Small Insectivorous Birds Research Articles

Observations on populations of a small insectivorous bird,

The use of chemical pesticides to manage locust populations in natural ecosystems is likely to impact non-target arthropods and their predators. However, the relative effects of different locust control applications on Australian birds are unknown. Aerial applications of fipronil and fenitrothion are examples of two pesticides used in locust control in semiarid Australia. To test the relative impacts of pesticides on non-target fauna, pesticides were applied to replicate sites using aerial ultra-low-volume application methods. The body condition and biomarkers of pesticide exposure in resident white-winged fairy wrens (Malurus leucopterus leuconotus) at treatment and control sites were measured for two weeks before and after treatments. No measures suggested negative impacts of pesticide applications. However, birds monitored at treatment sites gained mass, possibly due to indirect impacts of pesticides on bird feeding patterns or the availability or behaviour of insect prey. Bird mass measures remained high at fipronil sites, whereas the mass of birds at fenitrothion sites returned to baseline levels within one week. As this study was conducted during dry conditions, when locust plagues are less likely, future insecticide research should also consider the availability of insect prey, its effect on insectivore feeding behaviour and the interaction of rainfall events.

The Song Structure of the Siberian Rubythroat Luscinia [Calliope] Calliope: Branching Syntax Underlies Complex and Variable vocalization

Abstract The syntactical organization of the avian song is of particular interest in light of recently discussed analogies between the songs of birds and human speech. We present here a description of the song structure of the Siberian Rubythroat Calliope calliope, a small insectivorous bird, widespread in Siberia and the Russian Far East. This species sings predominantly discontinuously, but the duration of individual songs varies significantly. Each individual song is composed of a number of song units, a stereotypical set of different notes and syllables that are always presented together and in a strictly fixed order. Although the variety of song units in an individual's repertoire is significant, the diversity of units presented in the very beginning of individual songs was found to be much more limited. The song of the Siberian Rubythroat is not only extremely complex and variable, but it is also organized as a set of clusters rooted in strictly defined initial song units. Each cluster in turn contains several branching points with a limited number of branches. Despite its impressive variety, the rubythroat's song nevertheless contains numerous fixed sequences of song units.

Age-dependent carry-over effects in a long-distance migratory bird

Migratory birds usually respond to climate change by modifying breeding and/or wintering areas, as well as by reproducing earlier. In addition, changes in winter habitat use or breeding phenology could have important carry-over effects on subsequent breeding success. Here, we studied age- and sex-dependent carry-over effects from wintering to the breeding stage of a small aerial insectivorous long-distance migratory bird, the barn swallows (Hirundo rustica) breeding in Denmark during 1984–2013. First, we used stable isotope analyses combined with ringing recoveries to identify wintering areas. Second, we found that environmental conditions as inferred by Normalized Difference Vegetation Index (NDVI) have improved at the wintering grounds. Third, we used confirmatory path analysis to quantify the indirect effect of winter conditions on subsequent breeding success. Males delayed onset of breeding and raised fewer fledglings in the first brood when ecological conditions during the previous winter improved. This response was age dependent, since yearlings did not respond to this environmental cue but the response was increasingly stronger as males aged. Females showed a similar response to winter conditions, although not statistically significant. These results highlight the importance of studying carry-over effects within the context of climate change, especially in relation to age of individuals.

Polluted environment does not speed up age-related change in reproductive performance of the Pied Flycatcher

Environmental pollution can exacerbate deterioration in fecundity with advancing age, directly via the toxic effects of pollutants or indirectly via pollution-related resource (e.g. dietary antioxidants) constraints. Since there are very few studies on age-related changes in reproduction with regard to pollution, we analyzed a long-term (25 years) set of reproduction data from a small insectivorous and migratory passerine bird, the Pied Flycatcher Ficedula hypoleuca, to determine whether female birds showed a faster age-related decrease in average breeding parameters in a metal-polluted area around a copper–nickel smelter than in the control area. In our population-level analysis, all the breeding parameters (clutch size, hatching success, fledging probability, and fledgling number) were lower in the polluted area. Nevertheless, none of them indicated a faster decrease with age in the polluted area. Clutch size and fledgling number increased after the first breeding, but showed no significant change later on. Hatching probability decreased slightly after the second breeding, while fledging probability showed no significant age-dependent variation. Our results suggest that moderate long-term pollution does not reduce the viability of our study population via a faster age-related decrease in fecundity.

