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Winter is a critical period for the survival of local bird species in temperate regions. Some wintering birds may rely on transient food, such as that provided at birdfeeders, but bird communities around birdfeeders may also attract predators. However, these effects of birdfeeders on interspecific interactions between birds and their predators remain largely unexplored and have so far not been tested experimentally. We hypothesized that birdfeeders indirectly attract predators in winter because of the attraction of small birds, and tested this hypothesis using experimental feeders at 52 different urban and rural sites across western Poland. We found that the number of small birds increased around birdfeeders, particularly those with provided food. We found that birdfeeders that attracted more small birds (regardless of whether they provided food) attracted also more predators, such as sparrowhawks Accipiter nisus and feral cats Felis domesticus. Moreover, birdfeeders in urban habitats attracted relatively fewer small birds but not fewer predators compared to those in rural areas. Altogether, birdfeeders with food provided attracted small prey birds but they attracted also more predators, whose presence may hinder small birds from fully utilizing available resources, potentially impacting their winter survival through direct (mortality) and indirect (increased monitoring and vigilance) effects.

Winter is a critical period for the survival of local bird species in temperate regions. Some wintering birds may rely on transient food, such as that provided at birdfeeders, but bird communities around birdfeeders may also attract predators. However, these effects of birdfeeders on interspecific interactions between birds and their predators remain largely unexplored and have so far not been tested experimentally. We hypothesized that birdfeeders indirectly attract predators in winter because of the attraction of small birds, and tested this hypothesis using experimental feeders at 52 different urban and rural sites across western Poland. We found that the number of small birds increased around birdfeeders, particularly those with provided food. We found that birdfeeders that attracted more small birds (regardless of whether they provided food) attracted also more predators, such as sparrowhawks Accipiter nisus and feral cats Felis domesticus. Moreover, birdfeeders in urban habitats attracted relatively fewer small birds but not fewer predators compared to those in rural areas. Altogether, birdfeeders with food provided attracted small prey birds but they attracted also more predators, whose presence may hinder small birds from fully utilizing available resources, potentially impacting their winter survival through direct (mortality) and indirect (increased monitoring and vigilance) effects. [ABSTRACT FROM AUTHOR]

Even if some are essential for biological functions, the accumulation of heavy metals above tolerable physiological limits is potentially toxic to also wild animals. The present study aimed to investigate concentrations of environmentally relevant heavy metals (As, Cd, Cu, Fe, Hg, Mn, Pb, and Zn) in feathers, muscle, heart, kidney, and liver tissues of wild birds (golden eagle [Aquila chrysaetos], sparrowhawk [Accipiter nisus], and white stork [Ciconia ciconia]) from Hatay province, southern Turkey. The metal concentrations of tissues were determined by a validated ICP-OES analysis method after microwave digestion. The concentration differences of metals in species/tissues and the correlations between essential/non-essential metals were determined by statistical analysis. According to the results, Fe (326.87±3.60 mg kg-1) had the highest, and Hg (0.09±0.00 mg kg-1) had the lowest mean concentration in all tissues. Compared to the literature; Cu, Hg, Pb, and Zn concentrations were lower; Cd, Fe, and Mn concentrations were higher. The correlations between As and all essentials; Cd and Cu, Fe; Hg and Cu, Fe, Zn; Pb and all essentials were significantly positive. In the conclusion, while essential Cu, Fe, and Zn are below the threshold value and do not pose a risk, Mn is close to the threshold value. Therefore, periodically monitoring the pollutant concentrations in bioindicators is a key necessity for the early determination of biomagnification trends and prevention of potential toxic stress on wildlife ecology. [ABSTRACT FROM AUTHOR]

