Small Insectivores Research Articles

Foraging ecology of eucalypt forest and woodland birds in the Great Western Woodland I: Small insectivores

ABSTRACT Australian warblers (Acanthizidae) and pardalotes (Pardalotidae) are abundant keystone species in Australia. Collectively they help regulate arthropod populations and dampen outbreaks of phytophagous insects. Their conservation in the face of habitat degradation and climate change is essential for the retention of healthy forest ecosystems and biodiversity. Information at the level of detail required for effective conservation management is missing for most Australian birds, including warblers and pardalotes. It is unlikely the data needed for the conservation of these species will be obtained in time to prevent further losses of avian biodiversity. However, it is important to try. This paper describes the foraging behaviour during spring of seven species of Australian warblers and pardalotes (small insectivores) in the Great Western Woodland, Western Australia and expands our knowledge of the ecology of these birds. As reported for small insectivores elsewhere in the world, species differed in prey-attack behaviours, foraging substrates, plant species used for foraging, foraging heights, and habitats. These data are used to explain why, without changes in how Australia approaches the preservation of biodiversity, abundant birds, such as Australian warblers and pardalotes will decline towards extinction.

Artificial light affects the foraging behavior in greater white‐toothed shrews (CROCIDURA RUSSULA)

AbstractLight pollution is one of the forms by which human‐induced alterations are changing natural environments. Artificial light at night (ALAN) has been increasing over the past decades and it is already known that ALAN can have a major influence on the ecology, behavior, and physiology of different taxa. Nocturnal small mammals are particularly vulnerable, as ALAN can increase their predation risk while foraging. The aim of this study was to investigate foraging strategies under different light conditions in a nocturnal small insectivore, the greater white‐toothed shrew (Crocidura russula). Compared with rodents, shrews have a higher metabolic rate and thus present a good model for a foraging study. In three laboratory experiments with wild‐caught shrews we tested (i) food preference under dark conditions as well as the effect of different light conditions on (ii) foraging strategies and (iii) food choice. The results showed that shrews had a clear food preference under dark conditions. They also preferred to forage under dark over light conditions when presented with the same food in both conditions. However, when presented with the choice of foraging their preferred food under illuminated conditions or a lower food quality in the dark, the food preference of shrews overruled their preference for feeding in the dark. It seems that food preference, rather than risk perception, is the main driver determining the foraging strategy of the greater white‐toothed shrews. This study suggests that ALAN does not necessarily prevent high‐metabolic nocturnal insectivores from achieving their energetic needs, which might help explain their persistence in urban environments.

Movements and habitat connectivity of New Zealand forest birds: a review of available data

New Zealand’s original forested landscape has been greatly fragmented since human arrival, limiting connectivity and habitat quality for forest-dependent fauna. We review the limited available information about forest bird movement behaviour, especially whole-year sociality and movement, natal dispersal, and pasture- and water-gap crossing. Most small insectivores (17 species) and North Island kōkako are territorial year-round, but frugivore-nectivores (three species), raptors (two species), and volant parrots (four species) can be highly mobile, presumably to find scattered food.

Community assembly, functional traits, and phylogeny in Himalayan river birds.

Heterogeneity in riverine habitats acts as a template for species evolution that influences river communities at different spatio‐temporal scales. Although birds are conspicuous elements of these communities, the roles of phylogeny, functional traits, and habitat character in their niche use or species' assembly have seldom been investigated. We explored these themes by surveying multiple headwaters over 3000 m of elevation in the Himalayan Mountains of India where the specialist birds of montane rivers reach their greatest diversity on Earth. After ordinating community composition, species traits, and habitat character, we investigated whether river bird traits varied with elevation in ways that were constrained or independent of phylogeny, hypothesizing that trait patterns reflect environmental filtering. Community composition and trait representation varied strongly with increasing elevation and river naturalness as species that foraged in the river/riparian ecotone gave way to small insectivores with direct trophic dependence on the river or its immediate channel. These trends were influenced strongly by phylogeny as communities became more clustered by functional traits at a higher elevation. Phylogenetic signals varied among traits, however, and were reflected in body mass, bill size, and tarsus length more than in body size, tail length, and breeding strategy. These variations imply that community assembly in high‐altitude river birds reflects a blend of phylogenetic constraint and habitat filtering coupled with some proximate niche‐based moulding of trait character. We suggest that the regional co‐existence of river birds in the Himalaya is facilitated by this same array of factors that together reflect the highly heterogeneous template of river habitats provided by these mountain headwaters.