Human disturbance provides foraging opportunities for birds in primary subalpine forest

Interspecific foraging associations are well-documented phenomena, characterized by one or more species exploiting the behavior of another species to decrease predation or increase foraging success. In rare cases, birds directly exploit human behavior, but examples of these interactions are limited to species that naturally occur in edge, open, or disturbed habitats. With observations and experiments we provide evidence of insectivorous birds exploiting human disturbance in primary subalpine forest in the mountains of southern China, displaying behavioral flexibility to gain novel foraging opportunities. We cut and cleared small swaths of dense bamboo growth for an unrelated study. Multiple insectivorous species were recruited to the cleared areas, foraging extensively in the disturbed earth, often within 1 m of us. These species included Tarsiger chrysaeus, Tarsiger indicus, Cettia brunnifrons or Cettia major, and Heteroxenicus stellatus. This behavior is likely a modification of pre-existing interspecific foraging associations with pheasants and large mammals in the region. These larger animals disturb the earth and lower vegetation layers upon passage and while foraging, exposing previously inaccessible invertebrate prey items on which small insectivorous birds can feed. Our findings highlight a behavioral capacity in birds to utilize human disturbance in an ecosystem with limited human presence.

A Tale of Two Occupations

This article explores divisions over hunting game in postwar Japan, illuminating a neglected aspect of the u.s. Occupation—namely the interrelationship between General Headquarters, Armed Forces Pacific (ghq, afpac), its military organization, and the more familiar General Headquarters, Supreme Commander for the Allied Powers (ghq, scap), with the primary mission of democratic reform. It also examines the previously overlooked work of scap’s Natural Resources Section, particularly its wildlife branch under its leader Oliver Austin, who clashed with members of the u.s. military over the need to restrict their hunting activities. A keen ornithologist, Austin worked hard to uphold a conservation program based on sound economic and ecological principles, viewing the mist netting of small insectivorous birds for food as counter-productive in agricultural terms. In contrast, he regarded the netting of waterfowl on special preserves where shooting was illegal as an efficient and sustainable means of harvesting game for domestic consumption. Members of the u.s. military objected to such limits, choosing to shoot in protected areas despite the damage done to the livelihoods of Japanese netting communities. The behavior of these Americans, who resented any restrictions on their leisure activities, reveals a colonial mindset that supported the belief that u.s. military control over Japan excused them from complying with Japanese laws.

Population genetic structure of the Atlantic Forest endemic Conopophaga lineata (Passeriformes: Conopophagidae) reveals a contact zone in the Atlantic Forest

The Rufous Gnateater, Conopophaga lineata, is a small insectivorous understory bird which is endemic to and widely distributed in the tropical and subtropical Atlantic forest of South America. Its distribution makes it ideally suited for testing two major hypotheses for the origin of biodiversity, namely, the riverine barrier and the forest refuge hypotheses. In this study, we sequenced mitochondrial (control region) and nuclear markers (intron 5 of the β-fibrinogen gene) for individuals distributed in the southern Atlantic forest and obtained a strong genetic structure with one clear discontinuity in northern Brazilian state of Sao Paulo. We consistently detected signals of demographic expansion for both markers, with estimates indicating that expansion started in the Late Pleistocene (250,000 years ago), suggesting that the forest refuge hypothesis potentially explains Rufous Gnateater’s diversification. We also found evidence of gene flow between populations from each side of this discontinuity, with a possible secondary contact zone occurring in the states of Minas Gerais, Sao Paulo, and Rio de Janeiro.

