Structure of avian assemblages in Zambezian Baikiaea woodlands, northern Namibia

In April 2013, a transect c. 1100 km long with 100 points arranged in 5 sections was designed in northern Namibia between Ruacana Watefall (W) and Kongola (E) to study avian diversity in relation to gradual changes in precipitation (c. 350 mm in W to c.600 mm in E). In total, 81 bird species were recorded in all 100 points, but in particular section, the numbers were low, ranging from 22 to 38 species. In overall, the most frequent and most numerous (dominant) were the following species: Cape Turtle Dove, Blue Waxbill, Grey-headed Sparrow, Laughing Dove and Fork-tailed Drongo. Together they comprised 42.2 % of all individuals recorded. All of them, except for the Fork-tailed Drongo, were granivores. Only nine species were recorded in ten or more points. Besides the above-mentioned dominant species, the following other were in this group: Black-chested Prinia, Black-throated Canary, Pied Crow and White-browed Scrub Robin. In particular section the number of dominant species ranged from 5 to 7, without a gradient. Two species, the Cape Turtle Dove and Blue Waxbill, remained dominant in all fi ve sections. Th e Laughing Dove and Fork-tailed Drongo — in four sections, and the Grey-headed Sparrow — in three sections. Although, no gradient in species diversity, evenness, and dominance structure was recorded, signifi cant diff erences between two most western and two most eastern sections were apparent. Two species were more frequent and numerous in the eastern than in the western sections: White-browed Scrub Robin and Cape Turtle Dove; while the following species were more frequent and numerous in the western than the eastern sections: African Palm Swift , Black-chested Prinia, Black-throated Canary, Blue Waxbill, Grey-headed Sparrow and Pied Crow.

During the years 1996-2001, the line transect method has been employed to assess the species composition, dominance structure and relative abundance of birds resident in traditional farmlands, in the lowlands (10 transects with the total length of 43.9 km) and foothills (10 transects with the total length of transects 46.5 km) of Lesotho, southern Africa. This has been done to show the role of this farming in biodiversity conservation. A total of 76 resident species have been recorded in farmlands of Lesotho, 62 species in the lowlands and 53 species in the foothills. In the lowland farmlands the dominant group was composed of 6 species, namely the Prinia, Cape Bunting, Cinnamon-breasted Bunting, Cape Canary, Neddicky and Common Quail (35.8 %); in the foothills the group was composed 5 species: Karoo Prinia, Cape-turtle Dove, Laughing Dove, Cape Bunting and Cape Canary (35.9 %). Eighteen species bred in significantly different densities in lowlands and foothills. While insectivorous birds were more numerous in the lowland than foothill, the reverse was true with granivorous birds. Those two guilds comprised together 78% and 83% in the lowland and foothill respectively. The proportion of species in each guild was similar. In the lowland farmland the following eight species were more common that in the foothill farmlands, while in foothill farmland 10 species were more numerous than in lowland farmland. Species diversity and evenness were strikingly high and similar in lowlands and foothills, although Sorensen Similarity Index between these two areas was low (I = 0.44). Both species diversity and structure of dominance in avian communities in Lesotho farmlands indicate that the traditional farming play a positive role in biodiversity conservation.

The line transect method has been employed to assess species diversity, population densities and community structure of birds breeding in a mosaic of Kalahari Woodland and farmland, NE Namibia. The transect, 4.5 km long, was surveyed in 2014 and 2015. The total annual rainfall in 2014 was much higher than in 2015 (427 mm vs. 262 mm). In total, 40 breeding species in 2014, and 46 in 2015 were recorded. Six species were dominant in 2014 (Cape Turtle Dove, Laughing Dove, Emerald-spotted Dove, Blue Waxbill, and White-browed Scrub Robin) and only three species in 2015 (Cape Turtle Dove and Blue Waxbill and Yellow-fronted Canary). Although the cumulative dominance in 2014 almost doubled that in 2015, the Community Index in both years was almost identical. Also diversity indices and evenness index were very similar in both years compared. Granivorous birds were the most numerous feeding guild. Their contribution was similar in 2014 and 2015 (46.7 % vs. 43.4 %). Two other feeding guilds, insectivores and frugivores, comprised together more than 50 % in both years. The number of bird species and species diversity were not influenced by the differential rainfall. However, contrary to expectations, population densities of most bird species (at least the more numerous ones) were higher in the year with lower than in the year with higher rainfall. The number of species and species diversity was similar in the farmland and in neighbouring Kalahari Woodland in a pristine stage. However, population densities of most species were lower in the farmland than in the pristine woodland.

