Common Blackbird Turdus Merula Research Articles

Internal Architecture Differentially Affects Thermal Insulation in the Walls of Common Blackbird Turdus merula Nests

Nest construction may result in niche creation by the bird, i.e., modification of the immediate environment in terms of temperature or humidity. Here thermal insulation of nests of the Common Blackbird Turdus merula was investigated using a heat source placed inside the cup. The temperature profile of the nest wall was recorded using thermistors placed at different positions in the nest wall. Temperatures were affected by the layers in the wall with the grass cup lining and mud cup offering more insulation than the outer wall. Thermal conductance of the wall of Common Blackbird nests was relatively high compared to other reports for this variable in other passerine species from Australia. Variation among Common Blackbird nests in terms of temperature differences across layers, and thermal conductance overall, correlated with the thickness of the grass cup lining. Thermal insulation provided by a nest wall is dependent on the thicknesses and types of materials used in each part of the wall. Previous studies using nest deconstruction have demonstrated that the various layers in a wall have differing thermal characteristics. This is the first report of clear differences in the temperature profile across the different parts of the intact nest wall. Whether this pattern is also observed in nests of other species requires further investigation. The placement of different materials within the nest wall by the bird is not a random process and the results support the idea that the avian nest is involved in niche creation.

New records of feather mites of the genus Proctophyllodes (Acariformes: Proctophyllodidae) in China

A new feather mite species Proctophyllodes gracilitus sp. nov. is described from the mountain bulbul Ixos mcclellandii (Horsfield) (Passeriformes: Pycnonotidae) in China. The new species belongs to the mecistocaulus species-group and differs from the most similar species, P. stenophyllus Gaud & Mouchet, 1957, by having the following characters: in males of P. gracilitus, the terminal lamellae are thinner and longer (45–49×4–5) and the posterior part of the hysteronotal shield has circular lacunae; and in females setae h1 are situated at the level of posterior margin of supranal concavity, setae h2 are longer than terminal appendages, do not have enlargement in base, and setae h3 are about 2/3rds the length of terminal appendages. In addition, Proctophyllodes weigoldi Vitzthum, 1922 has been collected from the willow tit Poecile montanus (Baldenstein) (Passeriformes: Paridae) that is a new host record for this species. This species is redescribed, because it was found that specimens from Po. montanus have some minor morphological differences from specimens of the common blackbird Turdus merula Linnaeus (Passeriformes: Turdidae) (a type host) and eyebrowed thrush Turdus obscurus Gmelin (Passeriformes: Turdidae).

Sex and age differences in the diet of the Eurasian Sparrowhawk (Accipiter nisus) using web‐sourced photographs: exploring the feasibility of a new citizen science approach

Diet differences between the sexes and ages have often been recorded for bird species. Many raptor species show extreme sexual size dimorphism, with females often considerably larger than the males and these differences may be reflected in their diets. Diet studies in raptors most frequently focus on analysing prey remains or pellets collected at nest‐sites. These methods are subsequently limited to breeding birds in the breeding season and are also restricted by their inability to distinguish prey items between the sexes. The use of web‐sourced photographs to examine raptor diet has the potential to overcome some limitations of more traditional methods used to assess diet. We used this approach for the Eurasian Sparrowhawk Accipiter nisus in the United Kingdom, exploring diet between the sexes and ages throughout the entire year. In total, we obtained 843 web‐sourced photographs of Sparrowhawks with their prey items. There were 12 key prey items that had a frequency ≥ 10 in the Sparrowhawk diet: Common Wood Pigeon Columba palumbus, Common Starling Sturnus vulgaris, Eurasian Collared Dove Streptopelia decaocto, Rock Dove Columba livia, Common Blackbird Turdus merula, House Sparrow Passer domesticus, unidentified ‘small’ and ‘medium’ birds, European Goldfinch Carduelis carduelis, European Greenfinch Chloris chloris, Eurasian Blue Tit Cyanistes caeruleus and Stock Dove Columba oenas. Several prey species were more often seen in the diet of one sex or age group. Overall, average prey weights of adult females were two and a half times heavier than for adult males and one and a half times heavier for juvenile females. However, this method may be slightly biased towards larger prey items, which should be considered in future studies. Despite this limitation, our method enabled dietary differences between the sexes and ages of this highly sexual size dimorphic raptor species to be explored throughout the year.

