Ground-feeding Birds Research Articles

Long term evaluation of factors influencing the association of ixodid ticks with birds in Central Europe, Hungary

Birds play a crucial role in disseminating ticks that carry pathogens of high veterinary-medical importance. The aim of this study was to analyze data of a long-term tick collection from birds at a single stop-over site in Central Europe, Hungary. Over eight years (2015–2022) 5833 ticks (ten species) were collected from 2395 tick-infested birds. The most abundant species were Ixodes ricinus (n = 3971) and Haemaphysalis concinna (n = 1706). Ixodes ricinus nymphs and larvae were the most frequently occurring on resident and short-distance migratory birds with forest habitat but Ha. concinna was the most abundant species on reed-associated, long-distance migrants. Haemaphysalis concinna occurred mostly on birds feeding above the ground level, while I. ricinus predominated on ground feeding birds. Infestation with I. ricinus nymphs always peaked in the first half of the year, in contrast to larvae which were more abundant on avian hosts in the autumn. At the same time, Ha. concinna larvae and nymphs had their peak numbers in the summer. This is the first long-term study on the tick infestation of birds in Central Europe. The study shows that, migration distance, habitat type, and typical feeding level of birds, as well as characteristics of tick life cycle are all key factors in the role of birds as tick disseminators. It was revealed that Savi’s Warbler (Locustella luscinioides) is the most frequent hosts of Ha. concinna in Central Hungary.

Artificial grass in parks as a potential new threat for urban bird communities

Summary Green areas are key habitats for urban avifauna. Urban parks stand out from other anthropic habitats especially in providing trophic resources for many bird species. Consequently, modifications of these green zones can imply major changes in urban biodiversity. Potential pernicious urban remodelling is taking place in parks of eastern Spain because natural grass is being replaced with artificial grass to save water and to avoid management. This study aimed to determine whether remodelled parks with artificial grass harbour lower avian diversity (alpha, beta and gamma diversity) than traditional parks with natural grass. We surveyed 21 parks with artificial grass and 24 parks with natural grass in 18 towns of the Valencia Region in autumn 2020. In each park, we carried out 5-minute and 25-m radius point counts for determining bird species and their abundance. The effects of park area and grass type on alpha diversity (species richness, Shannon diversity index, Pielou’s Evenness and total abundance) were tested by means of GLMs. Differences in beta diversity and its components (nestedness and turnover) were also analyzed with the Bray-Curtis dissimilarity index. Gamma diversity was assessed by means of species accumulation curves. Finally, differences in community composition were tested by PERMANOVA and SIMPER tests. The parks with natural grass always harboured higher gamma diversity, species richness and abundance. Turnover was higher in parks with natural grass, whereas nestedness was higher in artificial grass parks. Differences in community composition were due mainly to abundance differences in common ground-feeding birds. We highlight that the trend of replacing natural by artificial grass in urban parks has harmful effects on urban bird communities and is a threat to bird conservation. Although artificial grass might save water, the effects on urban biodiversity should be carefully evaluated.

Snow depth drives habitat selection by overwintering birds in built-up areas, farmlands and forests.

AimAbundances of animals vary according to species‐specific habitat selection, but habitats are undergoing rapid change in response to anthropogenic alterations of land use and climate. The long‐term decline of snowfall is one of the most dramatic abiotic changes in boreal regions, with potential to alter species communities and shape future ecosystems. However, the effects of snow cover on habitat‐specific abundances remain unclear for many taxa. Here we explore whether long‐term declines in snow cover affect the abundances of overwintering birds.TaxonFifty bird species.LocationFinland, Northern Europe.MethodsWe used generalized linear mixed models to analyse citizen‐led monitoring data from 196 transects over a 32‐year period to assess whether abundances of birds have changed in built‐up areas, farmlands and forests, and whether these covary with warming temperatures and decreasing snow. We then explored if changes in abundance can be explained by body mass, migration strategy or feeding guilds of the species.ResultsOver the study period, the abundance of overwintering birds increased. This increase was most pronounced in farmlands (69.6%), where abundances were positively associated with decreasing snow depth. On the other hand, while abundances in built‐up habitats (19.5%) decreased over the study period, they increased in periods of high snow depths. Finally, we found that the short‐distance migration strategy explains changes in bird abundances with snow. In farmlands, ground feeding birds and heavier birds also show a positive trends in abundance with decreasing snow depths.Main conclusionsLocal snow conditions are driving habitat selection of birds in the winter; birds in farmlands were most responsive to a decrease in snow depth. Changing snow depths can affect bird movements across habitats in the winter, but also influence migratory patterns and range shifts of species.

