Seasonal variations in the structure of avian community in Zambezi riparian forest

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.

A simplified mapping method has been employed to quantify avian assemblages in a plot with a mosaic of built-up areas (129 ha) and semi-natural or open areas (85 ha; grass, trees, shrubs) in the Katima Mulilo town, Namibia. Overall, 65 breeding bird species were recorded in the study plots (51 in the built-up areas, and 50 in the ‘open’ areas). Five of them, Rock Dove Columba livia, Grey-headed Sparrow (Passer diffuses), Dark-capped Bulbul (Pycnonotus tricolor), Laughing Dove (Streptopelia senegalensis) and Blue Waxbill (Uraeginthus angolensis) were classified as dominants. The cumulative dominance was 69.9% in the built-up area and 55.6 % in the ‘open’ area. The structure of the avian community in the built-up area was unexpectedly similar to that in the ‘open’ area. Almost the same number of breeding species was recorded, and almost identical diversity and evenness indices were calculated. However, the Sorensen Similarity Index was rather low (I = 0.69). Also, the overall density of all breeding birds was much lower in ‘open’ than in the built-up area. Granivorous birds were by far the most numerous feeding guild comprising in the built-up area 68.1% and in ‘open’ area 62.2 % of all breeding birds. Also, similar between the two areas compared was the proportion of granivores (17.7% vs. 19.7%) and insectivores (11.5% vs. 13.2%). These were also similar to the proportions of the main nesting guilds. Only the guild nesting in/on buildings was much higher in built-up than in the ‘open’ area. Although species richness was not high, population densities of some species were very high in the urbanised habitat. It is recommended to protect the larger specimens of marulas and other tree species in this habitat, as they play a vital role in maintaining the high population densities.

Most studies on edge effect are related to the forest-field edge, i.e. to the ecotone. However, there is a lack of studies attempting to investigate the effect of the distance from the forest/field edge on the avian communities in large continuous forests. The purpose of this study was to investigate this issue. The study area comprised a continuous coniferous forest, the so called Niemodlin Forest, situated in Opole Silesia, SW Poland. The line transect method has been employed in this study. In total, 54 breeding bird species were recorded. On particular 0.5 km section, the numbers varied from 34 to 48. Both the number of species and number of breeding pairs only slightly decreased with the distance from the forest/field edge. Overall, the differences between the mean densities of breeding species on 10 sections were not statistically significant. The Chaffinch Fringilla coelebs was by far the most numerous bird species, recorded as eudominant in 164 out of 165 sections. The Chiffchaff Phylloscopus collybita, Willow Warbler Phyloscopus trochilus and Blackap Sylvia atricapilla were dominants in all 10 sections, while the Blackbird Turdus merula dominated in nine (90%) and the Robin Erithacus rubecula in eight (80%) sections. The communal dominance slightly increased, but the number of dominant species and Pielou’s Evenness Index remained stable with the increase of the distance from the forest/field edge. While Shannon’s Diversity Index remained constant, Simpson’s Diversity Index decreased markedly with the increase in distance from the forest/field edge. The proportion of long-distance migrants slightly decreased, while that of short-distance migrants and residents remained constant with the increase in the distance from the forest/field edge. Strikingly, no such changes in the proportion of all feeding guilds were shown. More than half of all breeding bird species show a negative correlation between population density and the distance from the forest/field edge. The dominance of some species decreased with the increase of the distance from the forest/field edge: Hawfinch Coccothraustes coccothraustes, Starling Sturnus vulgaris, Blue Tit Parusa caeruleus, Raven Corvus corax, Wren Troglodytes troglodytes, Wood Pigeon Columba palumbus, and Wood Lark Lullula arborea. With the exception of the Yellowhammer Emberiza citrinella, the clearcuts in this study, not only failed to increase, but most probably caused a decrease in the number of both species and individuals. It is because clearing not only creates edges, but also causes loss of forest habitat and often results in forest fragmentation. Edge and area effect may in fact interact, in such way that the edge effect may drive out the area effect, causing the increase.

Response of birds that rely on mature Piedmont Forests of Northwestern Argentina to fire severity

In larger river valleys of southern Africa, riparian forests are among the main vegetation types. The forests are regarded as ones of the most diverse and distinct terrestrial habitats on earth. They also play a crucial role in wildlife conservation as corridors and refugia for wildlife. It is hypothesized that the closer to the river bank, the higher the species diversity, while population densities may increase with the increase of the distance from the river bank. In 2014, quantitative studies (by means of the mapping method) on avian community breeding in such forest on Zambezi River in Katima Mulilo were undertaken to measure this gradient. Four plots were designed along an increasing distance from the river bank in this forest. In terms of the number of species, there was a significant gradual decrease with the increasing distance from the bank (from 91 to 54 species). The number of breeding pairs per 100 ha increased with the moisture gradient (from 222 to 677). Shannon's (H') and Simpson's (D) indices were higher in the two plots closer to the bank river (H'= 3.44–3.85; D = 0.97–0.99), than in the two remaining plots (H' = 3.13–3.15; D = 0.92–0.93). Also the Pielou's Evenness Index was higher in two plots closer to the bank (J' = 0.84–0.85 vs. 0.77–0.78). The proportion of granivores in the avian community declined along the moisture gradient, while that of insectivores and frugivores – increased. These gradual changes can be linked to a parallel gradual changes of the amount of fruits and invertebrates.