The Shetland Bird Survey: population trends for widespread breeding birds 2002–2019

ABSTRACT Capsule Population trends are estimated for the first time for 12 species based on Shetland Breeding Bird Survey data collected between 2002 and 2019. Aim To provide population trends for a selection of commoner breeding waders and passerines on the Shetland Isles, the most northerly region of the UK, which has historically been under-represented in national bird monitoring schemes. Methods One hundred and forty-five self-selected 1-km2 squares were surveyed between 2002 and 2019 using similar methods to the BTO/JNCC/RSPB Breeding Bird Survey (BBS), the main breeding bird monitoring scheme in the UK. Results Over 17 years, Eurasian Oystercatcher Haematopus ostralegus, Northern Lapwing Vanellus vanellus, and Common Redshank Tringa totanus populations declined whilst Eurasian Curlew Numenius arquata and Common Snipe Gallinago gallinago showed no significant changes in their population trends. For passerines, Common Skylark Alauda arvensis and Northern Wheatear Oenanthe oenanthe populations declined, whilst Common Starling Sturnus vulgaris, Common Blackbird Turdus merula, and House Sparrow Passer domesticus increased. Winter Wren Troglodytes troglodytes and Meadow Pipit Anthus pratensis showed no significant population changes. Comparisons with BBS trends for the UK and for Scotland are provided. For Eurasian Curlew, Common Starling, and House Sparrow, trends were more favourable in Shetland than elsewhere in UK. Conclusion The Shetland Breeding Bird Survey provides useful trends for several bird species, which include important breeding numbers of Winter Wren and Common Starling (both endemic subspecies), as well as nationally important wader populations. We recommend increasing the number of survey squares sampled each year, which would increase the precision of population estimates. The inclusion of a random or stratified element to square selection would help to ensure that these trends are representative of the wider region.

Wall Structure Affects Insulation of Nests Built by Thrushes

Incubation and rearing of nestlings are energetically demanding activities that can be affected by insulation conferred by the nest wall. Although thermal properties of nests are widely studied, no reports to date have dealt with the relative effects of the various structural parts of the nest wall. This experimental study investigated the effects of air movement, and for the first time, the effects of wall structure, on nest insulation for the Common Blackbird Turdus merula and Song Thrush Turdus philomelos of the Turdidae. Insulatory values, i.e. difference in cooling rate measured simultaneously inside and outside a nest, and internal cooling rates within the nest cup, were determined using temperature loggers under still-air and moving-air conditions. Moving-air increased insulatory values and internal cooling rates in both species. Insulatory values were positively correlated with the nest base thickness, but not nest side wall thickness. Removal of the outer nest wall and cup lining to reveal the internal mud cup of thrush nests reduced the insulatory value compared to the whole nest, the effect of which was exacerbated under moving-air conditions. These results may reflect that the nest wall confers huge insulatory advantages and especially so during periods of air movement. However, it is unclear whether this is related to the presence of particular nest materials that confer insulation, or to the amount of air trapped in the nest wall. Alternatively, the thermal conductivity of the materials lining the cup wall may be important.

First record of Common Blackbird Turdus merula nests built in a reedbed

ABSTRACT In May 2020, during our study on the breeding ecology of the Eurasian Reed Warbler Acrocephalus scirpaceus, we found two nests of Common Blackbird built within an unmanaged reedbed. The distance between the nests and dry land, overgrown by deciduous forest, was about 25 m. One of the nesting attempts was successful while the second was deserted during the incubation stage. To our knowledge this is the first record of Blackbirds nesting in reeds. This observation supports the notion of great flexibility of nest-site selection in this species. We conclude that Blackbirds use reedbeds as a nesting site more often, but such nests may be easily overlooked.

Diet of Eurasian Sparrowhawks in a Northwest Iberian Hedgerow Habitat throughout the Year

Abstract Little is known about Eurasian Sparrowhawk Accipiter nisus feeding habits outside the breeding season in its wide geographical range. The present study concerns the autumn-winter and spring-summer diet of this raptor species in Northwest Spain in a hedgerow habitat. A total of 23 avian prey species were recorded, only six of which occurred in both periods of the year. However, Eurasian Sparrowhawks fed mainly on medium-sized birds that often forage on the ground at some distance from shrubs and trees, mostly the Song Thrush Turdus philomelos and the Common Blackbird Turdus merula, both species together accounting for approximately half of the prey in any season of the year. The contribution of larger birds, i.e., pigeons, was considerable in terms of ingested biomass. In spring-summer, the mean body weight of avian prey was over 15 g less than in autumn-winter.

