Bird Density Research Articles

A characterization of autumn nocturnal migration detected by weather surveillance radars in the northeasternUSA

Billions of birds migrate at night over North America each year. However, few studies have described the phenology of these movements, such as magnitudes, directions, and speeds, for more than one migration season and at regional scales. In this study, we characterize density, direction, and speed of nocturnally migrating birds using data from 13 weather surveillance radars in the autumns of 2010 and 2011 in the northeastern USA. After screening radar data to remove precipitation, we applied a recently developed algorithm for characterizing velocity profiles with previously developed methods to document bird migration. Many hourly radar scans contained windborne "contamination," and these scans also exhibited generally low overall reflectivities. Hourly scans dominated by birds showed nightly and seasonal patterns that differed markedly from those of low reflectivity scans. Bird migration occurred during many nights, but a smaller number of nights with large movements of birds defined regional nocturnal migration. Densities varied by date, time, and location but peaked in the second and third deciles of night during the autumn period when the most birds were migrating. Migration track (the direction to which birds moved) shifted within nights from south-southwesterly to southwesterly during the seasonal migration peaks; this shift was not consistent with a similar shift in wind direction. Migration speeds varied within nights, although not closely with wind speed. Airspeeds increased during the night; groundspeeds were highest between the second and third deciles of night, when the greatest density of birds was migrating. Airspeeds and groundspeeds increased during the fall season, although groundspeeds fluctuated considerably with prevailing winds. Significant positive correlations characterized relationships among bird densities at southern coastal radar stations and northern inland radar stations. The quantitative descriptions of broadscale nocturnal migration patterns presented here will be essential for biological and conservation applications. These descriptions help to define migration phenology in time and space, fill knowledge gaps in avian annual cycles, and are useful for monitoring long-term population trends of migrants. Furthermore, these descriptions will aid in assessing potential risks to migrants, particularly from structures with which birds collide and artificial lighting that disorients migrants.

Bird fauna changes in a small urban park in South Sweden, over a period of 34 years

The density of birds in urban landscapes, including parks, is poorly known. In this study we present surveys of a small city park in south Sweden. The surveys were conducted in April–June 1980 and in May–June 2014. The study plot has an area of 5.1 ha. We found 143 pairs of 22 species in 1980 and 151 pairs of 26 species in 2014 (2,800 and 2,960 pairs/km2). Turdus pilaris was the most common species in 1980 and Columba palumbus in 2014. Three species showed significant decline: T. pilaris 38 to 15 pairs, Fringilla coelebs 12 to 5 pairs and Carduelis chloris 18 to 12 pairs, while Turdus merula increased from 11 to 15 pairs. Two species, T. merula and Sylvia atricapilla, nesting both 1980 and 2014, showed increasing numbers that are consistent with these species’ population increase in Sweden. The bird densities in this study are considerably higher compared to what is generally observed in southern Sweden. Further study is required to establish whether the high densities are due to chance or edge effect.

Breeding Bird Assemblage in a Mosaic of Urbanized Habitats in a Central European City

Abstract There is a lack of data on the population densities of birds breeding in a mosaic of typical urbanized habitats. This study was undertaken to partly fulfil this gap in our knowledge. Counts were conducted in 2008 by means of simplified territory mapping method in a fragment (1197 ha) of a large Central European city (Wrocław, SW Poland). In total, 50 bird species were breeding in the study area in 2008. The House Sparrow Passer domesticus, Common Swift Apus apus and Rock Dove comprised about 3/5 of all breeding pairs. The other group of species, each one with a density between 6 and 13 pairs per 100 ha, included seven species, namely the Starling, Sturnus vulgaris, Greenfinch, Carduelis chloris, House Martin, Delichon urbica, Tree Sparrow, Passer montanus, Great Tit, Parus major, Blue Tit, Parus caeruleus, and Jackdaw, Corvus monedula. They comprised together about 1/5. The remaining 40 species nested in a density between 0.1 and 3.5 pairs per 100 ha. The most numerous feeding guild were granivores (53.8%) and insectivores (37.9 %). Birds nesting on buildings comprised together 74 % of all breeding pairs. For a few species (Luscinia megarhynchos, Saxicola torquata, Corvus cornix and Turdus pilaris) an increase in their numbers in the last three decades has been evidenced.