Adaptive processes drive ecomorphological convergent evolution in antwrens (Thamnophilidae).

Phylogenetic niche conservatism (PNC) and convergence are contrasting evolutionary patterns that describe phenotypic similarity across independent lineages. Assessing whether and how adaptive processes give origin to these patterns represent a fundamental step toward understanding phenotypic evolution. Phylogenetic model-based approaches offer the opportunity not only to distinguish between PNC and convergence, but also to determine the extent that adaptive processes explain phenotypic similarity. The Myrmotherula complex in the Neotropical family Thamnophilidae is a polyphyletic group of sexually dimorphic small insectivorous forest birds that are relatively homogeneous in size and shape. Here, we integrate a comprehensive species-level molecular phylogeny of the Myrmotherula complex with morphometric and ecological data within a comparative framework to test whether phenotypic similarity is described by a pattern of PNC or convergence, and to identify evolutionary mechanisms underlying body size and shape evolution. We show that antwrens in the Myrmotherula complex represent distantly related clades that exhibit adaptive convergent evolution in body size and divergent evolution in body shape. Phenotypic similarity in the group is primarily driven by their tendency to converge toward smaller body sizes. Differences in body size and shape across lineages are associated to ecological and behavioral factors.

Complete mitochondrial genome of Yellow-browed warbler Phylloscopus inornatus inornatus (Passeriformes: Sylviidae)

Yellow-browed warbler Phylloscopus inornatus inornatus (Passeriformes: Sylviidae) is a small insectivorous leaf-gleaning bird which breeds in forests of the east Palaearctic. In this study, we used PCR-based method to determine the complete mitochondrial genome (mtDNA) of this warbler species. The complete mtDNA is a 16,875 bp circular molecule, containing 37 typical genes and an extra pseudo-control region. The gene order differs from the standard gene order in birds, but similar to genus Sylvia and Acrocephalus, which has the remnant CR2 gene order. All protein-coding genes start with a typical ATG codon. The termination codon is usually the standard TAA, but may be TAG (Cyt b and ND6), AGG (COI) or incomplete T-(COIII and ND4). All tRNAs have the typical clover-leaf structure, except the dihydrouridine (DHU) arm of tRNASer (AGN) and tRNALys (CUN), which forms a simple loop. The non-coding region contains some intergenic spacers, a control region and an extra pseudo-control region.

After the 2010 rains: changes in reporting rates of birds in remnant woodland vegetation in the central wheatbelt of New South Wales, Australia, from drought to post-drought

Loss and fragmentation of the native vegetation of the Central Western Plains of New South Wales was followed by declines of woodland-dependent species. Drought is likely to have further suppressed many animal populations. Here we report on changes in woodland bird reporting rates between surveys in 2005-2009 (drought declared period) and surveys in 2010-2013 following the drought-breaking rains of 2010. By 2013 the number of species detected per survey had just recovered to the level of surveys in 2005/6. The 2013 species composition of the region was similar to that recorded in the 2005-2009 drought surveys, with half of the small insectivorous and nectarivorous woodland birds remaining rare and restricted. Woodland remnants in the landscape continued to be dominated by the same, usually large, species of birds, but reporting rates of 13 of the 15 most common species declined. Conversely, several smaller, foliage gleaning passerines had higher reporting rates post-drought, with Striated Pardalote and We...

Influence of the yellow-throated miner (Manorina flavigula) on bird communities and tree health in a fragmented landscape

