Effects of hunting on guianan forest game birds

To assess the effect of on-going and of previous or near by hunting pressure on game birds in a neotropical rain forest (French Guiana), I compared species abundances between six hunted and disturbed areas, seven non-hunted and pristine areas and eight intermediate areas, undisturbed and not currently hunted, but formerly hunted or close to current hunting areas. I recorded all birds detected within 100 m-wide strip transects, walked at random through every forest type all day long. The frequency of records per 10 h and flock sizes on each transect were averaged over all surveys in each study site (N = 3025 h). Censused groups included terrestrial (tinamous, woodquails, curassow and trumpeter) and arboreal species (guans, macaws, parrots, toucans), but not waterbirds. The abundance of all game birds was higher in non-hunted than in hunted areas, though not always significantly for secretive understorey species (tinamous, guans, wood-quail) or canopy frugivores (parrots, macaws, toucans). The Black Curassow and Gray-winged Trumpeter exhibited the highest and most consistent increases (7–10-fold) and more so between intermediate and non-hunted sites than between hunted and intermediate sites. The mean flock size also increased along the hunting gradient, especially in flocking species (macaws, parrots, trumpeter). Low reproductive rates and/or seasonal movements may explain that hunting pressure could still be felt after hunting has ceased or when it persists only away from a given area. Such a persistent effect would affect some populations in small protected areas.     

Long-term changes in numbers and distribution of wintering waterbirds in the Czech Republic, 1966–2008

Capsule?Of 26 species of wintering waterbirds, 18 showed an increase in numbers, five showed a decrease and two showed no change.

Aim?To assess long-term trends in the numbers and distribution of the 26 most abundant wintering waterbird species in the Czech Republic.

Methods?We used International Waterbird Census data from between 48 and 639 wetland sites which had been counted annually in the Czech Republic from 1966 to 2008. From these data long-term changes in numbers and distributions were determined. Log-linear Poisson regression analysis was used to estimate missing data using trim software. The distribution of each species was described as the ratio of the number of sites occupied by that species to the total number of sites investigated.

Results?Increasing trends were found for 18 species, five species were found to be declining, one species was stable and two species were found with uncertain trends. Wintering distributions (the ratio of sites occupied by a given species to the total number of sites counted) increased in 16 species and decreased in two species, broadly correlated with the species changes in numbers.

Conclusion?In most species changes in numbers as well as changes in distribution followed the Western Palearctic population trends. Those species which increased were mainly piscivores and included geese, ducks and gulls. Scarcer species also exhibited an increase in numbers. The changes in numbers (both positive and negative) were more frequent among species associated with running water, whereas species which showed uncertain trends were more frequently recorded on standing water, which is more affected by variable weather conditions.     

Should we account for detectability in population trends?

Capsule?Accounting for changes in detectability over time which could invalidate population trends for common and widespread breeding birds in the UK, resulted in little change in trends for the majority of species considered.

Aims?To examine whether detectability has a significant influence on population trends for common and widespread breeding birds in the UK.

Methods?Using data collected over 16 years of the UK Breeding Bird Survey (1994–2009) and focusing on a random sample of 20 common and widespread bird species, we examine the extent to which controlling for temporal change in detectability would influence national population trends.

Results?Population trends were significantly different for only 2 of the 20 species, Common Blackbird and Winter Wren. This difference corresponds to an apparent fall off in detectability of these species between 2005 and 2009. For the remaining species, controlling for detectability resulted in no significant difference in population trends.

Conclusions?The importance of detectability should be examined as part of any long-term monitoring programme. However, currently we do not find sufficient support for routinely incorporating detectability into population trends for widespread and abundant breeding birds in the UK.     

Assessing and monitoring bird populations in Africa: an overview

Bennun, L. 2000. Assessing and monitoring bird populations in Africa: an overview. Ostrich 71 (1 & 2): 214–215.

