Bird Predation Research Articles

Transcriptomics of monarch butterflies (Danaus plexippus) reveals that toxic host plants alter expression of detoxification genes and down-regulate a small number of immune genes.

Herbivorous insects have evolved many mechanisms to overcome plant chemical defences, including detoxification and sequestration. Herbivores may also use toxic plants to reduce parasite infection. Plant toxins could directly interfere with parasites or could enhance endogenous immunity. Alternatively, plant toxins could favour down-regulation of endogenous immunity by providing an alternative (exogenous) defence against parasitism. However, studies on genomewide transcriptomic responses to plant defences and the interplay between plant toxicity and parasite infection remain rare. Monarch butterflies (Danaus plexippus) are specialist herbivores of milkweeds (Asclepias spp.), which contain toxic cardenolides. Monarchs have adapted to cardenolides through multiple resistance mechanisms and can sequester cardenolides to defend against bird predators. In addition, high-cardenolide milkweeds confer monarch resistance to a specialist protozoan parasite (Ophryocystis elektroscirrha). We used this system to study the interplay between the effects of plant toxicity and parasite infection on global gene expression. We compared transcriptional profiles between parasite-infected and uninfected monarch larvae reared on two milkweed species. Our results demonstrate that monarch differentially express several hundred genes when feeding on A.curassavica and A.incarnata, two species that differ substantially in cardenolide concentrations. These differentially expressed genes include genes within multiple families of canonical insect detoxification genes, suggesting that they play a role in monarch toxin resistance and sequestration. Interestingly, we found little transcriptional response to infection. However, parasite growth was reduced in monarchs reared on A.curassavica, and in these monarchs, several immune genes were down-regulated, consistent with the hypothesis that medicinal plants can reduce reliance on endogenous immunity.

Control of Bird Feeding Behavior by Tannin1 through Modulating the Biosynthesis of Polyphenols and Fatty Acid-Derived Volatiles in Sorghum

Bird predation during seed maturation causes great loss to agricultural production. In this study, through GWAS analysis of a large-scale sorghum germplasm diversity panel, we identified that Tannin1, which encodes a WD40 protein functioning in the WD40/MYB/bHLH complex, controls bird feeding behavior in sorghum. Metabolic profiling analysis showed that a group of sorghum accessions preferred by birds contain mutated tan1-a/b alleles and accumulate significantly lower levels of anthocyanins and condensed tannin compounds. In contrast, a variety of aromatic and fatty acid-derived volatiles accumulate at significantly higher levels in these bird-preference accessions. We subsequently conducted both sparrow feeding and sparrow volatile attractant assays, which confirmed, respectively, the antifeedant and attractant functions of these differentially accumulated metabolites. In addition, the connection between the biosynthesis pathway of anthocyanin and proanthocyanidin and the pathway of fatty acid–derived volatile biosynthesis was demonstrated by discovering that Tannin1 complex modulates fatty acid biosynthesis by regulating the expression of SbGL2 in sorghum, thus affecting the accumulation of fatty acid-derived volatiles. Taken together, our study identified Tannin1 as the gene underlying the major locus controlling bird feeding behavior in sorghum, illustrating an example of the identification of an ecologically impactful molecular mechanism from field observation and providing significant insights into the chemistry of bird–plant ecological interactions.

A primitive model for stochastic regular‐impulse population control and its application to ecological problems

AbstractA primitive mathematical model for population control in natural environment is formulated under a unified regular‐impulse stochastic control formalism. This kind of mathematical models, although they are candidates of the models of population control, seem not to be well studied. In this paper, the impulse control uses deteriorating items and is scheduled only at predetermined times as in many management problems. Finding the optimal control reduces to solving a system of recursive Hamilton‐Jacobi‐Bellman equations. Mathematical analysis on the system provides a viscosity characterization of its solution. The model is applied to management problems of the predatory bird and harmful benthic alga, both of which are concerns in recent inland fisheries. We show that the optimal regular controls for the two problems have qualitatively different behavior with each other, which is due to different interactions between the regular and the impulse controls.