Context Competition for space and resources within a fragmented landscape may change interspecific interactions within the remaining available habitat. These changes may inhibit the persistence of one species but facilitate the success of another. The yellow-throated miner (Manorina flavigula) is an example of a successful species, reportedly more common in the landscape as a result of fragmentation yet the consequences of its success are still relatively unknown. Aims To investigate whether the yellow-throated miner had negative impacts on bird community assemblages, particularly small insectivorous species, and whether its presence resulted in higher psyllid abundances and lower tree health, similar to impacts noted for other miner species. Methods We undertook this study near Walpeup in Victoria’s Mallee region, a highly fragmented, agriculture-dominated, semiarid landscape. Yellow-throated miner colonies and control sites free of miners were identified and surveyed for bird species present, psyllid abundance and measures of tree health. Conclusions The presence of the yellow-throated miner was associated with a significant reduction in bird species richness, lower abundance of small birds and a dissimilar community composition. Psyllid abundance was higher in miner colonies and tree health was significantly lower. Small insectivorous birds compete directly with miners for resources and, as such, are likely targeted by interspecific aggressive behaviour. The absence of small species from miner colonies most likely caused a trend in increased psyllid abundance and subsequently reduced tree health. Implications Our findings suggest that management of these miners is likely required to prevent further loss of biodiversity in this fragmented landscape. The loss of bird species and reduced tree health due to the influence of the yellow-throated miner presents one of the greatest threats to these communities nationally and a challenging conservation problem.

Birds in remnant woodland vegetation in the central wheatbelt of New South Wales during the drought declared years 2005 to 2009

The woodlands of southern Australia have been extensively cleared for agriculture. The loss and fragmentation of the native vegetation has been followed by dramatic declines in woodland-dependant species. Here we present data from the Central Western Plains of New South Wales on the occurrence of birds in woodlands that have been highly fragmented and structurally altered over the last 150 years. The species composition of the region is still very similar to that recorded 3 decades earlier but many small insectivorous and nectivorous woodland birds are rare and restricted, while the woodland patches and remnant tree groves in the landscape are now dominated by the Galah, Noisy Miner, Australian Magpie, Crested Pigeon, Apostlebird, Magpie-lark, Grey-crowned Babbler, Australian Raven, Eastern Rosella and Pied Butcherbird.

Pattern-oriented modeling of bird foraging and pest control in coffee farms

We develop a model of how land use and habitat diversity affect migratory bird populations and their ability to suppress an insect pest on Jamaican coffee farms. Bird foraging—choosing which habitat patch and prey to use as prey abundance changes over space and time—is the key process driving this system. Following the “pattern-oriented” modeling strategy, we identified nine observed patterns that characterize the real system's dynamics. The model was designed so that these patterns could potentially emerge from it. The resulting model is individual-based, has fine spatial and temporal resolutions, represents very simply the supply of the pest insect and other arthropod food in six habitat types, and includes foraging habitat selection as the only adaptive behavior of birds. Although there is an extensive heritage of bird foraging theory in ecology, most of it addresses only the individual level and is too simple for our context. We used pattern-oriented modeling to develop and test foraging theory for this across-scale problem: rules for individual bird foraging that cause the model to reproduce a variety of patterns observed at the system level. Four alternative foraging theories were contrasted by how well they caused the model to reproduce the nine characteristic patterns. Four of these patterns were clearly reproduced with the “null” theory that birds select habitat randomly. A version of classical theory in which birds stay in a patch until food is depleted to some threshold caused the model to reproduce five patterns; this theory caused lower, not higher, use of habitat experiencing an outbreak of prey insects. Assuming that birds select the nearby patch providing highest intake rate caused the model to reproduce all but one pattern, whereas assuming birds select the highest-intake patch over a large radius produced an unrealistic distribution of movement distances. The pattern reproduced under none of the theories, a negative relation between bird density and distance to trees, appears to result from a process not in the model: birds return to trees at night to roost. We conclude that a foraging model for small insectivorous birds in diverse habitat should assume birds can sense higher food supply but over short, not long, distances.

Local survival of pied flycatcher males and females in a pollution gradient of a Cu smelter

Survival is one of the most central population measures when the effects of the pollution are studied in natural bird populations. However, only few studies have actually measured rigorous survival estimates on adult birds. In recent years there has been a methodological advance in survival analyses by mark-recapture models. We modelled local survival (including mortality and emigration) with the program MARK in a population of a small insectivorous passerine bird, the pied flycatcher ( Ficedula hypoleuca), around a point source of heavy metals. The local survival of females in the polluted area was about 50% lower than in the other areas. Males, however, survived relatively well in the heavily polluted area, but showed somewhat lower survival in the moderately polluted area. Different pollution effects between two sexes might be due to pollution-related differences in reproductive effort in females and males, and/or more intensive uptake of heavy metals by laying females.

