Food of the rook (Corvus frugilegus L.) in Hawke's Bay,New Zealand

Abstract

Throughout a year gizzards from 160 adult and juvenile rooks and 105 large young in rookeries were collected from Hawke's Bay. The main foods were invertebrates (especially Diptera larvae and Coleoptera adults) during the warmer months and walnuts and acorns in autumn and winter. When these foods were scarce cereals were taken, mainly from stubble. Other important food items were carrion, earthworms, peas, grass, and clover. Foods fed to young rooks were similar to those eaten by adults except that the young were fed more striped dung fly (Hybopygia varia) larvae (P < 0.025) and fewer blow fly (Calliphoridae) larvae (P < 0.025).     

Sleep pattern in the rook, Corvus frugilegus

In the rook, Corvus frugilegus, electrographic and behavioural correlates of sleep and wakefulness have been determined under natural lighting conditions. Slow wave sleep (SWS) was characterized by high amplitude slow EEG activity, low neck EMG, and behavioural inactivity. Paradoxical sleep (PS) was characterized by low amplitude fast EEG activity and inconsistent decrease in EMG. PS episodes always commenced with head downward. Several eye movements occurred activity were present. The rook spent in sleep 31.8% of the 24-h period. PS however, eye movements, high tonic neck EMG activity, and behavioural activity were present. The rook spent in sleep 31.8% of the 24-h period. PS constituted 1.8% of total sleep, while the rest of total sleep was occupied by SWS. On the average, episodes of SWS and PS lasted 10.8 min and 24 s respectively. The daily percentage of SWS was highly correlated with the mean episode duration. PS amount was better correlated with the number of episodes than with their mean duration. Our data suggest that over-short period of recovery from surgery and adaptation with implanted electrodes could lead to underestimation of sleep duration in rook.     

The spatial distribution and size of rook (Corvus frugilegus) breeding colonies is affected by both the distribution of foraging habitat and by intercolony competition

Explanations for the variation in the number of nests at bird colonies have focused on competitive or habitat effects without considering potential interactions between the two. For the rook, a colonial corvid which breeds seasonally but forages around the colony throughout the year, both the amount of foraging habitat and its interaction with the number of competitors from surrounding colonies are important predictors of colony size. The distance over which these effects are strongest indicates that, for rooks, colony size may be limited outside of the breeding season when colony foraging ranges are larger and overlap to a greater extent.     

Local environmental effects and spatial effects in macroecological studies using mapped abundance classes: the case of the rook Corvus frugilegus in Scotland

1. The study of the spatial pattern of species abundance is complicated by statistical problems, such as spatial autocorrelation of the abundance data, which lead to the confusion of environmental effects and dispersal. 2. Atlas-derived data for the rook in Scotland are used as a case study to propose an approach for assessing the likely contribution of dispersal and local environmental effects, based on a Bayesian Conditional Autoregressive (CAR) approach. 3. The availability of moist grasslands is a key factor explaining the spatial pattern of abundance. This is influenced by a combination of climatic and soil-related factors. A direct link to soil properties is for the first time reported for the wide-scale distribution of a bird species. In addition, for this species, dispersal seems to contribute significantly to the spatial pattern and produces a smoother than expected decline in abundance at the north-western edge of its distribution range. Areas where dispersal is most likely to be important are highlighted. 4. The approach described can help ecologists make more efficient use of atlas data for the investigation of the structure of species abundance, and can highlight potential sink areas at the landscape and regional scale. 5. Bayesian spatial models can deal with data autocorrelation in atlas-type data, while clearly communicating uncertainty through the estimation of the full posterior probability distribution of all parameters.     

Breeding biology of rooks (Corvus frugilegus L.) in Hawke's Bay,New Zealand

Abstract

Three rookeries in Hawke's Bay were studied during 1966–68. First or replacement clutches were started between 26 August and 23 October. First clutches averaged 4.3 eggs and replacements 3.7 eggs. The mean size of first clutches varied between years from 4.1 to 4.6 eggs. Incubation took 17–18 days. Most losses occurred around hatching, when about 40% of the eggs or young were lost. Incubated eggs and small nestlings incurred losses of 20% and 10% respectively, and all nestlings older than 10 days survived to at least 20 days. On average, 1.4 young were reared per nest in which eggs were laid; successful nests averaged 2.2 young. First clutches averaged 1.3 young (2.4 per successful first clutch). During the season, mean clutch size declined from 4.2 to 3.5, the mean number of young hatched declined from 2.0 to 0.6 per clutch, and the mean number of young fledged from all clutches declined from 1.3 to 0.4 per clutch. Mean nestling weight increased with age from 14 g on the first day after hatching to 360 g on the 19th day. The causes of egg and nestling mortality and the adaptiveness of clutch size are discussed.     