Effects of Personality Traits on the Food-Scratching Behaviour and Food Intake of Japanese Quail (Coturnix japonica).

Simple SummaryScratching can help animals find more buried food and thus is an important food-searching behaviour for ground-feeding birds such as gamebirds. Due to the existence of animal personality, individuals within a population may exhibit different food-scratching patterns. This study tested the impacts of personality traits (i.e., boldness and exploration) on food-scratching behaviour and food intake of Japanese quail (Coturnix japonica). We found that boldness and exploration were repeatable, respectively, and were correlated. When entering a food patch, proactive (i.e., bolder and more explorative) quails scratched for food earlier and more frequently with a longer time. Frequent and longer food-scratching may motivate longer foraging time in proactive quails which can get more food intake. The correlation between personality and food intake was sex dependent. Proactive females had more food intake during the first half of the foraging process and the correlation became weak as time went on. The pattern was opposite in males. In conclusion, our study suggests that personality traits have significant effects on animals’ food-searching strategies which may be correlated with their foraging success and fitness.Overall foraging success and ultimate fitness of an individual animal is highly dependent on their food-searching strategies, which are the focus of foraging theory. Considering the consistent inter-individual behavioural differences, personality may have a fundamental impact on animal food-scratching behaviour, which remains largely unknown. In this study, we aimed to investigate how personality traits (i.e., boldness and exploration) affect the food-scratching behaviour and food intake of the domestic Japanese quail Coturnix japonica during the foraging process. The quails exhibited significant repeatability in boldness and exploration, which also constituted a behavioural syndrome. More proactive, that is, bolder and more explorative, individuals scratched the ground more frequently for food and began scratching earlier in a patch. Individuals that scratched more frequently had a longer foraging time and a higher food intake. The correlation between personality traits and temporary food intake during every 2 min varied over time and was sex dependent, with females exhibiting a positive correlation during the first half of the foraging stage and males after the initial stage. These findings suggest that personality traits affect the food-scratching behaviour and, thus, the food intake of quails. Our study provides insights into the impact of personality traits on animal’s foraging behaviour by influencing their food-searching strategies.

Serological evidence of exposure to Toxoplasma gondii infection in wild birds and local chickens (Gallus gallus domesticus) in Plateau State, North Central Nigeria.

