Egg Predation Research Articles

Non-target potential of neonicotinoid and fungicide seed cane treatments on Solenopsis invicta

Traditionally, Louisiana sugarcane has been grown vegetatively from whole stalks, but innovations in machinery and rising labor costs have increased interest in billet planting. Billets, short stalk pieces containing several viable eyes, are more susceptible to pathogen exposure and may require fungicide and/or insecticide applications at planting to increase stand potential. Work in other crops indicates such treatments may alter arthropod predator abundance, so the goal of this study was to evaluate the potential non-target effects of select treatments at planting on the red important fire ant (RIFA), Solenopsis invicta, and other arthropod predators of the sugarcane borer, Diatraea saccharalis, in sugarcane. We sampled predators and measured biological control potential in plots treated with a neonicotinoid insecticide and/or fungicide applied as in-furrow sprays or seed cane dips. We then assessed RIFA worker survival and behavior following 48 h exposure in the laboratory. With the exception of one in-furrow sprayed field trial, treatments did not significantly impact RIFA numbers. Treatments did not impact the abundance of other predator groups or biological control potential (borer damage and sentinel egg predation) in any field trial. Laboratory assessments indicated no treatment effect on RIFA behavior metrics after exposure but had mixed results on survival depending on application method. Our data indicate that these seed cane treatments may not disrupt biological control and the greater epigeal arthropod predator community in Louisiana sugarcane. However, tests should be replicated under different environmental conditions to ensure biological control, particularly by RIFA, is maintained with larger-scale use.

Predation of Daurian redstarts offspring in nest boxes by the Oriental magpie-robin and tree sparrow.

Birds select suitable nest sites for breeding to ensure their own and offspring's survival; however, they inevitably suffer some potential predation risk. We studied the breeding ecology of Daurian redstarts (Phoenicurus auroreus) by providing nest boxes for their breeding from March to August of 2022. We recorded the predation of both Daurian redstarts eggs or nestlings by Oriental magpie-robins (Copsychus saularis) and tree sparrow (Passer montanus). Oriental magpie-robin were recorded attacking a feeding female adult and depredating nestlings. After the nestling predation event, the Daurian redstarts abandoned the nest. This video evidence provide a better understanding of the potential predators of cavity-nesting birds.

Patterns in avian reproduction in the Prudhoe Bay Oilfield, Alaska, 2003–2019

The Arctic Coastal Plain is one of the most important avian breeding grounds in the world; however, many species are in decline. Arctic‐breeding birds contend with short breeding seasons, harsh climatic conditions, and now, rapidly changing, variable, and unpredictable environmental conditions caused by climate change. Additionally, those breeding in industrial areas may be impacted by human activities. It is difficult to separate the impacts of industrial development and climate change; however, long‐term datasets can help show patterns over time. We evaluated factors influencing reproductive parameters of breeding birds at Prudhoe Bay, Alaska, 2003–2019, by monitoring 1265 shorebird nests, 378 passerine nests, and 231 waterfowl nests. We found that nest survival decreased significantly nearer high‐use infrastructure for all guilds. Temporally, passerine nest survival declined across the 17 years of the study, while there was no significant evidence of change in their nest density. Shorebird nest survival did not vary significantly across years, nor did nest density. Waterfowl nest density increased over the course of the study, but we could not estimate nest survival in all years. Egg predator populations varied across time; numbers of gulls and ravens increased in the oilfields 2003–2019, while Arctic fox decreased, and jaeger numbers did not vary significantly. Long‐term datasets are rare in the Arctic, but they are crucial for understanding impacts to breeding birds from both climate change and increasing anthropogenic activities. We show that nest survival was lower for birds nesting closer to high‐use infrastructure in Arctic Alaska, which was not detected in earlier, shorter‐term studies. Additionally, we show that Lapland longspur nest survival decreased across time, in concert with continent‐wide declines in many passerine species. The urgency to understand these relationships cannot be expressed strongly enough, given change is continuing to happen and the potential impacts are large.