Abstract

Restricted accessAbstractFirst published online June 1, 2016AbstractVolume 9, Issue 2https://doi.org/10.3184/175815516X14552091807559

Common blackbirds Turdus merula use anthropogenic structures as nesting sites in an urbanized landscape

Abstract The common blackbird Turdus merula is one of the most highly urbanized bird species. However, to date, the use of anthropogenic structures as nesting sites in the common blackbird is rarely documented, and the factors influencing its use of the anthropogenic structures as nesting sites remain unclear. In this study, we systematically quantified and determined the factors influencing the use of anthropogenic structures as nesting sites in common blackbirds in a highly urbanized city of Hangzhou, China. We searched for nests of common blackbirds during four breeding seasons from 2010 to 2013. Among the 60 nests found, 34 nests were in anthropogenic structures such as wall ledges, air condition mounts, window canopies, cable poles, guardrails, eaves, balcony frames, flowerpots and flower shelves on balconies. We found that the available anthropogenic nest sites and the available nesting trees were main factors determining the use of anthropogenic structures as nesting sites in common blackbirds. In urban environments, the amount of available anthropogenic nesting sites increased significantly, whereas the number of natural nesting sites reduced greatly. Our results suggest that common blackbirds can adjust their nest sites in response to urbanization and such nesting behavior shifts may aid them to colonize urban environments. From a management viewpoint, our results indicate that behavioral flexibility should be taken into account for effective urban wildlife management and conservation.

Nest desertion cannot be considered an egg‐rejection mechanism in a medium‐sized host: an experimental study with the common blackbird Turdus merula

Two main mechanisms of egg rejection, the main defence of hosts against brood parasites, have been described: ejection and desertion. Desertion of the parasitized nest is much more costly and is usually exhibited by small‐sized host species unable to remove the parasitic egg. However, nest desertion is frequently assumed to be an anti‐parasite strategy even in medium or large‐sized host species. This assumption should be considered with caution because: 1) large‐sized hosts able to eject the parasitic egg should eject it rather than desert the nest, and 2) breeding birds may desert their nests in response to different disturbances other than brood parasitism. This problem is especially important in the common blackbird Turdus merula because this is a medium‐sized species, potential host of the common cuckoo Cuculus canorus, in which desertion has been frequently reported as a response to cuckoo egg models. Here, we seek to determine whether nest desertion can be considered a response unequivocally directed to the parasitic egg in medium‐sized hosts using the blackbird as the study species. In an experimental study in which we have manipulated levels of mimicry and size of experimental eggs, we have found that both colour (mimetic and non‐mimetic; at least for human vision) and size (small, medium, and large) significantly affected ejection rates but not nest desertion rates. In fact, although large eggs disproportionally provoked nest desertion more frequently than did small or medium‐sized eggs, cuckoo‐sized parasitic eggs were not deserted allowing us to conclude that desertion is unlikely to be an adaptive response to brood parasitism at least for this species.

Morphology and biomechanics of the nests of the Common Blackbird Turdus merula

Capsule Common blackbirds select different materials, with varying biomechanical properties, to construct different parts of their nest.Aims This study tested the hypothesis that outer components of a nest have a more structural role and so are stronger than materials used to line the cup.Methods Blackbird nests were measured prior to being dismantled to isolate structural components which were tested for mechanical strength and rigidity.Results Outer nest wall materials were significantly thicker, stronger and more rigid than materials in the inner structural wall or the cup lining. In the vertical plane materials used in the structural wall did not differ. By contrast, lining materials from the bottom of the nest cup were significantly thicker, stronger and more rigid than materials from the top of the cup.Conclusion Blackbirds use different materials in nest construction roles suited to their properties and so may be able to recognize the structural properties of these materials. Materials on the outside of the nest may have a key structural role during construction.

Haemoproteus minutus and Haemoproteus belopolskyi (Haemoproteidae): Complete sporogony in the biting midge Culicoides impunctatus (Ceratopogonidae), with implications on epidemiology of haemoproteosis

Species of Haemoproteus (Haemoproteidae) are cosmopolitan haemosporidian parasites, some of which cause severe diseases in birds. Numerous recent studies address molecular characterization, distribution and genetic diversity of haemoproteids. However, the information about their vectors is scarce. We investigated sporogonic development of two widespread species of Haemoproteus (Haemoproteus minutus and Haemoproteus belopolskyi) in the experimentally infected biting midge Culicoides impunctatus. Wild-caught flies were allowed to take blood meals on naturally infected common blackbirds Turdus merula and icterine warblers Hippolais icterina harboring mature gametocytes of H. minutus (lineage hTURDUS2) and H. belopolskyi (hHIICT1), respectively. The engorged flies were collected, transported to the laboratory, held at 15–18°C, and dissected daily in order to obtain ookinetes, oocysts and sporozoites. Mature ookinetes of H. minutus developed blisteringly rapidly; they were numerous in the midgut content between 1 and 4h post exposure. Ookinetes of H. belopolskyi developed slower and were reported 1day post exposure (dpe). Oocysts of both parasites were seen in the midgut wall 3–4dpe. Sporozoites of H. minutus and H. belopolskyi were first observed in the salivary glands preparations 7dpe. The percentage of experimentally infected flies with sporozoites of H. minutus was 82.1% and 91.7% with H. belopolskyi. In accordance with microscopy data, polymerase chain reaction amplification and sequencing confirmed presence of the corresponding parasite lineages in experimentally infected biting midges. Sporogonic stages of these parasites were described and illustrated. This study indicates that C. impunctatus is involved in the transmission of deadly H. minutus, which kills captive parrots in Europe. This biting midge is an important vector of avian haemoproteids and worth more attention in epidemiology research of avian haemoproteosis.