Trends in ixodid tick abundance and distribution in Great Britain

Abstract.  The popular, but rarely documented, view in Britain is that ticks have increased in distribution and abundance over recent years. To assess this, we gathered evidence for changes in tick distribution and abundance by distributing a survey questionnaire throughout Britain and by analysing trends in the prevalence of tick infestation on red grouse chicks Lagopus lagopus scoticus Latham (Galliformes: Tetranoidae), gathered over 19 years at three Scottish sites, and on deer (Cetartiodactyla: Cervidae) culled over 11 years on 26 Ministry of Defence (MoD) estates. Based on the survey, the current known distribution of Ixodes ricinus Linnaeus (Acari: Ixodidae) has expanded by 17% in comparison with the previously known distribution. The survey indicated that people perceive there to be more ticks today than in the past at 73% of locations throughout Britain. Reported increases in tick numbers coincided spatially with perceived increases in deer numbers. At locations where both tick and deer numbers were reported to have increased, these perceived changes occurred at similar times, raising the possibility of a causal link. At other locations, tick numbers were perceived to have increased despite reported declines in deer numbers. The perceptions revealed by the survey were corroborated by quantitative data from red grouse chicks and culled deer. Tick infestation prevalence increased over time on all grouse moors and 77% of MoD estates and decreased at six locations.     

Buzzards Buteo buteo and Ravens Corvus corax in the uplands of Britain: limits to distribution and abundance

The current breeding ranges of Buzzards Buteo buteo and Ravens Corvus corax in Britain are restricted to the west, and both are relics of former widespread but not necessarily even distributions. Moore (1957) attributed the Buzzard's contraction in range to persecution by gamekeepers, his evidence being the complementary nature of the Buzzard's distribution with those of gamekeepers in the lowlands and grouse moors in the uplands; others have attributed the Raven's decline to the same cause. Is Moore correct and, if so, are these species' ranges still limited by persecution? Here we adopt an approach similar to Moore's, whereby we compare the current geographical patterns of abundance of Buzzards and Ravens in the British uplands with that of an index of grouse moor density. Unlike Moore, however, we take into account climate, land cover, topography and sheep stocking density, as well as grouse moor distribution, using multiple logistic regression modelling. We show that in the uplands the distribution of grouse moors strongly limits that of Buzzards and Ravens but are unable to conclude that this is a result of persecution because there are several competing hypotheses (moor management, food and nest-site availability) between which we are unable to distinguish.     

Characterization of Pb and Cd contamination in the feces and feathers of rook (Corvus frugilegus) and the scalp hair of residents in Qiqihar,northeastern China

The concentrations of Pb and Cd, and trace elements (Cu and Zn) in the urban topsoil, rook (Corvus frugilegus) feces and feathers and human scalp hair were analyzed to examine the potential ecological risk posed by Pb and Cd on local residents of Qiqihar City, northeastern China. Results revealed that the Cd concentrations in the topsoil were ranged from 0.14 to 3.55 mg kg^?1 dry weight (dw). The maximal geoaccumulation indices [a value from logarithmic (a measured metal content/1.5 × background content of the metal in this region), introduced by Muller] of Cd exceeded 3.5, which suggested that this region was seriously contaminated by Cd. The corresponding average detectable concentrations in C. frugilegus feathers and feces were 1.38 and 3.97 mg kg^?1 dw for Pb and 1.04 and 0.69 mg kg^?1 dw for Cd. High Pb and Cd concentrations, respectively, ranging from 7.46 to 24.9 mg kg^?1 dw and from 0.35 to 0.92 mg kg^?1 dw were also detected in the human scalp hair samples. These high Pb and Cd concentrations in C. frugilegus and local people were possibly associated with local industrial wastes and vehicle exhausts. The external tissues (feces and feather) of the rook species can be considered as an indicator of potential Cd toxic risk in this species; however, the human scalp hair is not a reliable biomarker for risk of Pb and Cd in the human being. Effective measures should be established to reduce the inputs of Pb and Cd into the urban environment and to protect the health of local people.     