Habitat element associations in the bird fauna of an Australian farmland landscape

Context The decline of birds in farmland is of global concern. Aims The aim of this paper was to provide a local-scale case study of the bird fauna of temperate inland eastern Australia’s sheep–wheat belt. Methods Relationships between species occurrence and various habitat elements in the landscape were examined in a 342 km2 area of agricultural countryside near Wagga Wagga in southern inland New South Wales, Australia. The pre-agricultural bird fauna of this area was also investigated by collating records from previous studies of nearby larger woodland remnants. Key results The study identified a bird fauna of 115 species compared to 160 species known from nearby woodland remnants. Significant relationships were found with the presence of farm dams, extent of local woodland cover and roadside woodland at the levels of individual species, guilds and total fauna. A small ephemeral wetland also contributed substantially to waterbird diversity. Conclusion Twenty commonly recorded species typical of the farmland matrix and 15 species considered at particular risk of local extinction were identified. At the guild level, frugivore/granivores, small insectivores and hollow-users were found to be associated with remaining woodland elements in the agricultural landscape. Implications Ecologically sustainable management of agricultural areas is essential to avoid further local extinctions. Hollow-using species are expected to be particularly affected by the anticipated widespread loss of trees in the landscape over the next century.

Big Bird Plots: Benchmarking Neotropical Bird Communities to Address Questions in Ecology and Conservation in an Era of Rapid Change

Extensive networks of large plots have the potential to transform knowledge of avian community dynamics through time and across geographical space. In the Neotropics, the global hotspot of avian diversity, only six 100-ha plots, all located in lowland forests of Amazonia, the Guianan shield and Panama, have been inventoried sufficiently. We review the most important lessons learned about Neotropical forest bird communities from those big bird plots and explore opportunities for creating a more extensive network of additional plots to address questions in ecology and conservation, following the model of the existing ForestGEO network of tree plots. Scholarly impact of the big bird plot papers has been extensive, with the papers accumulating nearly 1,500 citations, particularly on topics of tropical ecology, avian conservation, and community organization. Comparisons of results from the plot surveys show no single methodological scheme works effectively for surveying abundances of all bird species at all sites; multiple approaches have been utilized and must be employed in the future. On the existing plots, abundance patterns varied substantially between the South American plots and the Central American one, suggesting different community structuring mechanisms are at work and that additional sampling across geographic space is needed. Total bird abundance in Panama, dominated by small insectivores, was double that of Amazonia and the Guianan plateau, which were dominated by large granivores and frugivores. The most common species in Panama were three times more abundant than those in Amazonia, whereas overall richness was 1.5 times greater in Amazonia. Despite these differences in community structure, other basic information, including uncertainty in population density estimates, has yet to be quantified. Results from existing plots may inform drivers of differences in community structure and create baselines for detection of long-term regional changes in bird abundances, but supplementation of the small number of plots is needed to increase generalizability of results and reveal the texture of geographic variation. We propose fruitful avenues of future research based on our current synthesis of the big bird plots. Collaborating with the large network of ForestGEO tree plots could be one approach to improve understanding of linkages between plant and bird diversity. Careful quantification of bird survey effort, recording of exact locations of survey routes or stations, and archiving detailed metadata will greatly enhance the value of benchmark data for future repeat surveys of the existing plots and initial surveys of newly established plots.

