Aerial Feeding Research Articles

Microfibers in the Diet of a Highly Aerial Bird, the Common Swift Apus apus.

Microplastic pollution is a pervasive global issue affecting various ecosystems. Despite the escalating production and well-documented contamination in both aquatic and terrestrial environments, the research focused on airborne microplastics and their interaction with terrestrial birds remains limited. In this study, we collected fecal sacs from Common swifts (Apus apus) to investigate their diet and to evaluate the potential ingestion of microplastics by both adults and nestlings. The diet was mainly composed of Hymenoptera and Coleoptera and did not differ among sexes and age classes. The 33% of nestlings' and 52% of adults' fecal sacs contained anthropogenic items, the totality of which was in the shape form of fibers. The 19.4% of the anthropogenic items were chemically characterized as microplastics, either polyethylene terephthalate (PET; two microfibers) or cellophane (four microfibers). Airborne anthropogenic items, including microplastic, might be passively ingested during the Common swift aerial feeding. In addition, our findings suggest that these ingested microparticles have the potential to be transferred to the offspring through food. While further research is essential to elucidate the pathways of microplastic ingestion, our results reinforce the evidence of the transfer of anthropogenic items from the atmosphere to the biota.

Demography of Common Swifts (Apus apus) breeding in the UK associated with local weather but not aphid biomass

In common with many other insectivorous birds, the Common Swift Apus apus is undergoing population declines, with an estimated 57% reduction in abundance between 1995 and 2017 in the UK. The ultimate drivers of this decline are poorly understood but links have been drawn to reductions in the abundance and availability of insect prey, as well as loss of nesting sites. The aim of this study is to improve understanding of the demographic and environmental drivers of Swift decline in Great Britain, with a particular focus on weather and aphid biomass. We explore spatio‐temporal trends in the biomass of aphids, an important source of food for these aerial feeders, from a network of 17 suction‐traps, each 12.2 m in length. We then use data from national nest recording and ringing schemes to describe temporal trends in, and covariates of, Swift breeding success and annual survival. Demographic data are sparse prior to the mid‐1990s but show stable adult survival, a reduction in first‐year survival and an increase in nest failure rate since the mid‐1970s. Despite marked declines in aphid biomass across much of southern and eastern England during this period, we find no association between aphid biomass and Swift demography. Weather was a stronger correlate of variation in Swift demography, with increased precipitation associated with smaller brood size, higher nest failure rate and lower first‐year survival. Our data suggest that falling first‐year survival, partly linked to wetter summers, may be the most likely demographic driver of population decline. Given that the only convincing correlates of Swift demography were weather‐related, we suggest it would be precautionary for conservation efforts to continue to focus on ensuring that safe and productive nesting sites are in sufficient supply. Further research to identify habitats and land management practices which provide foraging resources, particularly during periods of inclement weather, is required, and future demographic modelling exercises would benefit from increased nest recording and ringing efforts.

RECURRENT INGESTION OF GRIT BY COMMON NIGHTHAWKS (CHORDEILES MINOR)

Grit ingestion is widespread among birds, as an aid for grinding up food and as a dietary supplement of calcium, but is less common among insectivores, especially aerial feeders like nightjars (Caprimulgidae). I report recurrent visits by Common Nighthawks (Chordeiles minor) to a gravel driveway in British Columbia at dusk over a 4-y period. These ground visits were highly consistent (nighthawks landed during 93% of 72 dusk watches) and visits were highly concentrated both in time (95% of time on the ground between 10 and 57 min after sunset) and space (91% of the birds' time was spent in 2 areas comprising only 31% of the visible study site). Birds pecked at the ground in 97% of 198 focal-animal watches. In 43 visits the nighthawks picked up or swallowed some item; in 24 cases this was a small piece of gravel and no other items were identified. Surveys of ground arthropods in the study area over 3 y showed that potential prey were sparse (mean <2 insects m–2) and the most common insects were unsuitable prey (tiny 3-mm ants). I conclude that the only reason for the nighthawks to consistently visit this gravel area was to ingest grit. The gravel ingested was crushed limestone, which might support a calcium uptake hypothesis. Grit ingestion, occurring within a restricted dusk period, might not explain why nightjars often sit on gravel roads at night, which is a major source of mortality for several species. Information on ground behavior in Caprimulgidae is important for understanding their mortality risks and conservation.