Environmental pollution has sex-dependent effects on local survival

Environmental pollutants cause a potential hazard for survival in free-living animal populations. We modelled local survival (including emigration) by using individual mark-recapture histories of males and females in a population of a small insectivorous passerine bird, the pied flycatcher (Ficedula hypoleuca) living around a point source of heavy metals (copper smelter). Local survival of F. hypoleuca females did not differ between polluted and unpolluted environments. Males, however, showed a one-third higher local-survival probability in the polluted area. Low fledgling production was generally associated with decreased local survival, but males in the polluted area showed relatively high local survival, irrespective of their fledgling number. A possible explanation of higher local survival of males in the polluted area could be a pollution-induced change in hormone (e.g. corticosterone or testosterone) levels of males. It could make them to invest more on their own survival or affect the hormonal control of breeding dispersal. The local survival of males decreased in the polluted area over the study period along with the simultaneous decrease in heavy metal emissions. This temporal trend is in agreement with the stress hormone hypothesis.

Comparison of foraging behaviour of small, urban-sensitive insectivores in continuous woodland and woodland remnants in a suburban landscape

Small patches of remnant vegetation are often considered to have low conservation value. In urban landscapes their value may potentially be higher than in other landscapes because they can be the only representatives of original native vegetation. Despite this potential, many small insectivorous birds that rely on native vegetation demonstrate sensitivities within urban landscapes through reduced numbers or total absence. One reason for this sensitivity may be that remnants are of suboptimal quality, which may be reflected in behavioural changes. Using five insectivorous species that were present (in low numbers) in remnants surrounded by high-density housing, foraging behaviour was examined in relation to vegetation. The proportion of time birds spent on different foraging substrates and plant species was compared with that of conspecifics in continuous vegetation. Canopy and shrub foragers showed minimal behavioural changes. Ground foragers in remnants tended to forage at lower heights than those in continuous vegetation; however, these changes did not appear to reflect a negative effect. These changes were partially explained by structural differences between vegetation in remnants and continuous sites. The number of times a bird attacked prey items was significantly higher in continuous habitat for only two species. Overall, the foraging behaviour of small insectivorous birds in remnants surrounded by high-density housing was not adversely affected by urbanisation and it appears that remnants have potential value as habitat and foraging sources in an urban landscape. Despite this, small insectivores are still sensitive to urbanisation, suggesting that other factors, probably in the matrix, are important.

Differential use of habitat aids local coexistence of three species of wrens (Maluridae) and the White-browed ScrubwrenSericornis frontalis: Pardalotidae in Myall Lakes National Park

Four species of small insectivorous birds, the Superb Fairy-wren Malurus cyaneus, Variegated Fairy-wren M. lamberti, Southern Emu-wren Stipiturus malachurus and White-browed Scrubwren Sericornis frontalis have similar foraging methods which has often led to them being grouped into the same foraging guild. These four species occur in sympatry at Myall Lakes National Park, 300 km north of Sydney. Discriminant function analysis was used to test for any differential use of habitat between the four species. Malurus cyaneus was observed more often in open grassland habitats which is likely to be their preferred habitat. Stipiturus malachurus were more common in reedy (Baumea sp.) areas where their unique foraging behaviour may increase foraging efficiency. The remaining two species had some differences in habitat use, but foraged at significantly different heights in the vegetation.