Is nest predation an important selective pressure determining fecal sac removal? The effect of olfactory cues

The removal of nestling feces by adults is a common parental behavior in birds. However, this behavior is still poorly understood despite being an important component of parental care, especially in altricial bird species. The threat of nest predation is a major factor that influences many parental activities at the nest and, therefore, it could also be an important selective pressure determining fecal sac removal. To date, this ‘Nest Predation Hypothesis’ has not been tested despite being proposed more than a century ago. Furthermore, it is important to determine whether it is the olfactory and/or visual components of fecal sacs that attract predators. In this study, we have manipulated the presence of real droppings of Common Blackbird (Turdus merula) nestlings in active nests by hiding fresh fecal sacs (experimental), mud (control) or nothing (manipulation control) in a commercial Canary nest attached below natural nests. Our results showed that the presence of fecal sacs did not reduce the daily survival rate of experimental nests in comparison with the other two treatments. It would therefore appear that predation risk is not a selection pressure that maintains feces removal in nests of the Common Blackbird, at least in relation to the olfactory component of the feces. To date, all evidence suggests that this aspect of parental behavior could be affected by other selective pressures (i.e. parasitism) rather than nest predation. Nevertheless, the effect of the visual cues produced by fecal sacs should be further investigated before the Nest Predation Hypothesis is completely discarded.

Parasitic helminthes — probable cause of death of birds

Abstract Parasitic helminths were the probable cause of death of 41 passeriform birds (29 adults and 12 juveniles in their first year of life) caught in the net during the spring and autumn ringing (1986–2010). The birds (1 Chaffinch Fringilla coelebs, 1 House Martin Delichon urbica, 2 Blue Tit Cyanistes caeruleus, 9 Great Tit Parus major, 3 Willow Tit Poecile palustris, 1 Great Reed Acrocephalus arundinaceus, 1 Chiffchaff Phylloscopus collybita, 3 Blackcap Sylvia atricapilla, 2 Dunnock Prunella modularis, 1 Magpie Pica pica, 5 Robin Erithacus rubecula, 9 Common Blackbird Turdus merula and 3 Song Thrush T. philomelos) were caught in the environs of Přerov (Czech Republic). The helminths: trematodes, tapeworms, nematodes and hook worms, were located in the intestine, glandular and muscular stomach, cloaca, rectum, gall bladder, liver, pulmonary cavity, air sac, nasal and orbital cavity and subcutaneous tissue of the hosts. The intensity of invasion with different species of parasites was up to 734 per host. Some parasites Brachydistomum ventricosum, Mosesia sittae, Aprocta cylindrica, Diplotriaena tridens were acquired at the wintering grounds. All the helmniths were heteroxenous, with development cycle involving intermediate hosts (invertebrates) which are part of the birds’ diet.

Do passerine birds utilise artificial light to prolong their diurnal activity during winter at northern latitudes?

Boreal regions with a mild winter climate, such as the western coastal area of Norway, may hold a number of wintering passerine birds, in spite of the short day length in mid winter. To determine whether birds wintering under such conditions were able to use artificial light to increase their activity periods, day-time and night-time bird censuses were done from October to March in a residential area in Bergen, western Norway, along roads lit by street lights. Situated at latitude 60°N, the area has 18 hours of darkness in mid winter. Twenty-four passerine species were recorded. Of these European Robin Erithacus rubecula, Common Blackbird Turdus merula, and Eurasian Wren Troglodytes troglodytes regularly started their activity several hours before sunrise, whereas Great Tits Parus major and Blue Tits Cyanistes caeruleus did so to some extent. The other species did not start their activity until morning civil twilight. Measurements of distance from street lights for European Robins during night-time showed that the birds were closer than random to lights. The study shows that some passerine species are able to extend their activity period by 4-5 hours utilising artificial light during the darkest part of the winter .

