Populations Of Bird Species Research Articles

Towards the Automatic Acoustical Avian Monitoring System

One of the crucial aspects of the environmental protection is continuous monitoring of environment. Specific aspect is estimation of the bird species population. It is particularly important for bird species being in danger of extinction. Avian monitoring programs are time and money consuming actions which usually base on terrain expeditions. Certain remedy for this can be automatic acoustical avian monitoring system, described in the paper. Main components of the designed system are: digital audio recorder for bird voices acquisition, computer program automatically recognizing bird species by its signals emitted (voices or others) and object-relational database accessed via the Internet. Optional system components can be: digital camera and camcorder, bird attracting device, wireless data transmission module, power supply with solar panel, portable weather station. The system records bird voices and sends the recordings to the database. Recorded bird voices can be also provoked by the attracting device. Application of wireless data transmission module and power supply with solar panel allows long term operation of digital sound recorder in a hard accessible terrain. Recorded bird voices are analysed by the computer program and labelled with the automatically recognized bird species. Recognition accuracy of the program can be optionally enhanced by an expert system. Besides of labelled sound recordings, database can store also many other information like: photos and films accompanying recorded bird voices/ sounds, information about localization of observation/ recordings (GPS position, description of a place of an observation), information about bird features and behaviour, meteorological information, etc. Database on the base of geographical/ geological digital maps can generate actual maps of bird population (presence, number of individuals of each species). Moreover data-base can trigger alerts in case of rapidly decreasing bird population. It is also possible to obtain new knowledge about bird species with data mining methods. The paper presents collected data on observed bird species (audio recordings, photos and films) as well as results of experiments testing particular components of the automatic acoustical avian monitoring system.

The Role of Stubble Type and Spilled Seed Biomass on the Abundance of Seed-Eating Birds in Agroecosystems

Croplands are habitats with high availability of food resources for seed-eating birds. The use of particular fields by birds may vary considerably depending on crop type. Some crop stubbles hold high amounts of spilled grain after harvest, which may support seed-eating bird populations throughout the year. We examined the role of crop stubble type and biomass of spilled grain on species richness and abundance of seed-eating birds in the Pampas of central Argentina. During 2011–13 we sampled 166 stubble fields: 77 fields during the austral spring-summer of 2011–12 and 2012–13 (44 wheat and 33 barley stubbles); and 89 fields during the austral autumn of 2012 and 2013 (49 soybean, 27 corn and 13 sunflower stubbles fields). We recorded birds on a 700 × 100 m transect and estimated spilled grain on 1 m2 of stubble cover in each field. Comparisons among species accumulation curves showed that wheat and barley stubbles had similar bird species richness in spring-summer, whereas in autumn, sunflower stubbles supported higher bird richness than soybean stubbles. Generalized linear mixed models revealed that the abundance of some seed-eating birds had significant associations with crop stubble types. Some species were positively associated with spilled grain biomass on particular stubble types. In general, these associations varied seasonally, being more evident in autumn than in spring-summer. Knowledge of bird species populations and their specific association with given food resources during periods when crops remain only as stubble could be a key tool to help plan management strategies designed to reduce bird impacts on agricultural crops prior to harvest, when they are most susceptible to significant levels of damage.

Agricultural production and bird conservation in complex landscapes of the dry Chaco

The South American dry Chaco is a mosaic of woody vegetation and grasslands with high deforestation rates in recent decades. Considering forests and grasslands as the main natural habitats, we assessed the trade-offs between bird populations and agricultural production to compare the potential consequences of different land use strategies (‘sharing’, ‘sparing’, and intermediate) for populations of bird species sensitive to agriculture, while attaining a regional production target. We evaluated how populations responded to scenarios with different proportions of forest and grasslands, considering three reference states (100% forest, 80:20% and 50:50% forest and grasslands, respectively); and scenarios capable of meeting three after-farming scenarios, with land destined to reach a regional production target with three variations of forest:grasslands within spared land. We fitted curves to relate bird abundance to agricultural yield along a gradient of meat production intensity; and we classified bird species as ‘losers’ (if their populations were lower than the baseline population in the reference state, at any level of production) and ‘winners’ (if their current populations were higher than the baseline population). At the ‘current’ (c. 2010) level of regional agricultural production, we found a similar number of loser species maximized by land-sparing and land-sharing strategies; while intermediate strategies were the least favourable to balance production and bird populations. Under the most probable scenarios of increases in regional meat production, most loser bird species populations were maximized by a land-sparing strategy, suggesting that if meat production targets are going to increase in the region, this can be more efficiently achieved by combining well-protected forests and grasslands, and high-yielding mechanized agriculture (e.g. soybean). Our results highlight the importance of assessing all the important natural habitats (e.g. forests and grasslands) of a region to explore conservation strategies at a regional scale.