Geographic position and landscape composition explain regional patterns of migrating landbird distributions during spring stopover along the northern coast of the Gulf of Mexico

Annual migration of landbirds across the Gulf of Mexico (GOM) presents a unique opportunity to examine extrinsic processes operating at various spatial scales in determining animal distributions. Our objectives were to comprehensively quantify bird stopover densities across the northern GOM coast and model broad-scale factors explaining distributional patterns. We used weather surveillance radars to measure reflectivity of birds aloft at onset of nocturnal migratory flights and estimate bird stopover densities during four springs (2009–2012) for 6.7 million ha along the GOM. We aggregated bird densities to one longitudinal degree and 3 km of proximity to coast. Boosted Regression Tree models revealed that stopover density was related to year, longitude, proximity to coast, and amount of hardwood forest cover in the landscape. Average longitudinal patterns supported previous studies of broad-scale trans-Gulf migrant arrivals with highest density in Louisiana (92–93°W) and lowest in Alabama (88–89°W). Florida (83–84°W) supported a second peak in migrant density, suggesting an eastern trans-Gulf route or contribution from trans-Caribbean migrants. Longitudinal patterns in migrant distributions varied strongly between years and appear generally related to variability in GOM wind patterns. Densities increased with proximity to coast, highlighting constraints on migrants to travel inland, especially in Florida’s panhandle. Despite this, density was positively related to amount of forest cover more steeply along the immediate coast. Broad-scale stopover distributions of migrating landbirds along the GOM coast are heavily influenced by geographic constraints in the context of the GOM acting as a barrier to landbird migration.

Spatial distribution of Corvidae in transformed landscapes of Zhytomyr region

The spatial distribution and abundance of Corvidae species was studied in Zhytomyr region with a focus on rural and urban differences in the studied parameters. We selected Rook (Corvus frugilegus L.), Western Jackdaw (C. monedula L.), Hooded Crow (C. cornix L.), Eurasian Magpie (Pica pica L.), Eurasian Jay (Garrulus glandarius L.), and Common Raven (Corvus corax L.). All observations were made during 2009–2012. During the study period some 38 survey paths of more than 8,000 km were surveyed in 21 settlements of Zhytomyr region, among them 13 were in Zhytomyr city. The aim of our study was to establish the number and density of Corvidae in different seasons in the settlements of Zhytomyr region along a rural-urban gradient. The average density of Rooks was 55.9 ind./km2. We also found a strong correlation between Rook density and the rural-urban gradient and observed that the number of Rooks wintering in cities significantly increased due to the influx from villages. The peak number of Rooks in villages was registered in the breeding and post-breeding season while in the cities it was high in winter and during the spring migration. The average density of Eurasian Magpie in the study area was 8.7 ind./km2 and had a weak correlation with the urban-rural gradient. The density of Eurasian Magpies in urban areas differs significantly only from the density of birds in villages with a population of ca. 1,000 people. The density of Magpies varied insignificantly within a narrow range during the three years of research, remaining relatively stable, which suggests that the species successfully adjusts to conditions in transformed landscapes. The urban-rural gradient significantly affects the density of Hooded Crows. The average density of birds in towns was 6.6 ind./km2. In breeding period the urban birds had a low density and rural crows, on the contrary, had a high density, the density of birds in the nesting period was greater than in autumn and winter, due to the distribution of birds in their breeding territories and the start of the reproductive cycle. The average density of Eurasian Jackdaw was 9.7 ind./km2 and the rural-urban gradient significantly affected the number of birds. For jackdaws we registered high annual population dynamics. The peak number of birds was observed in the winter period in cities and small towns while in villages it was registered in the breeding and post-breeding season. The average density of Eurasian Jay was 2.4 ind./km2 and varied significantly in different settlements, although the fluctuation range was small (0.1–9.3 ind./km2). The number of this species naturally decreases along the gradient of landscape transformation. The highest average density was typical in small villages (4.9 ind./km2) and the lowest was found in medium-sized cities (1.5 ind./km2). We have identified certain patterns in the seasonal dynamic of Eurasian Jays relative to the type of settlement. In urban areas the birds’ density was much higher in winter compared to the nesting period, and in villages we observed the reverse situation. The average density of Common Raven was 1.3 ind./km2. The highest density was registered in small villages and was 2.2 ind./km2, and the smallest in the villages of urban type (0.6 ind./km2). The urban-rural gradient significantly affected the spatial distribution of Common Raven, but we cannot state that this bird increased or decreased its number along the gradient of urbanization, since the value of this indicator also depended on habitat conditions in specific settlements. The spatial distribution of Common Ravens varied seasonally and the highest density was typical in winter due to food migrations to human settlements.