Toxoplasma gondii, the cause of toxoplasmosis is an obligate intracellular protozoan parasite of veterinary and public health importance. Ground feeding birds play an active role in the epidemiology of the disease and are the best indicators of soil contamination with the oocysts. Thirteen (14.1%; 95% CI=7.7-23.0) of the 92 wild birds (6 of Coliformes; 4 of Columbiformes; 67 of Passeriformes and 15 of Piciformes) captured from Shere hills and 43 (9.3%; 95%CI=4.9-12.4) of the 460 local chickens obtained across 3 senatorial regions of Plateau State, Nigeria were positive for anti-T. gondii antibodies using enzyme linked immunosorbent assay (ELISA). Varying prevalence (16.7-100%) of anti-T. gondii antibodies were recorded across 10 of 35 wild bird species; 2 (28.6) of 7 African thrush (Turdus pelios), 2 (33.3) of 6 speckled mouse bird (Colius striatus), 1 (20.0%) of 5 speckled fronted weaver (Sporopipes frontalis), 1 (33.3%) of 3 Northern Red bishop (Euplectes franciscanus), 1 (50.0%) of 2 village weaver (Ploceus cucullatus), 2 (28.6%) of 7 common bulbul (Pycnonotus barbatus), 1 (50.0%) of 2 black crowned tchagra (Tchagra senegalus), 1 (50.0%) of 2 black billed wood dove (Turtur abyssinicus), 1 (100.0%) of 1 mocking cliff chat (Thamnolaea cinamomeiventris), 1 (16.7) of 6 vieillot's barbet (Lybius vieilloti). The prevalence did not vary significantly based on the sex (p=0.14), feeding guild (p=0.53) and the taxonomic order (p=0.62) of the wild birds. Regional based prevalence among local chickens ranged between 8.0 and 11.8% across the 3 senatorial zones. The source (p=0.513; 95% CI=4.9-16.8) and age (p=0.797; 95% CI=4.9-16.8) of local chickens were not associated with T. gondii seropositivity. Seropositivity was higher in the females (95% CI=9.1-18.3) than in the males (p=0.004; 95% CI=3.0-9.4). This is the first report of the serological evidence of exposure to T. gondii infection in a wide variety of wild birds and local chickens in the area. It suggest that birds in this region are important asymptomatic intermediate hosts and play a role in the maintenance of the organism in the ecosystem.

Using autonomous recorders and bioacoustics to monitor the globally endangered wildlife in the Annamite mountain landscape: A case study with crested argus in Song Thanh Nature Reserve

In Southeast Asia, the Annamite mountains and Central Vietnam lowlands are two of the most prioritized areas for preventing the extinction of large populations of phasianids. Ground-feeding birds in Southeast Asia may be going extinct, both inside and outside the protected areas, due to habitat loss and poaching, especially, snaring. Being endemic to the mainland of Southeast Asia, the crested argus is one of the largest and most threatened species of Phasianidae. Indeed, the crested argus has recently been upgraded to the “endangered” category from the “near-threatened” category in the IUCN RedList. Quantitative data on the occurrence of the crested argus for guiding conservation efforts is poor. Additionally, information on the species’ ecology is limited. In this study, we used autonomous recorders to detect the presence of the crested argus and to estimate its occurrence probability in Song Thanh Nature Reserve, Vietnam. We also examined the effects of environmental variables on the species’ distribution in space. We used four Song Meter SM3 recorders to record the calls of the crested argus at 38 recording posts from February to April 2019. We used RAVEN software to analyze the sound data. We used the Occupancy Estimation in MARK to estimate the detection probability and the occurrence probability. Elevation had a slight negative effect on occurrence probability. The occurrence probability of the crested argus was high (0.88; CI: 0.60−0.97). The high occurrence probability in the Song Thanh Nature Reserve reveals the importance of this protected area in galliform species conservation in general and for the crested argus in particular.

Grazing improves habitat suitability for many ground foraging birds in Mediterranean wooded grasslands