Diversidad de aves en el Centro Agropecuario Cotové, Santa Fe de Antioquia, Colombia

Fragmentation of natural habitats is a central concern of biodiversity conservation and is considered a significant factor contributing to species loss and populations decline. We studied this in Cotové Agricultural Center in the municipality of Santa Fe de Antioquia (Colombia),where the conversion of natural forests to different land use systems, has limited the amount of available habitat. With the aim to describe the effect of habitat loss on bird presence in five land uses (fruiting trees, silvopastoral systems, secondary forest, pasture low density of trees and grass cutting) in this area, we studied bird diversity using two methods: fixed point counts and mist nets to analyze the influence of land use in the composition, richness and abundance of birds present were studied. A total of 6633 individuals of 101 species were observed of which 11 species were migratory. The insectivorous and frugivorous foraging guilds were better represented. The Shannon index indicated the highest values of alpha diversity for the silvopastoral system, and the fruit with the lowest. The grazing and silvopastoral land systems shared more species with low tree density. The importance of the environmental heterogeneity found is highlighted as a positive factor for bird species richness, mostly of low and middle habitat specificity, and preferably from edge habitats and open areas. In order to preserve natural regeneration and connectivity between different land use types, and to promote stability of bird species populations, some management actions should be implemented in the area.

Impacts of anthropogenic activities and habitat degradation on breeding waterbirds

We investigated the effects of threats on breeding waterbirds in the Gediz Delta, Turkey. Breeding Bird Surveys were conducted in 2002 and 2006. The survey area comprised 305 UTM grids of 1 × 1 km^2. Populations and distributions of breeding birds were compared between 2002 and 2006 for the UTM grids under threat and without any threat using paired samples t-test, Wilcoxon signed-rank test, and GIS. Urbanization, industrialization, pollution, overgrazing, disturbance, and illegal reed cutting and burning were identified in 151 (49.5%) of 305 grids in 2002. The mean total number of breeding birds per UTM grid slightly decreased in areas under threat, but significantly increased (P < 0.05) in areas without threat. The mean total number of breeding waterbirds significantly decreased (P < 0.05) in both the grids under and without threat. Out of 30 waterbirds breeding in grids under threat, 23 shifted their breeding locations. The total number of breeding pairs of 9 waterbirds decreased, 7 species increased, and 6 species were stable. The maximum breeding code of 6, maximum number of breeding pairs of 11, total number of observed birds of 11, and frequency of occurrence of 15 species significantly decreased in UTM grids under threat. Threats have significantly affected (P < 0.05) the breeding populations of bird species even in a short period of 4 years.

Model to Track Wild Birds for Avian Influenza by Means of Population Dynamics and Surveillance Information

Design, sampling and data interpretation constitute an important challenge for wildlife surveillance of avian influenza viruses (AIV). The aim of this study was to construct a model to improve and enhance identification in both different periods and locations of avian species likely at high risk of contact with AIV in a specific wetland. This study presents an individual-based stochastic model for the Ebre Delta as an example of this appliance. Based on the Monte-Carlo method, the model simulates the dynamics of the spread of AIV among wild birds in a natural park following introduction of an infected bird. Data on wild bird species population, apparent AIV prevalence recorded in wild birds during the period of study, and ecological information on factors such as behaviour, contact rates or patterns of movements of waterfowl were incorporated as inputs of the model. From these inputs, the model predicted those species that would introduce most of AIV in different periods and those species and areas that would be at high risk as a consequence of the spread of these AIV incursions. This method can serve as a complementary tool to previous studies to optimize the allocation of the limited AI surveillance resources in a local complex ecosystem. However, this study indicates that in order to predict the evolution of the spread of AIV at the local scale, there is a need for further research on the identification of host factors involved in the interspecies transmission of AIV.