Effects of modest improvements in pellet quality and experiment pen size on broiler chicken performance

SUMMARY Improving the crumble/pellet percentage of feed has been argued to be difficult to obtain in the commercial industry due to the necessity of feed mills producing adequate feed volume within a time constraint. Broiler performance research often utilizes small numbers of birds per pen or experimental unit that may affect the estimation of variance components, potentially producing pen performance metrics that are less valuable for industry guidance. The objective of this study was to compare the performance of straight run Hubbard × Cobb broiler chickens receiving a standard crumble/pellet percentage (50%) vs a modestly improved crumble/pellet percentage (70%), in either large pen (46 birds) or small pen (23 birds) experimental units. All diets were batched, mixed, steam conditioned to approximately 82°C, extruded through a 4.8 × 38.1 mm pellet die, and crumbled at the West Virginia University pilot feed mill. Crumble/pellet percentage differences were obtained by grinding a portion of the complete feed then remixing. Treatments were replicated 10 times and fed for 1 to 38 d using a 2 × 2 factorial arrangement in a randomized complete block design to measure growth performance. Bird density and feeder space access was 0.06 m2/bird and 1.2 cm/bird, respectfully for both experimental units. Crumble/pellet percentage and pen size main effects did not interact for any growth performance metric. Broilers consuming improved crumble/pellet percentage had a tendency towards decreased feed intake (P = 0.07) and feed conversion ratio by 3 points (P = 0.1), but maintained a similar weight gain (P = 0.3). Large pens decreased live weight gain (P = 0.03). Improved crumble/pellet percentage increased pen coefficient of variation for ending weight (P = 0.05), likely due to competitive feeding behavior. These data suggest that modest improvements in crumble/pellet percentage may provide performance benefits, and feed quality variation effects on growth performance can be satisfactorily evaluated utilizing a small pen experimental unit.

Modelling future scenarios to improve woodland landscapes for birds in the Mediterranean

Agro-silvo-pastoral systems occupy much of the Mediterranean region. Promoting landscape heterogeneity in these systems is a potentially valuable management strategy to enhance woodland biodiversity. We evaluated the effects on birds of managing patches of olive groves and riparian galleries to promote heterogeneity of these systems in Portugal.For a large cork oak woodland we (i) used nesting season bird density estimates and habitat descriptors to generate suitability models for each studied species; (ii) identified areas suitable to establish new patches of riparian galleries and olive groves, and used this information to (iii) generate scenarios maps with different levels of cover of both habitats. Finally, (iv) the model of each bird species was applied over the future scenarios to estimate potential changes in its distribution and abundance.Future scenarios with greater availability of riparian vegetation resulted in major increases in projected populations of seven of the 21 studied species, but gains with increases of olive groves were predicted in just three species. Bird species predicted to increase the most with the recovery of riparian vegetation are presently among the least abundant in the region. Restoring riparian galleries would be highly beneficial for birds, whereas promoting traditional olive groves would have lower conservation implications.The methodology used proved helpful to select areas particularly appropriate for habitat management, generate simulated landscapes incorporating this management, and predict the population and spatial responses of species to these simulated scenarios, thus having a good potential to guide conservation management. Moreover, our results indicate that simple management measures should have substantial positive effects on the bird community of oak woodlands, without compromising the essential economic return of the system.