Mangroves are threatened worldwide yet they host diverse avian assemblages, especially in Australia. We examined the diversity, density and habitat use of birds in northern Australian mangroves to determine the influence of habitat patch-size and floristic composition on the structure of mangrove bird assemblages. Birds were surveyed using line transects in 13 mangrove patches. A total of 70 species was encountered, with a mean density of 11.7 individuals ha−1 including 11 of 12 known mangrove-dependent species. Many species were strongly associated with, and indicative of, a specific mangrove plant zone, emphasising the importance of the number of zones to bird diversity at a site. Of six functional guilds, the insectivores were most dominant, followed by nectarivores. Accordingly, avian assemblage structure was influenced by mangrove flowering phenology. Large mangrove patches supported fewer species than many smaller patches of equivalent combined area, and species richness was independent of area. In addition, there was no density compensation or a density—area relationship, implying that assemblages are not saturated with species and species interactions do not determine assemblage structure. In order of increasing importance, avian assemblage structure in mangroves is determined by the type and diversity of mangrove zones, the timing of mangrove flowering and the nature of the matrix surrounding mangroves.

Among the different biomes in southern Africa, tropical riparian forests appear to be especially rich in terms of biodiversity, but little is known about avian communities occupying these forests. In this paper, bird counts were conducted in May, July–August, and October–November in 2013 and 2014. The line transect method was used. A transect 16.6 km long was designed along the Zambezi River between S 17.4975 E 24.3478 and S 17.4874 E 24.447. In total, 146 bird species were recorded. The number of species detected each season varied from 95 to 100. The number of dominant species was consistently low, varying between 2 and 3 depending on the month. However, the cumulative dominance and the dominance index were much higher in the dry season (May–August) than in the wet season (October–November). Two species were dominant each month: Euplectes axillaris and Pycnonotus tricolor. Vidua macroura and Estrilda astrild were dominant only in October, while Streptopelia capicola was dominant only in May. The group of subdominants was much more diverse than dominants and included 13 species. The Shannon diversity index increased between July and November from 3.45 to 4.05 but Simpson's diversity index did not show any seasonal trend. Pielou's evenness index was higher in the wet season (0.82–0.88) than in the dry season (0.76–0.79). The proportions of the main feeding guilds were much the same throughout the year, except for November, when the proportion of insectivores markedly increased, while that of granivores decreased. Riparian forest corridors in urbanized environments may be viewed as main instruments for offsetting the negative effects of habitat loss and fragmentation. Dataset published through GBIF (DOI: 10.15470/0ssr1v)

Effect of stand age on bird communities in late-successional Macedonian pine forests in Bulgaria

Studies were conducted by means of the Line Transect Method in late rainy season (March), in the middle of dry season (July) and at beginning of rainy season (November).Th e total length of all transects was c. 11 km. In total, 70 resident and 13 nonresidentspecies were recorded. Th e number of species in dry season was significantly lower than in rainy season (x2-test: 14.1; p < 0.01). Th e highly significant seasonal differences in abundance were recorded for the following species: Streptopelia senegalensis, Streptopelia capicola, Uraeginthus angolensis, Cisticola juncidis, Upupa africana, Cynniris mariquensis, and Numida meleagris. In overall, five species have been classified as dominants: Streptopelia senegalensis, Streptopelia capicola, Uraeginthus angolensis, Plocepasser mahali and Cypsiurus parvus. They comprised together 43.9 %. Significant variations in the dominance structure between the wet and dry season have been evidenced. Granivores were much more numerous in the dry than in the wet season, while for the insectivores the reverse was true. Although Sorensen Coefficient was much the same between all three seasons, the Shannon’s Diversity Index was lower in July than in March and November.