Study of biodiversity and limiting factors of Ag-gol Wetland in Hamadan Province, Iran

Reyahi-Khoram M, Norisharikabad V, Vafaei H. 2012. Study of biodiversity and limiting factors of Ag-gol Wetland in Hamadan Province, Iran. Biodiversitas 13: 135-139. Ag-gol Wetland isone of the important and seasonal wetlands of Iran. This wetland islocated on southeast of Hamadan Province and was declared as a prohibited hunting area by Department of Environment (DoE) of Iran. Identifying the characteristics, capabilities and limiting factors of Ag-gol Wetland is the most important objective of this study. The present study was conducted during 2007 through 2010. Documentary and observation methods have been used to access to information. For general identification of the area, digital maps and Geographic Information System (GIS) were used. Identifying capabilities and limitation factors of the studied area was made through extensive field inspections and direct field observations. Bird species of the region were identified and statistics of the population of bird species were gathered. In this research, valid academic resources were used. According to field inspections and studies, 46 species of waterfowl birds and wader birds of Iran have been identified at this wetland. The results of this research showed that Ag-gol Wetland has a high potential regarding the variety of waterfowl and wader birds. Continuous study in order to determine the depth of wetland water in different time intervals to estimate the volume of wetland water during different seasons of the year is recommended.

The fine-scale utilization of forest edges by mammalian mesopredators related to patch size and conservation issues in Central European farmland

The marked negative impact of habitat fragmentation and the edge effect on many populations of bird species is a recent major concern in conservation biology. Here, we focus on the edge effect in different sized forest patches in Central European farmland. In particular, we tested whether the distribution of mammalian mesopredators is related to fragment size and distance to habitat edge, and whether the contribution of these factors is additive or interactive. To assess fine-scale utilization of forest edges, we established transects of four scent stations at different distances from forest edges into the interior (0, 25, 50, 100 m) in 146 forest fragments of variable patch size (3.2–5099.6 ha) from May to June, 2008–2009. This large sample size allowed us to perform detailed analyses separately for all detected species. Our findings confirm that mammalian mesopredators strongly prefer habitat edges and small forest fragments. The probability of occurrence tended to decrease with increasing distance from the edge for all seven carnivore species detected. The carnivores’ occurrence was also negatively correlated with forest fragment area. All detected species tended to prefer small fragments, with the exception of the Eurasian badger (showing the reverse but non-significant pattern) and the red fox (no effect of fragment size). In addition, the non-significant interaction between fragment size and distance to edge suggests that both of these factors contribute independently and additively to mesopredator-mediated effects on biota in a fragmented landscape.

Historical and Current Distribution and Populations of Bird Species in Prairie-Oak Habitats in the Pacific Northwest

The loss and degradation of prairie-oak habitats has resulted in significant changes in bird species breeding distributions and populations. Among the 49 species highly associated with prairie-oak habitats, 21 have experienced extirpations, range contractions, and/or regional population declines. Three species have been regionally extirpated as breeding species since the 1940s, including Lewis's woodpecker, which historically occurred throughout the region. Eleven species have experienced local or ecoregional extirpations and/or range contractions. The predominant pattern of range contraction starts at the northern edge of a species range and moves southward. Nine species have relatively small regional populations, six with limited distribution in the Klamath Mountains ecoregion, and three with small and patchily distributed breeding populations throughout the region. There are nine species with significantly declining regional population trends with a high degree of confidence based on Breeding Bird Survey data, and five with similar declines using Christmas Bird Count data. Several other species may be declining based on a lower degree of confidence in the data or anecdotal observations. These include both endemic subspecies, streaked horned lark and Oregon vesper sparrow, which have regional population estimates of <2,000 and <3,000 birds, respectively. Six species have expanded their range in prairie-oak habitats in the last 50 years. The predominant pattern of range expansion starts at the northern edge of a species range and moves northward. Recommended actions to support prairie-oak bird conservation include range-wide and local inventories and monitoring to determine status, and evaluations and implementation of reintroductions or federal listings as appropriate.

