveniles and 0.50 (±0.03) for adults. The population size of adult flying squirrels decreased from 65 (±11) individuals in 1995 to 29 (±6) individuals in 2009. The number of flying squirrels was associated with the amount of available habitat, but the decline in population size was more rapid than the loss of habitat area. If the current decreasing trend in habitat availability continues, the population might become extinct by the year 2020. To halt the population decline, it is necessary to refrain from clear‐cutting mature spruce stands until new suitable habitats develop from the maturation of younger forests.

Changes in the Norwegian breeding population of European shag correlate with forage fish and climate

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 489:235-244 (2013) - DOI: https://doi.org/10.3354/meps10440 Changes in the Norwegian breeding population of European shag correlate with forage fish and climate Jan Ove Bustnes1,*, Tycho Anker-Nilssen2, Kjell Einar Erikstad1,3, Svein-Håkon Lorentsen2, Geir Helge Systad1 1Norwegian Institute for Nature Research, FRAM - High North Research Centre on Climate and the Environment, 9296 Tromsø, Norway 2Norwegian Institute for Nature Research, 7485 Trondheim, Norway 3Centre for Biodiversity Dynamics (CBD), Dept of Biology, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway *Email: jan.o.bustnes@nina.no ABSTRACT: While many seabird species in the North Atlantic have declined over the last decades, the Norwegian population of the European shag Phalacrocorax aristotelis has increased. In the present study, we assessed the impact of food availability and climate on the shag population by analysing 25 years of data (1985 to 2009) on breeding numbers in 3 large colonies: 2 in the Norwegian Sea (65°N and 67°N) and 1 in the Barents Sea (70°N). Predictor variables were ICES abundance estimates of young saithe Pollacius virens, the most important forage fish for shags in the Norwegian Sea, and for the Barents Sea colony also total stock size estimates of Barents Sea capelin Mallotus villosus. As proxies for climate variation, we used the North Atlantic Oscilliation index (NAO) for the last and the preceding winter (lagged by 1 yr). Finally, the annual population size of the study colonies in the preceding year was included in the models to control for potential density-dependent effects. The predictor variables explained 46 to 67% of the variation in annual growth rate in the colonies. In the Barents Sea colony, the shag population growth rate was only associated with capelin abundance, whereas for the Norwegian Sea colonies, there were strong positive relationships with 1 yr old saithe and a negative effect of the lagged NAO winter index. The latter effect may be a result of unfavourable weather conditions with high winds and precipitation in winter increasing mortality among non-breeding age classes of shag. Our study is the first to demonstrate a close correlation between stock estimates of the primary forage fish for European shags and shag breeding numbers. This suggests that the population growth rate and diet of shags may be used as cost-efficient and reliable indicators of major shifts in saithe stock recruitment. KEY WORDS: Phalacrocorax aristotelis · Norwegian Sea · Barents Sea · NAO · Saithe · Breeding numbers Full text in pdf format Supplementary material PreviousNextCite this article as: Bustnes JO, Anker-Nilssen T, Erikstad KE, Lorentsen SH, Systad GH (2013) Changes in the Norwegian breeding population of European shag correlate with forage fish and climate. Mar Ecol Prog Ser 489:235-244. https://doi.org/10.3354/meps10440 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 489. Online publication date: August 28, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Golden eagle population trends in the western United States: 1968–2010

AbstractIn 2009, the United States Fish and Wildlife Service promulgated permit regulations for the unintentional lethal take (anthropogenic mortality) and disturbance of golden eagles (Aquila chrysaetos). Accurate population trend and size information for golden eagles are needed so agency biologists can make informed decisions when eagle take permits are requested. To address this need with available data, we used a log‐linear hierarchical model to average data from a late‐summer aerial‐line‐transect distance‐sampling survey (WGES) of golden eagles in the United States portions of Bird Conservation Region (BCR) 9 (Great Basin), BCR 10 (Northern Rockies), BCR 16 (Southern Rockies/Colorado Plateau), and BCR 17 (Badlands and Prairies) from 2006 to 2010 with late‐spring, early summer Breeding Bird Survey (BBS) data for the same BCRs and years to estimate summer golden eagle population size and trends in these BCRs. We used the ratio of the density estimates from the WGES to the BBS index to calculate a BCR‐specific adjustment factor that scaled the BBS index (i.e., birds per route) to a density estimate. Our results indicated golden eagle populations were generally stable from 2006 to 2010 in the 4 BCRs, with an estimated average rate of population change of −0.41% (95% credible interval [CI]: −4.17% to 3.40%) per year. For the 4 BCRs and years, we estimated annual golden eagle population size to range from 28,220 (95% CI: 23,250–35,110) in 2007 to 26,490 (95% CI: 21,760–32,680) in 2008. We found a general correspondence in trends between WGES and BBS data for these 4 BCRs, which suggested BBS data were providing useful trend information. We used the overall adjustment factor calculated from the 4 BCRs and years to scale BBS golden eagle counts from 1968 to 2005 for the 4 BCRs and for 1968 to 2010 for the 8 other BCRs (without WGES data) to estimate golden eagle population size and trends across the western United States for the period 1968 to 2010. In general, we noted slightly declining trends in southern BCRs and slightly increasing trends in northern BCRs. However, we estimated the average rate of golden eagle population change across all 12 BCRs for the period 1968–2010 as +0.40% per year (95% CI = −0.27% to 1.00%), suggesting a stable population. We also estimated the average rate of population change for the period 1990–2010 was +0.5% per year (95% CI = −0.33% to 1.3%). Our annual estimates of population size for the most recent decade range from 31,370 (95% CI: 25,450–39,310) in 2004 to 33,460 (95% CI: 27,380–41,710) in 2007. Our results clarify that golden eagles are not declining widely in the western United States. © 2013 The Wildlife Society.