Access to reliable population data is crucial for effective conservation and management of birds. So far, relatively little attention has been paid to assessing and monitoring bird populations in Africa. This is beginning to change. Regional meetings, for example in East Africa, are discussing and defining standard methodologies, and making technical information more widely available. Researchers are using these methods to access the populations of threatened species, or those of economic value. Projects involving long-term monitoring, particularly of waterbirds, are beginning to yield results that are useful for management. Some challenges that remain include: securing institutional and financial support for long-term monitoring work; integrating monitoring efforts (especially of migratory species) across borders; understanding the ecological significance of population trends; finding robust and reliable methods to census economically important species, such as game-birds; and making accurate global assessments of the populations of threatened species.     

Against the trend: increasing numbers of breeding Northern Lapwings Vanellus vanellus and Black-tailed Godwits Limosa limosa limosa on a German Wadden Sea island

Capsule The increase in population sizes over the last 30 years cannot be explained by reproductive success.

Aims To establish whether the positive population trends are due to increasing and self-sustaining populations or to immigration.

Methods We studied the population development of breeding lapwings from 1971 until 2005 and of godwits from 1977 until 2005 on Wangerooge, a German Wadden Sea island. Both species increased significantly during the last three decades. For each species we used a logistic growth model to derive the reproductive output required to explain the past population development without assuming immigration. We compare the values derived by this model with empirical findings of reproductive output of the respective populations.

Results For neither lapwings nor godwits can empirical reproductive success explain the observed population development.

Conclusion Our results imply that the increase in breeding pairs of Northern Lapwing and Black-tailed Godwit on Wangerooge Island is not due to reproductive output. We propose that it is mainly caused by immigration onto the island.     

Recent changes in the abundance of British upland breeding birds

Capsule Breeding wader populations have more often shown declines than passerine populations during the last 10–20 years.

Aims To determine abundance changes in British upland breeding birds during the last 10–20 years.

Methods We re-surveyed 1348 km², in nine study areas, of the British uplands in 2000 and 2002, which had been previously surveyed between 1980 and 1991. In addition, we included data from recent repeat surveys in four other upland areas, covering approximately 365 km², to broaden the scope of our study.

Results We found evidence of widespread population declines in three species of breeding waders, Lapwing Vanellus vanellus, Dunlin Calidris alpina and Curlew Numenius arquata. Among the passerines, some species declined, including Twite Carduelis flavirostris and Ring Ouzel Turdus torquatus, while others showed strong gains, including Stonechat Saxicola torquata and Raven Corvus corax.

Conclusion Overall, abundance changes were characterized by a high degree of variability across study areas, even when close together. This variability may have been partly due to the different time intervals between the original and repeat surveys. Improved upland breeding bird population monitoring is needed to allow better detection of trends. Action is needed to restore upland breeding bird populations in areas where they have declined.     

Unraveling the importance of rice fields for waterbird populations in Europe

Rice fields are an alternative habitat for waterbirds and provide food and shelter for many avian species, but there is a lack of information about how the use of rice fields translates into population level effects. The aim of this study was to test the relationship between the use of rice fields by European waterbirds and trends in their populations. We tested this relationship during the autumn migration season and during the breeding season. Based on counts conducted over the last 23 years in natural marshes and areas of rice fields in Doñana (SW Spain), an index of rice field use was constructed for 76 bird species, which was then compared to these species’ European population trends obtained from the literature. A positive relationship was found between waterbird population trends and the use of rice fields during autumn migration season. Our study suggests that changes in the Common Agriculture Policy in Europe leading to reductions in areas of rice cultivation may have important effects on waterbirds. The restoration of former marsh areas and the maintenance of rice cultivation would seem to be more environmentally friendly approaches than the use of these areas to grow alternative crops or solar farms.     

Breeding ecology of a suburban population of Woodpigeons Columba palumbus in northwest England

Capsule Between 1981 and 2008 population size was stable, but there were negative trends in breeding parameters.

Aims To determine the current status and long‐term population trend of an isolated breeding population of Bearded Vultures Gypaetus barbatus (Corsica, Mediterranean).

Methods The total Bearded Vulture population was monitored between 1981 and 2008.

Results The current effective breeding population size of Bearded Vultures in Corsica is ten pairs/trios with a slight increase of one to two pairs since 1983. The population is currently estimated at 25 individuals. Breeding parameters (laying rate, breeding success and productivity) have decreased significantly over the full 28‐year study period, although the decrease was not significant when the data set was restricted to 1988–2008. A mean of 60.3% (n = 204) of pairs have laid, but this proportion is highly variable between years. Productivity has been very low (0.16 young/pair/year, n = 233). Breeding parameters of the Corsican population of Bearded Vultures are very low compared with those of other western European populations in the Pyrenees.