Wooded grasslands, usually grazed, cover vast areas in Southern Europe and Northern Africa. They host rich resident bird communities and, in winter, receive large numbers of migrants from Central and Northern European woodlands. Many species are partly or entirely dependent on ground foraging and, since in winter food is often the most limiting factor for birds, maintaining suitable ground habitat is crucial.To study how grazing influences suitability of winter ground habitat for birds, we carried out an experiment in a wooded grassland in Southern Iberia, whereby grazing was controlled in 12 purposely fenced two-hectare plots (4 × 15 sheep/ha, 4 × 3 sheep/ha and 4 × no grazing). We quantified ground habitat features, food abundance and intensity of use by ground-foraging birds in each of these 12 plots. In addition, we made focal observations of birds feeding on the ground and compared the habitat of 1m2 foraging patches with those of nearby control patches.We found that virtually all birds prefer to forage in patches with short ground vegetation and high food abundance. Measurements of these parameters in the experimental plots showed that while grazing shortens vegetation it decreases food availability, and thus has opposing effects on important determinants of habitat suitability. Nevertheless, the numbers of birds foraging in the plots indicate that, overall, grazing benefits the assemblage of ground-feeding birds, presumably because for most species the advantages of foraging in less cluttered habitats more than compensate the lower abundance of prey. However, arboreal bird species that make short foraging forays to the ground had lower numbers in grazed plots.Most bird species that forage on the ground benefited from grazing, and although they can forage under a broad range of grazing levels, some showed clear preferences along the gradient of grazing intensity. Such preferences should be taken into consideration by managers. In general, grazing should be maintained at a level sufficient to open up ground vegetation, increasing the area occupied by patches of short vegetation, in which almost all bird species prefer to forage. At moderate levels, grazing is thus a valuable management tool to promote winter bird habitat quality in Mediterranean wooded grasslands, while increasing the economic value of these threatened landscapes.

Large decline of birds in Sahelian rangelands due to loss of woody cover and soil seed bank

The large and widespread decline of European migratory birds spending the northern winter in the Sahel suggests – on top of adverse changes in the breeding quarters ‒ pivotal changes in African overwintering areas. This paper attempts to answer three questions related to the sub-Saharan region: (1) can a change in the woody vegetation explain the decline of migratory birds feeding in trees, (2) ditto for the ground vegetation and bird species searching for food on the ground, and (3) are African bird species also in decline? The analysis is confined to the western Sahel (annual rainfall 100–400 mm, 15.5–18°N and 14.7–16°W), a region intensively used as rangeland but too dry for agriculture. The woody cover, largely stable before 1970, declined in the driest zone by 90% between the 1960s and 2000s, and by 40% in the more humid zone where the woody cover was already low in the 1960s. The woody vegetation changed in many places from an Acacia savanna into an open savanna with scattered bushes and few trees, concomitant with a shift in species composition. These changes took place during a prolonged drought (1969–1992), and were aggravated by increased grazing pressure after the construction of boreholes as evident from the loss of woody cover close to boreholes. A comparison of bird composition and densities in grazed and ungrazed areas and in three study sites intermittently surveyed between 1960 and 1994, with our surveys in the same sites in 2014–2015, revealed about 80% losses for birds feeding on the ground. The increased grazing pressure of livestock must have caused a large reduction of the soil seed bank and most likely also of insects. Between 15 and 16°W an estimated 8 million arboreal birds, mainly migrants, and 30 million ground-feeding birds, mainly granivorous residents, lost their habitat. Assuming that this zone is representative for the Sahelian rangelands as a whole, 1.5–2.0 billion birds have lost their habitat in half a century.

Capture and injury rates of Band-tailed Pigeons using whoosh nets

ABSTRACT Catching ground feeding birds has typically been accomplished through small, walk-in funnel-style traps. This approach is limited because it requires a bird to find its way into the trap, is biased toward less wary birds, and does not allow targeted trapping of individual birds. As part of a large study on Band-tailed Pigeons (Patagioenas fasciata) in New Mexico, we needed a trapping method that would allow more control over the number of birds we could trap at one time, when a trap was deployed, and target trapping of specific individuals. We adopted a relatively novel trapping technique used primarily for shorebirds, whoosh nets, to trap Band-tailed Pigeons at 3 different sites where birds were being fed by local landowners. During 2013–2015, whoosh nets were used to trap 702 Band-tailed Pigeons at 3 different locations in New Mexico. We captured 12.54 ± 8.19 pigeons per shot over 56 capture events across 3 locations (range: 2–39). Some superficial injuries occurred using this technique and typ...

First evidence of established populations of the taiga tick Ixodes persulcatus (Acari: Ixodidae) in Sweden.