Dietary analysis of the House Swift (Apus nipalensis) in Hong Kong using prey DNA in faecal samples

BackgroundTo understand the dietary composition of the highly aerial swift (Apodidae), ecologists conventionally depend on the morphological identification of prey items from food boluses or stomach contents, but these techniques are often invasive, require expertise in identification, and often cannot produce accurate identifications at the species level.MethodsDNA barcoding was used to analyse the dietary composition of House Swifts (Apus nipalensis) in Hong Kong, China. Faecal samples from five different colonial nest sites were collected between 2019 and 2020. We used universal primers to amplify a region of the cytochrome C oxidase gene from prey DNA in the faecal samples for identification purposes.ResultsTen different orders and 44 families from three different classes of Arthropoda were identified in the collected faecal samples. Hymenoptera, Hemiptera and Diptera were the most prevalent groups of prey found in the samples. Differences in the dietary composition of House Swifts during the breeding (April to September) and non-breeding (October to March) season were also found. Hymenoptera, particularly ants (Formicidae), were predominant in the diet during the breeding season, whereas Diptera and Hemiptera were predominant during the non-breeding season.ConclusionThe prey groups identified in this study were similar to those identified in a previous study of the diet of House Swift, which also suggests a possible role of House Swifts in reducing the numbers of local insect pests. This study demonstrates the usefulness of applying molecular tools for the dietary analysis of aerial feeders. Conserving local forested areas may be crucial for the maintenance of House Swift population.

Feeding Ecology, Behaviour and Habitat Utilization of Black Drongo (Dicrurus Macrocercus) in Pothwar Plateau, Pakistan

Black Drongo is an insectivorous bird native to Pakistan. The present study focused on its feeding preferences, behaviour, ecology and habitat relationships. The study was carried out from first week of December, 2019 to the second week of April, 2020 in the two villages of Rawalpindi named as Daultala (Location-I) and Nata Gujarmall (Location-II). Observations were made by point count method on foot using line transect method. Air (52.27%) was the most commonly used feeding substrate. Aerial feeding mode (52.27%) is preferred over plant or tree gleaning (n=58) and ground feeding (n=47). Most common perching site was man made obstacle, wire (37.72%). Thirteen indigenous tree species and two exotic trees including Eucalyptus (Eucalyptus camaldulensis) and Bottle brush (Callistemon citrinus) were used as perching site by Black Drongo throughout the study. Black Drongo remained solitary (36.36%) during feeding rituals and shared (63.63%) its intimate habitat with other birds. At Location-I and Location-II, habitat was shared with 12 and 16 bird species, respectively. The mean time of prey capturing attempt was lower at Location-I (1.93±0.17 min) than Location-II (2.16±0.16 min). The time range of prey capturing attempt was (0.1±0.16 min) to (11.5±0.17 min). Black Drongo captured prey successfully by first attempt (59.54%), maximum attempts noted were 6. After preying attempts Black Drongo came back to same perch site (67.27%); which is a representative of resource abundance.