A tiny cuckoo: Risk‐dependent interspecific brood parasitism in a predatory mite

Abstract Many animal species protect their eggs against predators, and other species may profit from this by adding their eggs to those of the protecting species. We studied two tiny species of predatory mites that share a food source, are engaged in intraguild predation, and which eggs are attacked by the same egg predator. One of these predatory mites (Neoseiulus californicus) adds its eggs to those of the other species (Gynaeseius liturivorus) which guards its eggs from egg predators, resulting in reduced predation of the eggs of the nonguarding species. The guarding species experiences costs in the form of intraguild predation of her offspring, and the addition of eggs to the guarding species therefore qualifies as brood parasitism. In the presence of egg predators, the brood parasite preferentially adds its eggs to those of the guarding host species, not to those of another, nonguarding mite species. This cuckoo behaviour comes with a cost for the parasite when egg predators are absent, and therefore only occurs when egg predators are present. Our findings emphasize the importance of the risk of egg predation as a factor driving facultative brood parasitism. Read the free Plain Language Summary for this article on the Journal blog.

A simple trail camera modification reveals red-bellied woodpeckers as important egg predators of box-nesting wood ducks

Artificial nesting structures have been used to aid the recovery and maintenance of certain avian populations such as the wood duck (Aix sponsa). The success of nest boxes for wood ducks relies on excluding common nest predators such as raccoons (Procyon lotor) and rat snakes (Pantherophis spp.) via the use of predator guards; however, woodpeckers cannot be excluded. Red-bellied woodpeckers (Melanerpes carolinus) are foraging generalists and have been anecdotally observed preying on wood duck eggs where documenting predation events is difficult to accomplish through traditional nest box monitoring. Here, we used custom-modified trail cameras to document egg depredations and foraging events by red-bellied woodpeckers and the removal of damaged eggs by wood ducks during the laying and incubation periods. We captured 35,686 videos and documented 1173 different events consisting of 608 (51.8%) videos of red-bellied woodpeckers and 565 (48.2%) of wood ducks. We determined 38 (30.6%) eggs were depredated during the laying period and 14 (11.3%) during incubation. Wood ducks removed 23 (60.5%) eggs depredated during the laying period and 13 (92.9%) depredated during incubation. We found no difference in the daily number of times red-bellied woodpeckers visited boxes with nests in the laying or incubation period (t = −0.967, df = 14.699, P = 0.349). Red-bellied woodpeckers depredated 1.0 ± 0.2 eggs during each event and returned to forage on previously depredated eggs 5.3 ± 4.4 times each day spending 2.1 ± 1.1 min during each return. Our results suggest that red-bellied woodpeckers forage on eggs when nests are unguarded, and they have previously been under-recognized in the literature as predators of wood duck eggs. Future nest box programs should consider the impact red-bellied woodpeckers have on wood duck egg loss and nest survival.

Tritrophic analysis of the prospective biological control of brown marmorated stink bug, Halyomorpha halys, under extant weather and climate change

The highly destructive Asian brown marmorated stink bug (Halyomorpha halys, BMSB) invaded Europe, Caucasus region, and North and South America. Efforts to control it are ongoing in the Palearctic European-Mediterranean Basin and North America by introducing and redistributing two Asian stenophagous scelionid egg parasitoids (Trissolcus japonicus and T. mitsukurii) that are attacked by an adventive oligophagous pteromalid Asian hyperparasitoid (Acroclisoides sinicus). Large BMSB nymphs and adults may be parasitized by new associations of oligophagous tachinid flies and immature stages by egg parasitoids and predators. The terms stenophagous and oligophagous are commonly used to define narrow and wider ranges, respectively, of food eaten, but here they refer to the range of hosts attacked by adult female parasitoids. A holistic weather-driven physiologically based demographic model (PBDM) of the tritrophic interactions was developed to evaluate prospectively the impact of natural enemies on the biological control of BMSB under current and climate change weather. Our study focuses on the European-Mediterranean region, with the results for the USA, Mexico, and Central America reported as supplementary information. The PBDM analysis suggests that biotypes of the egg parasitoids T. japonicus and T. mitsukurii with high search capacity could suppress BMSB regionally, but the requisite levels of parasitism by these parasitoids for economic control are not observed in their native range nor in invaded areas. The model suggests that the action of T. japonicus is greater than that of T. mitsukurii, but that joint interactions of the two egg parasitoids would provide higher mortality of BMSB. Field data and model results suggest that the egg hyperparasitoid A. sinicus has a modest negative impact on the suppression of BMSB. Moreover, tachinid parasitoids of adults could have an important supplemental role in suppressing BMSB densities. Analysis suggests that new biotypes of egg parasitoids and species of tachinid parasitoids of large nymphs and adults be sought.

