Influence of habitat features of urban streetscapes on richness and abundance of avian species

In human-dominated landscapes, roads are known to negatively influence birds causing decline in species richness, as well as reduction in the number of avian species. However, linear stretches of green spaces formed by roadside plantations in urban streetscapes can support diverse avian communities. In spite of being an integral habitat feature of urban areas, there is a clear paucity of studies on avian diversity in urban streetscapes. The present study was carried out in Kolkata, where data on avian species richness and abundance was collected from 16 randomly placed belt transects (replicates), each of 500 m length and 20 m width, on different major roads throughout the study area keeping a minimum gap of 200 m between adjacent transects to avoid data overlapping. Each of these transects were traversed on foot twice in a month from January to March 2017 during days with calm weather conditions. We recorded 31 species of birds belonging to 8 orders and 19 families, of which maximum species belonged to the order Passeriformes (13 species). We found that both abundance and species richness of birds in transects with higher number of trees (78±4.1 individuals and 19.55±1.703 species of birds) were significantly higher than transects with fewer trees (53.74±2.5 individuals and 9.5±0.789 species of birds). Amongst various habitat features along these streetscapes, the total number of trees positively influenced both species richness (GLMM: F1, 90=14.485, P<0.05) and abundance of birds (GLMM: F1, 90=8.081, P<0.05). However, the other land use variables (i.e. number of bushes, waterbodies, markets and buildings) neither influenced the abundance of birds nor the species richness. Our findings can be useful for urban development to perceive the importance of various habitat features in urban streetscapes in sustaining avian diversity.

Windscapes and olfactory foraging in a large carnivore

The theoretical optimal olfactory search strategy is to move cross-wind. Empirical evidence supporting wind-associated directionality among carnivores, however, is sparse. We examined satellite-linked telemetry movement data of adult female polar bears (Ursus maritimus) from Hudson Bay, Canada, in relation to modelled winds, in an effort to understand olfactory search for prey. In our results, the predicted cross-wind movement occurred most frequently at night during winter, the time when most hunting occurs, while downwind movement dominated during fast winds, which impede olfaction. Migration during sea ice freeze-up and break-up was also correlated with wind. A lack of orientation during summer, a period with few food resources, likely reflected reduced cross-wind search. Our findings represent the first quantitative description of anemotaxis, orientation to wind, for cross-wind search in a large carnivore. The methods are widely applicable to olfactory predators and their prey. We suggest windscapes be included as a habitat feature in habitat selection models for olfactory animals when evaluating what is considered available habitat.

Environmental factors associated with amphibian breeding in streams and springs: effects of habitat and fish occurrence

Streams are among the most threatened aquatic habitats for amphibians. Amphibians often demonstrate a complex community structure and investigations are mainly performed on pond-dwelling species, whereas data regarding stream-dwelling species is still scarce. The aim of this study was to evaluate the relevance of stream features and the effects of the occurrence of predatory fish on the community structure of amphibians. To assess the occurrence of breeding among amphibians (in Northern Apennine streams), sampling was performed on 57 stream and spring sites between early March and late May 2014. The research process recorded the presence of four breeding species (Salamandra salamandra, Salamandrina perspicillata, Bufo bufo, and Rana italica) and discovered that the community structures of amphibians were significantly connected to different habitat features. The investigation showed that fish presence is the primary habitat feature that affects the communities of amphibians: B. bufo was the only amphibian species not affected by fish presence, while the other species avoided sites with fish. Sun exposure, depth of water and slope inclination played important roles in affecting amphibian breeding. Our study confirms that fish presence in small streams can be detrimental for different amphibian species.