Impact of routine Bacillus thuringiensis israelensis (Bti) treatment on the availability of flying insects as prey for aerial feeding predators

Since 1980, mosquito breeding habitats in the Upper Rhine Valley were routinely treated with Bacillus thuringiensis var. israelensis (Bti). Bti is considered to significantly reduce the number of mosquitoes, and - especially when used in higher dosages - to be toxic to other Nematocera species, e.g. Chironomidae, which could be food sources for aerial feeding predators. To investigate direct and indirect effects of routine Bti treatment on food sources for aerial feeding predators, the availability of flying insects in treated and untreated areas was compared. A car trap was used for insect collection, which allowed their exact spatiotemporal assignment. The statistical analysis revealed that insect taxa abundance was influenced differently by the factors season, temperature and time of day. Nematocera (Diptera) were the most frequently collected insects in all areas. Chironomidae were the predominant aquatic Nematocera. The comparison of treated and untreated sites did not show significant differences that would indicate any direct or indirect effect of routine Bti treatment on the availability of flying insects. Additional to food availability, food selection must be considered when investigating food resources for aerial feeding predators. In this study, food selection of Delichon urbicum (House Martin) as an example was investigated with the help of neck ring samples. The preferred prey of the investigated D. urbicum colony consisted of diurnal insects with terrestrial larvae (Aphidina, Brachycera, Coleoptera). Chironomidae were consumed, but not preferred.

Evolution of island warblers: beyond bills and masses

In this paper, we take a closer look into the evolution of Acrocephalus warblers on islands in the Atlantic, Indian and Pacific Oceans. The shape‐related morphological evolution of island species is characterized by changes in the hind limb, flight, and feeding apparatus. Birds on islands converged to a morphology with strong legs, shorter rictal bristles, and rounder, more slotted and broader wings. Because of their high variance among islands, body size and bill dimensions did not contribute to the separation of continental and island forms, although bills tend to be longer on islands. The wings of island birds hardly vary among islands, unsurprisingly due to a lack of the adaptive features associated with long distance flights. The tendency towards shorter rictal bristles in the island warblers can be explained by the diminished role of aerial feeding, and closer contact with various substrates in the course of extractive foraging. The shift towards stronger legs in several insular species is remarkable because reed warblers on continents have even stronger legs than other passerines of comparable size. This trait correlates with diverse, acrobatic feeding techniques that are typically associated with broad habitat use. Bills reach extreme lengths on some islands. However, short bills occur as frequently, rendering this character highly variable among islands. Short bills indicate gleaning feeding techniques, whereas long bills are typical for species that pursue hidden and difficult‐to‐access prey. Body sizes differ greatly from island to island. On average, the sizes of island birds do not differ from continental ones, however. We suggest that vegetation clutter is the major driving force for this variation.The main conclusion following from our results is that evolution on islands pertains to all functional complexes, and not only the hitherto studied body size and bill dimensions.

Black-headed Gulls Chroicocephalus ridibundus capturing chironomids in flight: have flight costs been overestimated?

The diurnal and seasonal occurrence of flight foraging for midges (Chironomidae) by Black-headed Gulls Chroicocephalus ridibundus was studied at a shallow semi-eutrophic lake in South Sweden and their capture rates were recorded. The gulls captured 0.28 chiromids s(-1) (1,012 h(-1)). With a dry mass of 2.08 mg ind(-1) and an energy content of 22.7 kJ g(-1), they achieved an energy intake of c.47 kJ h(-1). It seems that estimates of flight costs may have been over-estimated, and it is concluded that aerial feeding on chironomids by Black-headed Gulls results in a positive energy balance.

Factors affecting the use of waste-stabilization ponds by birds: A case study of conservation implications of a sewage farm in Europe