Age-specific differences in the winter foraging strategies of rooks Corvus frugilegus

Summary Foraging efficiency and intraspecific competition were compared between wild adult and immature rooks Corvus frugilegus with respect to flock size. Behavioural time budgets, and observations of prey selection and prey energetic values revealed that adult rooks in large flocks (> 50 individuals) consumed smaller, less profitable prey, but allocated more time to feeding and fed at a faster rate and with greater success than adults in small flocks. By contrast, immature rooks in flocks of more than 30 individuals allocated proportionally less time to feeding, fed at a lower rate and fed with no increase in success rate than when foraging in smaller flocks. Agonistic encounters and the avoidance of adults by immature rooks appeared responsible for such inefficient foraging. Hence immature rooks showed a preference for smaller flocks (< 50 individuals) with low adult: immature ratios while adults preferred larger flocks (> 50 individuals). We discuss the possible influence of competitive disadvantages on immature rook distribution, flock composition and post-natal dispersal.     

Thermal conditions for successful breeding in Great Tits (Parus major L.)

Summary The development of temperature regulation in relation to the growth and age of the nestlings is described in a way permitting use of the data in a model designed to predict the range of temperature tolerance of broods of Great Tits in the nestling stage. Such a model is described in a second paper. The physiological part of that model is made up mainly of six equations (nos. 6, 10, 11, 12, 14 and 15), which are all presented and discussed here. It is shown in this paper that the development of temperature regulation is a function of body weight rather than of age. The level of the basal metabolic rate of nestling Great Tits is lower than that of adult passerines of comparable size. The basal metabolic rate of a newly hatched Great Tit is only about one fourthe of the metabolic rate expected from Lasiewski and Dawson's equation for adult passerine birds. This discrepancy diminishes gradually during the nestling period and disapears shortly before fledging.Basal and maximum metabolic rates, as well as the body temperatures coinciding with these rates, are described in allometric equations as functions of nestling body weight. The evaporative heat loss of the nestlings is described as a function of body weight and body temperature, and an estimate of the maximum amount of water available to them for evaporative heat loss is given. A distinction is made between a long-term risk of hyperthermia, which results in mortality through dehydration of the nestling body, and an immediate risk of hyperthermia, which occurs when the maximum rate at which nestlings can evaporate water is insufficient to cope with the required heat loss by water evaporation. It is concluded that this immediate risk of hyperthermia is the most important of the factors affecting the upper limit of the range of temperature tolerance.     

Prevalence of Listeria sp. in droppings from urban rooks (Corvus frugilegus)

Droppings from 112 urban rooks ( Corvus frugilegus ) were cultured for the presence of Listeria sp. Overall, 46% of rooks sampled harboured one or more Listeria species. Of all birds examined, 33%, 24% and 8%, respectively, were infected with Listeria monocytogenes, Listeria innocua and Listeria seeligeri. Differentiation of L. monocytogenes and L. seeligeri carried out by several phenotypic typing methods proved the diversity of strains and the major role of rooks which widely contribute to spreading this bacteria in our environment. The results also suggest that the ability to recover specific Listeria strains from the same sample is at least partially dependent on the methodology. These findings reinforce the need for strain-specific typing of multiple L. monocytogenes isolates from the same sample.     

Factors causing long-term dynamics in the abundance of the Trans-Volga Great bustard (Otis tarda L.) population

The results of our survey of bustards in the southern part of the Saratov Trans-Volga region over an area of 12000 sq. km in 1990–2010 are presented; analysis of the abundance dynamics is performed; and the factors causing it are revealed. Data on the distribution of bustards over their biotopes in the period of premigration roaming are studied, and the demographic and spatial structure of the population is analyzed.     

The Plymouth Laboratory and the Institutionalization of Experimental Zoology in Britain in the 1920s

The Plymouth Laboratory of the Marine Biological Association of the United Kingdom (1884) was founded in 1888. In addition to conducting morphological and other biological research, the founders of the laboratory aimed at promoting research in experimental zoology which will be used in this paper as a synonym for e.g. experimental embryology, comparative physiology or general physiology. This dream was not fully realized until 1920. The Great War and its immediate aftermath had a positive impact on the development of the Plymouth Laboratory. The war greatly upset the operation of the Zoological Station in Naples and the ensuing crisis in its operations was closely related to the establishment of the physiological department in Plymouth in 1920. Two other key factors in the Plymouth story were the establishment of the Development Fund in 1909, which began contributing funds to the Plymouth Laboratory in 1912, and the patronage of the Cambridge zoologist George P. Bidder (1863–1954). This paper will focus on the combined influence of the Development Fund and Bidder on the development of the Plymouth Laboratory from around 1902 through the early 1920s, and the important role the laboratory played in promoting experimental zoology in Britain in the 1920s.     