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.

Tropical savannas are known for the fire‐prone ecosystems, yet, riparian evergreen forests are another important landscape feature. These forests usually remain safe from wildfires in the wet riparian zones. With global changes, large wildfires are now more frequent in savanna landscapes, exposing riparian forests to unprecedented impact. In 2017, a large wildfire spread across the Chapada dos Veadeiros National Park, an iconic UNESCO site in central Brazil, raising concerns about its impact on the fire‐sensitive ecosystems. By combining remote sensing analysis of Google Earth images (2003–2019) with detailed field information from 36 sites, we assessed wildfire impacts on riparian forests. For this, we measured the structure of trees, saplings and herbaceous plants, as well as topsoil variables. Since 2003, all riparian forests had canopy cover above 90%, but after 2017, canopy cover dropped to 20% in some forests, indicating large variation in wildfire damage. A closer look in the field revealed that, on average, the wildfire killed 52% of adult trees and 87% of tree saplings in flooded forests. In non‐flooded forests, impacts on adult trees were negligible, but fire killed 75% of tree saplings. Opportunistic vines and the invasive grass Melinis minutiflora were already present in severely disturbed flooded forests. In all forests, impacts on many ecosystem variables were related to canopy damage, a variable measurable from satellite. Overall, seasonally flooded riparian forests were the most severely impacted, possibly due to the relatively thinner barks of their trees. Synthesis and applications. Our findings reveal how riparian forests embedded in tropical savanna landscapes are in danger from large wildfires. The destruction of some forests has opened space for new plant species that may propel a shift to an alternative ecosystem state. Riparian forests are habitat of large savanna animals and their loss could affect entire trophic networks. Managing wildfires and invasive grasses locally is probably the best strategy to maintain riparian forests resilient. As wildfire regimes intensify in tropical savanna landscapes, our findings stress the need for an integrated management that considers riparian forests as a vulnerable element of the system.

In the African brood parasitic finches (Viduidae), complex nestling mouth markings have evolved to mimic those of their estrildid finch hosts, reducing the chances of detection or discrimination by host parents. Most Vidua species are highly host-specific whereas the Pin-tailed Whydah Vidua macroura is less so, potentially limiting its evolutionary potential for mimicry. Here we document parasitism of a novel host, the Black-crowned Waxbill (Estrilda nonnula), by the Pin-tailed Whydah. Of the 28 active Black-crowned Waxbill nests that we located in central Cameroon, six were parasitized by Pin-tailed Whydahs. Unlike the remarkable similarity of Pin-tailed Whydah nestling mouth markings to those of a previously described host in southern and central Africa, the Common Waxbill (Estrilda astrild), Pin-tailed Whydahs have mouth patterns that differ conspicuously from their Black-crowned Waxbill hosts in central Africa. Across its range, the Pin-tailed Whydah appears to be a generalist brood parasite ...

The ecology of the <i>fusca</i> group of tsetse flies (<i>Glossina</i>) in southern Nigeria

In Poland, forests comprise 31% of the total surface area, while the lowland coniferous forests comprise 51% of 94 000 km2 afforested areas. The line transect method was employed in 2002 and 2004 to estimate population densities and dominance of all bird species breeding in a selected fragment of such forest (eight transects with 165 sections and 77.7 km in total length). In total, 54 breeding bird species were recorded. The numbers varied between 37 and 44 on the particular transect. The number of breeding pairs per 10 ha varied on each transect from 41.0 to 93.6 (x=64.8; SD=102.22). Shannon’s diversity index varied between 1.2 and 1.4 on particular transects, while Simpson’s diversity index varied between 0.7 and 0.9. Also Pieleau’s evenness index varied slightly between 0.05 and 0.07. In overall, the differences between densities of breeding species on 8 transects were not statistically significant. The Chaffinch Fringilla coelebs was by far the most numerous bird species, recorded as eudominant in all eight transects and present in all 165 sections. The second to the Chaffinch was the Chiffchaff Phylloscopus collybita; also recorded in all sections and as a dominant in all transects. Three other species, namely the Blackbird Turdus merula, Willow Warbler Phylloscopus trochilus and Blackcap Sylvia atricapilla were recorded each one in more than 90% sections (N=165), and on particular transects their dominance varied between 4 and 11%. Residents comprised 57.5% of all breeding pairs. Short-distance migrants were almost twice more common than long-distance migrants. Insectivores were by far the most numerous feeding guild represented 88.9% of all breeding pairs. Overall density, cumulative dominance, diversity and evenness were unexpectedly very similar in this study (managed forest) and in natural primeval lowland coniferous forests of Białowieża.

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 &lt; 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.