Revisiting «Malaya Sosva» state reserve characteristics of fauna and population structure of small mammals

The paper deals with the study of species composition and small mammals population structure of Malaya Sosva (Little Sosva) state nature reserve, Khanty-Mansi Autonomous Okrug Yugra, Russia. The research was conducted within the last ten days of June, 2019 on the Malaya Sosva River flood plain (Shukhtungort ranger station neighborhood, northern taiga). The animals were registered in typical biotopes of the research area: a herb-oxalis pinery, a lingonberry-lidum pinery, a lingonberry-pleurocarpous moss pinery, a herb-oxalis spruce forest, a herb-woodreed pinery, on the skirts of a mixed forest around the ranger station on the border of a mowed secondary meadow. In the course of investigation, the following five species of small rodents and insectivores were registered: Myodes rutilus, Myodes rufocanus, Sorex caecutiens, Talpa europaea, Pteromys volans. M. rutilus was an absolute dominant species in terms of numbers in the majority of the studied biotopes. S. caecutiens is co-dominating in the herb-oxalis pinery and herb-oxalis spruce forest, and M. rufocanus is co-dominating in the lingonberry-lidum pinery. In the herb-woodreed pinery, only individuals of S. caecutiens species were caught in a pitfall trap. Communities of small mammals in different types of habitats show low values of species diversity and sustainability due to harsh natural-climatic conditions of the region. A small mammals community of mature herb-oxalis pinery on the bank of Svyatoy Sor Lake, where the protected species, Pteromys volans, was registered, shows the highest values of abundance of small mammals and a maximum level of overall welfare index. It suggests that the habitat under study should be studied further and protected.

Bat portraits in times of pandemic

In this Photo Essay, photographs are combined with drawings collected in Burkina Faso in the years following the 2014–2016 Ebola outbreak. Portraits of bats are shown. The blacklisting of these animals following the recommendations of health authorities collides with local realities, where it is not possible to talk about bats in a ‘general’ sense. The same is true today in the period of COVID-19, when chiropterans are once again in the etiological hot seat: bats are behind the pandemic, according to Ridley's shock phrase (2020). In Burkina Faso's Lobi country, between the red and black fruit-eaters (which have always been eaten) and the small insectivores (which have never been eaten as such, but are very useful to animist healers), there is a chasm of representation that is unveiled by these images.

Relationships among side‐scan sonar classified substrates and fish‐catch rates at multiple spatial scales

AbstractPhysical habitat is crucial for structuring local fish assemblages. Understanding habitat structure is important for fish management and conservation. Herein, we assessed whether sonar‐derived substrate data could explain spatial variation in species‐catch rates. Using a side‐scan sonar, we mapped the substrates of two non‐wadeable rivers in Illinois, USA and conducted standardized fish surveys at 40 sites over a 3‐year period. We used four fish species from lentic and lotic guilds, with each guild represented by a large piscivore and small insectivore. For each of the 40 sites, we characterized substrate composition at five spatial scales (0.1, 0.5, 1, 2, and 5 km) and used linear regression to explain site variations in species abundance or biomass. We hypothesized that larger spatial scales would better explain the catch rates of large species, and that biomass would be better explained than abundance. The proportion of variance in fish‐catch rates, explained by substrate composition, varied greatly (0.02 ≤ adjR2 ≤ 0.74, mean adjR2 = 0.38) with respect to species, spatial scales, and predictors used. However, we did not observe a consistent relationship between body size and the most relevant scale. Species biomass was more closely related to substrate composition than was species abundance and the best models selected based on AICc reached an average adjR2 of 0.49 (0.25–0.74) across the four species, compared with that of 0.43 (0.20–0.64) obtained via the best abundance‐based models. We conclude that substrate data obtained using side‐scan sonar are useful for improving our understanding of river fish ecology.

Ecological Limits as the Driver of Bird Species Richness Patterns along the East Himalayan Elevational Gradient.