Secondary exposure of predators to anticoagulant rodenticides, and in particular second generation anticoagulant rodenticides (SGARs), is a global phenomenon. The widespread and large-scale nature of this exposure has attracted considerable concern, although the consequences in terms of likelihood of poisoning of individuals and resultant impacts on populations are not well characterised. Secondary exposure of predators may as rise from once or more of: (i) eating contaminated commensal rodents subject to control (target species are typically rats and house mice); (ii) consumption of contaminated non-target small mammals (such as Peromyscus, Microtus, and Apodemus species) that encounter and feed on what are rodent-attractive baits; (iii) consumption of non-rodent vertebrate and invertebrate prey that may also incidentally encounter and eat baits. We hypothesised that predators feeding primarily on target species may be most at risk of exposure to SGARs while those predominantly taking non-mammalian prey may be at least risk. We tested this hypothesis by comparing exposure, determined from the presence and magnitude of SGAR liver residues, in red kites (Milvus milvus), which feeds extensively on rats, in barn owls (Tyto alba), kestrels (Falco tinnunculus), and tawny owls (Strix aluco) that feed widely on non-target small mammals, and in sparrowhawks (Accipiter nisus) that feed predominantly on small birds. We found that the scale and magnitude of exposure was broadly consistent with our hypothesis, and that controlling for age in the analysis could be important as older birds can accumulate residues with age. However, exposure in kestrels was typically greater than that in barn owls and tawny owls, despite what is thought to be a general similarity among the species in their diets. We discuss the relative importance of trophic pathways relative to other factors that may drive secondary exposure in predators, and confirm that species that feed on rats or other target species may be at most risk of exposure and poisoning.

Traditional methods to study raptor diet are usually limited temporally, e.g. prey remains at nesting sites, and are unsuitable to examine dietary changes throughout the year. Using web-sourced photography, we explore temporal patterns in prey size and key prey species between sexes of the sexually dimorphic Eurasian sparrowhawk (Accipiter nisus) throughout the United Kingdom. We examined 666 photographs of sparrowhawk on prey and identified the prey species involved, together with sparrowhawk sex. Changes in prey size and proportions of key prey species over time (seasonally and monthly) were explored for each sex. Prey weight was substantially higher for females than males. However, on average, prey size for both sexes declined during the summer period (May–June) being the lowest in June, which is the main nestling-rearing month for both sparrowhawks and their prey. Compared with summer, rock doves (Columba livia) were more important prey for female sparrowhawk in winter. Whereas, for males, Eurasian blackbirds (Turdus merula) were more important in spring compared with autumn. Web-sourced photography can overcome several limitations of previous methods used to study raptor diet including the ability to quantify diet between the sexes throughout the entire year, however, may also introduce a prey-size bias toward larger prey items.

The mitogenome of the Accipiter nisus is a circular module of 18,352 bp, which consists of 39 genes, containing 2 rRNA genes (12S rRNA and 16S rRNA), 13 protein-coding genes, 22 tRNA genes, and two non-coding regions (control region and pseudo control region). The mitogenome of A. nisus is composed of 31.3% A, 25.5% T, 30.4% C, 12.8% G, and 76.3% AT. The phylogenetic analysis revealed that A. nisus individuals was well grouped in Accipitridae and more closely related to genus Circus than other Accpiter species

The article focuses on Eurasian Sparrowhawk (Accipiter nisus) is a small bird of prey distributed throughout Europe and Asia and closely linked to forest environments. Topics include the male Eurasian Sparrowhawk typically captures small birds whereas females prey on larger birds, and the females gradually start hunting as the nestlings demand more food.

Five raptor species were recorded as breeding in the city of Wrocław (293 km2) during the years 2002-2010: Falco tinnunculus (2.4 pairs per 10 km2), Buteo buteo (4.1 pairs/10 km2 of wooded area), Accipiter gentilis (3.1 pairs/10 km2 of wooded area), Accipiter nisus (1.6 pairs/10 km2 of wooded area), Circus aeruginosus (0.2 pairs per 10 km2). All these species have increased in numbers over the last 20-30 years, both in the inner and outer zone of the city. Falco tinnunculus is a well-established raptor in the inner part of the city, while Accipiter nisus, A. gentilis, Buteo buteo started to infiltrate to the inner zone. In the last 70 years, a few cases of nesting were recorded for four other raptor species in Wrocław: Milvus migrans, Milvus milvus, Pernis apivorus and Falco subbuteo, but none of them was recorded in the inner zone of the city. Abundant and stable food supply (small mammals, columbids, corvids and small passerine birds), and freely available nesting and perching sites may contribute to this success. [ABSTRACT FROM AUTHOR]