The second species of Sorellevania Engel, 2006 (Evanioidea: Evaniidae) from the mid-Cretaceous Burmese amber

The representatives of the superfamily Evanioidea are easily distinguishable from all other extant and extinct Hymenoptera because of their metasoma (sometimes rounded) articulated high on the propodeum and well above the metacoxae (e.g., Goulet & Huber, 1993). Recent phylogenetic studies on the superfamily Evanioidea have shown strong support for its monophyly and for the monophyly of the Evaniidae even when fossil taxa are included (e.g., Li et al., 2018; Parslow et al., 2020; Jouault et al., 2022). According to the most recent analysis, the superfamily arose during either the Upper Triassic or the Lower Jurassic. Still, its earliest species are recorded in the younger Middle Jurassic, and its crown-group representatives during the Lower Cretaceous (Jouault et al., 2022: fig. 8). The stem Evaniidae are estimated to arise during the Upper Jurassic while their crown group has a more recent origin, likely around the Cretaceous-Paleogene boundary. Extant evaniid wasps are common, nearly cosmopolitan, and moderately diversified (about 580 extant species in 21 genera) even if this diversity is underestimated (Deans, 2005; Mullins et al., 2012). Little is known about the biology of extant evaniids, but their larvae are considered predators of cockroach eggs in oothecae (Huben, 1995). The Evaniidae have a good fossil record with the oldest species known from the late Hauterivian, numerous species documented up to the Miocene, and an important diversity in Burmese amber (e.g., Rasnitsyn et al., 1998; Nel et al., 2002; Deans et al., 2004; Jennings et al., 2012; Shih et al., 2020). Nevertheless, their past diversity is still underestimated.

Taking care of the enemy: egg predation by the Darwin wasp Tromatobia sp. (Ichneumonidae) on the cobweb spider Chrysso compressa (Araneae, Theridiidae)

Some wasp species use spiders as food resources, overcoming several anti-predator barriers that are exerted by spiders. Tromatobia ichneumonid wasps are spider egg predators that usually attack Araneidae species, although there are few records of predation on Clubionidae, Philodromidae, Linyphiidae, Tetragnathidae, and Theridiidae spiders. Here, we describe the interaction between Tromatobia sp. and Chrysso compressa, a subsocial theridiid spider that exhibits extended maternal care, in the Atlantic Forest of southeastern Brazil. We observed that the larva of Tromatobia sp. develop inside the egg sacs of C. compressa, preying on the entire egg mass and building cocoons that change the color and morphology of the egg sacs. Despite these structural modifications, we registered an adult female of C. compressa guarding and caring for the cocoons (attacked egg sac) of the predators as if they were offspring (non-attacked egg sac). To the best of our knowledge, this study represents the first record of Tromatobia preying on Chrysso eggs.

Factors influencing tropical lizard reproduction vary by microhabitat but not forest type

Abstract To understand mechanisms behind enigmatic declines of tropical reptiles, knowledge of species interactions and how they vary over space and time is important. Some tropical lizard population dynamics can be highly influenced by egg survival. Yet relatively few studies have examined relationships between lizard reproductive success and egg predators across forest and microhabitat types. In this study, we examined variation in probability of egg depredation, predatory ant abundance, prey availability, and the number of lizards and eggs encountered across four different forest types (abandoned agroforestry, abandoned plantation, secondary forest, and old-growth forest) and three microhabitats (buttress, fallen log, and leaf-litter) at La Selva Biological Station, Costa Rica. Based on previous studies, we made three hypotheses about how lizard egg abundance, egg survival, and predatory ant numbers would be related across microhabitat and forest type. Of these hypotheses, only one was supported: we found more lizard eggs in buttress and fallen log microhabitats than leaf-litter. We did not observe any differences in lizard reproduction or numbers of invertebrates by forest type alone. Based on patterns observed in this study, we suggest that future studies investigating tropical leaf-litter lizard declines focus on environmental variation at the microhabitat scale.