The progressive loss of natural wetlands globally means that anthropogenic water reservoirs are increasingly important as habitat for wetland bird species. During yearly bird counts (in one-week intervals) on seven waste-stabilization ponds (size range=0.379–4.450ha; total=8.392ha) located on a large sewage farm in a Wrocław city suburb (south-west Poland), I recorded a total of 7776 individuals from 84 bird species. The most numerous bird guild was waterbirds (45.8% of the community), followed by shorebirds (35.7%), passerines (14.9%) and aerial feeders (3.5%). In general, the density (including all bird guilds) and species diversity of birds was positively related to the bed exposure and ‘naturalness’ (artificial≈small ponds with preliminary treatment versus natural≈large ponds after preliminary treatment) of the waste-stabilization ponds. The compulsory European Union (EU) law regulating urban wastewater treatment (The Council Directive 91/271/EEC, Urban Waste Water Treatment Directive) does not permit use of open sewage farms as a method of treatment for domestic and other wastewater. In many new EU member states, the sewage fields are still used, although this method of sewage treatment will function only until 2015, and after that all wastewater must be purified in modern sewage treatment works. It is recommended that areas historically used as sewage farms located on the outskirts of large cities should be converted into protected areas. However, due to the contamination of invertebrates that inhabit and emerge from sewage treatment works, and the potential high risk of detrimental effects on bird species that feed on such prey, empty waste-stabilization ponds should be re-filled with clean natural water sources such as rain and spring water or alternatively with well-treated waste water. The strategy for managing such areas requires a proper water regime and maintenance of the periodically dry bottom, a crucial feeding area for birds.

Diet breadth and overlap in three sympatric aerial insectivorous birds at the same location

Capsule We found significant differences in the composition and diversity of diet among House Martins, Barn Swallows and Swifts breeding in the same village in Poland.Aims To evaluate the character and extent of diversity, specialization and overlap of diet between trophically similar nestlings of three species of aerial feeding birds breeding at the same location and differing considerably in foraging height.Methods Diet was determined based on faecal analysis. Differences in composition and diversity of diet and food niche overlap were assessed through multivariate analysis of variance (manova), Shannon Diversity Index and the Pianka index. Diet specialization was measured by application of the Berger–Parker index of dominance.Results manova indicated significant differences in diet composition among all three species. House Martins showed the most diverse diet, Swallows were intermediate and Swifts least diverse. Average body mass of all prey found in the diet of Swifts was nearly three times smaller than in Swallows and two times smaller than in House Martins.Conclusion Our findings show that these three species consume the same types of insect prey, but they take different proportions, and hence biomass, of the major prey groups. House Martins had the widest niche and greatest overlap.

The ecological energetics of birds in New Guinea

The energetics of 79 species of birds living in greater New Guinea, data for 44 of which are presented here for the first time, is examined to determine the extent to which it reflects the behavior of species and the conditions they encounter in the environment. Body mass alone accounts for 86.6% of the variation in the basal rate of metabolism of these species, whereas the combination of body mass, foraging sub- strate, flightless condition, activity, and life on islands or continents collectively account for 95.2% of its variation. When the passerine/non-passerine dichotomy is added to the analysis, the six factors account for 96.7% of the variation in basal rate. Basal rate also correlates with other factors, including maximal altitude of distribution, torpor, and food habits when individually combined with body mass, but they lose significance when other factors are brought into the analysis. Altitudinal limits to distribution can be included in the analysis only if activity is dropped because of the correlation between these factors. Torpor correlates with an aerial feeding strategy. Food habits correlated with activity level and the passerine/non-passerine dichotomy. The attempt to account for the variation in the energetics of birds by a phylogenetic analysis is inappropriate because the fundamental basis of energetics is physiological with strong behavioral and ecological overtones. Body mass accounts for 90.4% of the variation in thermal conductance. The regulated level of body temperature varies from ca. 39 to 41°C at masses &gt; 100 g, below which it decreases to 37 and 39°C at 10 g, with a few small species having body temperatures as low as 35°C. New Guinea is an important source for the terrestrial avifauna of South Pacific islands. The characteristics of its birds therefore are appropriate standards by which to judge the adjustments occurring in, and required of, birds endemic to these islands.

Corticosterone secretion patterns prior to spring and autumn migration differ in free-living barn swallows (Hirundo rustica L.)