The phenomenon of partial migration in birds in which some individuals of a population are migratory while others stay in the breeding area is of increasing scientific interest. The strategies of partial migratory raptors from Central Europe are, however, unclear for most species. We analysed ring re-encounter data of Eurasian Sparrowhawks Accipter nisus and Common Buzzards Buteo buteo ringed in Germany in terms of distances and directions between ringing and re-encounter sites. We investigated possible differences between sexes (only in Sparrowhawks) and age classes, as well as effects of ringing region, seasonal weather (in the form of North Atlantic Oscillation indices) and long-term temporal changes (including climate change) on migratory strategies by means of generalized linear models. We found that, in both species, migration is mostly conducted by juveniles, although migratory adults were also found. In general, male Sparrowhawks tend to migrate less than females. Sparrowhawks from different regions showed no differences in migration activity and no responses to long-term temporal changes. They did not respond to seasonal weather either. Buzzards showed strong responses to winter weather ('winter escapes') predominantly in highland regions, and a reduction of migratory intensity probably due to global warming. We compared our results to ones for Common Kestrels Falco tinnunculus and found most similarities between Kestrels and Sparrowhawks. [ABSTRACT FROM AUTHOR]

The reaction of wildlife to humans is known to differ with surroundings. In urban environments that provide suitable habitats for breeding birds, animals adapt to humans and their response is accordingly altered. This study examined the nest defense behavior of female Eurasian sparrowhawks (Accipiter nisus) during the breeding season in urban and rural areas of Prague. The females showed four different types of reaction to humans that approached the nest and differed significantly between the two study areas. Contrary to expectations, urban nesting females were more aggressive than rural conspecifics. The intensity of response increased as the season progressed, and females defended their broods to a much greater degree than their clutches in both urban and rural habitats, suggesting a differential effort as a function of their relative investment in the breeding attempt conforming with the parental investment hypothesis.

In 2006–2008, mapping the sparrowhawk (Accipiter nisus L.) and kestrel (Falco tinnunculus L.) occurred in the SE part of the Chřiby Upland. At the same time, the food spectrum of these birds of prey was determined during nesting periods. The area under monitoring represented about 25–30 km2.In each of the species, food was always monitored in a period from February to July at four nesting localities. The food spectrum was analysed by the direct observation of birds of prey, according to leftovers of food in the surroundings of nests and in nests of the predators. In Accipiter nisus, the food spectrum consisted of birds (85 %), mammals (3 %) and other animals (12 %). Turdus merula was the most frequent prey. In Falco tinnunculus, the food spectrum consisted of birds (18 %), mammals (76 %) and other animals (6 %). Microtus arvalis was unambiguously the most frequent prey.

The present study was carried out to determine the plexus sacralis and its branches in sparrowhawk(Accipiter nisus). Fifteen sparrowhawk were used in this study. Following the anaesthesing of the materials, cavity of the body was opened. Animals were fixed with formaldehyde after draining of their bloods. The nerves of plexus sacralis were separately dissected and photographed. Plexus sacralis was formed by the union of the branches of the synsacral spinal nerves which leave from ventrolaterale of os lumbosacrale. The plexus consisted of six (4–9) synsacral spinal nerves in sparrowhawk(Accipiter nisus). The nerves originating from plexus sacralis from cranial to caudal were nervus coxalis caudalis, the common root of nervus peroneus and nervus tibialis, nervus cutaneus femoris caudalis and the common branches of rami musculares. It was determined that general macroanatomical shapes of plexus sacralis and the distribution of nerves originating from this plexus were found to be similar with the other bird species in hawk which is one of the predatory bird species. However, it was determined that responsible for innervation of the leg and foot nervus peroneus and nervus tibialis common root and terminal branches of these nerves were significantly thick and strong in appearance. [ABSTRACT FROM PUBLISHER]