BackgroundThe tick species Ixodes ricinus and I. persulcatus are of exceptional medical importance in the western and eastern parts, respectively, of the Palaearctic region. In Russia and Finland the range of I. persulcatus has recently increased. In Finland the first records of I. persulcatus are from 2004. The apparent expansion of its range in Finland prompted us to investigate if I. persulcatus also occurs in Sweden.MethodsDog owners and hunters in the coastal areas of northern Sweden provided information about localities where ticks could be present. In May-August 2015 we used the cloth-dragging method in 36 localities potentially harbouring ticks in the Bothnian Bay area, province Norrbotten (NB) of northern Sweden. Further to the south in the provinces Västerbotten (VB) and Uppland (UP) eight localities were similarly investigated.Results Ixodes persulcatus was detected in 9 of 36 field localities in the Bothnian Bay area. Nymphs, adult males and adult females (n = 46 ticks) of I. persulcatus were present mainly in Alnus incana - Sorbus aucuparia - Picea abies - Pinus sylvestris vegetation communities on islands in the Bothnian Bay. Some of these I. persulcatus populations seem to be the most northerly populations so far recorded of this species. Dog owners asserted that their dogs became tick-infested on these islands for the first time 7–8 years ago. Moose (Alces alces), hares (Lepus timidus), domestic dogs (Canis lupus familiaris) and ground-feeding birds are the most likely carriers dispersing I. persulcatus in this area. All ticks (n = 124) from the more southern provinces of VB and UP were identified as I. ricinus.ConclusionsThe geographical range of the taiga tick has recently expanded into northern Sweden. Increased information about prophylactic, anti-tick measures should be directed to people living in or visiting the coastal areas and islands of the Baltic Bay.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1658-3) contains supplementary material, which is available to authorized users.

Seroprevalence of Toxoplasma gondii antibodies in wild birds in Taiwan

Toxoplasma gondii is a zoonotic protozoon which is well known for infecting humans and wild animals. In the present study, antibodies to T. gondii were evaluated in 394 wild birds, belonging to 37 species, from 15 different administrative regions in Taiwan. Using modified agglutination test (MAT), the overall seroprevalence of infection was 23.35% (CI 95%=19.17%–27.53%). Antibodies were detected in birds of prey (25.73%, CI 95%=19.76%–31.70%), birds living in freshwater or marine systems (34.29%, CI 95%=18.56%–50.01%) and ground-feeding birds (18.12%, CI 95%=11.94%–24.31%). Adult birds showed higher seroprevalence than that in juvenile birds, and the presence of clinical abnormalities was associated with T. gondii seropositivity. The results showed that this pathogen has spread widely in Taiwan. This suggests the zoonotic potential of the disease, with transmission from urban to rural regions, and from terrestrial to aquatic systems. The pathogenicity of T. gondii infection in wild birds in Taiwan needs further investigation. This is the first study of the seroprevalence of T. gondii in wild birds in Taiwan.

Morphometrical and genetic comparison of two nematode species: H. spumosa and H. dahomensis (Nematoda, Heterakidae)

Heterakis is a genus of parasitic nematodes, the majority of which are found in ground-feeding birds and only rarely in mammals. The best-known species is Heterakis spumosa, a parasite associated with the cosmopolitan invasive rodent Rattus rattus of Asiatic origin. Heterakis dahomensis was described in 1911 as a parasite of the Gambian giant rat (Cricetomys gambianus) from Benin (Africa), subsequently synonymized to H. spumosa by Hall (1916). The study of helminths in African rodents is scarce and patchy. Since the original description of H. dahomensis, there have been only a few reports from Africa of species belonging to the genus Heterakis and the validity of this species has never in fact been confirmed or rejected. In the present study individual Heterakis spp. were collected from C. gambianus from Senegal. The morphological data taken point to differences between Heterakis dahomensis and H. spumosa, specifically in the number of tail papillae in males and in the vulva cuticular processes of females. In addition, molecular data revealed differences between these taxa and so H. dahomensis should be considered as a valid species. Moreover, recent changes in the systematics of the genus Cricetomys mean that it is now necessary to study the morphology and genetics of the Heterakis specimens collected from Cricetomys spp. (previously assigned to C. gambianus) in order to determine their taxonomic status as either H. dahomensis o H. spumosa.