Population Dynamics of Lacewing, Chrysoperla carnea in Cotton Fields in the Central Region of Syria

Hawis, B., Z. Chikh Khamis and M. Al-Nabhan. 2023. Population Dynamics of Lacewing, Chrysoperla carnea in Cotton Fields in the Central Region of Syria. Arab Journal of Plant Protection, 41(4): 375-383. https://doi.org/10.22268/AJPP41.4.375383 Dynamics of Chrysoperla carnea population dynamics were studied for two growing seasons (2017 and 2018) in cotton fields in Hama at central Syria. Adults of C. carnea were prevalent in the field from July until the end of the season. The highest numbers of the predator adults caught by the sweeping net were in the middle of September (4 and 8 adults per 50 sweeping net beats in 2017 and 2018, respectively). The correlation between predator adults and maximum, minimum, and average temperatures were negative with low significance, and positive with weak significance between C. carnea adult population and relative humidity in 2017, but no correlation between these variables in 2018 were recorded. The correlation between adults and sunshine duration was negative in both seasons. C. carnea eggs were recorded in cotton fields in July of both seasons and continued to be present all during the season until 14 October in 2017 (22.96 eggs/100 leaves), and in 2018 predator eggs were reduced at the end of September to 7.41eggs/100 leaves. The highest number of eggs were noticed at the third week of 382 مجلة وقاية النبات العربية، مجلد ،41 عدد 4 ) 2023( august (38.52 and 49.63 eggs in 2017 and 2018, respectively). There was intermediate positive significance between eggs and minimum and average temperature in 2018. Positive correlations were recorded between the predator eggs and whitefly and aphid’s nymphs in both seasons. The low and middle levels of the cotton plant leaves were the preferred sites for females to put their eggs, and the proportion of eggs placed on these parts of plant in both seasons was 76.34%. Keywords: Chrysoperla carnea, population dynamics, weather parameters, Bemisia tabaci, Aphis gossypii, oviposition preference

<i>Euborellia annulipes</i> Mortality and Predation on <i>Diatraea saccharalis</i> Eggs after Application of Chemical and Biological Insecticides

Chemical and biological insecticides have been frequently used in sugarcane fields to control insects-pests, including the sugarcane borer, Diatraea saccharalis. Among the products used, those based on chlorantraniliprole and Metarhizium anisopliae entomopathogenic fungus, stand out. Euborellia annulipes is an insect of the order Dermaptera considered a potential predator of sugarcane borer eggs. This study aimed to evaluate the direct and indirect effects of the bioinsecticide based on M. anisopliae (Metarril®) and the chemical insecticide chlorantraniliprole (Altacor®) on the mortality of E. annulipes nymphs and adults, the predation and feeding preference of earwigs in eggs treated with the formulated products. Predator mortality was evaluated for seven days after treatment, while the effect on predation was analyzed by preference tests with and without choice, using prey eggs. The products tested were selective to the predator, causing ≤ 2% mortality and not affecting predation. The application of M. anisopliae on sugarcane borer eggs favored the food preference of fourth-instar nymphs, males, and females of the predator. Our results show that Metarril® and Altacor® can be used to control D. saccharalis when associated with the predator E. annulipes.