This preliminary study was aimed at determining the occurrence of haemosporidian parasites in the blood of sparrowhawks. For this purpose, blood samples were prepared from 9 sparrowhawks. All birds had been collected from different areas of Northeast Turkey. Blood smears were stained with 5% Giemsa solution and examined under the light microscopy. A total of 7 individuals were infected (77.8%). Haemoproteus spp., Leucocytozoon spp. and Plasmodium spp. were detected in 5 (55.6%), 6 (66.7%) and 4 (44.4%) birds, respectively. There were no haemosporidian parasites in 2 birds (22.2%). We observed mixed infections in 85.7% of the birds and single infections (14.3%). Each of the 3 parasites was observed together in 2 birds. Both Haemoproteus spp. and Leucocytozoon spp. were detected in 3 birds. Leucocytozoon sp. and Plasmodium sp. were detected in one bird. This is the first report of the occurrence of hemosporidian parasites in sparrowhawks in Northeastern Turkey. [ABSTRACT FROM AUTHOR]

Phenological shifts and associated changes in the temporal match between trophic levels have been a major focus of the study of ecological consequences of climate change. Previously, the food peak has been thought to respond as an entity to warming temperatures. However, food peak architecture, that is, timings and abundances of prey species and the level of synchrony between them, determines the timing and shape of the food peak. We demonstrate this with a case example of three passerine prey species and their predator. We explored temporal trends in the timing, height, width, and peakedness of prey availabilities and explained their variation with food peak architecture and ambient temperatures of prebreeding and breeding seasons. We found a temporal match between the predator's breeding schedule and food availability. Temporal trends in the timing of the food peak or in the synchrony between the prey species were not found. However, the food peak has become wider and more peaked over time. With more peaked food availabilities, predator's breeding success will depend more on the temporal match between its breeding schedule and the food peak, ultimately affecting the timing of breeding in the predator population. The height and width of the food peak depended on the abundances and breeding season lengths of individual prey species and their reciprocal synchronies. Peakednesses of separate prey species' availability distributions alone explained the peakedness of the food peak. Timing and quantity of food production were associated with temperatures of various time periods with variable relevance in different prey species. Alternating abundances of early and late breeding prey species caused high annual fluctuation in the timing of the food peak. Interestingly, the food peak may become later even when prey species' schedules are advanced. Climate warming can thus produce unexpected changes in the food availabilities, intervening in trophic interactions. [ABSTRACT FROM AUTHOR]

This study was aimed at determining the morphology of the aortic arch in the sparrowhawk. For this purpose, arteries near the heart of six sparrowhawks were assessed. Latex injection method was applied to the three materials and barium sulphate solution was injected into the aorta for angiography in three other materials. It was observed that two major arteries arose from aortic arch in the sparrowhawk: the left brachiocephalic trunk and the right brachiocephalic trunk. These trunks were contiguous arteries but separately originated from the aorta. The brachiocephalic trunks were divided into the common carotid and subclavian arteries after their origins. First, the common carotid arteries are given off by the brachiocephalic trunks. The common carotid artery was giving off esophagotracheobronchial artery and vertebral trunk. Vertebral trunk was locating under the brachial plexus. The subclavian artery was continuations of the brachiocephalic trunk and it was bifurcating to the axillar artery and the pectoral trunk just from its own beginning. The axillary artery passed the brachial plexus crosswise from above, and reached to the wing. The sternoclavicular artery stemmed from ventral aspect of the begining of the axillary artery. The thickest branch of the subclavian artery was the pectoral trunk, which was branched the cranial external thoracic artery, the caudal external thoracic artery, the dorsal thoracic artery, and the internal thoracic artery. It is hoped that the results of this morphological study will contribute to the species specific anatomical data in the birds. [ABSTRACT FROM AUTHOR]

The article discusses the unusuality in the Eurasian sparrowhawk (Accipiter nisus) fishing behavior. It reports that the sparrowhawks' prey on birds and fishes, they prefer fishing in the cold temperature, and the researchers' observation of similarity in sparrowhawks' hovering flight with Eurasian Kestrel (Falco tinnunculus). It examines sparrowhawks' attempt of fishing post-their attempt failure.