Conclusions This isolated insular population is of small size (eight to ten pairs/trios) but shows a stability of distribution and numbers, but low (and decreasing) breeding rates, making this insular population one the most threatened in Europe.     

Breeding biology of the endangered Dupont’s Lark Chersophilus duponti in two separate Spanish shrub-steppes

Capsule: The Dupont’s Lark Chersophilus duponti in Iberia has relatively high breeding success in both core and fragmented habitats, so population declines are more likely to be the result of low juvenile or adult survival.

Aims: To measure important aspects of the reproductive biology of one of the most endangered and least known larks: the Dupont’s Lark C. duponti.

Methods: We monitored 36 nests in 2 Spanish shrub-steppes, one holding one of the largest European populations (250 pairs) and one composed by fragmented habitat patches holding a smaller population (50 pairs).

Results: The breeding season went from late-March to early July. Overall mean (±sd) clutch size was 3.47?±?0.56, and the number of fledglings per successful nest was 3.0?±?1.15. Mean nestling period was short (8.2 days). Nests showed similar daily survival rate during the incubation period (0.9750?±?0.0110) as during the nestling period (0.9545?±?0.0168), with a mean breeding success of 50%. Predation was the main cause of complete nest failure (83.3% of failed nests in both localities).

Conclusion: Breeding parameters did show no significant variation between populations. Breeding success in both sites was generally higher than recorded in previous studies of this and most other lark species, which suggests that breeding success does not compromise long-term viability of these populations. The decline of the studied populations should be explained by other causes, such as a general decrease in habitat quality, habitat loss or habitat fragmentation.     

The importance of hunting pressure, habitat preference and life history for population trends of breeding waterbirds in Finland

Populations of migratory species have undergone dramatic changes in recent decades, but little is known about the factors actually driving those changes. Of particular concern are quarry species such as migratory ducks (Anatidae), many of which have an unfavourable conservation status in Europe. By including both quarry and non-quarry species, as well as habitat preference and life history characteristics of the species, we investigated the relative importance of hunting pressure, both in Finland and at the European level, in explaining population changes of 16 species of migratory waterbirds in Finland during 1986–2011. Ban of lead shot in 1996 resulted in considerably lower annual hunting bags in Finland thereafter. Species which had the highest hunting pressure had the most negative slopes in population trends from 1986 up to 1997, suggesting that hunting probably limited those populations. However, in general population trends of the species were not strongly associated with hunting pressure in Finland or in Europe. Nor were basic life history characteristics (body mass and clutch size) associated with population trends of the species. In contrast, recent population declines were associated with habitat preferences of the species: those breeding mainly in eutrophic lakes had more negative population trends than those breeding in oligotrophic lakes or generalist species. Reasons for the relatively poor status of species preferring eutrophic lakes probably include over-eutrophication of nutrient-rich lakes, resulting in less abundant food resources, and increased nest depredation.     

Identifying important bird habitats in a sub-arctic area undergoing rapid land-use change

Capsule Habitats in lowland South Iceland sustain bird populations of international importance, with highest densities in wet habitats.

Aims In areas important for biodiversity there is an urgent need to assess large-scale variation in the biodiversity value of habitats to inform management. We carried out a large-scale survey to assess the conservation value of sub-arctic, Icelandic bird habitats.

Methods Bird counts were carried out on 200 transects in the five most common vegetated habitat types in South Iceland. Based on these counts, breeding bird density and diversity were compared between habitats and total population sizes of common species in these habitats were calculated.

Results Overall, eight species (seven waders and Meadow Pipit) composed over 95% of all birds counted. The combined density of those species exceeded 275 birds/km² in all habitats. The two wettest habitat types had the highest density of birds.

Conclusion Wet habitats in lowland South Iceland held particularly high densities of breeding birds, notably waders, which constitute populations of international importance. Wet habitat types are generally of higher value for more species, than dryer ones.     