Effect of diet composition and temperature on the gastric evacuation rate of European sardine: implication for egg predation estimates

Cannibalism and intraguild predation of fish eggs are frequently observed for small and medium pelagic fish and can be an important cause of natural mortality. The European sardine Sardina pilchardus is the major predator of pelagic fish eggs in Atlantic Iberian waters. Estimates of egg mortality due to predation rely on a number of parameters that are frequently unknown for most species, such as gastric evacuation rate (GER) and feeding periodicity, and rates obtained for other fish species are generally used. These assumptions can severely affect egg mortality estimates. We conducted laboratory experiments to estimate the GER of European sardine that were fed diets composed of different proportions of fish eggs and other food types, such as Artemia franciscana nauplii, Brachionus plicatilis and microalgae, at different temperatures experienced by sardine in the wild (15, 17 and 21°C). Temperature, predator size and sex did not influence the gastric rates. Prey type significantly affected the GER of sardines, with slower evacuation when offered diets containing a higher concentration of fish eggs rather than microalgae, rotifers and Artemia nauplii. Fish eggs are more nutritionally rich compared to microalgae, rotifers and Artemia nauplii, and therefore more difficult to digest. GERs obtained here for S. pilchardus were similar to those obtained for Sardinops sagax in South Africa. This study provides important information that allows for improving estimates of daily feeding rates and egg mortality by predation, thus increasing our understanding of small pelagic fish population dynamics.

Heightened heart rate but similar flight responses to evolved versus recent predators in an Arctic seabird

Predator-prey dynamics in the Arctic are being altered with changing sea ice phenology. The increasing frequency of predation on colonial nesting seabirds and their eggs by the polar bear (<em>Ursus maritimus</em>) is a consequence of bears shifting to terrestrial food resources through a shortened seal-hunting season. We examined antipredator responses in a colony of nesting Common Eiders (<em>Somateria mollissima</em>) on East Bay Island, Nunavut, Canada, which is exposed to established nest predators, such as arctic fox (<em>Vulpes lagopus</em>), but also to recent increases in polar bear nest predation due to the bears’ lost on-ice hunting opportunities. Given eiders’ limited eco-evolutionary experience with bears, we aimed to experimentally contrast eider responses to the recent predation pressure by polar bears to those induced by their more traditional mammalian predator, the arctic fox. Our goal was to characterize whether this population of eiders was vulnerable to a changing predator regime. Using simulated approaches of visual stimuli of both predator types, we measured eider heart rate and flight initiation distance as physiological and behavioral metrics, respectively, to characterize the perceived risk of and subsequent response to imminent threat posed by these two predators that differ in historical encounter rates. Eider heart rates were more responsive to impending visual cues of arctic foxes compared to polar bears, but birds responded behaviorally to all simulated threats with similar flight initiation distances. Results suggest eiders may not perceive the full risk that bears pose as egg and adult predators, and are therefore expected to suffer negative fitness consequences from this ongoing and increasing interaction. Eiders may therefore require conservation intervention to aid in their management.

Offspring mortality factors and parental care efficiency of the spider Manogea porracea (Araneidae) in the Brazilian savanna

The expressions of parental care can vary in space and time because factors driving offspring mortality depend on variable abiotic and biotic conditions. Manogea porracea is a spider that exhibits biparental care and widespread distribution in the Neotropical region. Parents can protect their offspring against abiotic conditions that may damage their webs, or compromise their egg sacs, and against araneophagic spiders that prey on their eggs. However, the current knowledge of the parental care in the species is restricted to a population located in areas covered by Eucalyptus plantations. This study investigates parental care efficiency in a new ecological context, a protected area of Brazilian savanna. We described the substrates in which M. porracea built webs and the agents of egg mortality. We also performed a parent removal experiment to test the effect of parental care on the integrity of nursery webs, offspring survival, and the presence of egg predators. Spiders built webs at variable heights and many distinct substrates but were mainly associated with the bromeliad Ananas ananassoides. We found two previously reported egg predators, Faiditus caudatus and Argyrodes elevatus (Araneae Theridiidae), and a new one emerging from the egg sacs, the insect Zeugomantispa virescens (Neuroptera Mantispidae). The presence of parents in the webs of M. porracea prevented the webs from collapsing and effectively increased offspring survival. However, the occurrence of egg predators was not reduced by the presence of parents. Overall, parental care increased offspring survival in both populations, but variation in biotic and abiotic factors between areas influenced offspring mortality and the efficiency of parental behaviours. Our results emphasise the importance of investigating multiple populations in behavioural studies of parental care.