Recent studies of long-distance migratory birds show that behavioural and physiological changes associated with predictable or unpredictable challenges during the annual cycle are distinctively regulated by hormones. Corticosterone is the primary energy regulating hormone in birds. Corticosterone levels are elevated during stresses but they are also modulated seasonally according to environmental conditions and life-history demands. We measured the baseline and stress-induced levels of corticosterone in the barn swallow (Hirundo rustica L.) just before spring and autumn migrations in South Africa and Finland, respectively. Barn swallows completing their pre-breeding moult had low body condition (residual body mass) and high baseline corticosterone levels in the wintering grounds. In contrast, baseline corticosterone levels in Finland were low and not related to residual mass. These data contradict the first prediction of the migration modulation hypothesis (MMH) by showing no association with baseline corticosterone levels and pre-migratory fuelling. Yet, the adrenocortical response to the capture and handling stress was notably blunted in South Africa compared to a strong response in Finland. Further, individuals that had started fuelling in Finland showed a reduced response to the handling stress. Taken together, elevated baseline corticosterone levels and high residual mass may blunt the adrenocortical response in long-distance migrants and aerial feeders such as the barn swallow. This observation lends support to the second prediction of the MMH.

THE NEARCTIC-NEOTROPICAL BIRD MIGRATION SYSTEM

ABSTRACT A review of the Nearctic—Neotropical migration system reveals that: (1) 90% of breeding land and fresh-water species in the sub-Arctic are migrants, 80% in southern Ontario, and 50–60% in Florida and Arizona. (2) Insectivorous Parulinae winter from 30°N to 10°S; seed-eating Emberizinae from 40° to 15°N; aerial feeding Tyrannidae and diurnal birds-of-prey trans-equatorially; and ducks from 50° to 5°N. (3) Co-occurrence of migrant species is facilitated by geographic and habitat allopatry, varying levels of ecological distinctness, sparse dispersal, and, sometimes, intraspecific spatial separation of sexes and age-groups. (4) Migrant—resident co-occurrence is facilitated by high proportions of the two belonging to different taxonomic and ecological groups and, within families, partial feeding zone and habitat segregation. All, however, draw on a common food pool. Too little is known about the winter food support base, differential habitat utilizations, species abundances, and biological needs, eith...

Bird traits in urban–rural gradients: how many functional groups are there?

Recent analyses of communities have examined the variation of species traits along environmental gradients. These papers highlight a combination of several traits, instead of variation of individual traits, to better explain the effect of urbanization on bird communities. Exploratory factor analysis (EFA) allows the identification of an underlying structure of a broad set of data. EFA can be a useful tool for generating functional groups from highly correlated biological traits in bird communities and determining its variation along gradients of urbanization. Birds were counted along an urban–rural gradient during spring 2009–summer 2010. Species were classified using 15 biological traits related to the use of space. The EFA was calculated from a matrix where rows were sampling units (n = 75), and columns represented counts of individuals with each trait (n = 15). Four functional groups were obtained. Functional group 1 comprised resident species feeding gregariously on the grond, nesting in buildings, having an omnivorous diet, and being most abundant in the more urbanized areas. Functional group 2 was most abundant at intermediate levels of urbanization and represented solitary species that nest in trees, feeding on vegetation and with carnivorous and nectarivorous diets. Migratory behavior, insectivorous and granivorous diets, aerial feeding and ground nesting were representative of two functional groups in rural areas. Responses to urbanization by these functional groups are consistent with the classifications of response guilds (urban exploiters, urban adapters, and urban avoiders). Thus, EFA allows a link between concepts generated from the analysis of species and the analysis based on biological traits.

自動車のヘッドライトで攪乱されたサヨリ&lt;i&gt;Hyporhamphus sajori&lt;/i&gt; のウミネコ&lt;i&gt;Larus crassirostris&lt;/i&gt; による空中採餌

北海道函館市小安漁港で，ウミネコLarus crassirostris によるサヨリHyporhamphus sajori の夜間採餌を観察した。サヨリは自動車のヘッドライトに照らされた海面から飛び出したところを，ウミネコに空中で捕食されていた。本報告は，人工光が餌生物を攪乱するというユニークな方法で，海鳥に夜間採餌の機会を与えることを示した。

Creating ephemeral resources: how long do the beneficial effects of grass cutting last for birds?