Hen Harrier Circus cyaneus population trends in relation to wind farms

Capsule: The data presented here demonstrate a considerable spatial overlap between wind farms and the breeding distribution of Hen Harriers in Ireland, but evidence for a negative impact of wind farms on their population is weak.

Aims: To assess the extent of the overlap between wind farms and breeding Hen Harriers and to investigate their potential impact on Hen Harrier population trends.

Methods: Data on Hen Harrier breeding distribution in 10?km?×?10?km survey squares from national surveys were used in conjunction with information on the location of wind farms to examine whether, and to what extent, changes in Hen Harrier distribution and abundance between 2000 and 2010 were related to wind energy development.

Results: Of the 69 survey squares holding Hen Harriers during the 2010 breeding season, 28% also overlapped with one or more wind farms. Data from 36 of the squares with breeding Hen Harriers during the 2000 survey revealed a marginally non-significant negative relationship between wind farm presence and change in the number of breeding pairs between 2000 and 2010.

Conclusions: A considerable overlap exists between Hen Harrier breeding distribution and the location of wind farms in Ireland, particularly in areas between 200 and 400?m above sea level. The presence of wind farms is negatively related to Hen Harrier population trends in squares surveyed in 2000 and 2010, but this relationship is not statistically significant, and may not be causal. This is the first study to assess the influence of wind energy development on Hen Harriers at such a large geographic and population scale.     

Long‐term declines in multiple waterbird species in a tidal embayment,south‐east Australia

Worldwide, local extinctions and severe declines in waterbird densities are being reported from many important waterbird sites. Waterbird sites often exist as a network, collectively providing crucial habitat for different life history stages of different species. Therefore, population changes at one site may strongly influence others. In Australia, many waterbird species are highly mobile, and move rapidly over long distances in response to rainfall. Large tidal wetlands often serve as drought refugia or alternative breeding habitat for these species. These sites are also the migration terminus of many species of shorebirds that spend their non‐breeding season in Australia. One such site in south‐eastern Australia is Western Port, a Ramsar‐listed tidal embayment forming part of the East Asian–Australasian Shorebird Site Network. We measured waterbird population trends over nearly 40 years in Western Port to see whether changes showed consistent trends over time across multiple species. Thirty‐nine species were recorded often enough to allow an analysis of trends over time using dynamic linear models and, where appropriate, piecewise linear regression. Twenty‐two species had declined, including four species of duck, five species of fish‐eating bird (cormorants, terns and pelicans), one species each of grebe, gull and heron, and 10 species of shorebird. Only two species (Australian pied oystercatcher Haematopus longirostris and straw‐necked ibis Threskiornis spinicollis) increased significantly over the same time period. Patterns of decline in non‐migratory waterbirds may reflect diminishing wetland availability, local reductions in fish prey, increased predation pressure and changes in inland wetland resources. Declines in migratory shorebirds are most likely related to loss of habitat elsewhere in their trans‐equatorial migration routes. These trends in waterbirds that use Western Port reflect widespread impacts on populations elsewhere in Australia and overseas, necessitating more than simply local management of this tidal embayment.     

Using repeated winter surveys to estimate changes in abundance of seed‐eating passerines

Capsule Winter Atlas surveys of 16 species on lowland farmland revealed significant changes in count for four species.

Aims To estimate changes in abundance between the early 1980s and late 1990s, of wintering seed‐eating passerines, in ‘core’ areas of lowland Scotland.

Methods Ninety‐five Scottish 10‐km squares were selected that held high numbers of seed‐eating passerines in the 1981–84 Atlas of Wintering Birds in Britain and Ireland. The same survey methods were used to resurvey these in winters 1997/98 and 1998/99, and visits were matched as closely as possible for duration and date. Analyses compared counts between the two survey periods for 16 species of seed‐eating passerines and, for 12 of these, differences were also compared with national breeding population trend information for the same period.

Results Mean Corn Bunting Emberiza calandra count per visit declined by 62% between the early 1980s and late 1990s, a difference which was statistically significant (P = 0.026). Significant increases were recorded for Yellowhammer Emberiza citrinella (up 62%), Common Linnet Carduelis cannabina (up 3.4‐fold) and European Goldfinch Carduelis carduelis (up 13‐fold). For 12 species for which national breeding population trend data were available, trends were weakly positively correlated (r _s = 0.43, P = 0.08) with those from our results, but several species trends were more positive in our study. This difference was particularly marked for Eurasian Tree Sparrow Passer montanus, Goldfinch and Linnet.