Zebrafish embryos hatch early in response to chemical and mechanical indicators of predation risk, resulting in underdeveloped swimming ability of hatchling larvae.

Plasticity in hatching time allows embryos to maximize fitness by balancing the benefits and costs of remaining bound within the chorion against the benefits and costs of emerging as a free-swimming larva. Here, in the first experiment, we exposed zebrafish (Danio rerio) embryos to either chemical cues from crushed embryos (simulating egg predation) or to blank water control. Embryos exposed to alarm cues hatched sooner, and had shorter body lengths and underdeveloped fins, relative to larvae from the water treatment. Burst swimming speed was significantly slower for larvae that hatched from the alarm cue treatment than for larvae from the water treatment. In a second 2×2 experiment, we exposed zebrafish embryos to either chemical alarm cues from conspecific embryos, mechanical disturbance (magnetic stir bar) to simulate a predator probing the substrate for developing embryos, both chemical and mechanical indicators of risk, or neither (control). We found similar effects in terms of earlier time to hatch at an earlier stage of development and poorer swimming performance of hatchling larvae. In the second experiment, these effects occurred in response to mechanical disturbance with or without the presence of chemical alarm cues. Alarm cues alone produced no effects in the second experiment. Taken together, these data indicate that zebrafish embryos demonstrate a facultative trade-off between risk of predation acting on two stages of their life history.

Nest fidelity of purple sunbird (Cinnyris asiaticus) on communal webs of a spider

Nest predation is a major cause of avian breeding failure and parent birds adopt various anti-nest predation strategies to increase the survival rate of offspring. Purple sunbird uses snake moults as nest-building material, which could be a tactic to avoid predation of eggs and hatchlings inside the nest.

The effects of landscape complexity and local management on a generalist predator in Kenyan maize push‐pull systems

AbstractFarmers looking to maximize ecosystem services often use diversification practices on their fields to increase abundance and diversity of insect natural enemies. These practices affect functional traits of natural enemies such as body size that can play an important role in their effectiveness as biological control agents. However, landscape features out of the control of farmers might also affect functional traits of natural enemies and their herbivores, including land use surrounding farms. There have been few studies elucidating how landscape complexity and local diversity interact to affect functional traits, and ultimately ecosystem services such as predation on herbivore pests. We examined combined effects of landscape complexity and a local management practice (push‐pull) on lady beetle size, and its consequences for egg predation of lepidopteran pests in Kenyan smallholder maize farms. Cheilomenes sulphurea (Olivier) (Coleoptera: Coccinellidae), a potential predator of the invasive fall armyworm, Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), was collected in push‐pull and control fields along a landscape gradient. We measured beetle size and conducted feeding assays with fall armyworm eggs. We found that female beetles had larger bodies in landscapes with greater complexity. Predation rates not only increased as a response to beetle size but also in response to landscape complexity, suggesting it is not just size that determines predation. Surprisingly, we did not find any effect of the local management practice or its interaction on functional traits or predation rates. Our study suggests that landscape complexity could benefit pest control through two mechanisms: (1) increase in predator body size, leading to higher predation rates; and (2) changes in predator behavior as a function of landscape characteristics – increasing egg predation. Further studies on these mechanisms would allow deeper understanding of landscape simplification's effect on ecosystem services, as mediated by morphological and behavioral traits, and help us harness these traits to increase biological control.

Direct and indirect effects of management and landscape on biological pest control and crop pest infestation in apple orchards