Pollution related effects on immune function and stress in a free‐living population of pied flycatcher Ficedula hypoleuca

We investigated whether exposure to heavy metal pollution affected the immune function of individuals in a free living population of a small insectivorous passerine bird, the pied flycatcher Ficedula hypoleuca. We measured humoral immune responses in two study areas: a polluted area in the vicinity of a copper smelter and a control area far from the smelter. Plasma corticosterone level and blood heterophil/lymphocyte ratio (H/L) were used as more general physiological measures of stress. The immune response of F. hypoleuca was not suppressed by pollution stress. In contrast, we found that F. hypoleuca males showed stronger humoral immune responses to a novel antigen (tetanus toxoid) in the polluted environment than in the unpolluted one. After the immunization of males, numbers of lymphocytes rose significantly more in the polluted area, leading to a smaller H/L ratio than in males from the control area. Females showed no pollution related effects on their immune responses. Corticosterone levels of males and nestlings were not related to pollution levels. Nestlings showed somewhat higher H/L ratios and lower fledging success in the polluted area, both factors indicating increased stress levels in a polluted area. Our results suggest that humoral immune response of male F. hypoleuca may be enhanced under moderate levels of heavy metal pollution. Enhanced immune function may, however, also be costly for birds and the higher humoral immune responses in polluted areas may thus have negative effects on the birds’ breeding performance and survival.

Prey Escape Direction is Influenced by the Pivoting Displays of Flush‐Pursuing Birds

AbstractPainted redstart, Myioborus pictus, and its congeners in Central and South America, belong to a small fraction of insectivorous flush‐pursuing birds. Unlike most of the small insectivorous birds, which glean prey from substrates, the flush pursuers spread and pivot their conspicuously patterned tails and wings. This display triggers prey escape flights which are hypothesized to occur through visual stimulation of prey escape circuits [giant descending neuron cluster (GDNC) in Diptera] sensitive to the looming motion of an approaching bird, translational motion of a pivoting body with widely spread tail and contrast of the white‐black plumage pattern. In this paper, data from field observations of redstarts and experiments with bird models show an increase in the frequency of prey escapes away from the strong visual stimulation of an open tail, and in the direction opposite to that of the horizontal translational motion present in the pivots. We discuss how the effect on prey escape direction may enhance prey interception capabilities of redstarts during aerial pursuits. Combined with an earlier study the results show that, unlike the movements of typical gleaner–foragers, the flush displays by redstarts affect prey escape direction in a manner that may facilitate prey tracking and capture by birds. Because the GDNs, which mediate escape initiation, are not sensitive to motion direction, we hypothesize that other neurons, in addition to the GDNs, are involved in influencing the direction of escape responses.

A particular case and a general pattern: hyperaggressive behaviour by one species may mediate avifaunal decreases in fragmented Australian forests

We quantitatively assessed edge effects associated with elevated abundance of a hyper aggressive bird species, the noisy miner Manorina melanocephala, in fragmented eucalypt forest adjoining developed land. Long‐term data from Toohey Forest, subtropical Australia, show that noisy miner colonies intensively occupy a zone of 20 m from the forest edge, with frequent use occurring up to 100 m from the edge, but little beyond 200 m. Within noisy miner colonies, the abundance and species richness of other birds were both about half those recorded at nearby transects which were outside the colonies' main activity area. Bird species smaller than noisy miners, which are also those with similar diets, were collectively 20–25 times more abundant, and their species richness tenfold greater, outside miner colonies than within them, whereas larger species, which have less dietary overlap, did not differ. Exclusion of small insectivorous birds has been hypothesised to cause elevated insect herbivore density, but we found no difference between tree crown defoliation or dieback rates within versus outside miner colonies.Aggression by noisy miners can be viewed as a mechanism of interspecific competition, since miners have a relatively large body size for their diet and are hence able to exclude virtually all potential competitors at relatively little cost. We examine evidence indicating that reduced bird diversity in eucalypt forest fragments of eastern Australia is often simply the effect of noisy miner occupancy of edges, acting directly on the densities of other species through their aggressive behaviour. With an edge effect 200 m deep, a remnant 10 ha in size is likely to become entirely occupied by noisy miners, and this is a size threshold that has been commonly reported in association with area‐standardised avian diversity reductions. Convergent patterns of species loss from small forest fragments in different continents are the result of different underlying ecological processes.