An assessment of spatio-temporal relationships between nocturnal bird migration traffic rates and diurnal bird stopover density.

BackgroundDaily magnitudes and fluxes of landbird migration are often measured via nocturnal traffic rates aloft or diurnal densities within terrestrial habitats during stopover. However, these measures are not consistently correlated and at times reveal opposing trends. For this reason we sought to determine how comparison methods (daily magnitude or daily flux), nocturnal monitoring tools (weather surveillance radar, WSR; thermal imaging, TI), and temporal scale (preceding or following diurnal sampling) influenced correlation strength from stopover densities estimated by daily transect counts. We quantified nocturnal traffic rates at two temporal scales; averaged across the entire night and within individual decile periods of the night, and at two spatial scales; within 1 km of airspace surrounding the site via WSR and directly overhead within the narrow beam of a TI.ResultsOverall, the magnitude of daily bird density during stopover was positively related to the magnitude of broad-scale radar traffic rates of migrants on preceding and following nights during both the spring and fall. These relationships were strongest on the following night, and particularly from measures early in the night. Only during the spring on the following nights did we find positive correlations between the daily flux of transect counts and migration traffic rates (both WSR and TI). This indicates that our site likely had a more consistent daily turnover of migrants compared to the fall. The lack of general correlations between seasonal trends or daily flux in fine-scale TI traffic rates and stopover densities across or within nights was unexpected and likely due to poor sampling of traffic rates due to the camera’s narrow beam.ConclusionsThe order (preceding or following day) and metric of comparisons (magnitude or flux), as well as the tool (WSR or TI) used for monitoring nocturnal migration traffic can have dramatic impacts when compared with ground-based estimates of migrant density. WSR provided measures of the magnitude and daily flux in nocturnal migration traffic rates that related to daily stopover counts of migrants during spring and fall. Relationships among migrating bird flux measures are more complex than simple measures of magnitude of migration. Care should be given to address these complexities when comparing data among methods.

Farmland bird diversity in contrasting agricultural landscapes of southwestern Poland

Breeding bird communities were investigated in three contrasting agricultural landscapes of SW Poland to assess differences in abundance and determine the importance of field margins for bird populations. Counts were conducted in twelve 50-ha plots differing in landscape structure (density of all, permanent and shrubby field margins, and occurrence of high vegetation). Maps of bird distributions were used to analyze the associations of birds with four habitats: cropped fields, permanent fallows, field margins, mid-field woodlots. Ordination and classification techniques were applied to check between-plot differences in community composition. All landscapes supported high densities of total communities and farmland specialists. Species richness and bird densities were significantly related to field margin aggregations and arranged along a decreasing gradient of landscape heterogeneity: shrubby mosaic, open mosaic, open plain plots. Between-plot differences suggest that the occurrence of non-cropped habitats is more important for bird abundance than diversification of land-use. PCA and cluster analysis identified differences in species composition between the landscape types; and RDA revealed the significance of the shrubby and permanent margins for the community structure. The aggregation of shrubby margins seems to be a particularly useful predictor of bird abundance and overall biodiversity. Most species and breeding pairs were preferentially associated with margins, despite the habitat covering merely 4% of the area. The data confirmed that landscape heterogeneity with mosaic seminatural field margins is responsible for the persistence of internationally important bird populations in Poland. In such complex arable systems, preventing landscape simplification is the most effective method of biodiversity protection.