Food color preferences against a dark, textured background vary in relation to sex and age in house finches (Carpodacus mexicanus)

AbstractMany animals consume colorful foods, because bright coloration either enhances conspicuousness of food items or signals nutritional rewards. A comparatively under-studied aspect of food color preferences is the role of the background environment in shaping food detectability and choices. Previous work with house finches (Carpodacus mexicanus), for example, showed that individuals preferred red and green food items and avoided yellow ones. However, this study of desert, ground-feeding birds was done with seeds presented against an artificial white background that is unlikely to reflect natural conditions. Therefore, we performed a similar experiment, but quantified selection of colorful foods using a different visual environment that better mimicked natural conditions. We mixed dark, inedible distractor pellets (i.e., analogous to natural desert sand and rocks) with sunflower kernels that were colored red, green, yellow, or orange to test for differences in foraging patterns by sex, age, and expression of male plumage coloration in non-molting house finches. This food presentation resulted in yellow seeds having a significantly greater chromatic, but not achromatic, contrast with the background than red or green seeds. Under these conditions, all birds consumed yellow, and to a lesser extent red, seeds most often, and both adult males and females had a strong preference for yellow kernels; adult males also tended to prefer green kernels, but females tended not to prefer green kernels. Juveniles showed no significant preferences for any seed color, and adult male plumage coloration was not related to seed color preference. Therefore, in contrast to studies using different foraging environments, house finches tended to prefer yellow seeds, supporting models that suggest that visual background and contrast may be more important than color per se in visually mediated foraging decisions of birds. Moreover, the fact that adult males and females differed in food color preference has not been reported previously in songbirds.

Serological and Parasitological Prevalence of Toxoplasma gondii in Wild Birds From Colorado

Ground-feeding birds are considered important in the epidemiology of Toxoplasma gondii because they serve as indicators of soil contamination by oocysts, and birds of prey are indicators of T. gondii prevalence in rodents and other small mammals. Cats excrete environmentally resistant oocysts after consuming tissues of T. gondii -infected birds. In the present study, sera and tissues from 382 wild birds from Colorado were tested for T. gondii infection. Antibodies to T. gondii were found in 38 birds with the use of the modified agglutination test (MAT, 1∶25 titer). Tissues (brains, hearts) of 84 birds were bioassayed in mice. Viable T. gondii was isolated from 1 of 1 barn owl (Tyto alba), 1 of 5 American kestrels (Falco sparverius), 1 of 7 ferruginous hawks (Buteo regalis), 1 of 4 rough-legged hawks (Buteo lagopus), 2 of 13 Swainson's hawks (Buteo swainsoni), and 1 of 25 red-tailed hawks (Buteo jamaicensis). This is the first time T. gondii has been isolated from the barn owl, ferruginous hawk, rough-legged hawk, and Swainson's hawk.

Seasonal distribution of larvae and nymphs of Amblyomma tigrinum Koch, 1844 (Acari: Ixodidae)

The seasonality of immature stages of Amblyomma tigrinum was studied in an area of the Chaco phytogeographical province in Córdoba, Argentina by monthly collection of larvae from ground feeding birds and Sigmodontinae rodents, and nymphs from Caviidae rodents from May 2005 to April 2007. An apparent peak of abundance was found from December to May but differences with other months of the year were not significant ( P > 0.05). These and previous results suggest that the parasitic stages of A. trigrinum are active throughout the year and has more than one generation per year at the study site. Its life cycle appears to be regulated by temperature with no occurrence of diapause.

