Egg Predation Research Articles

PREDATION OF PALE-BREASTED THRUSH EGGS BY THE ARIEL TOUCAN IN BRAZIL: FAILURE OF THE ANTI-PREDATORY STRATEGY

The Channel-billed Toucan (Ramphastos vitellinus ariel) is an omnivorous bird that eventually is nest-robbers. Several birdsongs display anti-predatory strategies such as attacks and mobbing calls to face this kind of predators. This note reports a predatory event of one Channel-billed Toucan upon eggs of Pale-breasted Thrush (Turdus leucomelas), and describe the anti-predatory behavior, principally alert and mobbing calls of the thrush. Even though the Pale-breasted Thrush displayed the anti-predatory behaviors to harass the toucan, the egg predation was not avoided. Although the predation upon eggs by Ramphastos vitellinus has been reported several times, the majority of reports lacks of identity of the bird species affected, this being the first confirmed record in Turdus leucomelas.

The serotonin 1A receptor modulates the social behaviour within groups of a cooperatively-breeding cichlid

The neurotransmitter serotonin (5-HT) reduces aggressive behaviour in a number of vertebrates, and the 5-HT1A receptor is known to be involved in this regulation. However, the role of this receptor in the modulation of sociopositive behaviour remains largely unknown. Here we investigated the role of the 5-HT1A receptor in the regulation of aggressive, submissive and affiliative behaviour in the cooperatively-breeding cichlid Neolamprologus pulcher. In two experiments, we performed intramuscular injections of a 5-HT1A agonist (8-OH-DPAT) and antagonist (Way-100635) followed by recordings of social behaviour of injected fish within their social groups. We determined the concentrations and post-injection times when the drugs had the greatest effect on social behaviour. We recorded spontaneous social behaviour in both experiments. In the second experiment we also recorded behaviour after social groups received a territorial challenge by live presentations of either conspecifics or egg predators. The 5-HT1A agonist caused an increase in aggression and a decrease in submission and affiliation, whereas the antagonist had the opposite effects. Thus, the 5-HT1A receptor plays an important regulatory role not only for aggressive but also sociopositive behaviour.

Method Development and Determination of Chlorinated Polycyclic Aromatic Hydrocarbons in Different Matrices

The aim of this study was to develop an analytical method, which separates selected chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs) from fat, and fat-free or vegetable matrices. The method contains extraction-, cleanup-, and quantification steps. Integration of automated analysis actions, as in extraction and cleanup, should enhance the reproducibility, precision, and efficiency of the method. This was confirmed by validation of the overall analytical process. In the end, as a performance check, the developed method was applied on different matrices, e.g., tea, rice, grilled pork, and eel and predator eggs, as a non-food example. An inter-laboratory check was initiated as replacement for the lack of proficiency tests. Due to the high level of automation, both personnel and time effort are very low. In addition, the method is very robust with regard to the variability of the solvent selection and the loss of analytes by evaporation to dryness. It could be demonstrated that the developed method is applicable to different matrices with reproducible and precise results. This applies also to low-fat food and feed.

COVID-19 lockdown reveals tourists as seabird guardians

The widespread lockdowns put in place to limit the spread of the new coronavirus disease (COVID-19) offers a rare opportunity in understanding how human presence influence ecosystems. Using data from long-term seabird monitoring, we reveal a previously concealed guarding effect by tourist groups on an iconic seabird colony in the Baltic Sea. The absence of tourists in 2020 lead to a sevenfold increase in presence of white-tailed eagles Haliaeetus albicilla, a sevenfold increase in their disturbance of breeding common murres Uria aalge and causing 26% lower murre productivity than the long-term average. Eagles did not prey on murres, but their frequent disturbances delayed egg laying and facilitated egg predation from herring gulls Larus argentatus and hooded crows Corvus cornix. Based on our findings, we suggest that human presence could be used as a strategic measure in guarding seabird colonies, and that a social-ecological systems perspective is vital for long-term success in protected area management.

Natural Biological Control of Bagrada Hilaris by Egg Predators and Parasitoids in North-Central Californianatural Biological Control of Bagrada Hilaris by Egg Predators and Parasitoids in North-Central California

Natural Biological Control of Bagrada Hilaris by Egg Predators and Parasitoids in North-Central Californianatural Biological Control of Bagrada Hilaris by Egg Predators and Parasitoids in North-Central California

Prey identity but not prey quality affects spider performance.