Evolution of aposematism and mimicry in butterflies: Causes, consequences and paradoxes

Evolution of aposematism and mimicry in butterflies: Causes, consequences and paradoxes

Biomonitoring of toxic metals in feathers of predatory birds from eastern regions of Hungary

The aim of our study was to investigate the concentrations of toxic metals in the feathers of predatory birds in the Hortobágyi Madárpark (Bird Hospital Foundation). Samples were collected from different predatory birds originated from the eastern and north-eastern region of Hungary. Inductively coupled plasma optical emission spectrometry was used to determine the concentration of toxic metals. The mean values varied between bird species groups, their concentrations were between 0.29 ± 0.24 and 0.40 ± 0.30 mg/kg for arsenic (As), 0.09 ± 0.03 and 0.20 ± 0.18 mg/kg for cadmium (Cd), 1.15 ± 1.40 to 2.30 ± 1.52 mg/kg for lead (Pb) and 0.58 ± 0.31 to 2.19 ± 1.25 mg/kg for mercury (Hg), respectively. The measured values are not over the considered threshold values for these toxic metals and in accordance with similar concentrations of them recorded in similar species within Europe. No significant differences were found in their concentration between genders or age in the species. According to the detected concentrations of these metals, their levels accumulated in the feather of the investigated birds do not indicate the possibility of poisoning.

Epizootic Situation in the Mongolian Part of the Transboundary Sailugem Natural Plague Focus in 2018

Objectiveof the study was monitoring of epizootic situation in the Mongolian part of the trans-boundary Sailugem natural plague focus through 2018 for optimization of preventive and anti-epidemic activities to decrease the level of risk of human plague cases among the population in the border areas of Mongolia and Russia.Materials and methods. Epizootic survey was conducted across the area of 2668 km2 ; 282 mammals, 261 ectoparasites, including 257 fleas, were tested for plague. All laboratory investigations of the field material were carried out in the mobile laboratory for monitoring and diagnostics, mounted on the platform of KAMAZ. Field samples were subjected to molecular-genetic (PCR) and serological tests. Fresh and mummified pickings of birds of prey, corpses, caught rodents and lagomorphs, fleas collected from corpses, were tested using immune-chromatographic method (ICM) to detect capsular antigen (F1) of plague microbe. PCR and ICM positive samples were investigated applying bacteriological method. In the course of epizootiological survey, GIS-tools were employed. All the results obtained were plotted on electronic maps using QGIS 2.12.3 software package.Results and discussion. The total of 47 Yersinia pestis ssp. pestis strains were isolated from grey marmots and their fleas. Y. pestis DNA was detected in 60 objects. Serological testing showed 60 positive results. Contamination of the caught souslik with plague agent reached 4.5 % (n=22), fresh corpses and picking of predatory birds – 63.4 % (n=41), mummified corpses and leftovers, skeletal remains – 10.0 % (n=140). It was established that in the border territory, adjacent to Russia, an intensive diffused plague epizooty, caused by the agent of the main subspecies, takes place. All epizootic manifestations were revealed at the altitudes of 2400–2800 m above sea level, in densely populated grey marmot settlements. The epizooty was registered in most of the southern macro-slope of Sailugem ridge, throughout 100 km and along the whole Karalakhtu ridge – throughout 30 km. The epizooty area, confirmed by plague agent isolation, amounted to 1207 km2 (45.2 % of the examined territory).

Polymorph stability, and changed flight period, of Declana floccosa Walker, 1858 (Lepidoptera: Geometridae) in New Zealand, 1974–2016

ABSTRACTThe advantage for camouflage of variation in colour forms (binary, multi, or continuous) is a topic of increasing interest, but there are few long-term studies. We found that the ratios of colour forms of 337 polymorphic Manuka moths (Declana floccosa), recorded at one location, did not change over 42 years. This unexpected stability, in the face of probable bird predation against commoner forms and genetic drift, might result from the moth’s continuous variation that prevents predators forming a specific search image, or an unchanged food supply for the larvae. The flight period change from summer to winter, apparently the first recorded, was possibly driven by wasp (Vespula vulgaris) predation after their arrival about 1980.

STUDY RESULTS OF NATURAL FOCI OF TULAREMIA IN THE CRIMEA

We analyzed the observations’ results of natural foci of tularemia on the territory of Crimea during 2015–2018. Material from small mammals, ticks and pellets of predatory birds by means of polymerase chain reaction (PCR), enzyme-linked immunoassay (ELISA) and the reactions of indirect (passive) hemagglutination (RIHA) was investigated. Positive samples were detected in the zoological and entomological material. Synanthropic and hemisinanthropic species are found among infected small mammals, which indicates the existing risk of human diseases in human settlements. The activity of natural foci registered in 14 of the 26 municipal territories of the peninsula. To clarify the boundaries of natural foci and determine the degree of their activity, it is necessary to continue monitoring of natural ecosystems, conduct a comprehensive analysis of the populations’ status of small mammals and blood-sucking ectoparasites, epizootic and epidemic manifestations in various areas of Crimea for a longer period.