Data on the response of bird communities to surface mining and habitat modification are limited, with virtually no data examining the effects of mining on bird communities in and along riparian forest corridors. Bird community composition was examined using line transects from 1994 to 2000 at eight sites within and along a riparian forest corridor in southwestern Indiana that was impacted by an adjacent surface mining operation. Three habitats were sampled: closed canopy, riparian forest with no open water; fragmented canopy, riparian forest with flood plain oxbows; and reclaimed mined land with constructed ponds. Despite shifts in species composition, overall bird species richness, measured as the mean number of bird species recorded/transect route, did not differ among habitats and remained unchanged across years. More species were recorded solely on mined land than in either closed forest or forested oxbow habitats. Mined land provided stopover habitat for shorebirds and waterfowl not recorded in other habitats, and supported an assemblage of grassland-associated bird species weakly represented in the area prior to mining. A variety of wood warblers and other migrants were recorded in the forest corridor throughout the survey period, suggesting that, although surface mining reduced the width of the forest corridor, the corridor was still important habitat for movement of forest-dependent birds and non-resident bird species in migration. We suggest that surface mining and reclamation practices can be implemented near riparian forest and still provide for a diverse assemblage of bird species. These data indicate that even narrow (0.4 km wide) riparian corridors are potentially valuable in a landscape context as stopover habitats and routes of dispersal and movement of forest-dependent and migratory bird species.

The Zambezian Baikiaea woodlands fall entirely within the Kalahari Woodland biome, a subset of savanna. In 2015, the line transect method was employed to study avian assemblages associated with Zambezian Baikiaea. In total, 10 transects were designed along a straight 12 km long line, so that each transect was 1.2 km long. A total of 88 species represented by 1190 pairs were recorded. On average, there were 42.9 species per transect. The overall density was 35.8 pairs/km, ranging from 29.2 to 44.2 on particular transects. Overall, Streptopelia capicola was the only dominant species. It was also the only species recorded as dominant on all the transects. The following other species were recorded as dominant: Cercotrichas leucophrys, Laniarius aethiopicus, Turtur chalcospilos, Dicrurus adsimilis, Lamprotornis nitens, Upupa africana, Apalis flavida, Ploceus velatus, Tchagra australis and Numida meleagris. The proportion of dominant species (cumulative dominance) varied from 18.9 to 37.7 (x = 28.5; n =...

ABSTRACTSpatial subsidies of energy and nutrients can influence the distribution of consumers in riparian habitats. This study compared the abundance and composition of bird assemblages and the availability of volant insect prey within the riparian zone (≤ 30 m from the stream) and further inland (100–250 m away) within a secondary forest in monsoonal Hong Kong. Replicated point‐counts of birds and insect light trapping were conducted in each zone during the wet and dry season of 2006–2007. The biomass of adult aquatic insects in the riparian zone was nine to 12 times higher than inland during both seasons, however, total insect biomass (aquatic plus terrestrial insects) in the riparian zone was only 49 percent (wet season) and 18 percent (dry season) greater. More birds (both numbers of individuals and species) were recorded in the riparian zone, and this difference was particularly conspicuous during the wet season. Most of the wet‐season difference was due to the greater number of insectivorous birds in the riparian zone (123% greater than inland), and may have reflected the relative availability of adult aquatic insects. These findings confirm the importance of riparian zones as feeding habitats for forest birds, and have implications for conservation planning and setting the boundaries of protected areas.

Island ecology plays an important role in explaining various ecological and evolutionary processes. Small, isolated oceanic islands, exemplified by the Azores Archipelago, are especially vulnerable to adverse environmental conditions and human impact. The study aims to evaluate the impact of urbanization, especially the urban greening space, on the structure and dynamics of avian communities associated with various landforms in an urbanized landscape in one of the nine islands of the Azores Archipelago, São Miguel Island, in the northeast Atlantic Ocean. Samples were collected in the second half of April 2024. The line transect method (43 transects with a total of 37.4 km) was employed to count all bird species breeding in different landforms distinguished in the city: coastal land, urbanized land, rural land, and urban greening space. The obtained results showed that the number of breeding species was much higher in urban greening spaces (n = 20) than in the other lands (n = 10–14 species). Both cumulative dominance and dominance indices were much lower in urban greening space than in the other landforms. The Sørensen Index of Similarity between the four main land categories distinguished in the city varied between 0.62 and 0.96, being the lowest between the coastal and urban greening space, and the highest between the urbanized and rural lands. Two main feeding guilds were distinguished in the study area: granivores and insectivores. The former guild clearly dominated over the latter in all major land categories distinguished. Clearly, the proportion of granivores increased with urbanization. Also, two nesting guilds were distinguished: buildings and trees/shrubs. The former was dominant in all land categories except for the urban greening space where the tree/shrub nesting guild was more numerous than the building guild. The tree/shrub guild declined with urbanization. A general trend was recorded: the higher the level of urbanization, the lower the percentage of urban greening space, and in consequence, the lower the number of bird species and diversity indices, but the higher the cumulative dominance and dominance indices. The overall density of birds remains, however, distinctively similar. In the future, data on the population densities and dominance of particular species should be collected in urbanized landforms in other towns of the Azores Archipelago and Macaronesia at large.