Increasing host plant quality affects higher trophic level predators, but whether such changes are simply a result of prey density or are also affected by changes in prey quality remain uncertain. Moreover, whether changes in prey quality affect measures of predator performance is understudied. Using a combination of field and greenhouse mesocosm experiments, we demonstrate that the survival and body size of a hunting spider (Pardosa littoralis Araneae: Lycosidae) is affected more by prey species identity than the trophic level of the prey. Furthermore, increasing host plant quality does not necessarily propagate through the food web by altering prey quality. While changes in plant quality affected spider body mass, they did so in opposite ways for spiders feeding on Prokelisia (Hemiptera: Delphacodes) herbivores relative to Tytthus (Hemiptera: Miridae) egg predators, and had no impact on spider body mass for two additional species of intraguild prey. These changes in body mass were important because greater body mass increased spider egg production. To examine the generality of this pattern, we reviewed the literature and found a consistent positive relationship between female body size and egg production for Pardosa species, indicating that body size is a reliable proxy for fitness. While many studies emphasize the importance of nitrogen to arthropod diets, this focus may be driven largely by our understanding of herbivore diets rather than predator diets. Thus, the positive impact of host plant quality on higher trophic level predators appears to be driven more by altering prey composition, density, and availability rather than simply providing predators with more nutritious prey.

Inferred predation of Fairy Tern eggs by Ruddy Turnstones at Rottnest Island, Western Australia, an internationally significant shorebird site

Ruddy Turnstones Arenaria interpres have been identified as egg-predators at seabird and shorebird colonies, including gull and tern colonies in the tropics and Northern Hemisphere. The Australian Fairy Tern Sternula nereis nereis is a threatened (Environment Protection and Biodiversity Conservation Act 1999: Vulnerable) coastal seabird, whose breeding behaviour and ecology expose it to a wide range of threats. This study describes inferred predation on Fairy Tern eggs at a small breeding colony on Rottnest Island, Western Australia, by Ruddy Turnstones, a previously unsuspected predator for thisspecies. Unlike the behavioural response shown towards Silver Gulls Larus novaehollandiae and Australian Ravens Corvus coronoides, which includes collective group defence and dive-bombing, Fairy Terns showed a lack of aggression towards Turnstones within the colony. The lack of a behavioural response suggests that the Terns did not recognise the Turnstones as predators, which may increase the risk of egg-predation. This study suggests that we should be alert to threats from unsuspected predators, which have the potential to reduce the breeding success of this Vulnerable tern.

Review of inter and intraspecific predation by shorebirds

Predation is often the most important driver of breeding productivity and population dynamics in birds, with an increasing impact in the currently rapidly changing world. Despite decades of intensive research, our understanding of trophic interactions and food webs is still limited. Although there is good knowledge of regular predators within particular groups of animals, focused overviews of such predator-prey interactions are often lacking. Here, I review predation behaviour by shorebirds: plovers, sandpipers and allies, over the globe – presenting 16 cases of interspecific predation relationships and two cases of intraspecific predation of eggs or chicks, altogether involving 11 species of predators and 13 species of prey.

On collection of predatory thrips (Insecta: Thysanoptera) in wheat fields

Some thrips species are known as predators of eggs, exist as the inactive stages of mites, and can be tiny, especially phytophagous thrips. This study aimed at evaluating the population fluctuation and species diversity of predatory thrips in wheat fields of Eyvan county (Ilam province, Iran) in the year 2016. Thrips specimens were collected and identified by weekly sampling during wheat growth stages (from early April to late June). Wheat bushes were shaken on a white dish. Finally, microscopic slides were prepared and all samples were enumerated. The population fluctuation of predatory thrips was calculated. In this study, six species of predatory thrips belonging to three genera were identified. Amongst them, Aeolothrips intermedius Bagnall (family Aeolothripidae) was the dominant species in both irrigated and rainfed wheat fields accounting for 72.43% and 50.85% of all species, respectively. Biodiversity indices were calculated using the number of species and their relative abundance. Shannon diversity, Simpson’s, Margalef’’s and species richness indices were 1.76, 0.86, 1.25 and 1, respectively. The highest biodiversity was in rainfed fields and during the wheat flowering stage, and the highest Shannon-Wiener evenness index was also in rainfed fields and at the ripening stage. The richness of thrips in rainfed wheat fields during the stem elongation stage was higher than in other wheat stages. Correlation of the density of predatory thrips with temperature and humidity showed a significantly positive correlation with temperature.