Ticks collected on birds in the state of São Paulo, Brazil

The present study reports a collection of Amblyomma spp. ticks in birds from several areas of the state of São Paulo, Brazil. A total of 568 tick specimens (404 larvae, 164 nymphs) were collected from 261 bird specimens. From these ticks, 204 (36%) specimens (94 larvae, 110 nymphs) were reared to the adult stage, being identified as Amblyomma longirostre (94 larvae, 90 nymphs), Amblyomma calcaratum (13 nymphs), Amblyomma nodosum (2 nymphs), and Amblyomma cajennense (5 nymphs). Additionally, 39 larvae reared to the nymphal stage and 8 nymphs that died before reaching the adult stage were identified as A. longirostre according to peculiar characters inherent to the nymphal stage of this species: scutum elongate, and hypostome pointed. The remaining 271 larvae and 46 nymphs were identified as Amblyomma sp. Ticks were collected from 51 species of birds distributed in 22 bird families and 6 orders. The order Passeriformes constituted the vast majority of the records, comprising 253 (97%) out of the 261 infested birds. Subadults of A. longirostre were identified from 35 species of Passeriformes, comprising 11 families (Cardinalidae, Dendrocolaptidae, Fringillidae, Furnariidae, Parulidae, Pipridae, Thamnophilidae, Thraupidae, Turdidae, Tyrannidae, and Vireonidae), and from 1 species of a non-passerine bird, a puffbird (Bucconidae). Subadults of A. calcaratum were identified from 5 species of Passeriformes, comprising 5 families (Cardinalinae, Conopophagidae, Pipridae, Thamnophilidae and Turdidae). Subadults of A. nodosum were identified from 2 species of Passeriformes, comprising two bird families (Thamnophilidae and Pipridae). Subadults of A. cajennense were identified from 2 species of non-passerine birds, belonging to 2 different orders (Ciconiiformes: Threskiornithidae, and Gruiformes: Cariamidae). Birds were usually infested by few ticks (mean infestation of 2.2 ticks per bird; range: 1-16). Currently, 82 bird species are known to be infested by immature stages of A. longirostre, with the vast majority [74 (90%)] being Passeriformes. Our results showed that Passeriformes seems to be primary hosts for subadult stages of A. longirostre, A. calcaratum, and A. nodosum. However, arboreal passerine birds seem to be the most important hosts for A. longirostre whereas ground-feeding passerine birds seem to be the most important for both A. calcaratum and A. nodosum. In contrast, the parasitism of birds by subadults of A. cajennense has been restricted to non-passerine birds.

Ecological factors facilitating city-dwelling in red-rumped parrots

The red-rumped parrot (Psephotus haematonotus), which appears to be undergoing range expansion, started colonising metropolitan Melbourne ~30 years ago. The factors that have facilitated this colonisation have not been evaluated. We investigated aspects of the parrot’s ecology at six parkland sites through late autumn and winter 2006 to elucidate these factors. The predominantly ground-feeding red-rumped parrot consumed mainly seeds of exotic grass and herb species, four of which were particularly important in providing a continuous winter food resource. Two of these species were common turf grasses and their visible and concealed seeds provided >50% of the diet. Sites occupied by parrots had relatively more native trees, tall trees and dense canopy cover than unoccupied sites; this may be important in providing suitable daytime and nocturnal roost sites. Little aggressive interference competition occurred with other ground-feeding birds. Mean population density in occupied sites was 1.3 parrots ha–1. Mean flock size was 10 ± 6 and, on average, males comprised 67 ± 19% of a flock’s members. We suggest that abundant, continuously available food (seed) resources, apparently limited competition for food and the presence of suitable roosting sites are probably important in facilitating winter occupancy of parkland by red-rumped parrots in Melbourne.