Does song repertoire size in Common Blackbirds play a role in an intra-sexual context?

Bird song is thought to have a function in both inter- and intra-sexual contexts with song complexity serving as an honest signal of male quality. Theory predicts that males use repertoire sizes to estimate rivals’ fighting ability. Here we tested whether element repertoire size plays a role in an intra-sexual context in the Common Blackbird Turdus merula, a songbird with a large repertoire. In a territory intrusion playback experiment, we broadcast Common Blackbird song with different element repertoire sizes to territorial males. The test birds did not respond differently to the different repertoire sizes. This was also the case when we considered the test birds’ own repertoire sizes in the analysis. Thus, we found no evidence for the hypothesis that males use repertoire size for estimating rivals’ fighting force. However, this does not exclude the possibility that repertoire size plays a role in different intra-sexual contexts in Common Blackbirds. In the discussion, we address alternative scenarios.

Unexplained recurrent features of the plumage of birds

Unexplained recurrent features of the plumage of birds

Potential impact of grey squirrels Sciurus carolinensis on woodland bird populations in England

Several woodland bird species have declined markedly in abundance in England over the past 40 years, whilst the grey squirrel Sciurus carolinensis, a non-native nest predator, has increased. Given the timing, there has been concern that grey squirrels have driven these declines, although there is little data to support this view. Using novel analytical methods and extensive national bird and grey squirrel monitoring data, we examine whether there is evidence that woodland bird populations in England have been depressed by grey squirrels and whether there is a relationship between nest failure and squirrel numbers. Our results indicate that grey squirrels are very unlikely to have driven observed declines of woodland birds in recent years, although the number of associations, positive as well as negative, between grey squirrels and woodland birds is greater than expected by chance. For this reason, we cannot exclude the possibility that the populations of a small number of bird species, principally increasing species, have been depressed to some degree at sites where a greater number of grey squirrels were present. Of these species, perhaps the most convincing evidence is for Common Blackbird Turdus merula and Eurasian Collared Dove Streptopelia decaocto where nest record data also identified a positive relationship between nest failure at the egg stage and squirrel abundance.

Nest predators of woodland open‐nesting songbirds in central Europe

I used time‐lapse videotaping to identify predators of open songbird nests in fragmented deciduous woodland (nine plots, 2–10 ha each) in the Czech Republic from 2002 to 2006. I documented 22 species of predators at 171 nests of 13 species (mainly Blackcap Sylvia atricapilla, Song Thrush Turdus philomelos, Common Blackbird Turdus merula, Yellowhammer Emberiza citrinella and Chaffinch Fringilla coelebs). The main predators were Pine Marten Martes martes (37% of 178 predation events), Jay Garrulus glandarius (29%), Buzzard Buteo buteo (7%) and Great Spotted Woodpecker Dendrocopos major (7%); mammals accounted for 48% of total predation. At least 3% of nests were depredated by multiple predators. In spite of their local abundance, Hooded Crows Corvus cornix did not present a serious threat for shrub nesting songbirds (< 1% of total predation). No predation by mice was recorded, suggesting that their importance has been overestimated in artificial nest studies. The proportional species composition of predators depended on which species occupied the monitored nest and location (study plot), but not on the year or the time of season. Corvids and raptors accounted for a relatively larger percentage of total predation of small (‘warblers’) and large (‘thrushes’) prey species, respectively, whereas carnivores were important predators of all prey species. Active nests of thrushes were only rarely robbed by Jays (< 4% of 52 events), presumably due to parental nest defence. Predation by woodpeckers was spatially clumped, probably due to individual foraging specialization. Predation by the other major predators was documented on most/all study plots.

Comparison of Plumages of White-Throated DipperCinclus cinclusand BlackbirdTurdus merula

Abstract. This study compares the plumage of a single Eurasian White-throated Dipper Cinclus cinclus with that of three Common (European) Blackbirds Turdus merula (all road casualties). As expected, the Dipper had far more down and contour feathers (3,322) than the Blackbirds (mean 1,704), with Dipper down and contour feathers being significantly shorter than those of Blackbirds. However, contrary to published information, the plumage of dippers is not exceptionally dense; the mean follicle density of the Dipper was 59.2 follicles cm-2, that of the Blackbirds 58.6–61.7 follicles cm-2. Instead, the enhanced insulation of diving Dippers stems from a) much more extensive plumage (the apterylae between feather tracts are fully feathered, whilst naked in Blackbirds), b) substantial down cover of head (absent in Blackbirds), c) extensive down cover of wings. Much of the higher number of feathers in the Dipper is made up of contour feathers rather than down/semiplume feathers (the ratio between Dipper contour an...