CapsuleBeneficial effects of cutting grass are relatively short-lived for a range of bird species. AimsTo investigate how cutting affects a range of birds occurring on farmland, how long these effects last, and whether there is any effect of the timing of cutting operations. MethodsWe surveyed birds on 33 grass fields on three farms in northern England, both before and after agricultural cutting operations. The data were then modelled using generalized linear mixed models (GLMMs). Results Species relying on below-ground invertebrates (e.g. corvid species) prefer cut swards, while some species make greater use of longer grass swards (e.g. pheasant). Use of fields after cutting declined by 50 % by day 11 for corvids, by day 8 for aerial feeders (e.g. hirundines), by day 6 for gulls, and by day 4 for kestrels. ConclusionsWe recorded mainly common, generalist species that make use of agricultural grassland. The foraging behaviour of these species is similar to other, rarer or declining species, and so our findings can be extrapolated to a range of farmland birds. However, it is important to note that some studies indicate direct negative effects of cutting on some species not found in our surveys.

Trophic niche partitioning of cryptic species of long-eared bats in Switzerland: implications for conservation

Dietary niche partitioning is postulated to play a major role for the stable coexistence of species within a community, particularly among cryptic species. Molecular markers have recently revealed the existence of a new cryptic species of long-eared bat, Plecotus macrobullaris, in the European Alps. We studied trophic niches as well as seasonal and regional variations of diet in eight colonies of the three Plecotus species occurring in Switzerland. Faeces were collected monthly from individuals returning to roost after foraging. Twenty-one arthropod categories were recognized from the faeces. All three species fed predominantly on Lepidoptera, which made up 41%, 87% and 88% (means across colonies) of the diet composition of P. auritus, P. macrobullaris and P. austriacus, respectively. The occurrence of numerous fragments of both diurnal and flightless insects in the diet of P. auritus (but rarely in the diet of the other two species) indicates that this species mostly gleans prey from substrates. P. austriacus and P. macrobullaris are more typical aerial feeders. The latter two species have narrow trophic niches, whilst P. auritus has a much broader diet. Comparison of intraspecific and interspecific niche overlaps in P. auritus and P. macrobullaris in sympatry suggests dietary niche partitioning between these two species. In contrast, the high similarity of the trophic niches of P. austriacus and P. macrobullaris, associated with a typical parapatric distribution, indicates competitive exclusion. The best conservation measures are preservation and restoration of habitats offering a high abundance of moths, the major prey of the three Plecotus species.

Summarizing Spatial Distribution Density, Movement Patterns and Food Resources to Study the Impacts of Logging and Forest Conversion on Orang-utan Population