Temperature and rainfall related to altitudinal gradients influence ecological and evolutionary responses of organisms to physical factors. In this study, the line transect method was used during the years 1996–2001 to compare resident (potentially breeding) bird communities in three altitudinal divisions in Highveld/Drakensberg grasslands in Lesotho: lowlands (< 1700 m a. s. l.), foothills (1700–2200 m a. s. l.) and highlands (> 2200 m a. s. l.). In total, 105 resident species were recorded. The total number of species recorded in lowlands was higher than that in highlands and foothills, but this difference was not statistically significant. The highland and foothill did not differ in numbers of species. A group of five species dominated at all three sites, and the proportion of dominant species in relation to the whole assemblage was very similar. The composition of the dominant group (species with more than 5 % of pairs) and the group of species most often encountered (in more than 80 % of transects) was, however, different. Only two species, Cape Canary Serinuscanicollis and Karoo Prinia Priniamaculosa were dominant in all three study areas, and just one species, the Cape Bunting Emberizacapensis, was dominant in two plots. Similarly, only two species, the Cape Turtle-Dove Streptopelia capicola and Cape Canary had a high frequency of occurrence in all three study areas, and two otherspecies, theKaroo Prinia and Cape Bunting — in two study areas. Simpson’s Diversity Index was strikingly the same (S = 0.96) for all three avian assemblages (lowland, foothill and highland) investigated. However, proportions of breeding pairs of some congeneric species were found to change with the altitude. The granivores were more common (44–45 %) in the foothills and highlands than in lowlands (36%), while insectivores were more common in the highlands (50 %) than in foothills and lowlands (36–37 %). In general, avifauna is relatively diverse and unique in the Highveld/Drakensberg grasslands. Results presented here provide data for further investigation of the effect of the supposed climate warming on the diversity and structure of avian communities.

Estimates of abundance of threatened and endangered species are crucial for monitoring population status and recovery progress. For most wildlife species, multiple abundance estimation methods are available and the choice of method should depend on cost and efficacy. We field-tested the cost and efficacy of line transect, total count, sample count, and double observer methods for estimating abundance of gopher tortoise (Gopherus polyphemus) burrows in two habitats that differed in vegetation density (sparse and dense) at the Ordway-Swisher Biological Station in north-central Florida. In the dense vegetation stratum, density of burrows estimated using the line transect method (8.58 ± 0.94 burrows ha−1) was lower than that obtained from the total count method (11.33 burrows ha−1). In the sparse vegetation stratum, estimated burrow density using the line transect method (11.32 ± 1.19 burrows ha−1) was closer to the burrow density obtained from the total count method (13.00 burrows ha−1). Density of burrows estimated using the double observer method was identical to that obtained from the total count method in dense vegetation stratum, but slightly greater than that obtained from the total count method in sparse vegetation stratum. Density of burrows estimated using the sample count method varied widely depending on the proportion of plots sampled. The cost of sampling as well as estimates of burrow density varied with habitat type. The line transect method was the least costly of the methods, and we were able to sample a larger effective area with the same effort. Using burrow cameras and patch occupancy modeling approach, we also estimated the probability of burrow occupancy by gopher tortoises (active: 0.50 ± 0.09; inactive: 0.04 ± 0.04), and used these values to estimate abundance of gopher tortoises. Using estimates of burrow abundance based on the line transect method, density of gopher tortoises was 2.75 ± 0.74 ha−1 in the sparse vegetation stratum. We recommend that gopher tortoise monitoring programs use rigorous methods for estimating burrow abundance (e.g., line transect methods) and the probability of burrow occupancy by gopher tortoises (e.g., patch occupancy modeling approach).