Sparrowhawks are commonly used for quail hunting in northeastern Turkey. Despite it is importance in Turkey, there is a dearth of information concerning the anatomy of the syrinx in the sparrowhawk. The objective of this study was to assess the structure and morphological differences of the sparrowhawk's syrinx from those of other avian species. The syrinx, which is the main source for vocalization for birds is located on the caudal end of the trachea. To the best knowledge of the authors this is the first study of the syrinx of the Sparrowhawk. The syrinx of the sparrowhawk was found to be of the tracheobronchial type and consists of four tracheosyringeal cartilages cartilage and five bronchosyringeal cartilages. For the histological specimens, syrinx tissues were stained with Crossman modified triple stain for histological evaluation, Verhoeff's elastic fibers stain for elastic fiber density, and Alcian blue (pH: 2.5) and periodic acid Schiff (PAS) stain for mucopolysaccharide and neutral mucins, respectively. The pessulus of hyaline cartilage was found to be covered with pseudo-stratified epithelium. The medial labia and medial tympaniform membrane consisted of double-ply layers of epithelium, which consisted of collagen and elastic fiber layers. In addition, the bronchosyringeales muscle consisted of extrinsic muscles only. In conclusion, the results of this study may contribute to knowledge of morphologic and histologic structure and variations between bird species. [ABSTRACT FROM AUTHOR]

Prey typically respond to potential predators by taking flight. This results in an optimal flight initiation distance (FID) at which the risk of remaining and the cost of flight are equal. Thus, FID is strongly negatively correlated with susceptibility to predation by the spar-rowhawk Accipiter nisus across species of small European birds. However, not everything that looks like a hawk is in fact a hawk. Aggressive mimicry arises from the resemblance between a dangerous model such as a predatory hawk and an innocuous mimic such as a cuckoo that makes errors made by individuals that encounter models and mimics potentially dangerous and life threatening. A prime example of such aggressive mimicry is the hawk-like appearance of common cuckoos Cuculus canorus and other cuckoos. If mimicry is efficient, we should expect that species of small birds that are prey of hawks and hosts of cuckoos react just as strongly to a cuckoo as to the presence of a dangerous model like a sparrowhawk. We used FID of small birds as a measure of the reaction of prey to models and mimics, predicting that FID would be negatively related to susceptibility to predation and positively to risk of cuckoo parasitism. Both susceptibility to sparrowhawk predation and rate of brood parasitism by the common cuckoo independently explained variation in FID, consistent with the expectation that both hawks and cuckoos have imposed significant selection pressures on FID and that species of small birds perceive cuckoos as true mimics of hawks. [ABSTRACT FROM AUTHOR]

The close resemblance between the common cuckoo, Cuculus canorus, and the Eurasian sparrowhawk, Accipiter nisus, is often viewed as Batesian mimicry evolved by the cuckoo in response to the aggression of its host. However, the effectiveness of such mimicry is poorly known. We examined cuckoo–hawk discrimination ability in the great reed warbler, Acrocephalus arundinaceus, a well-known and aggressive cuckoo host. We measured the responses of birds to three combinations of simultaneously presented taxidermic mounts of the cuckoo, sparrowhawk and turtle dove, as a harmless control, placed near their nests. Great reed warblers clearly discriminated the two enemies from the innocuous species. They always attacked cuckoos and sparrowhawks more often than turtle doves suggesting they considered both a danger to their broods. However, when we confronted the tested birds with the simultaneously presented mounts of these species, the parents attacked the cuckoo more frequently than the sparrowhawk. The results revealed that although great reed warblers attacked both cuckoo and sparrowhawk mounts near their nest, they were able to discriminate between them. This may suggest that if cuckoos had evolved the visual mimicry of a sparrowhawk to avoid host attacks, this mimicry may be unsuccessful not only because it is imperfect and hosts can learn to discriminate but also because of the generalized nest defence of more aggressive hosts. [Copyright &y& Elsevier]