Experimental burning changes the quality of fallen timber as habitat for vertebrate and invertebrate fauna: implications for fire management

Context Fallen timber is a key habitat feature in forests and woodlands for vertebrate and invertebrate fauna, and is either consumed or left partially burnt after the passage of fire. This impact on habitat quality assumes significance because increasing areas of land are subject to frequent hazard-reduction burning and wildfire in eastern Australia. Aims We test here whether partially burnt or charred fallen timber is employed as habitat to the same extent as unburnt fallen timber. Methods Vertebrate and invertebrate abundance beneath burnt and unburnt fence posts was monitored for 13 months in unburnt forest and forest burnt by a wildfire. Key results Both vertebrate and invertebrate fauna made significantly less use of charred refuges. In most taxa, twice as many animals occurred under unburnt as under burnt artificial timber refuges, ant nests being the exception. Fauna made greater use of experimental refuges in burnt forest. Key conclusions Partially burnt fallen-timber refuges, where the log surface is left charred, are inferior habitat for fauna. Habitat quality in burnt forest may be enhanced by introducing fallen timber. Implications The study highlights an ecological consequence of fire for habitat quality, whether through wildfire or hazard-reduction burning, which should be considered in fire management.

Nesting With The Wasp Ropalidia Cincta Increases Nest Success of Red-Cheeked Cordonbleu (Uraeginthus Bengalus) in Ghana

Associations between birds and social Hymenoptera (ants, wasps, bees) are common in tropical regions and are usually assumed to be commensal relationships that benefit birds but neither help nor harm the arthropods. However, benefits to birds have been documented in only four such associations, and no previous research has rigorously investigated costs or benefits to associated hymenopterans. We followed the nesting cycles of an estrildid finch, the Red-cheeked Cordonbleu (Uraeginthus bengalus), and a common nesting associate, the wasp Ropalidia cincta, during 2002 and 2003 in northern Ghana to compare reproductive success of birds and wasps nesting in association with that of birds and wasps nesting separately. Red-cheeked Cordonbleus and wasps nested together in the same tree 3.7 × as often as expected if nesting decisions were made independently, with 74% of bird nests and 74% of wasp colonies occurring in associations. Bird nesting was initiated ≈33 days after founding of an associated wasp colony; bird nests and wasp colonies were, on average, 42 cm apart. In both years, Red-cheeked Cordonbleus in nesting associations with wasps were twice as likely to fledge young as birds nesting in trees without wasps. Reduced predation was apparently a major reason for increased fledging success: we documented four cases of nest predation on 122 Red-cheeked Cordonbleu nests associated with wasps, and 11 cases on 90 nests not associated with wasps. Association with birds did not affect the success of wasp colonies. Although our observational study cannot rule out the possibility that both species coincidentally shared a preference for a habitat feature in limited supply, suitable nest sites did not appear to be limiting (74% of potential nest trees had neither bird nor wasp nests). Reproductive success of Red-cheeked Cordonbleu populations in this region may be limited by the number of available wasp colonies. By designing our study to address four working hypotheses (commensalism, mutualism, parasitism, coincidence of habitat preference), we have provided strong evidence that this relationship is commensal.Augmentation du Succès de Nidification de Uraeginthus bengalus Nichant avec des Guêpes Ropalidia cincta au Ghana

Distributional relations of two species of Psednura (Orthoptera : Pyrgomorphidae) in the Evans Head area of New South Wales

The distribution of Psednura pedestris and the northern race of P. musgvavei was studied in relation to habitat in the heathy vegetation of the sandy coastal plain near Evans Head, N.S.W. The density of both species was in general very low, corresponding to an average of only one specimen captured per man-hr; in a few patches it rose to several times that figure. The distribution of the two species was in the main mutually exclusive in a mosaic pattern reflecting the mosaic distribution of the respective preferred habitats, pedestvis occurring on the margins of swamps and musgravei on somewhat better drained sites. However, at three locations mixed populations were found in the ecotone between the two habitats. At one of these, which was studied in detail, the zone of overlap was never wider than 12 m, and the highest density of each species occurred within a 2-m strip on either side of a median line related to a prominent habitat feature. The situation is compared and contrasted with that in parapatric species and races of morabine grasshoppers.