Effects of dominant tree species on insectivorous birds breeding in Mediterranean oak woodlands

Capsule Differences in Cork Oak Quercus suber and Holm Oak Quercus rotundifolia dominance had little influence on bird communities though bark-gleaners showed a foraging preference for Cork Oak.Aims Examine the use of Cork and Holm Oak trees by insectivorous birds in Mediterranean oak woodlands.Methods Point-counts were used to compare species abundance among Cork Oak-dominated, Holm Oak-dominated and mixed woodlands. Focal foraging observations were used to evaluate the use of Cork and Holm Oaks in the three habitats and to relate tree characteristics with the foraging time of foliage- and bark-gleaners.Results Bird densities in the three habitats were not different for most foliage- and bark-gleaners. Tree preference index values and foraging time per tree showed no significant differences between tree species and foraging guilds, however bark-gleaners had positive index values for Cork Oak in the three habitats. The foraging time of foliage- and bark-gleaners on both tree species showed a positive relationship with characteristics associated with arthropod abundance.Conclusion Cork and Holm Oak trees are equally preferred by foliage-gleaners but bark-gleaners moderately preferred Cork Oak. Characteristics regarding morphology, phenology and physiological condition of trees can be used to predict habitat quality for insectivorous forest birds in Mediterranean oak woodlands.

Avian abundance and communities in areas revegetated with exotic versus native plant species

Degradation of ecosystems and introductions of invasive species pose a threat to global biodiversity. Ecosystem restoration and revegetation actions are important for amending habitat loss and for the protection of species of plants and animals. Iceland has the highest rate of soil erosion and desertification in Northern Europe and counteractions to erosion and revegetation measures have taken place for over a century. We studied the effect of revegetation on the density and composition of birds and invertebrate abundance in 26 survey areas comparing: a) unvegetated eroded areas, b) native heathlands restored on eroded land, and c) revegetation by the introduced and exotic Nootka lupin (Lupinus nootkatensis) on eroded land. Birds were counted on transects and invertebrates sampled with a sweep net. Both revegetation methods greatly increased the abundance of birds. The highest total numbers of invertebrates and birds were recorded on land revegetated with Nootka lupin. On average 31 birds km -2 were recorded on barren land, 337 on heathland and 627 in Nootka lupin. Bird species composition differed between the two revegetation methods. Restored heathland provided habitat for waders of internationally decreasing populations, whereas Nootka lupin stands harboured more common bird species. Golden Plover (Pluvialis apricaria) and Dunlin (Calidris alpina) were most common on restored heathland, while Snipe (Gallinago gallinago) and Meadow Pipit (Anthus pratensis) were most common in Nootka lupine. The abundance of birds was positively correlated with that of invertebrates. The abundance of different bird species differed by successional stage in each habitat. The study showed the generally positive effects of revegetation on animal biodiversity and also how different revegetation methods produce different trajectories of ecosystem development.

Хищные птицы Международного аэропорта «Стригино», Россия

In this article we discuss the seasonal dynamics and population density of Birds of Prey at the Nizhniy Novgorod International airport “Strigino”, based on data collected fro m November, 2013 to November, 2014. During this period a total of 71 raptors of 9 species were observed, including one breeding species – the Eurasian Marsh Harrier ( Circus aeruginosus ) . The seasonal population dynamics and species composition of Birds of Prey on the territory of the airport was studied. The highest population density and species number occurred during end of June – July, in September and in April. The summer population peak was caused by regular observations of hunting birds, whose nests were located on the territory of the airport and in the close vicinity. Young birds also made a contribution to this peak. Autumn and spring population peaks were caused by more frequent observations of migrating raptors during the seasonal migrations. The lowest number of raptors in the airport was observed in winter.

Alternative scenarios of bioenergy crop production in an agricultural landscape and implications for bird communities.