The article presents a study on sex determination of Eurasian Sparrowhawks (Accipiter nisus). It is said that sex determination among Eurasian Sparrowhawks is not a problem in adults because sexual dimorphism is evident. However, juvenile sparrowhawks can only be sexed using biometric measures or molecular methods. The study examined sparrowhawks in Spain in order to develop a sexing tool for field sites. It was found that it was possible to sex sparrowhawks on three variables, namely bill length, forearm and eighth primary length (P8).

Amodal completion enables an animal to perceive partly concealed objects as an entirety, and to interact with them appropriately. Several studies, based upon either operant conditioning or filial imprinting techniques, have shown that various animals (both mammals and birds) can perform amodal completion. Before this study, the use of amodal completion by untrained animals in the recognition of objects had not been considered. Using two feeders, we observed in a field experiment the reaction of tits to the torso of a sparrowhawk (partly occluded or an ‘amputated’ dummy) in two different treatments (sparrowhawk torso vs. complete dummy pigeon; and torso vs. complete dummy sparrowhawk). It is clear that the birds considered the two torso variants as predators and kept away from both of them when the second feeder offered a ‘pigeon’ instead. On the other hand, when a ‘complete sparrowhawk’ was present on the second feeder, the number of visits to the occluded torso remained low; while the number of visits to the amputated one increased threefold. Birds risked perching near what was clearly an amputated torso; while the fear of a “hiding” (occluded) torso remained unchanged, when the second feeder did not provide a safe alternative. Such discrimination between torsos requires the ability for amodal completion. Our results demonstrate that in their recognition process, the birds not only use simple sign stimuli, but also complex cognitive functions. [ABSTRACT FROM AUTHOR]

We investigated the physiological and behavioral consequences for prey breeding at different distances from a nesting predator. In a natural setting, Pied Flycatchers (Ficedula hypoleuca) made territory location decisions relative to established Sparrowhawk (Accipiter nisus) nests. From female flycatchers attending nests at different distances from Sparrowhawk nests, we measured body mass, blood stress protein (HSP60 and HSP70), and plasma immunoglobulin levels at the beginning (initial) and end (final) of the flycatcher breeding cycle, and provisioning rates during the nestling phase. We found that individuals breeding in closer proximity to Sparrowhawk nests, under higher perceived predation risk, showed significantly lower body mass, higher stress protein and immunoglobulin levels, and higher nestling provisioning rates compared to those individuals breeding farther away. Across the range of distances investigated (30-610 m), final stress protein levels decreased linearly with distance, whereas the final measures of the other variables showed unimodal trends, increasing or decreasing until an intermediate distance (~350 m) and reversing the direction of the trend. Within 300 m, however, all measures showed significant linear associations with distance from the Sparrowhawk nest. Body mass and stress protein associations with distance from Sparrowhawk nests were only present during late breeding, and not in early incubation. Spatial proximity to Sparrowhawk nests consistently explained significant variation in both physiological and behavioral measures, despite the multitude of potential sources of variation for these measures in a natural setting. This suggests that predictable spatial patterns in these measures in avian communities are determined by the sites of breeding predators. Habitat selection decisions of migrant prey that vary only slightly spatially have consequences even at the cellular level, which plausibly have impacts on individual survival. In addition, this study suggests that predation risk is an important factor affecting physiological condition of prey, including stress protein induction in terrestrial vertebrates. [ABSTRACT FROM AUTHOR]

The article discusses a study examining the predatory role of the Eurasian Sparrowhawk in the declining population of House Sparrow in Great Britain. Evidence of decline among prey species of sparrows has been reported in the data published by the Garden Bird Feeding Survey (GBFS) of the British Trust for Ornithology. Statistical information illustrating the differences in temporal trends in Eurasian Sparrowhawk incidence and House Sparrow population data between rural and urban sites studied are noted.