Variation in species richness across environmental gradients results from a combination of historical nonequilibrium processes (time, speciation, extinction) and present-day differences in environmental carrying capacities (i.e., ecological limits affected by species interactions and the abundance and diversity of resources). In a study of bird richness along the subtropical east Himalayan elevational gradient, we test the prediction that species richness patterns are consistent with ecological limits using data on morphology, phylogeny, elevational distribution, and arthropod resources. Species richness peaks at midelevations. Occupied morphological volume is roughly constant from low elevations to midelevations, implying that more species are packed into the same space at midelevations compared with low elevations. However, variance in beak length and differences in beak length between close relatives decline with elevation, which is a consequence of the addition of many small insectivores at midelevations. These patterns are predicted from resource distributions: arthropod size diversity declines from low elevations to midelevations, largely because many more small insects are present at midelevations. Weak correlations of species mean morphological traits with elevation also match predictions based on resources and habitats. Elevational transects in the tropical Andes, New Guinea, and Tanzania similarly show declines in mean arthropod size and mean beak length and, in these cases, likely contribute to declining numbers of insectivorous bird species richness along these gradients. The results imply that conditions for ecological limits are met, although historical nonequilibrium processes are likely to also contribute to the pattern of species richness.

A true “migrant trap”: Boerhavia (Nyctaginaceae) entanglement as a recurring cause of avian entrapment and mortality

Bird entanglement in plants is a relatively uncommonly documented occurrence, with only a handful of plant species known to recurrently trap birds and cause mortality. Here I describe a large number of bird entanglement events, including 3 confirmed bird deaths, involving Boerhavia torreyana (Torrey's spiderling) in an arid canyon in northern Arizona. Like many species of Boerhavia, B. torreyana possesses sticky rings on its stems that are hypothesized to enhance herbivory defense. I document that these sticky rings also frequently capture birds, and identify 39 separate bird entanglement events involving at least 9 different bird species in a small area where B. torreyana is common. Because B. torreyana is an annual plant that germinates with the arrival of the Southwestern monsoon in mid-summer, it matures and presents an entanglement risk at a time that coincides with the fall bird migration. Small ground-dwelling passerines and insectivores appear to be particularly at risk of being trapped. There are very few known examples of plant species that regularly causes bird entanglement and associated mortality, and the observations presented here document a new case of this phenomenon.

Radical changes in the avifauna of a Sydney suburb, 1971–2014

We document changes in the avifauna of Longueville, a residential suburb of Sydney, between 1971–73 and 1977–79 based on daily bird lists, and make comparisons with the present avifauna based on surveys in 2013–14. Of the 31 most common native terrestrial bird species, 17 were ‘decreasers’, present in 1971–73 but not recorded in 2013–14 (although 16 of them were recorded in a large bushland remnant 5 km away), and 14 were ‘increasers’, seven of which were absent or very rare in 1971–73. Eleven species decreased during the 1970s, and six species afterwards. Eight species increased during the 1970s and six species afterwards. The decreasers were predominantly small insectivores and nectarivores. The increasers were of three main types: medium to large carnivores, large frugivores or granivores, and medium-sized nectarivores. Two of the nectarivores, the noisy miner (Manorina melanocephala) and rainbow lorikeet (Trichoglossus haematodus), now dominate the urban bird community of Longueville and are by far the most numerous birds. The increase of both species dates from the late 1970s. The noisy miner is highly aggressive towards other birds and its dramatic increase (it was absent in 1971–73) appears to be the chief cause of the decline of small native birds in Longueville.

Влияние интенсивной лесоэксплуатации на фаунистические комплексы мелких насекомоядных и грызунов Восточной Фенноскандии

Влияние интенсивной лесоэксплуатации на фаунистические комплексы мелких насекомоядных и грызунов Восточной Фенноскандии

Effect of anthropogenic transformation of forest landscapes on populations of small insectivores in eastern Fennoscandia

Responses of small insectivores (Sorex L.) to clear felling and formation of an anthropogenic landscape have been studied and found to be ambiguous. Under such conditions, the total population density of the common shrew (S. araneus) increases, but its populations become unstable and sharply fluctuate seasonally and from year to year. The abundance of the Laxmann’s shrew (S. caecutiens) in transformed habitats becomes slightly lower, but its populations acquire certain additional stability. In general, this species negatively responds to felling but nevertheless regularly occurs in young secondary conifer stands. Finally, low-abundance species are either highly tolerant of forest exploitation (the Eurasian least shrew, S. minutissimus) or, on the contrary, show a distinctly negative response to felling in conifer forests (the taiga shrew, (S. isodon).