Increased demand and government mandates for bioenergy crops in the United States could require a large allocation of agricultural land to bioenergy feedstock production and substantially alter current landscape patterns. Incorporating bioenergy landscape design into land-use decision making could help maximize benefits and minimize trade-offs among alternative land uses. We developed spatially explicit landscape scenarios of increased bioenergy crop production in an 80-km radius agricultural landscape centered on a potential biomass-processing energy facility and evaluated the consequences of each scenario for bird communities. Our scenarios included conversion of existing annual row crops to perennial bioenergy grasslands and conversion of existing grasslands to annual bioenergy row crops. The scenarios explored combinations of four biomass crop types (three potential grassland crops along a gradient of plant diversity and one annual row crop [corn]), three land conversion percentages to bioenergy crops (10%, 20%, or 30% of row crops or grasslands), and three spatial configurations of biomass crop fields (random, clustered near similar field types, or centered on the processing plant), yielding 36 scenarios. For each scenario, we predicted the impact on four bird community metrics: species richness, total bird density, species of greatest conservation need (SGCN) density, and SGCN hotspots (SGCN birds/ha ≥ 2). Bird community metrics consistently increased with conversion of row crops to bioenergy grasslands and consistently decreased with conversion of grasslands to bioenergy row crops. Spatial arrangement of bioenergy fields had strong effects on the bird community and in some cases was more influential than the amount converted to bioenergy crops. Clustering grasslands had a stronger positive influence on the bird community than locating grasslands near the central plant or at random. Expansion of bioenergy grasslands onto marginal agricultural lands will likely benefit grassland bird populations, and bioenergy landscapes could be designed to maximize biodiversity benefits while meeting targets for biomass production.

Long-term decline of southern boreal forest birds: consequence of habitat alteration or climate change?

Climate change and habitat degradation due to land use are the key factors threatening biodiversity. It is important to study both the separate and joined effects of climate warming and land use on biodiversity. In this work long-term population changes of southern boreal forest birds were studied in relation to climate change and direct habitat alteration due to forestry. The study was based on annually repeated bird censuses in 23 consecutive years (1993–2015) in a managed forest landscape. Results were compared with population changes in protected areas where logging is not allowed. During the study period, total bird density declined by 18 % with a change in the bird community composition. Out of the 12 most abundant species seven showed a significant negative trend and only one species a positive trend. Population declines could be connected with the direct alteration of habitat as a consequence of forestry or with the effect of climate change in the case of those species which declined also in protected areas. The increased species are abundant across Europe in human-modified habitats. Due to habitat alteration and climate warming, specific characteristics of southern boreal forest bird communities are changing with communities representing a pattern towards global homogenization. Thus, habitat alteration strengthens the negative effects of climate change.

Assessing strategies to reconcile agriculture and bird conservation in the temperate grasslands of South America.

Globally, agriculture is the greatest source of threat to biodiversity, through both ongoing conversion of natural habitat and intensification of existing farmland. Land sparing and land sharing have been suggested as alternative approaches to reconcile this threat with the need for land to produce food. To examine which approach holds most promise for grassland species, we examined how bird population densities changed with farm yield (production per unit area) in the Campos of Brazil and Uruguay. We obtained information on biodiversity and crop yields from 24 sites that differed in agricultural yield. Density-yield functions were fitted for 121 bird species to describe the response of population densities to increasing farm yield, measured in terms of both food energy and profit. We categorized individual species according to how their population changed across the yield gradient as being positively or negatively affected by farming and according to whether the species' total population size was greater under land-sparing, land-sharing, or an intermediate strategy. Irrespective of the yield, most species were negatively affected by farming. Increasing yields reduced densities of approximately 80% of bird species. We estimated land sparing would result in larger populations than other sorts of strategies for 67% to 70% of negatively affected species, given current production levels, including three threatened species. This suggests that increasing yields in some areas while reducing grazing to low levels elsewhere may be the best option for bird conservation in these grasslands. Implementing such an approach would require conservation and production policies to be explicitly linked to support yield increases in farmed areas and concurrently guarantee that larger areas of lightly grazed natural grasslands are set aside for conservation.