Evaluation of lethal control of introduced sugar gliders as a tool to relieve bird nest predation

Lethal control of invasive mammalian predators can be controversial and is rarely a ‘silver bullet’ for conservation problems. Evaluating the efficacy of lethal control is important for demonstrating the benefits to threatened species are real and detecting unexpected perverse outcomes. We implemented a pilot study to evaluate if lethal control of introduced sugar gliders Petaurus breviceps can reduce the rate of nest predation on Tasmanian hollow nesting birds including swift parrots (Lathamus discolor). Using a before-after-control-impact design, we implemented a lethal control treatment whereby we attempted to remove sugar gliders from three treatment sites. In each time period across sites we monitored quail eggs in nest boxes to record predation, and used cameras to detect sugar gliders. We caught nine sugar gliders over three treatment sites. The model best supported by the data indicated an effect of site×time period on both egg survival and the rate of glider detection on cameras. There was no support for an effect of treatment on our data. We also recorded predation of a real swift parrot nest by sugar gliders at a treatment site where we recorded no predation of quail eggs. Our pilot study shows that at small scales, intensive lethal control of gliders yields low capture rates and no discernible effect on the metrics we measured. We conclude that alternative approaches to controlling the impact of sugar gliders, such as habitat protection, are critical in this study system before lethal control is widely implemented as a management tool.

No significant effects of insecticide use indicators and landscape variables on biocontrol in field margins

Insecticides are used widely to manage pests, but they may cause mortality in natural enemy populations and non-target prey. On the other hand, resources provided by the landscape – often associated with semi-natural habitat – may enhance natural enemy communities. While there is substantial information on how insecticide use and semi-natural habitats influence biocontrol in crop fields, little is known about how local insecticide use interacts with landscape variables to govern natural biocontrol in field margins. In this 2-year study we assessed predation and parasitism rates of eggs of the cabbage moth (Mamestra brassicae) on potted cabbage plants in field margins adjacent to 20 organically managed fields and 18 conventionally managed fields We analysed egg predation and parasitism rates in field margins using three predictors for insecticide use: (i) farming system (organic or conventional), (ii) frequency of insecticide use in the adjacent focal fields, and (iii) estimated insecticide use quantity within a radius of 1 km from the sampling sites. Insecticide use included foliar or soil-applied applications, including mineral oils. Landscape variables were used as covariables to account for landscape effects. Mean predation and parasitism rates were 14 % and 6%, respectively. There were no significant associations between predation and parasitism rates in field margins with insecticide use in the adjacent field or the wider landscape. Our findings suggest that field margins can be valuable habitats for natural enemies in agricultural landscapes, irrespective of the insecticide use intensity at the local and landscape scale.

Predator–prey relationships within natural, restored, and created vernal pools

We performed a multiyear monitoring study to compare amphibian habitat quality among four natural, four restored, and six created pools. We used successful reproduction and metamorphosis of two vernal pool indicator species, the wood frog and spotted salamander, to represent desired outcomes. Ordination techniques were used to identify the aspects of habitat quality that were most correlated with desired outcomes. Previously published results indicated that pool depth, volume, and hydroperiod were among the best predictors of success, regardless of pool type. Observations in the first few years of monitoring also suggested that pools with longer hydroperiods had a greater abundance of aquatic predators of eggs and larvae of indicator species. This follow‐up study further explores and compares predator–prey relationships among pool types. We quantified within‐pool predator and prey abundance and diversity and collected another year of data on the reproductive success of indicator species. Our results confirmed that mean predator abundance was eight times higher in pools with longer hydroperiods. We documented a 96% decrease in wood frog survival rates in a semi‐permanent, natural pool following a 41% decrease in overhead canopy cover and an increase in green frog abundance. At the same time, wood frog reproductive success increased in nearby restored pools with lower predator abundance. Pools with the highest mean survival rates for the two indicator species combined were short‐ or long‐cycle pools (i.e. hydroperiod of 12–35 weeks) with low predator abundance (i.e. <1 organism L−1) and greater proportions of arthropod prey relative to other food items.

A Comparison of 2 Methods to Deter Fish Crows from Depredating Seabird Eggs

ABSTRACTFish crows (Corvus ossifragus) can be important seabird egg predators. In southwestern Florida, USA, crows were previously documented as causing the abandonment of black skimmer (Rynchops niger) colonies. While lethal crow control might be the most effective strategy, there are ethical and practical concerns about corvid control in an urban setting. Illness‐induced aversion to egg eating (conditioned taste aversion) is an alternative that has the potential for decreasing corvid depredation of seabird eggs. In addition, conditioned stimulus aversion using nonlethal shocks on corvids taking electrified eggs might also be effective. We tested conditioned taste aversion using quail eggs injected with carbachol (emetic eggs) at 3 black skimmer colonies during the 2016 breeding season. We tested conditioned stimulus aversion using electrified quail eggs at the same colonies during the 2017 breeding season. We compared the number of skimmer eggs in a colony depredated by crows before and after a 10‐day treatment. Both methods of treatment significantly decreased the number of skimmer eggs depredated by crows and were relatively inexpensive to conduct. In urban settings, electrified eggs are the safer option as many of the crows took the emetic eggs, but did not consume them while near the colony, potentially exposing non‐target species to a toxicant. © 2020 The Wildlife Society.