Mammal disparity decreases during the Cretaceous angiosperm radiation

Fossil discoveries over the past 30 years have radically transformed traditional views of Mesozoic mammal evolution. In addition, recent research provides a more detailed account of the Cretaceous diversification of flowering plants. Here, we examine patterns of morphological disparity and functional morphology associated with diet in early mammals. Two analyses were performed: (i) an examination of diversity based on functional dental type rather than higher-level taxonomy, and (ii) a morphometric analysis of jaws, which made use of modern analogues, to assess changes in mammalian morphological and dietary disparity. Results demonstrate a decline in diversity of molar types during the mid-Cretaceous as abundances of triconodonts, symmetrodonts, docodonts and eupantotherians diminished. Multituberculates experience a turnover in functional molar types during the mid-Cretaceous and a shift towards plant-dominated diets during the late Late Cretaceous. Although therians undergo a taxonomic expansion coinciding with the angiosperm radiation, they display small body sizes and a low level of morphological disparity, suggesting an evolutionary shift favouring small insectivores. It is concluded that during the mid-Cretaceous, the period of rapid angiosperm radiation, mammals experienced both a decrease in morphological disparity and a functional shift in dietary morphology that were probably related to changing ecosystems.

Eastern rock sengis as reservoir hosts of Anaplasma bovis in South Africa

Recent work has identified the presence of Anaplasma bovis, a tick-borne pathogen of cattle, in a previously undescribed species of tick collected from eastern rock sengis, Elephantulus myurus, in Limpopo Province, South Africa. These small insectivores are endemic to Africa and are important hosts of immature ticks, however, their role as reservoirs of tick-borne pathogens has not been investigated. In order to elucidate the role of sengis in the epidemiology of A. bovis, we screened the blood of 105 sengis from Limpopo Province, South Africa, for the presence of members of the genera Anaplasma and Ehrlichia by PCR. A total of 30/105 (28.6%) of individuals were infected with A. bovis, and nucleotide sequencing revealed the presence of a novel genetic variant of this pathogen. This represents the first evidence that sengis may be natural reservoir hosts of A. bovis.

Long‐term Changes in Bird Communities after Wildfires in the Central Brazilian Amazon

AbstractWe examined long‐term responses of an Amazonian bird assemblage to wildfire disturbance, investigating how understory birds reacted to forest regeneration 1, 3, and 10 years after a widespread fire event. The bird community was sampled along the Arapiuns and Maró river catchments in central Brazilian Amazonia. Sampling took place in 1998, 2000, and 2008 using mist‐nets in eight plots (four burned, four unburned sites). Species richness did not change significantly in unburned sites. In burned sites, however, we found significantly lower richness in 1998, higher richness in 2000, and similar richness in 2008. Multi‐dimensional scaling ordination showed consistent differences in bird communities both within burned sites sampled in different sampling years, and between burned and unburned sites in all years. Of the 30 most abundant species, 12 had not recovered 10 years after the fires, including habitat specialists such as mixed flocks specialists and ant‐followers. Fire‐disturbance favored three species (two hummingbirds and a manakin) in the short term only. All other species were either favored throughout the study (seven species of omnivores and small insectivores) or did not show a clear response (eight species). In burned sites, we also found significantly lower abundance of species sensitive to disturbances and habitat specialists over the entire study period. Although the bird community seems to be recovering in terms of richness, the overall community composition and abundance of some species in post‐burned and unburned sites remain very different, and have not recovered after 10 years of forest regeneration.