Detection Probabilities and Absolute Densities of Birds in Trees

For a study of long-distance migrants in sub-Saharan Africa, a census method was developed that combined precision and accuracy regarding bird numbers and tree choice. The number of birds present in trees and shrubs can be counted accurately, although it is time-consuming. We describe how much time is needed to detect all birds present in trees, using data collected in over 2000 plots across West Africa during the dry season (October–March in 2007–2015). The observation time per tree depended on tree size, number of birds present and the opacity of the crown. The giving-up time of the observers increased with canopy volume, but was independent of the number of birds in a tree. Detection probabilities of bird species differed relative to microhabitat choice and feeding techniques. Species-specific detectabilities hardly varied during the day or the season. All foraging birds and immobile birds (save a few percent in dense canopies) were detected using the individual-tree-approach. Bird density is expressed as number per canopy volume, but little information is lost when density is given as number per canopy surface. The variation in bird density was large and differed per tree species. Within tree species, bird density was related to the opacity of the crown, the abundance of insects and whether there were berries or flowers. These findings suggest that, to collect biologically relevant information, the density of tree-dwelling birds should be measured at the level of the individual tree, and not per surface area, habitat type or tree species (as is typical in published studies).

Moreau's Paradox Reversed, or Why Insectivorous Birds Reach High Densities in Savanna Trees

In West Africa, tree preferences of wintering migratory birds (and African residents) were quantified in order to assess the importance of wintering conditions on distribution, abundance and trends of insectivorous woodland birds. This study encompassed 2000 plots between 10–18°N and 0–17°W, visited in October-March 2007–2015, and covered 183 woody species and 59 bird species. Canopy surface (measured in a horizontal plane) and birds present were determined in 308,000 trees and shrubs. Absolute bird density amounted to 13 birds/ha canopy, on average, varying for the different woody species between 0 and 130 birds/ha canopy. Birds were highly selective in their tree choice, with no insectivorous birds at all in 65% of the woody species. Bird density was four times higher in acacias and other thorny species than in non-thorny trees, and seven times higher in trees with leaves having a low crude fibre content than in trees with high crude fibre foliage. Salvadora persica shrubs, but only when carrying berries, were even more attractive. Overall, densities of migratory woodland birds were highest in the (thorny) trees of the Sahelian vegetation zone. This counterintuitive finding, with highest numbers of wintering birds in the driest and most desiccated parts of West Africa (short of the Sahara), also known as Moreau's Paradox, can be explained by the foliage palatability hypothesis. The Sahelian vegetation zone has always been subject to heavy grazing from large herbivores, and as a consequence woody species have evolved mechanical defences (thorns) to withstand grazing of large herbivores, at the expense of chemical defence against arthropods. South of the Sahel, with a much lower grazing pressure, thorny trees (rich in arthropods) are replaced by (usually non-thorny) trees with less palatable foliage and a higher crude fibre content, and hence with less arthropod food for insectivorous birds.

Do trees flower longer in the city? A comparison of flowering eucalyptus trees in streets, remnants and continuous forest and their association with nectarivorous birds

Human-dominated environments are often subjected to increased nutrient and moisture regimes which have the potential to influence the flowering phenology of plants. Protracted flowering periods within urban landscapes may result in increased food resources, in the form of nectar, and this high resource availability may support a high density of nectarivorous birds within cities. In order to determine whether there was a difference in the productivity and flowering period associated with urbanisation, we compared the number of flowers produced and duration of flowering period for three species of native tree that were present in streetscapes, remnant vegetation and continuous forest. We also recorded the presence of nectarivorous parrots at flowering trees to determine if the presence of nectarivores was associated with flower productivity. All three species in streetscapes produced more flowers and flowered for longer than in remnants and continuous forest. The number of flowers per tree significantly predicted the presence of nectarivorous parrots in streetscapes. This study demonstrates that the flowering phenology of plants within streetscapes can differ from continuous forest, with remnants appearing to be intermediate. This increased flower productivity within urban landscapes may be partially responsible for the high abundance of nectarivorous parrots within some cities.