The impact of shrub encroachment on savanna bird diversity from local to regional scale

AbstractAim Evidence is accumulating of a general increase in woody cover of many savanna regions of the world. Little is known about the consequences of this widespread and fundamental ecosystem structural shift on biodiversity.Location South Africa.Methods We assessed the potential response of bird species to shrub encroachment in a South African savanna by censusing bird species in five habitats along a gradient of increasing shrub cover, from grassland/open woodland to shrubland dominated by various shrub species. We also explored historical bird species population trends across southern Africa during the second half of the 20th century to determine if any quantifiable shifts had occurred that support an ongoing impact of shrub encroachment at the regional scale.Results At the local scale, species richness peaked at intermediate levels of shrub cover. Bird species composition showed high turnover along the gradient, suggesting that widespread shrub encroachment is likely to lead to the loss of certain species with a concomitant decline in bird species richness at the landscape scale. Finally, savanna bird species responded to changes in vegetation structure rather than vegetation species composition: bird assemblages were very similar in shrublands dominated by Acacia mellifera and those dominated by Tarchonanthus camphoratus.Main conclusions Shrub encroachment might have a bigger impact on bird diversity in grassland than in open woodland, regardless of the shrub species. Species recorded in our study area were associated with historical population changes at the scale of southern Africa suggesting that shrub encroachment could be one of the main drivers of bird population dynamics in southern African savannas. If current trends continue, the persistence of several southern African bird species associated with open savanna might be jeopardized regionally.

Bird's nesting success and eggs predation within Arusa National Park, Arusha, Tanzania

Nesting success and eggs predation is among the factors that affect the population dynamics of bird species. The study was carried out to determine predation impact on selected bird species population in Arusha National Park, Arusha, Tanzania. Specifically the study assessed the potential predators to ground (Scaly Francolin) and (Ruppell’s Robin- Chat, Striped-cheeked Greenbul, Tambourine Dove and Tropical Boubou) to establish if nesting success and eggs predation vary with habitat fragments types and nesting heights. Artificial nests were constructed in three different heights, and both artificial and true eggs were put on the nests in eleven habitat fragments and their associated forests. Identification of predators was obtained indirectly through punched signs left by predators on artificial and true eggs. Observation was done daily and data were analyzed both qualitatively and quantitatively. The study showed no significant difference in predation effect on eggs in glade versus glade edge X2 = 3.08, Df = 1, P > 0 .05, glade edge versus forest interior X2 = 0.04, Df = 1, P > 0 .05, while glade versus forest interior showed to differ significantly X2 = 0.08, Df =1, P 0 .05 in level 1, X2 = 3.81, Df = 2, P > 0.05 at level 2 and X2 = 0.67, Df = 2, P > 0. 05 at level 3. The percentage egg failure was 41.54 % with predation effects contributing 92% of the total impact, followed by floods 5% and trampling 3%. Although habitat predation varied among habitat types and vertical levels, the type of predators did not vary. However, among predators rodents contributed the highest level of predation effects. Nesting failure was a result of predation, trampling and flooding with the later two affecting more the ground nester birds’ species. Key words: Predators, birds’ population, edge effects, Tanzania

Influence of within‐patch habitat quality on high‐Andean Polylepis bird abundance

Habitat restoration strategies for fragmented high Andean forest landscapes must consider the influence of within‐patch habitat quality on bird abundance. I examined vegetation and bird abundance at three locations within a highly fragmented Polylepis forest landscape in the Cordillera Vilcanota, southern Peru. Across the landscape, there was significant variation in the vegetation structure of Polylepis forest patches of different size categories, especially in terms of tree girth, tree height, tree density, and canopy vegetation structure. Principal Component Analysis extracted five factors of habitat quality, which together accounted for 74.2% of the variability within 15 habitat variables. Polylepis bird species differed in their responses to habitat quality but, overall, variation in Polylepis bird abundance was not fully captured by the range of habitat quality variables. Tall, dense vegetation cover was clearly important for 11 conservation‐important species, a high density of large trees was important for 10 species and primary forest ground cover was important for eight species. Habitat quality exhibited no significant influence on the abundance of only one species –Asthenes urubambensis. The abundance of seven species was associated with lower elevation forest, but only one species was associated with higher elevation forest. Management of habitat quality in large and medium remnant forest patches throughout the Cordillera Vilcanota, particularly in the 3800–4200 m elevation range, will be a cornerstone in ensuring the persistence of the majority of conservation‐important bird species populations.