Conclusion Repeating Winter Atlas surveys offers a useful additional method for assessing population trends. They are particularly useful in a region with low observer coverage and for species that are poorly covered by long‐term bird monitoring data sets. It would be valuable to validate this approach at a regional level, especially in a region for which detailed long‐term bird monitoring data are available.     

Continued declines of Redshank Tringa totanus breeding on saltmarsh in Great Britain: is there a solution to this conservation problem?

Capsule: Over 50% of saltmarsh breeding Common Redshank have been lost since 1985, with current conservation management having only limited success at halting these declines.

Aims: To update population size and trend estimates for saltmarsh-breeding Redshank in Britain, and to determine whether conservation management implemented since 1996 has been successful in influencing grazing intensity and Redshank population trends.

Methods: A repeat national survey of British saltmarsh was conducted in 2011 at sites previously visited in 1985 and 1996. Redshank breeding density and grazing pressure were recorded at all sites; the presence of conservation management was additionally recorded for English sites. Results from all three national surveys were used to update population size and trend estimates, and to investigate changes in grazing pressure and breeding density on sites with and without conservation management.

Results: Of the 21 431 pairs breeding on saltmarsh in 1985, 11 946 pairs remained in 2011, with the highest proportion of this population found in East Anglia. From 1985, British breeding densities declined at a rate of 1 pair km^?2 year^?1, representing a loss of 52.8% of breeding pairs over 26 years, although regional trends varied across different time periods. Grazing pressures did not change markedly with conservation management. Redshank declines were less severe on conservation-managed sites in East Anglia and the South of England where grazing pressures remained low, though were more severe on conservation-managed sites in the North West where heavy grazing persisted.

Conclusion: Saltmarsh-breeding Redshank declines continue and are likely to be driven by a lack of suitable nesting habitat. Conservation management schemes and site protection implemented since 1996 appear not to be delivering the grazing pressures and associated habitat conditions required by this species, particularly in the North West of England, though habitat changes may not be linked to unsuitable grazing management in all regions. An in-depth understanding of grazing practices, how conservation management guidelines could be improved, and the likely success of more long-term management solutions is needed urgently.     

Long-term population declines in Danish trans-Saharan migrant birds

Capsule Long-distance migrant birds show less favourable trends than sedentary/short-distance species.

Aims To use breeding bird surveys to contrast population trends amongst common species according to their migration pattern.

Methods Changes in abundance of 62 Danish breeding sedentary, short-distance (Europe/North Africa) or long-distance (trans-Saharan) migrants were described by fitting log linear regression models to point-count census data gathered during 1976–2005.

Results Trans-Saharan migrants declined by 1.3% per annum during this period, while short-distance migrants and sedentary species increased by 1.4% and 1.0% per annum, respectively. There were no significant decadal declines amongst species using different summer breeding habitats, except for wetlands, and there was no consistent variation in trends associated with wintering regions or habitats or diet.

Conclusions More information is urgently needed on diet, feeding ecology, habitat requirements, winter distribution and intra-African movements of the commoner European summer visitors to identify causes of the declines and highlight when in the annual cycle detrimental effects occur. Studies linking individuals on their breeding, staging and wintering grounds are especially needed. Danish trends resemble those from elsewhere in Europe, confirming that restoration to favourable conservation status requires inter-continental action to meet European and global targets to reduce or halt biodiversity loss.     

Population trend and breeding biology of Montagu's Harrier Circus pygargus in a natural vegetation site in northeast Spain

Capsule Reproductive output in a natural habitat was higher than in birds breeding in cereal crops, highlighting the importance of natural habitats for the species.

Aims To evaluate breeding in a natural habitat in inland Castellon province, Spain, and compare breeding parameters with other European populations.

Methods Breeding population size in inland Castellon was recorded between 1981 and 2003. A logistic growth model was used to describe population increase. We also calculated clutch size, brood size, productivity, percentage of successful nests and fledging success for the period 1989–2003.