1. Changes in community composition are expected to entail cascading effects at different trophic levels within a food web. However, empirical evidence on the impact of changes in prey communities on the population dynamics of generalist predators, and on the extent of possible feedback processes, remains scarce. 2. We analysed the dynamics of a generalist predator, the European sparrowhawk Accipiter nisus L., in a rural area of Northern Denmark. Over a 20-year period, the diet of the predator has been thoroughly assessed (>30 000 identified prey items) and quantitative information about its avian prey community, based on standard breeding bird surveys, has revealed significant trends for several passerine species, although the overall prey biomass available remained stable. 3. The growth rate of the sparrowhawk breeding population was negatively related to the previous sparrowhawk density and to winter temperature, but was positively related to available prey biomass. Contrary to expectations for a generalist predator, sparrowhawks seemed to be predominantly sensitive to changes in the cumulative abundance of their two main prey species, the skylark Alauda arvensis L. and the blackbird Turdus merula L., but less so to changes in the wider prey community. 4. In demographic terms, the two-phase sparrowhawk dynamic recorded here (a recovery following an initial decrease) was mainly driven by recruitment of yearling females into the breeding population rather than by variation in the apparent survival of breeding females. 5. Our findings emphasize that changes in the composition of a prey community, affected by environmental changes, impacted population dynamics of a generalist predator. Finally, we found conditions that might enable apparent competition between blackbirds and song thrushes Turdus philomelos L. to occur. High blackbird abundance, maintaining sparrowhawks at a relatively high density may, in turn, push song thrushes into a predator pit. [ABSTRACT FROM AUTHOR]

A central problem in population ecology is to use time series data to estimate the form of density dependence in the per capita growth rate (pgr). This is often accomplished with phenomenological models such as the theta-Ricker or generalized Beverton-Holt. Using the theta-Ricker model as a simple but flexible description of density dependence, we apply theory and simulations to show how multimodality and ridges in the likelihood surface can emerge even in the absence of model misspecification or observation error. The message for model fitting of real data is to consider the likelihood surface in detail, check whether the best- fit model is located on a likelihood ridge and, if so, evaluate predictive differences of biologically plausible models along the ridge. We present a detailed analysis of a focal data set showing how multimodality and ridges emerge in practice for fits of several parametric models, including a state-space model with explicit accommodation of observation error. Best-fit models for these data are biologically dubious beyond the range of the data, and likelihood ratio confidence regions include a wide range of more biologically plausible models. We demonstrate the broad relevance of these findings by presenting analyses of 25 additional data sets spanning a wide range of taxa. The results here are relevant to information-theoretic and Bayesian methods, which also rely on likelihoods. Beyond presentation of best-fit models and confidence regions around individual parameters, effort toward understanding features of the likelihood surface will help ensure the most robust translation from statistical analysis to biological interpretation. [ABSTRACT FROM AUTHOR]