Ravens exploit wildlife roadkill and agricultural landscapes but do not affect songbird assemblages

ABSTRACTFuture land-use change could supplement populations of opportunistic predatory birds, such as corvids, resulting in amplified predation pressure and negative effects on populations of other avian species. We investigated whether Forest Ravens (Corvus tasmanicus) were more likely to be observed in modified landscapes and in areas of higher roadkill density in south-eastern Tasmania. Following this, we examined the effect of Forest Raven density on the abundance of other birds. We surveyed birds along roadsides to investigate the effects of land-use and raven population density on the presence of smaller birds/songbirds. We used species distribution models and generalised linear models to assess the habitat and population dynamics of Forest Ravens. Roadkill presence increased the probability of observing ravens more than six-fold. Forest Raven presence was also higher in agricultural areas than in forested and urban areas. There was no effect of Forest Raven abundance on species richness or abundance of smaller songbirds. This null result may be due to seasonal effects or because ravens moderate the presence or abundance of other avian predators. However, the interactions of meso-predators with other species are complex, and further work is required to assess the long-term effects of anthropogenic supplementation of ravens on the ecosystem.

The behaviour of Cotinis nitida Linnaeus, the green June beetle (Coleoptera: Scarabaeidae), on mowed lawns makes them especially vulnerable to bird predators

ABSTRACTMales of the green June beetle Cotinis nitida are regularly attacked by birds as they search for females on lawns but which bird species feeds on the beetle changes from year to year. In 2018 for the first time on a farm in northern Virginia, brown thrashers (Toxostomum rufum) joined blue jays (Cyanocitta cristata) as major predators of the beetles. The two species employed very different tactics when hunting for June beetles, with the thrashers searching while walking forward on the mowed lawn while the jays scanned for beetles when perched in trees about the lawn. The beetles became very scarce at the lawn in early July in 2017 and 2018 and their predators apparently moved elsewhere. Subsequently, male beetles were occasionally observed patrolling a nearby hayfield in search of mates with rare copulations recorded after July 15. Because predatory birds could not exploit the beetles in the tall grass of the hayfield it seems likely that the mowed lawn constituted an evolutionarily novel ecological trap which made searching beetles conspicuous and easily captured by beetle-hunting birds.

Bird predation on larvae of the box tree moth, Cydalima perspectalis (Walker, 1859)

[This paper indicates, by describing their predatory behaviors, seven species of birds observed to catch Cydalima perspectalis larvae; moth infestations widespread in the Far East and accidentally introduced to Europe in 2006, larvae that cause considerable damage to the box tree, Buxus sp., removing all leaves from the area. The observations were made in Piedmont (NW Italy) in 2016 in relation to the Blackbird, Turdus merula and Great tit, Parus major; and in the Holland (Noord Brabant) in 2017 in relation to Oystercatcher, Haematopus ostralegus; Great tit, Parus major; Blue tit, Cyanistes caeruleus; Magpie, Pica pica; Starling, Sturnus vulgaris; House sparrow, Passer domesticus.]
 
 [Article in Italian]

New policies for a new wildlife: A road map for the wildlife manager of the future

Historical human persecution of wildlife unintentionally shaped a shy fauna of large bird and mammalian predator and prey species that has survived in ecological refuges until recently in Europe. Rural exodus and changed human attitudes have decreased human persecution of these species and they are now getting out of their refuges, losing fear to humans and getting closer to urban areas. These changes have followed a non-linear pattern during the last few decades and are now starting to being noticed. Wildlife management policies will have to adjust rapidly to this new paradigm. We review the current situation in Europe and suggest a number of policy changes that may be necessary to cope with wildlife shifts in distribution and behaviour. New policies could include downgrading some protected areas but increasing the protection of currently unoccupied sites, changes in translocation programs, prevention of accidents, promotion of scavenging wildlife access to anthropogenic food sources far from urban areas or new awareness agendas, among others, to face the new paradigm and preserve the biodiversity inherited from the recent past.

Analysis of skull morphometric characters in diurnal raptors (Accipitriformes and Falconiformes)

Abstract Diurnal birds of prey (Accipitriformes and Falconiformes) has traditionally been known as comprising a single order. Recently, this classification has been used in the non-taxonomic sense as referring to a convergent group of birds that are largely classified as predatory birds. Although these birds are similar in their morphology, the species differ in their foraging methods and prey preference. The cranial shape and the physical attributes determine the efficiency of the resource use. The aim of this study is to increase our knowledge of the relationship between skull shape, prey preference, and foraging habits. A geometric morphometric approach was used to analyse two-dimensional cranial landmarks. We used principal component (PC) analyses on measurements that may be related to prey preference and foraging habits. The PCs are resulted described the relative height of the skull and beak, the variation in the relative size, the orientation and robustness of the lacrimal bone, the variation in the relative size of the neurocranium compared to the viscerocranium, and the orientation of the palatine bone. The dietary categories significantly overlap. The skull morphology reflects more on foraging habits than diet or prey preference.