Visitor patterns on southern heaths: a review of visitor access patterns to heathlands in the UK and the relevance to Annex I bird species

Many lowland heathlands have been designated as Special Protection Areas under the European Union Birds Directive as they support populations of bird species of European importance listed in Annex I of the Directive, including Nightjar Caprimulgus europaeus, Woodlark Lullula arborea and Dartford Warbler Sylvia undata. Many lowland heaths are near to human settlements and are heavily used as open spaces by those living nearby. A number of past visitor surveys have established the range of uses to which urban heaths are subject, and the attitudes of those who use them. We have collated a number of these visitor surveys, many of which are unpublished reports relating to single sites, in order to provide a broad summary of access to heathlands. The majority of visitors to urban and suburban lowland heaths visit sites regularly and live nearby (within 5 km). A large proportion of visitors drive to sites and dog walking is the usual purpose for a visit. Visits are typically short, with the average dog walker travelling less than 2.5 km on the heath. Dog walkers typically stay on the paths, but most let their dog off the lead and consider it important to be able to do so. On large regionally or nationally known rural sites such as the New Forest, more visitors are day trippers and tourists, fewer are dog walkers, they stay for longer and their reasons for visiting differ from those of local residents. The information presented here is relevant in helping to inform decisions on the location of new housing development, and mitigating the impacts of existing and new settlements, as well as helping the heathland manager to make provision for visitors in ways that are most compatible with wildlife conservation.

Lead and lead toxicity in domestic and free living birds

At present, domestic and wild fauna are being exposed to aspects and factors which are foreign to the habitat in which they live. One that stands out is the enormous amount and variety of chemical compounds which, in many cases, are highly complex and which are constantly being released into the atmosphere, mainly from agricultural and industrial activity. All these substances affect some species more than others, whether they be plants or animals, from the most insignificant micro-organism to the most evolved species, among them birds. Finally, another cause of mortality in many birds is plumbism, namely death caused by the ingestion of lead. Lead has been one of the main causes of poisoning in man since ancient times due to its use in many activities although it is only recently that this toxicity has been recognized. Moreover, the use of lead pellets for shooting has resulted in the release into the environment of millions of these over many years, with serious repercussions for many bird species populations, which have ingested them either directly or indirectly. Added to this use of lead in cynegetic activities is the fate of the lead weights (sinkers or ballast) used by rod fishers, which sink to the bottom or accumulate on the banks of rivers, lakes, lagoons or reservoirs. The problem arises when these pellets or weights are ingested by birds, mainly Anatidae, which mistake them for the small stones or grit they use to triturate food in their gizzards. Small particles of lead enter the digestive tract, start dissolving in the form of lead salts, are incorporated into the bloodstream and the rest of the body, accumulate in organs like the liver or kidneys, and cause physiological or behavioural changes. When certain concentrations of lead are reached, the birds then die. If lead-poisoned birds are consumed by carrions or predators, the latter also ingest the lead so that they may also be affected or die from plumbism since, being a heavy metal, its degradation and/or elimination is very difficult. There is, therefore, no doubt that millions of birds die annually worldwide from lead poisoning (in the U.S.A., around 3 000 000), this problem being most acute in marshland. The solutions could include the introduction of legislation regulating or banning shooting, in the use of non-toxic ammunition in marshes and protected areas, the substitution of lead pellets for other non-toxic ones, such as steel, bismuth, tungsten or other suitable metals, and to go on studying other possible alternatives to end such a dramatic situation for birds all over the world.