“Where ignorance is bliss, 'tis folly to be wise”: Indiscriminate male care in a neotropical spider

AbstractCertainty of paternity is considered an important condition for the evolution and maintenance of extended male care. In some species, males may cannibalize unrelated offspring or abandon the progeny when the uncertainty of paternity is high, or when they take over nest sites or females from other males. However, male protection of offspring can also evolve in situations of uncertainty of paternity, especially when males cannot recognize offspring relatedness. In such cases, males may take care of all their mate's offspring, regardless of paternity. In Manogea porracea (Araneidae), the only known spider species where males care for offspring, males repel competitors by assuming and defending specific positions within a female's web, but females accept multiple partners during the reproductive season. Consequently, males may care for some offspring produced with the sperm of their mate's previous partners. If males cannot detect offspring relatedness, we expect that they will not cannibalize progeny and will actively protect all offspring against predation. The main goal of this study was to investigate whether the extended male care depends on offspring relatedness recognition. Therefore, we experimentally manipulated offspring relatedness and the presence of foster males and two egg predators usually found invading M. porracea webs. We also compared our results with data from an experiment performed by Moura, Vasconcellos‐Neto, & Gonzaga (2017) using the same laboratory procedures, but introducing egg sacs fathered exclusively by the males. Males did not cannibalize offspring and protected the progeny against predation regardless of offspring relatedness. In addition, all males moved the egg sacs to the center of the web, remaining close to the progeny. We conclude that M. porracea males protect all progeny present in their partner's web and increase offspring survivorship regardless of relatedness. We discuss the behavioral and evolutionary implications of our findings, and potential triggers of male care in M. porracea.

Why pygmy snails lay giant eggs: the kiwi syndrome

Some minute land snails lay disproportionally large eggs, and the reason is unknown. A possibility is the “Kiwi Syndrome”, in which natural selection pressures associated with low egg predation, heavy predation of the young, and a minimal viable size for hatchlings, force small females to invest in relatively large offspring at the cost of reduced fecundity.

P class="ZootaxaTitle"First description of immature stages of Gastropini, Gastrops willistoni Cresson (Diptera: Ephydridae) preying on eggs in a foam nest of Leptodactylus knudseni Heyer (Anura: Leptodactylidae) in Central Amazon.

The third instar larva and puparium of Gastrops willistoni Cresson (Diptera: Ephydridae), preying on eggs in a foam nest of Leptodactylus knudseni Heyer (Anura: Leptodactylidae), in a central Amazonian dryland forest (Brazil) are described for the first time. The fusiform larva has a short breathing tube, its anterior spiracles are fan-shaped and posterior spiracles with three spircular openings. Pupa is ovoid with a broad anterior margin and bifurcate posterior tip. The taxonomic relationship of the frog egg predators, Gastrops Williston and Typopsilopa Cresson, are discussed.

A New Species of Lestodiplosis (Diptera: Cecidomyiidae) Preying on Pineus (Hemiptera: Adelgidae), with a Redescription of Lestodiplosis juniperina (Felt)

A new species, Lestodiplosis pinei Gagné (Diptera: Cecidomyiidae), from the United States is described from males, females, pupae and larvae. Larvae are egg predators of Pineus strobi Hartig, Pineus pini Goeze and Pineus cembrae (Cholodkovsky) (Hemiptera: Adelgidae). This is the first North American record for P. cembrae, which was found feeding on Pinus cembra L. planted at Arnold Arboretum in Massachusetts. Lestodiplosis juniperina (Felt) is redescribed as similar to L. pinei and for having once been considered to include specimens now identified as L. pinei. Lestodiplosis cerasi Felt and Lestodiplosis novangliae Felt are new synonyms of L. juniperina.