Results Population size increased from three pairs in 1981 to 98 pairs in 2003. During 1989–2003, productivity (2.74 ± 1.49 fledglings/pair) and percentage of successful nests (84.%) were higher than observed in other European populations.

Conclusions Our results show the importance of our study area for the conservation of this species in the Iberian Peninsula, as it might act as a source of colonists for other areas. Food and protection against predators might explain the high breeding output, which may in turn explain the rapid population growth in the area. The study also suggests that natural habitats might be important for the species elsewhere.     

The geographical range of British birds expands during 15 years of warming

Capsule Abundance monitoring data suggest that the short-term response of breeding birds to recent warming in Great Britain has been range expansion, caused by poleward shifts of leading range margins and no significant shifts of trailing range margins.

Aims To quantify latitudinal and elevational shifts of breeding bird populations in Great Britain and test for differential shifts in range margins during a period of warming (1994–2009).

Methods We modelled the population density of 80 species as a smooth function of latitude, longitude, elevation and year. Reference points on the distribution curve were used to describe latitudinal and elevational shifts.

Results Across species, poleward shifts in the leading range margin were greater than in the range-centre. The trailing range margin was largely static, providing evidence for significant range expansion. The magnitude of latitudinal range shift lagged behind the equivalent shift in temperature, suggesting that species may be accumulating a climatic debt. There was no evidence for consistent elevational shifts.

Conclusion Contrary to the generally expected long-term consequences of climate change of range contraction, we show that the short-term response to recent warming has been range expansion. This suggests the mechanisms of short-term and long-term consequences of climate change may differ.     

The breeding population of Peregrine Falcon Falco peregrinus in the United Kingdom,Isle of Man and Channel Islands in 2014

Capsule: Overall numbers of Peregrines are higher than previously recorded, due primarily to the growth of lowland populations, despite declines in many upland areas.

Aims: To estimate the breeding population of Peregrines, and changes in this population over time, as well as to relate variation in trends and observed breeding success to variation in region, breeding site type and other ecological influences.

Methods: Two types of survey methods were used. Site-based visits focussed on locations where Peregrines were known to have bred previously, while area-based searches aimed to find all Peregrines breeding in randomly chosen 5?km?×?5?km squares. Findings from each method were used to estimate population size in different parts of the survey area. Breeding outcome and site type were assessed for most of the pairs found during either survey.

Results: In 2014, the breeding population of Peregrines in the UK, Isle of Man and Channel Islands was estimated at 1769 pairs. This is 22% larger than the population estimate from the previous survey in 2002. Most of this increase is accounted for by increases in lowland England. Populations in some upland areas have declined.

Conclusions: The gap between the fortunes of lowland and upland Peregrines has continued to grow, along with the overall UK population. Likely reasons for the continued success of Peregrines in the lowlands include increasing uptake of breeding sites on human structures, abundant availability of prey in many lowland situations and, in many areas, a relative lack of conflict with humans. Factors likely to be limiting upland Peregrine populations vary between different regions, and include ongoing illegal killing and deliberate disturbance, and food supply.     

Breeding ecology of Kentish Plover Charadrius alexandrinus in an extremely hot environment

Capsule Hot environments are associated with more biparental care, high nest‐site fidelity and low mate fidelity.

Aims To investigate the breeding ecology and parental behaviour of Kentish Plovers in an extremely hot environment. Kentish Plovers have an unusually diverse breeding system in which the frequencies of biparental, female‐only and male‐only care vary between populations. A common, but rarely tested, explanation for such a variation is local adaptation: birds exhibit social traits that are adaptive to their breeding environment. In particular, we investigated the effect of a hot environment on breeding success, distribution of care types, and mate and site fidelity.

Methods A breeding population of approximately 200 pairs of Kentish Plovers was investigated in 2005 and 2006 at Al Wathba Wetland near Abu Dhabi in the United Arab Emirates.

Results We found high nest‐site fidelity, low mate fidelity and more biparental care in Al Wathba than in most temperate zone populations of Kentish Plovers.

Conclusions Our results are consistent with the argument that a harsh environment can select for biparental care. However, further studies are warranted to distinguish between alternative hypotheses for the different distribution of social behaviours of breeding populations.