1. Climate change has been shown to affect the phenology of many organisms, but interestingly these shifts are often unequal across trophic levels, causing a mismatch between the phenology of organisms and their food. 2. We consider two alternative hypotheses: consumers are constrained to adjust sufficiently to the lower trophic level, or prey species react more strongly than their predators to reduce predation. We discuss both hypotheses with our analyses of changes in phenology across four trophic levels: tree budburst, peak biomass of herbivorous caterpillars, breeding phenology of four insectivorous bird species and an avian predator. 3. In our long-term study, we show that between 1988 and 2005, budburst advanced (not significantly) with 0·17 d yr−1, while between 1985 and 2005 both caterpillars (0·75 d year−1) and the hatching date of the passerine species (range for four species: 0·36–0·50 d year−1) have advanced, whereas raptor hatching dates showed no trend. 4. The caterpillar peak date was closely correlated with budburst date, as were the passerine hatching dates with the peak caterpillar biomass date. In all these cases, however, the slopes were significantly less than unity, showing that the response of the consumers is weaker than that of their food. This was also true for the avian predator, for which hatching dates were not correlated with the peak availability of fledgling passerines. As a result, the match between food demand and availability deteriorated over time for both the passerines and the avian predators. 5. These results could equally well be explained by consumers’ insufficient responses as a consequence of constraints in adapting to climate change, or by them trying to escape predation from a higher trophic level, or both. Selection on phenology could thus be both from matches of phenology with higher and lower levels, and quantifying these can shed new light on why some organisms do adjust their phenology to climate change, while others do not. [ABSTRACT FROM AUTHOR]

Brood parasites and predators pose unique threats that may favour the evolution of enemy-specific defence strategies. We considered whether reed warblers, Acrocephalus scirpaceus, have a specific alarm call for common cuckoos, Cuculus canorus, and whether their alarms attract mates and neighbours. Mounts of cuckoos (threat to nest but harmless to adults) were significantly more likely to be mobbed and were mobbed more strongly, with rasp calls and mandible snaps, than mounts of sparrowhawks, Accipiter nisus (threat to adults only), or teal, Anas crecca (a harmless control). However, calls were not acoustically specific to the kind of enemy presented, but rather varied in usage with mount distance from the nest and mount species. This suggests that reed warbler alarm signals are not functionally referential, but rather convey immediacy of threat to the nest. Mates and neighbours often approached during calling, and playback experiments confirmed they were more likely to be attracted by mobbing calls than by control calls. The response was graded, with higher repetition rates of mobbing calls attracting more individuals. Nevertheless, it is unlikely that mobbing calls functioned solely to attract mates and neighbours because calling continued even after these were attracted and was not more likely when there were close neighbouring nests, and attracted neighbours were sometimes chased away by residents. Our results show that reed warblers discriminate a brood parasite from both a dangerous species and an innocuous species by using graded alarm signals that attract conspecifics. This is compatible with the idea that nest defence by reed warblers includes a specific evolved response to brood parasitism. [Copyright &y& Elsevier]

Predators have been hypothesized to prey on individuals in a poor state of health, although this hypothesis has only rarely been examined. We used extensive data on prey abundance and availability from two long-term studies of the European Sparrowhawk (Accipiter nisus) and the Eurasian Goshawk (Accipiter gentilis) to quantify the relationship between predation risk of different prey species and infection with malaria and other protozoan blood parasites. Using a total of 31 745 prey individuals of 65 species of birds from 1709 nests during 1977-1997 for the Sparrowhawk and a total of 21 818 prey individuals of 76 species of birds from 1480 nests for the Goshawk during 1977-2004, we show that prey species with a high prevalence of blood parasites had higher risks of predation than species with a low prevalence. That was also the case when a number of confounding variables of prey species, such as body mass, breeding sociality, sexual dichromatism, and similarity among species in risk of predation due to common descent, were controlled in comparative analyses of standardized linear contrasts. Prevalence of the genera Haemoproteus, Leucocytozoon. Plasmodium, and Trypanosoma were correlated with each other, and we partitioned out the independent effects of different protozoan genera on predation risk in comparative analyses. Prevalence of Haemoproteus, Leucocytozoon, and Plasmodium accounted for interspecific variation in predation risk for the two raptors. These findings suggest that predation is an important factor affecting parasite-host dynamics because predators tend to prey on hosts that are more likely to be infected, thereby reducing the transmission success of parasites. Furthermore, this study demonstrates that protozoan infections are a common cause of death for hosts mediated by increased risk of predation. [ABSTRACT FROM AUTHOR]