Mortality of light brown apple moth egg masses in coastal California: Impact of resident Trichogramma parasitism and predation

Egg mortality of light brown apple moth (LBAM), Epiphyas postvittana (Walker), was studied during the early years of its discovery and establishment in California from 2008 to 11. Sentinel egg cards were used to quantify mortality by parasitoids and predators at an intensively monitored location in Santa Cruz to reveal seasonality, and at other sites in Santa Cruz and San Francisco to measure spatial variation and parasitoid species composition. In addition to egg mortality, egg mass use efficiency by Trichogramma parasitoids was also examined under field conditions. The egg parasitoids primarily consisted of three Trichogramma species, T. deion, T. fasciatum and T. platneri. Previously unknown to California, T. fasciatum was shown to displace the indigenous T. platneri over a two-year period as the predominant egg parasitoid attacking LBAM egg masses. Based on the number of parasitized eggs per sentinel egg card, it is argued that individual females of at least some Trichogramma species have the capacity to oviposit more than 50 eggs in the egg mass of a host, warranting further studies to document the egg mass use efficiency and oviposition traits of other trichogrammatids under field conditions. Although egg parasitism was limited to causing elevated mortality during the summer and fall only, egg predation occurred more consistently throughout the year and is likely to be of considerable significance in suppressing LBAM populations in California. Combined with the use of a Type II survivorship curve, the importance of using a temperature-dependent physiological time scale to quantify egg mortality is illustrated when sentinel hosts are exposed to natural enemies in the field for less than the entire duration of the ‘window of susceptibility’ to parasitism and predation.

Biological control of Halymorpha halys (Stål) (Hemiptera: Pentatomidae) in apple orchards versus corn fields and their adjacent woody habitats: High versus low pesticide-input agroecosystems

Halymorpha halys is an invasive pest in the USA that inflicts damage to specialty crops, and conventional growers have increased use of broad-spectrum insecticides to manage this pest. The impacts of pest management programs on natural enemies of H. halys were examined in high vs. low intensity insecticide input agroecosystems in western North Carolina (USA). Apple orchards and corn fields, with their adjacent wooded habitats, served as the high and low-input environments, respectively. Sentinel egg masses and yellow sticky cards were deployed in these agroecosystems to compare predation and parasitism on H. halys eggs, and presence, abundance, and richness of natural enemies. A total of approximately 85% of all sentinel eggs deployed in apple orchards in both 2018 and 2019 produced a healthy stink bug nymph, higher than all other habitats. A total of 26.6% and 32.9% of eggs deployed in wooded habitats bordering corn exhibited mortality due to natural enemy attack in 2018 and 2019, respectively. Comparatively, eggs deployed in apple borders had 10.0% and 17.8% of total eggs killed by natural enemies, in 2018 and 2019, respectively. Corn agroecosystems generally had greater predation and parasitism of sentinel eggs, and greater richness and abundance of predators detected on yellow sticky cards compared to apple agroecosystems. Wooded habitats bordering crops serve as population reservoirs for H. halys, allowing for egg laying and dispersal into crops. If these areas are protected as refuge areas free from insecticide drift, such as from apple orchards, they can also harbor thriving natural enemy populations that could reduce populations of H. halys. Wooded areas free from harsh broad-spectrum insecticides are an important component for successful conservation and augmentative biological control in neighboring crops.

Amino acid cues emanating from Pacific salmon eggs and ovarian fluid.

The eggs of salmonid fishes are an important food source for many aquatic predators that detect eggs using olfaction. Moreover, chemicals from eggs and ovarian fluid aid sperm cells in detecting and locating eggs for fertilization, and ovarian fluid is attractive to conspecific males. Thus chemicals from eggs and ovarian fluid may facilitate reproduction but may also attract egg predators. The authors sampled mature females of three Pacific salmon species - Chinook (Oncorhynchus tshawytscha), coho (Oncorhynchus kisutch) and sockeye (Oncorhynchus nerka) - and determined the proportional representation of amino acids, potent fish odorants, from their eggs and ovarian fluid (Chinook and coho salmon only). They then tested juvenile coho salmon, an egg predator, for responses to ovarian fluid and egg odours using the electro-olfactogram (EOG) recording technique. The amino acid compositions of the salmon species were significantly and positively correlated with each other, and the interspecific differences were comparable to those between individuals of the same species. The egg water samples were, on average, dominated by lysine, alanine and glutamine (12.6%, 12.4% and 10.9%, respectively). The ovarian fluid samples were dominated by lysine (20.5%), followed by threonine (9.7%), glycine (9.2%) and arginine (8.8%). EOG recordings demonstrated the ability of juvenile coho salmon to detect the chemical traces of eggs and ovarian fluid. It is concluded that salmon eggs are a potent source of odours for potential predators but likely not highly differentiated among salmon species.