Population trends of Rooks Corvus frugilegus in Spain and the importance of refuse tips

Anthropogenic food from refuse tips can affect population dynamics in birds, especially gulls, but the evidence is mostly circumstantial. We combine analyses of long-term population data and natural experiments to show a positive effect of refuse tips on the growth of the Spanish breeding population of Rooks Corvus frugilegus . In this isolated population of around 2000 breeding pairs, monitored since 1976, birds in colonies less than 10 km from tips fed largely on refuse, particularly during periods of lowest natural food availability. Three lines of evidence support the hypothesis that the supply of refuse influenced breeding numbers, suggesting that this population is limited by food: 1) between 1976 and 2003, the two population nuclei that had access to tips increased 2.1 and 3.7 times more than that without a tip nearby; 2) annual colony growth between 1996 and 2003 was strongly correlated with the availability of tips when other potentially important variables were taken into account; 3) the number of breeding pairs in refuse-foraging colonies declined rapidly after the closure of the local tip and recovered only when a supply of refuse was restored. The effect of tips on colony growth was stronger when the availability of natural foraging habitat around the colonies was low, suggesting that anthropogenic food acts as a buffer against shortage of natural food. Artificial food supplementation may be an effective tool to increase the breeding population of target species, especially those facing a reduction of their foraging habitats. The potential effects on bird species of Directive 1999/31/CE, which is enforcing a massive closure of tips in Europe, are discussed.     

The status of the otter (L. lutra L.) in Britain in 1977

Two surveys based on otter hunt records showed a 40% fall in the otter population 1957–1967, arrested and in places reversed by 1971 save in the central Midlands. The possible causes of that decline and of its apparent continuation in the Midlands are discussed. While accepting those two surveys most conservationists have since then refused to accept or consider any evidence from otter hunts: the writer does not. Reports of the presence of otters by naturalists are shown plotted on a map and suggest that they are present in sufficient numbers and at a sufficient density over the whole of Great Britain, save the central Midlands, to ensure a recovery to the pre-1960 density. Positive evidence found by hunts in a number of places in which naturalists had found none suggest that negative evidence should be accepted with caution.     

A population study of the Rook Corvus frugilegus in Leon Province, northwest Spain

A resident population of Kooks Corvus frugilegus in Leon, Spain, decreased by 247; from 197679. Migrant Rooks appear not to enter the range of this population which is unique in the Iberian Peninsula. During the breeding seasons colonies are attacked by man: 17–19% of birds failed to breed and only 0.5-0.7 young per nest survived to fly. The trees chosen for nesting are in plantations subject to regular cropping, after which colonies are scattered. Adult mortality was 16–26% annually. Young formed 17.6–23% of the population in June; 11–15.6% of birds in March were in their first year and many of these bred successfully. Communal roosts were used only from mid-July to mid-October.     

Antibiotic resistant Escherichia coli and Salmonella in Russian rooks (Corvus frugilegus) wintering in the Czech Republic

AIMS: To characterize antibiotic resistant Escherichia coli and Salmonella isolates in rooks wintering in the Czech Republic. METHODS AND RESULTS: Three hundred and sixty-three faeces samples from rooks were examined for antibiotic resistant Escherichia coli and Salmonella. Altogether 13.7%E. coli isolates were resistant to antimicrobial agents tested. The dominant type of resistance was to tetracycline. Resistant E. coli isolates were examined for antibiotic resistance genes and class 1 integrons. Five of 29 antibiotic resistant isolates possessed the int1 gene. Nine Salmonella isolates (2.5%) were found in rook faeces. All the isolates belonged to serotype Salmonella enterica serovar Enteritidis phage type PT8 and PT23. CONCLUSIONS: The study suggests that rooks can be infected by antibiotic resistant E. coli and Salmonella isolates, probably reflecting the presence of such isolates in their sources of food and/or water in the environment. SIGNIFICANCE AND IMPACT OF THE STUDY: Rooks can serve as reservoirs and vectors of antibiotic resistant E. coli and Salmonella isolates and potentially transmit these isolates over long distances.