Abstract Biological pest control, relying on naturally occurring predator–prey dynamics, is considered a key element to achieve more sustainable farming systems. However, the combined effects of local management and landscape factors on communities of natural enemies as well as the cascading effects on pest infestations are rarely addressed, especially in perennial crops. Here, we used Piecewise Structural Equation Modelling (PSEM) to test direct and indirect effects of landscape composition, landscape configuration and local management practices on natural enemy communities, the pest control services they provide and ultimately on pest infestation and pest‐related yield damage in apple crops. To this end, we surveyed 12 organic and 12 Integrated Pest Management (IPM) orchards during three consecutive years, and we also established a semi‐natural benchmark to quantify the extent to which predator communities in the orchards were degraded. Natural enemies had a different community composition and were more abundant in organic orchards compared with IPM orchards. This had a small and positive effect on sentinel egg predation rates in organic orchards, but overall had very little impact on actual apple pest infestation. On the contrary, apple pest infestation levels were directly and positively affected by organic management practices and by increasing semi‐natural habitat cover and landscape edge density. Compared with a semi‐natural benchmark, both agricultural management systems showed degraded predator communities, which translated into an impaired delivery of biological control services. Synthesis and applications. Our results indicate that organic management and habitat conservation can enhance natural enemies and stimulate pest control, but also show that these factors can enhance pest infestations and can even lead to an overall increase in pest‐related crop damage. Our study thus highlights the complex interplay of ecosystem services and disservices provided by biodiversity, which should be taken into account when advising farmers, policy makers and land managers on effective and sustainable strategies to control pest species and safeguard crop production.

Prays oleae (Bernard), its potential predators and biocontrol depend on the structure of the surrounding landscape

Arthropod populations from agricultural fields sometimes depend on the surrounding landscape structure, both composition and configuration, which affects multiple life-history traits of arthropods such as resources for survival, dispersion or death risk (e.g., predation or parasitism). Moreover, the effect of the landscape may vary with the distance to the crop, depending on factors such as the organism requirements and dispersion capabilities. This work addresses the effect of landscape (at five different scales from 250 to 1500 m) on the olive moth (Prays oleae Bernard, a key pest in olive orchards), some of its most relevant natural enemies, and biological control. The two-years study in 15 olive groves in southeastern Madrid, Spain shows that landscape complexity favours control of the olive moth, P. oleae. Simple landscapes favour P. oleae attack to the crop (measured as oviposition of the anthophagous generation) and that egg predation of the carpophagous generation is in some cases enhanced in complex landscapes. Lacewings (Neuroptera: Chrysopidae) are responsible for egg predation and populations increase in complex landscapes. On the other hand, the role of pirate bugs (Hemiptera: Anthocoridae) as a biological control agent of this part of the life cycle of P. oleae was not demonstrated. They respond primarily to Euphyllura olivina (Costa) (Hemiptera: Psyllidae) populations and are more abundant in simple landscapes. Most of the significant relationships of pest attack were detected at 750–1000 m radii buffers around the sampled olive groves suggesting that this is the main activity range for adults of P. oleae anthophagous generation. In sum, our results suggest complex configurations of the landscape enhance the biological control of P. oleae through favouring lacewings and egg predation of the carpophagous generation.

Distribution and breeding numbers of a recently split species, the West African Crested Tern Thalasseus albididorsalis

This study investigated the distribution, numbers and conservation threats of the West African Crested Tern, which was recently elevated to full species after it was split from the Royal Tern with an American and African subspecies. In the period 1998–2019, a total of 13 West African coastal islands were identified as breeding localities, stretching from Mauritania to Guinea. All the islands are isolated, usually sandy and subject to erosion. There was great yearly variation in the numbers of breeding pairs within and between sites. A complete census of all breeding locations in 2015 and 2019 resulted in estimates of 79 000 and 77 000 pairs, respectively. The threats identified are predation, human disturbance, nest flooding and loss of breeding habitat as a result of coastal erosion. Predation of eggs and chicks by Sacred Ibises and especially Great White Pelicans may heavily impact on the species’ breeding output. Human disturbance is slight because most of the breeding islands are within protected areas. Flooding of nests has increasingly been observed in recent years, occurring at nine of 11 islands occupied by the terns in 2015. Most islands are subject to erosion, which has resulted in substantial loss of suitable breeding habitat over the 22-year study period. Two important islands have become completely unsuitable. We conclude that West African Crested Terns have an uncertain future. Food shortage resulting from industrial fishing is suspected, and the effects of climate change might negatively impact on habitat suitability and food availability. Monitoring of the total population at three-year intervals is recommended.