Predation risk is a function of alternative prey availability rather than predator abundance in a tropical savanna woodland ecosystem

Typically, factors influencing predation risk are viewed only from the perspective of predators or prey populations but few studies have examined predation risk in the context of a food web. We tested two competing hypotheses regarding predation: (1) predation risk is dependent on predator density; and (2) predation risk is dependent on the availability of alternative prey sources. We use an empirical, multi-level, tropical food web (birds–lizards–invertebrates) and a mensurative experiment (seasonal fluctuations in abundance and artificial lizards to estimate predation risk) to test these hypotheses. Birds were responsible for the majority of attacks on artificial lizards and were more abundant in the wet season. Artificial lizards were attacked more frequently in the dry than the wet season despite a greater abundance of birds in the wet season. Lizard and invertebrate (alternative prey) abundances showed opposing trends; lizards were more abundant in the dry while invertebrates were more abundant in the wet season. Predatory birds attacked fewer lizards when invertebrate prey abundance was highest, and switched to lizard prey when invertebrate abundance reduced, and lizard abundance was greatest. Our study suggests predation risk is not predator density-dependent, but rather dependent on the abundance of invertebrate prey, supporting the alternative prey hypothesis.

An Analysis of Osprey/Chewing Lice Interaction, with a New Record for Saudi Arabia

Parasitism is a hostile relationship that helps greatly in the development and evolution of many creatures in their race for survival. Chewing lice of nestlings of the osprey Pandion haliaetus (L.) have been studied in Farasan Island, Saudi Arabia. All previous chewing lice records from this bird have also been reviewed. Four species of chewing lice are previously known to infest P. haliaetus. The nestlings of the osprey in Farasan were only infested by Colpocephalum turbinatum Denny, 1842. This species of chewing lice is recorded herein for the first time from the Kingdom of Saudi Arabia and its distributional pattern is very characteristic among three different avian orders (Accipitriformes, Columbiformes, and Strigiformes). Colpocephalum turbinatum was found mainly on terrestrial birds of the order Columbiformes and it may be transferred to predatory birds in the other two orders, but the presence of this parasite on some aquatic birds of prey like osprey may indicate that the ancestors of these birds were terrestrial hunters that acquired this louse from their prey such as doves and pigeons before their transference to aquatic life. The pattern of chewing lice distribution through their host populations and habitats may reveal some important ecological and evolutionary events that happened to their hosts in the past.

How conspicuous are peacock eyespots and other colorful feathers in the eyes of mammalian predators?

Colorful feathers have long been assumed to be conspicuous to predators, and hence likely to incur costs due to enhanced predation risk. However, many mammals that prey on birds have dichromatic visual systems with only two types of color-sensitive visual receptors, rather than the three and four photoreceptors characteristic of humans and most birds, respectively. Here, we use a combination of multispectral imaging, reflectance spectroscopy, color vision modelling and visual texture analysis to compare the visual signals available to conspecifics and to mammalian predators from multicolored feathers from the Indian peacock (Pavo cristatus), as well as red and yellow parrot feathers. We also model the effects of distance-dependent blurring due to visual acuity. When viewed by birds against green vegetation, most of the feathers studied are estimated to have color and brightness contrasts similar to values previously found for ripe fruit. On the other hand, for dichromat mammalian predators, visual contrasts for these feathers were only weakly detectable and often below detection thresholds for typical viewing distances. We also show that for dichromat mammal vision models, the peacock’s train has below-detection threshold color and brightness contrasts and visual textures that match various foliage backgrounds. These findings are consistent with many feathers of similar hue to those studied here being inconspicuous, and in some cases potentially cryptic, in the eyes of common mammalian predators of adult birds. Given that birds perform many conspicuous motions and behaviors, this study suggests that mammalian predators are more likely to use other sensory modalities (e.g., motion detection, hearing, and olfaction), rather than color vision, to detect avian prey. This suggests new directions for future behavioral studies and emphasizes the importance of understanding the influence of the sensory ecology of predators in the evolution of animal coloration.