Effectiveness of commercial harvesting in controlling feral-pig populations

Context The feral pig (Sus scrofa) is a widespread pest species in Australia and its populations are commonly controlled to reduce damage to agriculture and the environment. Feral pigs are also a resource and harvested for commercial export as game meat. Although many other control techniques are used, commercial harvesting of feral pigs is often encouraged by land managers, because it carries little or no cost and is widely perceived to control populations. Aims To use feral-pig harvesting records, density data and simple harvest models to examine the effectiveness of commercial harvesting to reduce feral-pig populations. Methods The present study examined commercial harvest off-take on six sites (246–657 km2) in southern Queensland, and 20 large blocks (~2–6000 km2) throughout Queensland. The harvest off-take for each site was divided by monthly or average annual population size, determined by aerial survey, to calculate monthly and annual harvest rates. A simple harvest model assuming logistic population growth was used to determine the likely effectiveness of harvesting. Key results Commercial harvest rates were generally low (&lt;~20%) and are likely to provide only modest reductions in population size. Additionally, harvest rates capable of substantial reductions (&gt;50%) in long-term population size were isolated occurrences and not maintained across sites and years. High harvest rates were observed only at low densities. Although these harvest rates may be sufficiently high to hold populations at low densities, the population is likely to escape this entrapment following a flush in food supply or a reduction in harvest effort. Implications Our results demonstrated that, at current harvest rates, commercial harvesting is ineffective for the landscape-scale control of feral-pig populations. Unless harvest rates can be significantly increased, commercial harvesting should be used as a supplement to, rather than as a substitute for, other damage-control techniques.

An evaluation of monitoring methods for the endangered giant kangaroo rat

AbstractAccurate, reliable, and efficient monitoring methods for detecting changes in the distribution and abundance of wildlife populations are the cornerstone of effective management. Aerial surveys of active burrow sites and ground counts of open burrows have been used to estimate distribution and abundance, respectively, of a number of rodent species. We compared the efficacy of these and other methods for estimating distribution, abundance, and population growth of the endangered giant kangaroo rat (Dipodomys ingens) to determine the best practices for monitoring. Specifically, we compared aerial surveys, rapid expert assessments, and live‐trapping for estimating giant kangaroo rat range, and burrow counts and live‐trapping for estimating abundance and growth. We carried out the study in the Carrizo Plain National Monument, California, USA, from 2007 to 2011. Expert rapid assessment of sites performed nearly as well as trapping in determining range extent, while aerial surveys provided estimates of total range extent but with less precision. Active burrow counts were adequate to determine relative abundance averaged over multiple years, but were not reliable as an estimate of annual population size or growth. © 2012 The Wildlife Society.

Genetic variability characterization of the moroccan houbara bustard (Chlamydotis undulata undulata) inferred from pedigree analysis

A Moroccan Houbara Bustard pedigree was analyzed to evaluate the genetic variability in captive breeding population using genealogical approaches. The whole Houbara breeding flock (WP) for the period 1993-2004 was made up of 531 birds comprising 346 females and 185 males. The reference population (RP) comprised 198 individuals ready for reproduction from 2000 to 2004 cohorts. The corresponding percentage of known ancestors was estimated as 98.23% for the parent generation, 41.19% for the grandparent generation and 7.00% for the great grandparents generation. The average generation interval for Houbara was computed as 4.64 years. Genetic variability loss per generation was ascertained using the effective population size (Ne), the founder genome equivalent (fge), the effective number of ancestors and founders (fa) and (fe), respectively, for the RP and across each cohort. The results showed no bottleneck events in the breed but some loss of genetic variability just after the initiation of the conservation program. However, the annual effective population size based on the realized increase in inbreeding (ΔF) was estimated to be 207 for the RP and 1,000 for the WP. With regard to conservation breeding schemes, the genealogical evidence presented here is very useful as it revealed the positive effect of migration on Houbara breeding. The mating strategies will assist in the future control and management of the genetic variability of this population.

Effects of re‐breeding rates on population size estimation of biennial breeders: results from a model based on albatrosses

Estimating total breeding populations (I) for species that exhibit biennial breeding is generally done from counts of individuals that breed in each year (N), but can be complicated by the fact that the proportion of individuals breeding varies from year to year. Partly, this reflects the proportion of individuals that re‐breed in successive years (re‐breeding rate, p), which is largely, although not exclusively, governed by reproductive failure. Here we show that variation in counts of breeding individuals not only reflects changes in total breeding population but can be sensitive to and powerfully driven by variation in p. A simulation of annual field counts of a bird exhibiting biennial breeding was constructed to explore the effect of re‐breeding attempts on estimations of the total breeding population. The model was used to simulate the consequences of adult mortality and different annual patterns of nesting failures on total breeding population estimates, and to explore the consequences of variation in p on N, when total breeding population remains constant. N is shown to be very sensitive to variations in p, so that even short‐term fluctuations in p can cause changes in N that oscillate for many years ahead. We compare our modelled results with real data for Grey‐headed Albatrosses Thalassarche chrysostoma and demonstrate that, when I is held constant in the model, actual counts may be simulated by variations in p only. Normally, I is unknown and is extrapolated from N on the assumption that N mirrors changes in the size of the total population. Consequently, applying average values of p can result in misleading estimates of total breeding population. We recommend that annual counts of breeding individuals are supplemented with annual estimates of p. Field protocols that aim to estimate annual breeding population size from counts of breeding individuals should be complemented by independent measures of rates of re‐breeding and nest failure.