Problem statement: Orang-utan is classified as a totally protected species and is listed as an endangered species in Borneo. The survival of this species is highly dependent on the existence and quality of the lowland forest of Sabah. However, most of the pristine habitats in the lowland area have been converted into other land use activities such as a large scale plantation. This is due to the fact that most of the lowland forests are facing a continuous degradation process that will decrease its commercial value when it comes to generating revenue to the state government. Thus, the efforts to restore the forest are very vital. The main objectives of this study include establishing the relative spatial distribution of orang-utan in order to assess and determine the effects of the forest conversions in four main wild orang-utan population landscape, demonstrating the orang-utan population movement pattern as a response to the heavy logging activities and also quantifying the effect of logging activities on the status of food trees or plant species for orang-utan in their current forest habitat. Approach: In this research, relevant features are constructed in order to study the impacts of logging and forest conversion on Orang-utan population in Borneo. These features include aerial surveys and feeding behaviors. An aerial survey on orang-utan’s nest in four out of six main forest habitats for orang-utan in Sabah has been conducted between May 2005 and June 2009 in order to map the relative distribution and spatial density of the orang-utans. This is conducted in order to determine the impacts of the forest conversion for the last 20 years upon the orang-utan spatial distribution. In this project, three series of aerial surveys, covering Malua Forest Reserve, have been conducted to demonstrate the dynamic movement and habitat utilization by the orang-utan population, due to the logging activities within the forest habitat. A long term observation of the orang-utan feeding behavior in the degraded forest in North Ulu Segama (NUS) has been also conducted to determine their feeding ecology in a logged over forest. Results: This study suggested that (i) forest conversion and logging activities have effects on the orang-utan habitat utilization and movement pattern; (ii) due to the influx of the forest conversion, some of the orang-utan in the forest reserve is concentrated in certain area, adjacent to the boundary of the forest reserve due to their movement limitation by the river network; (iii) the orang-utan population in degraded forest of NUS consumed almost different species of food plants in 2009, compared to year 1974. Conclusion: These results demonstrated that forest conversion and unsustainable logging activities are the main threat for the orang-utans conservation in Sabah. Therefore, the conservation of orang-utan populations are not guaranteed by the establishment of more protected area, but by ensuring that more forest habitats can be managed in sustainable way in order to avoid further forest degradation and to ensure their habitats remain connected to the large forest landscape.

A multi-gene phylogeny disentangles the chat-flycatcher complex (Aves: Muscicapidae)

Zuccon, D. & Ericson, P. G. P. (2010). A multi-gene phylogeny disentangles the chat-flycatcher complex (Aves: Muscicapidae).—Zoologica Scripta, 39, 213–224. We reconstructed the first well-sampled phylogenetic hypothesis in the chat-flycatcher complex combining nuclear and mitochondrial sequences. The dichotomy between chats-terrestrial feeders and flycatchers-aerial feeders does not reflect monophyletic groups. The flycatching behaviour and morphological adaptations to aerial feeding (short tarsi, broad bill, rictal bristles) evolved independently from chat ancestors in three different lineages. The genera Alethe, Brachypteryx, and Myiophonus are nested within the Muscicapidae radiation and their morphological and behavioural similarities with the true thrushes Turdidae are presumably the result of convergence. The postulated close relationships among Erithacus, Luscinia and Tarsiger cannot be confirmed. Erithacus is part of the African forest robin assemblage (Cichladusa, Cossypha, Pogonocichla, Pseudalethe, Sheppardia, Stiphrornis), while Luscinia and Tarsiger belong to a large, mainly Asian radiation. Enicurus belongs to the same Asian clade and it does not deserve the recognition as a distinct subfamily or tribe. We found good support also for an assemblage of chats adapted to arid habitats (Monticola, Oenanthe, Thamnolaea, Myrmecocichla, Pentholaea, Cercomela, Saxicola, Campicoloides, Pinarochroa) and a redstart clade (Phoenicurus, Chaimarrornis and Rhyacornis). Five genera (Muscicapa, Copsychus, Thamnolaea, Luscinia and Ficedula) are polyphyletic and in need of taxonomic revision.

Foraging behavior of selected insectivorous birds in Cauvery Delta region of Nagapattinam District, Tamil Nadu, India

This paper reports the foraging behavior of five insectivorous birds, namely White-breasted Kingfisher Halcyon smyrnensis, Small Bee-eater Merops orientalis, Indian Roller Coracias benghalensis, Common Myna Acridotheres tristis and Black Drongo Dicrurus macrocercus in Nagapattinam District of Tamil Nadu, India. The birds used a variety of perch types for hunting insect prey; in general the electric power line was a common perch type used by all species except the Common Myna. The perching and foraging height used by birds were classified into 3 meter categories, up to 12m. Aerial feeding or hawking in Bee-eaters and ground feeding in Common Mynas were major feeding techniques, recorded 68% and 86% of the time respectively. The other three species used gleaning as a feeding technique. The highest niche overlap was recorded between Indian Rollers and Black Drongos and between White-breasted Kingfishers and Indian Rollers.