Physiological impacts of pollution exposure in seabird's progeny nesting in a Mediterranean contaminated area

Aquatic wildlife is exposed through trophic transfer of hazardous substances to several threats inducing physiological impairments. We aimed at assessing the impact of contamination in one of the hot spots of pollution along Mediterranean coasts, the gulf of Gabes in Tunisia, on Common tern Sterna hirundo, a piscivorous top predator bird. Firstly, we compared the reproductive effort of breeding adults through clutch size distribution in three sites with different levels of pollution. Then, a battery of genotoxicity and oxidative stress biomarkers was carried out to assess physiological impairments in chicks. While defense mechanisms showed a depletion, lipid peroxidation and genotoxicity increased significantly according to pollution level. The multi-biomarker approach used here, discriminated chicks according to contamination degree of their nesting sites. Increases in genotoxicity and oxidative stress were correlated to a decrease in chick body mass known to lead to long-term impacts on juvenile survival and recruitment in birds.

Invasive coqui frogs are associated with differences in mongoose and rat abundances and diets in Hawaii

With the increasing rate of species being introduced to areas outside of their native ranges, non-natives are likely to interact in ways that influence each other’s populations. The high densities of invasive coqui frogs (Eleutherodactylus coqui) in Hawaii have been hypothesized to increase non-native mongoose (Herpestes auropunctatus) and rat (Rattus spp.) abundances, and in turn increase bird nest depredation rates. We compared the relative abundances of rats and mongooses and artificial bird nest predation rates at 12 sites that had plots with similar habitat invaded and not invaded by coqui frogs across the island of Hawaii. We interpret our results considering mongoose and rat stomach analyses and camera trap data collected to monitor coqui scavengers. We found that coqui presence was associated with 30% greater mongoose abundance and 17% lower Pacific rat (R. exulans) abundance. Based on our diet analyses and scavenging data, both mongooses and rats consume coquis, but mongooses were the most important consumers of coquis, which may have contributed to their increase in coqui plots. We speculate that coquis are competing with rats for invertebrate prey due to reduced Pacific rat abundance and greater amounts of fruit in rat stomachs collected in coqui-invaded compared to uninvaded plots. We did not observe any difference in bird nest predation rates in coqui-invaded and uninvaded plots. Our results suggest that the coqui invasion may increase or decrease non-native mammal populations, and non-native amphibians may serve as both novel prey and competitors to non-native mammals.

Kindness to the Final Host and Vice Versa: A Trend for Parasites Providing Easy Prey?

Traditionally the 'extended phenotype' concept refers to parasites that manipulate host phenotype to increase parasite fitness. This includes parasites who render intermediate hosts more susceptible to predation by final hosts. We explore here the proposition that an evolutionary driver in such cases is the energetic benefit to the final host, in addition to increased parasite fitness. We will review some well established host-manipulation models, where such a scenario seems likely. One example is provided by the protozoan Toxoplasma gondii, which conspicuously impairs predator avoidance in rodents. Pathologies in humans that acquire T. gondii are known, but infection in adult feline definitive hosts are most commonly asymptomatic and apparently innocuous. In another well documented case of parasite-mediated trophic transmission, trematode (Euhaplorchis californiensis) infected killifish (Fundulus parvipinnis) abandon normal caution and exhibit a range of behaviors which makes them more conspicuous to predatory birds. The birds get a free meal, but the presence of adult trematodes in the gut would seem to incur few if any negative consequences for the birds. There are exceptions to this pattern also among cases of parasite mediated trophic transmission, but major pathology in definitive hosts seems for the most part restricted to cases where manipulated intermediate hosts are of minor energetic importance. Current theories for the evolution of reduced pathogenicity in predatory final hots primarily focus on parasites minimizing pathogenicity to increase their own reproductive output and/or avoid selection on host preference for non-infected prey types. Here we advocate another alternative: If or when the benefit of increased prey acquisition outweighs pathogenicity or resource drain, there should be little or no selection on final hosts to minimize parasite infections. This mean that not only will host avoidance of infection not develop, but the molecular arms race for increased immunological defense will also likely be halted in such cases.

Some important overlooked aspects of odors in avian nesting ecology

Although outdated opinions about poor avian olfaction have largely disappeared in recent decades, there has been inadequate attention paid to olfaction of other organisms that interact with birds and their nests. In particular, olfaction is likely more important than vision for many biting arthropods and for many reptilian, mammalian, and likely even some bird predators of nests (e.g. some procellariiforms, piciforms, and corvids), but crypsis (or attractiveness) of nest odors has largely been ignored in the literature. Given the pivotal importance of nest success to a bird's fitness, there has likely been strong selection to conceal inadvertent cues to nest locations, including odors. Here, I summarize what is known about this, and discuss a few important topics I deem worthy of deeper investigation.