The population status, feeding behaviour and habitat preference of the helmeted guinea fowl (Numida meleagris) were investigated in this research. The period of carrying out the research comprised from january to october, of 2021. The line transect method was used to collect data on the population status of the species. The quadrate vegetation sampling method was used to investigate the preferred habitat. Data generated from the research were analyzed using descriptive statistics, while results were compared using chi-square (X2) test, one way Analysis of Variance and t-test. The average number Numida meleagris in the study area was 434 and 293 during the wet and dry seasons, respectively. The most important daytime activities of the species were feeding, resting, scanning and running. The observed population differ significantly across sectors during the wet and dry seasons (X2 = 8.00, p = 0.03). The relationship between allocated time to each activity and time of the day was greatly significant (X2= 4.04, p = .001). The number of individuals was 3.0±4.0 and 5.0±0.2 individuals/km2 during the dry and wet seasons, respectively. The importance value index (IVI) for Gmelina arborea, Tectona grandis and Elaeis guineensis were 24.41, 20.39, and 18.17, representing the dominant plant species in the study area. Human disturbance was responsible for loss of habitat, nesting and foraging sites. Protection of the habitat against exploitation will reduce poaching habitat destruction, and restore its nesting sites, thereby increasing its population.

Roads may have negative or positive effects on wildlife. I surveyed birds along a c. 21 km transect alongside a road from Katima Mulilo to Ngoma bridge in the Zambezi Region, north-eastern Namibia, and on a second transect (control) parallel to the first one and 200–400 m away from the road. The habitat is Kalahari Woodland, partly transformed to cultivated fields. The number of bird species was similar on both transects (56 vs. 48 species; x2 = 0.62, p > 0.05), but the number of breeding pairs (overall population density) was much higher away from the road than close to it (409 vs. 283 pairs; x2 = 22.9, p < 0.01). The Shannon’s Diversity Index was very similar, while Pielou’s Evenness Index was identical in both transects compared. Five species (Blue Waxbill, Burchell’s Starling, Cape Turtle Dove, Fork-tailed Drongo and Grey-headed Sparrow) were dominant on both transects, while the African Grey Hornbill was dominant only on the transect away from the road, whereas the Red-billed Hornbill and Grey Go-away-bird were dominant only close to the road. Four species (African Grey Hornbill, Cape Turtle Dove, Meyer’s Parrot and White-browed Scrub Robin) had population densities significantly higher on the transect away from the road than close to it. However, population densities of nine other species did not differ significantly between the two transects. In general, the avian communities along and away from the road were similar, probably because traffic volume was rather low and the land cover on both transects was similar in terms of natural vegetation and degree of transformation.

The line transect method was applied to assess the linear index of abundance and community structure of birds breeding in an area of Kalahari woodland used as range land for cattle. Four transects were designed along roads traversing the ranch. Each transect was 2.5 km long and was surveyed three times in 2014 and 2015. A total of 47 bird species were recorded but only 25-31 species were recorded on any particular transect. In the neighbouring pristine Kalahari woodland, the number of bird species on a12 km long transect was much higher (n = 88), and ranged in some sections (each 1.2 km in length) from 35 to 53. On any particular section, the number of dominant species ranged from 5 to 7, and their cumulative dominance on each section was similar, ranging from 53-56 %, while the community dominance index ranged from 0.23 to 0.35. The most numerous species were the Cape turtle dove and emerald-spotted wood dove, which were dominant on all sections. Together they comprised 28 % of all breeding birds. The avian community in the Kalahari woodland in Sachinga LDC did not differ from the neighbouring pristine woodland either in terms of species diversity or evenness. However, it differed significantly in terms of species richness, the proportion of main ecological guilds, and linear index of abundance of particular species. These differences could be mainly due to the structure of woody vegetation, which is much thicker in Sachinga than in the pristine woodland not used as pasture for cattle. The thickening of this vegetation on the ranch could have been caused by heavy grazing pressure by the cattle. Data published through GBIF (Doi: https://doi.org/10.15470/rova7r)