Molecular Diagnosis of Beak and Feather Disease in Native Brazilian Psittacines

The incidence of the psittacine beak and feather disease virus (BFDV) was investigated in Brazilian native parrots with normal feathering arriving at rescue and triage centers for wild animals (CETAS, IBAMA) in the state of Minas Gerais, Brazil. BFDV DNA was investigated by previously described PCR technique for the partial amplification of BFDV ORF-1 in DNA extracts from blood, cloacal swab or liver of psittacines. Some birds provided more than one sample. Nine species of psittacines were sampled between January 2009 and October 2010. Blood (n=46) or cloacal swab (n=128) samples were obtained from psittacines immediately upon arrival at the triage centers. Liver samples were collected from necropsied birds dead on arrival (n=167). All swab samples were negative, except for one Ara ararauna individual (n=3) which blood presented the BFDV DNA. On the other hand, 11 liver samples were positive for BFDV DNA, with a prevalence of 7.8% in Amazona aestiva (n=140). No BFDV DNA was detected in the liver of Amazona amazonica (n=11), A. vinacea (n=5), A. rhodochorytha (n=4), Anodorhynchus hyacinthinus (n=3), Ara ararauna, (n=3), Aratinga leucophtalma (n=2), Guarouba guarouba (n=1) and Pionus maximiliani (n=1). In most cases, alopecia was not associated with BFDV detection in liver, and liver histopathology was inconclusive. Although all cloacal swab samples were negative, a few psittacines (n=19) that died at CETAS-Belo Horizonte were retested, and 21% were detected as positive in liver. A group of psittacines (n=16) was clinically evaluated, and despite showing feather dystrophy, all birds were negative in the cloacal swabs, except for one, which blood sample was positive (A. ararauna). The obtained sequences of the BFDV strains BH 215 and BH 732 were deposited in the GenBank (JQ649409 and JQ649410). A 98% similarity with strain sequences described in Australia, Japan, and New Zealand was observed. It is possible that these strains arrived in Brazil through the legal and illegal trade of parrots. However, it was not possible to associate BFDV infection with the geographical origin of birds and no local marker was detected. The rates of detection, although similar to other studies, indicate the tendency of a high incidence of the disease, possibly associated with stress, and high bird density and wide transmission in captivity conditions.

First Off-Shore Site Bird Monitoring In Poland (Debki-Białogóra, 2002–2004)

Abstract Due to the presence along the Polish Baltic coast of migratory bird flyways from north-eastern European breeding grounds to wintering areas distributed on continental shelf waters of western and southwestern Europe, the area has been designated as a NATURA 2000 site (PLB 990002). Therefore the site of a planned off-shore wind farm in this area requires monitoring as to its potential influence on birds. This was the first such monitoring performed in Poland. The expanse of water covered by the research included the planned location of the wind farm as well as adjacent areas. A series of 15 investigative cruises were undertaken from the beginning of October to the beginning of May. The period of observations was divided into five seasons: early autumn, late autumn, winter, early spring and late spring. The standard method of counting birds on transects in the form of strips reaching 300 m from the ship was used in the research, as well as the ‘snapshot’ technique (scan with bands transect with snapshot technique). Additional observations were made from a point on the shore. In the study area maritime birds are present in low or moderate densities, with localized clusters. Two diving benthophagous species dominate: the Long-tailed Duck (58.9%) and the Velvet Scoter (34.3%). The next two commonest species have a share of over 1% within the community – the Common Scoter (3.2%) and the Herring Gull (2.4%). Other species are very uncommon. There is very high fluctuation in the number of birds both observed on the water surface and seen in the air. In the area studied no pronounced migratory passage of waterfowl was observed; the usual migratory flyways probably lie farther to the north and the birds observed in flight perform mainly local movements. Observed bird densities in the study area are considerably lower (52.0 ind./km2) than those estimated for the entire NATURA 2000 area (116.7 ind./km2). In the area of the planned wind farm densities are even lower (36.1 ind./km2, i.e. 31% of the NATURA 2000 level), while densities in neighbouring areas are still below the NATURA 2000 average. In the subsequent administrative procedure the area was not accepted as the location of the planned wind farm.