Habitat use by Collared Crescentchest (Melanopareia torquata) in a Cerrado in southeastern Brazil: implications for management

The Collared Crescentchest (Melanopareia torquata) is a small insectivore endemic to the Cerrado. We examine the habitat use of this bird in a preserved Cerrado area in southeastern Brazil. Despite its occurrence in grassland with shrubs, the species used these areas less frequently than expected. The Collared Crescentchest mainly used areas of campo cerrado, but it was not recorded in a disturbed one. The common occurrence of exotic grass (U. decumbens) and cattle grazing may have brought about factors for its occurrence. However, the preference for native grasses may indicate an adverse indirect relationship against its occurence as there is competition between native and exotic grasses in the Cerrado. The presence of the Collared Crescentchest included the highest density of tall shrubs (>1 m) and native grasses. Conservation of the species should involve preserved areas of campo cerrado with a dominance of native grasses and tall shrubs.

Differential feeding success of two paralysis-inducing ticks, Rhipicephalus warburtoni and Ixodes rubicundus on sympatric small mammal species, Elephantulus myurus and Micaelamys namaquensis

Rodents are recognised as important hosts of ixodid ticks and as reservoirs of tick-borne pathogens across the world. Sympatric insectivores are usually inconspicuous and often overlooked as hosts of ticks and reservoirs of disease. Elephant shrews or sengis of the order Macroscelidea are small insectivores that often occur in sympatry with rodents in southern Africa. Sengis are invariably parasitised by large numbers of immature ticks while sympatric rodents are infested with very few. The reason for the difference in tick parasitism rates between these hosts is unknown. While a number of mechanisms are possible, we hypothesised that certain tick species exhibit “true host specificity” and as such would only attach and feed successfully on their preferred host or a very closely related host species. To investigate this, we conducted feeding experiments using two economically important tick species, the brown paralysis tick, Rhipicephalus warburtoni and the Karoo paralysis tick, Ixodes rubicundus and two sympatric small mammal species as potential hosts, the eastern rock sengi, Elephantulus myurus and the Namaqua rock mouse, Micaelamys namaquensis. Ticks attached and fed readily on E. myurus, but did not attach or feed successfully on M. namaquensis suggesting that these ticks exhibit true host specificity. We suggest that a kairomonal cue originating from the odour of E. myurus may stimulate the attachment and feeding of these ticks and that they further possess immunosuppressive mechanisms specific to E. myurus, allowing them to feed on this host species but not on M. namaquensis. This study highlights the importance of small mammalian insectivores as potential hosts of ixodid tick species and hence their potential as reservoirs of tick-borne pathogens.

Conservation management of eastern Australian farmland birds in relation to landscape gradients

Summary 1. Birds inhabiting farmland are of conservation concern around the world. In Australia, conservation management has focused primarily on woodland environments. By contrast, semi-natural open areas have received less attention. We argue that long-term conservation strategies should consider broad gradients of environmental conditions. Otherwise, there is a risk that semi-natural open areas will degrade through ‘benign neglect’, and currently common species using these areas will become uncommon. 2. We examined how birds responded to three environmental gradients in an Australian livestock grazing landscape: tree density, grazing intensity and nutrient enrichment. First, we investigated changes in species composition across the environmental gradients in multivariate space. Secondly, we modelled species richness and the response of selected individual species in relation to the gradients. Thirdly, we examined if there were patterns in guild composition and body mass distribution. 3. Tree density was the primary driver of virtually all patterns observed. Species richness peaked at moderately high tree densities. With increasing tree density, species composition changed, foraging guild composition changed and the median body mass of bird species decreased. Small insectivores were more likely to occur in areas with high tree densities, whereas large granivores were more likely to occur in areas with relatively low tree densities. Grazing intensity and nutrient enrichment were less strongly related to bird distribution patterns, although the indirect effects of these gradients may be substantial because they affect tree regeneration. 4. sSynthesis and applications. Relatively dense woodland patches were important for species already of conservation concern, lending support to their active conservation management, for example through livestock exclusion. However, semi-natural open areas also were used by many birds, which represented a different mix of body sizes and foraging guilds. Scattered trees occurring at a range of densities are key habitat elements in semi-natural open areas. However, many scattered trees are dying and are not being replaced by natural regeneration or tree planting. If areas with scattered trees continue to degrade, there is a risk that currently common farmland birds will decline. Management strategies aiming to maintain scattered trees therefore are important, including the planting of individual trees and the adoption of grazing practices that allow for natural tree regeneration.