Abstract. The White-fronted Woodpecker (Melanerpes cactorum) drills holes in branches and trunks to feed on sap flows, providing an energy-rich food resource for other birds. Here we describe ecological and behavioral traits of the White-fronted Woodpecker related to its sap-feeding habits in the semiarid Chaco of Argentina and explore the structure of the avian assemblage in relation to the sap resource. Sap consumption by the White-fronted Woodpecker and other sap-feeding species was strongly seasonal and positively associated with periods of resource scarcity. The White-fronted Woodpecker actively defended the sap wells from smaller birds. Specialist and facultative nectarivores that assimilate sucrose at a high rate represented an important proportion of sap-feeding birds. In this system of woodpecker, sap, and other sap-feeding species, each species' consumption depends on its physiological and behavioral characteristics as well as on the availability of other food in the surrounding environment.

ABSTRACTWhile there is intense debate regarding the impact of domestic cat populations on wildlife, its resolution is hindered by the lack of quite basic information. Domestic cats are generalist and obligate predators that receive supplementary food, and their population density reflects that of humans more than the density of their prey. In such a predator–prey system there is the potential for cat populations to have negative impacts on avian assemblages, which may be indicated by negative correlations between cat density and avian species richness and density. Here we report on the nature of such correlations across urban areas in Britain both for groups of species classified regarding their vulnerability to cat predation and individual species. Taking the availability of green space into account, we find negative relationships between cat densities and the number of bird species breeding in urban 1 km × 1 km squares. These relationships are particularly strong among groups of species that are vulnerable to cat predation. We find positive correlations between cat and avian densities; these have low explanatory power and shallow slopes among the species groups that are particularly vulnerable to cat predation. Evidence that the densities of individual species that are vulnerable to cat predation are negatively correlated with cat densities is equivocal, with at least half the species showing no marked pattern, and the remainder exhibiting contrasting patterns. Our results appear not to be confounded by the density of nest‐predating corvids (carrion crow, magpie, and jay), as the density of these species was not strongly negatively correlated with avian species richness or density. The general lack of marked negative correlations between cat and avian densities at our focal spatial scale may be a consequence of consistently high cat densities in our study areas (minimum density is 132 cats per square kilometre), and thus uniformly high impacts of cat populations on urban avian assemblages.

Small, isolated oceanic islands, exemplified by the Azores Archipelago, are especially vulnerable to adverse environmental conditions and human impact. The structure and dynamics of avian communities associated with various land form in an urbanized landscape in one of the nine islands of the Azores Archipelago were subjects of this study. Studies were conducted in the second half of April 2024. The line transect method (43 transects with a total of 37.4 km) has been employed to count all bird species breeding in the study area. The number of breeding species was much higher in green land (n=20) than in built-up lands (n=10-14 species). The number of breeding species were also different in particular subcategories of the built-up lands ranging from 8 to 12, being the lowest in the oldest most densely built-up lands. The number of dominant species (n=5-9), cumulative dominance (>85%) and dominance index were relatively high. Both cumulative dominance and dominance index were much higher in built-up urbanized lands than in green urbanized lands. Two main feeding guilds were distinguished in the study area: granivores and insectivores. The former guild clearly dominated over the later one in all major land categories distinguished. Clearly the proportion of granivores increased with the urbanization. A general trend is recorded: the higher the level of urbanization, the lower the percentage of green land forms, and in consequence, the lower the number of bird species and diversity indices, but the higher the cumulative dominance and dominance index. The overall density of birds remain, however, distinctively similar.