Foraging ecology of ground-feeding woodland birds in temperate woodlands of southern Australia

Ground-foraging birds of temperate woodlands of southern Australia are prominent among bird species considered to be susceptible to population decline. We examined the foraging ecology, including foraging substrates, actions and heights, of 13 ground-foraging species at four woodland sites in northern Victoria. Nine species are regarded as declining in southern Australia and four are considered common. Ten foraging substrates were identified, of which leaf-litter (54% of observations) and bare ground (17%) were most frequently used. In all woodland sites, litter was used more frequently than expected from its proportional cover. Bare ground was frequently used as a substrate by individual species, and fallen timber and grass were important for some species. Most species were generalists in their use of substrates. Six foraging actions were observed, of which gleaning and pouncing were most frequently recorded. All species foraged close to the ground and four foraged almost entirely at ground level. For pouncing birds, dead branches and fallen timber were the most important launch substrates from which pouncing actions were initiated. Eight of the 13 species differed in some aspect of their foraging ecology between woodland sites, especially in relation to the use of substrates (seven species). Fewer species (four) displayed differences in foraging ecology between seasons, with the greatest seasonal variation being in use of foraging substrates (three species). Overall, no significant differences were evident in the foraging ecologies of common and declining species. Species in both groups encompassed a wide range of foraging behaviours. Owing to this range in foraging ecology, the conservation of diverse assemblages of ground-foraging birds requires the maintenance of heterogeneous ground layers and careful management of disturbance processes.

Testing for peripheral vigilance: do birds value what they see when not overtly vigilant?

Previous studies showed that dark-eyed juncos, Junco hyemalis, gain only partial information when their flockmates detect threats, and that they can detect threats peripherally even when they are feeding intensely. Here, we tested how this ‘peripheral (head-down) vigilance’ interacts with overt (head-up) vigilance and the collective detection of threats. Low barriers were used to prevent juncos from seeing to the side while pecking for food on the ground; a bird with its head raised could easily see over the barriers. Juncos and other ground-feeding birds preferred to feed without the barriers. When the barriers were present, birds generally took longer scans but spent similar periods between scans. Also, scanning patterns were less variable when the barriers were present. Following the threat-induced departure of a single bird, nondetectors were more likely to initiate scans when feeding among barriers. Barriers prevented feeding juncos from seeing the early stages of threat-induced departures of flockmates and thus impeded the collective detection of attack. The results suggest that juncos value peripheral vigilance and that scanning patterns are affected by interactions between peripheral vigilance and overt scanning behaviour.

Death and danger at migratory stopovers: problems with “predation risk”

related terms, including, ‘‘escape performance’’, ‘‘predation hazard’’, ‘‘vulnerability’’, ‘‘falling victim to’’, ‘‘exposure to predators’’, and ‘‘perceived predation risk’’ has further complicated matters. Exact definitions are lacking, which has allowed a variety of different meanings to march under the common term of ‘‘predation risk’’. To illustrate the definitional problem, imagine a situation in which predators hunt ground-feeding birds. The birds avoid attacks by cautious behavior, such as repeatedly scanning the environment for predators. A field ecologist studying this situation, even for a long time, might observe no or very few predation events, and could conclude that there was little ‘‘risk of predation’’. But if the ground-feeding birds did not scan, the predators could catch them easily, and another field ecologist might conclude that the situation is very ‘‘risky’’. This meaning refers to the probability of mortality that would occur if the birds did not scan. Thus, ‘‘predation risk’’ can mean quite different things. Which meaning is used has a great effect on the interpretation of what is ‘‘biologically’’ or ‘‘ecologically significant’’. Our primary purpose here is to outline possible meanings of terms relating to ‘‘predation risk’’, and suggest a general scheme that relates them one to another. We show that the two hypotheses Dierschke considers are not contradictory alternatives, as he suggests. Rather, they address different meanings of ‘‘predation risk’’ that are in our view not only compatible, but complementary. We suggest that recognizing four concepts will help to clarify thinking and analysis of issues relating to ‘‘predation risk’’: ‘‘mortality’’, ‘‘danger’’, ‘‘escape performance’’, and ‘‘anti-predator behavior’’. To help avoid ambiguity, we will henceforward avoid the term ‘‘predation risk’’ when describing what we mean.