Improving bird population models using airborne remote sensing

This work was undertaken to devise a technique to measure the height of crops in farmland fields through remote sensing. Crop height is a useful spatial variable which, when measured by ground-based manual survey, has proven to be an important predictor of bird species population. An airborne scanning laser system capable of measuring topography to a height accuracy of better than 10 cm was used to acquire height data over a region of farmland near Oxford, UK. A scanning laser was pulsed from an aircraft at the ground, measuring the time between transmission and receipt of the last significant return signal. Differential Geographical Positioning System (GPS) and onboard attitude sensors were combined with these delay times to construct a set of spot heights through the region. Crop height was also measured from the ground. Pulses were returned from mainly within the crop, rather than predominantly the canopy or ground, so an algorithm to measure the variation of the returned height, after detrending the heights for topography, was developed. A simple relationship was found between the mean crop height and the standard deviation of detrended return heights within a field. This relationship could be used to derive crop height from Light Detection and Ranging (LiDAR) data with an accuracy better than 10cm.

Changes in populations of bird species in roadside softwood scrub remnants/farmland and open eucalypt forest in south-east Queensland, 1981 to 1993

Long-term monitoring of bird species provides information on base-line populations and population trends required to ensure that habitat management is effective for their conservation. Two surveys in both spring and autumn over 12 years monitored populations at fixed points in roadside softwood scrub remnants plus adjoining farmland (softwood/farmland) and in eucalypt open forest in south-east Queensland. The main aims were to determine the status of species in each habitat, especially whether the status of any species was changing, and to assess the usefulness of the monitoring procedure. In all, 92 species were observed; 79 in the softwood/farmland and 74 in the eucalypt forest. From 49 to 56 species were observed each year in softwood/farmland and 34 to 46 in eucalypt forest. Annual species turnover in softwood/farmland was about half that in eucalypt forest; 39% of all species were observed every year in the former habitat, but only 19% in the latter. The Torresian Crow was most often observed in softwood/farmland and the Noisy Miner in eucalypt forest. The Torresian Crow was the only species to be among the five most observed in each habitat. Among other common species, 95% or more observations of Bar-shouldered Doves, Superb Fairy-wrens, Yellow Thornbills and Silvereyes were in softwood/farmland, whereas for Weebills, White-throated Gerygones, Buff-rumped Thornbills, White-throated Treecreepers and White-throated Honeyeaters at least 95% of observations were in eucalypt forest, confirming their strong habitat specificities. The number of birds observed increased linearly for eight species in softwood/farmland and six species in eucalypt forest, and decreased for five and four species, respectively, over the 12 years. The most significant trends were for the Crested Pigeon (increase) and Willie Wagtail (decrease) in softwood/farmland, while Peaceful Dove and Rufous Whistler decreased in both habitats. Several species which increased adapt well to partial clearing of woody vegetation and aggressively exclude others, e.g., Noisy Miner, butcherbirds and Pied Currawong. The trends may reflect insidious degradation of habitats. The main value of the survey method was for detecting changes of species that could be used as indicator species ? those that respond most rapidly to habitat change. While the method was efficient, wildlife managers would need to use it regularly to maintain skills, especially because most observations are of bird calls.

Population Variabilities of Bird Guilds in Kansas during Fall and Winter: Weekly Censuses versus Christmas Bird Counts

Fall and winter (September through March) weekly census data from 1978 through 1992 were examined for 18 species of birds in forests and cultivated fields near Manhattan, Kansas. The 18 species were grouped into five feeding guilds: frugivores; granivores on the ground; acorn cachers; leaf, bud, and twig gleaners; and trunk and branch gleaners. Frugivores exhibited the most variable populations, both within years and between consecutive years. Granivores on the ground exhibited the second most within-year population variability. Among the remaining guilds, there were no statistically significant differences among either the within- or between-year variabilities. Although data were limited, there were significant correlations between the mean numbers in some species of frugivores, granivores, and acorn cachers and relative annual fruit or seed crop size in the area. The size and mobility of feeding flocks, the annual variability of food crops, and the manner of food exploitation all influenced the between-year variability of winter bird species population density. The rank order of between-year variability for species populations censused on Christmas Bird Counts in the same area correlated significantly with between-year variability of our weekly censuses. The within-year nomadic tendencies of some of the species with the greatest between-year variability decreased the correlation between Christmas Bird Counts and mean weekly censuses for these species.