Floating bird nests provide resources for wildlife: ecological roles of vertebrates using <Emphasis Type="Italic">Aechmophorus</Emphasis> grebe nests at Clear Lake,California

Floating bird nests occur ephemerally in many wetlands, providing resources for wildlife, but the species using such nests and their ecological roles are poorly studied. Grebes (Podicipedidae) construct floating nests anchored to vegetation. During 2010–2017 we studied the vertebrates using nests of the colonially-nesting western grebe (Aechmophorus occidentalis) and Clark’s grebe (A. clarkii) at Clear Lake, California. In addition to both grebe species using each other’s nests for copulation and egg dumping, we identified 47 other species of vertebrates using Aechmophorus grebe nests, including one fish, one amphibian, two turtles, one snake, 39 birds, and three mammals. Ecological roles of vertebrates using grebe nests included: egg dumping (one bird); predation on grebe eggs, chicks, or adults (four birds and three mammals); scavenging on broken grebe eggs (five birds); resting (one amphibian, three reptiles, and 15 birds); foraging for non-avian prey on nests (13 birds) or in adjacent water (five birds); and incidental destruction of grebe eggs (one fish and two reptiles) and nests (many species). Floating grebe nests undergo a process of ecological succession. Egg dumping, predation, and scavenging occur during early stages of nest development and maintenance. Once abandoned, older nests are used for resting or foraging for prey in nearby water. Decomposing nests are colonized by arthropods which are preyed upon by birds. Because floating bird nests increase food web complexity by attracting aquatic, semiaquatic, and terrestrial organisms at all trophic levels, protecting the engineers and their nests should be considered a conservation priority by wetland managers.     

Bird predation affects diurnal and nocturnal web-building spiders in a Mediterranean citrus grove

Spiders and birds can greatly decrease insect populations, but birds also limit spider densities in some habitats. Bird predation is thought to be one of the causes behind nocturnal activity in spiders, so night-active spiders that hide in retreats during the day should be less affected by bird foraging than day-active spiders. However, this hypothesis has not yet been tested. We investigated the importance of bird predation on the spider community of a Mediterranean organic citrus grove. We excluded birds by placing net cages over the trees and we conducted visual searches in the canopies to sample web-building spiders. As there are many nocturnal species in the family Araneidae, we conducted searches both by day and by night to compare the abundance of active araneids in these two time periods. We sampled the tree trunks with cardboard bands to collect hunting spiders. In bird-excluded canopies there were more spiders of the families Araneidae and Theridiidae. There were higher numbers of active Araneidae at night, but these were just as negatively affected by bird predation as day-active Araneidae, so there was no evidence of nocturnal activity serving as an anti-predator strategy. We did not find any negative impact of birds on hunting spiders. Our results contrast with other studies reporting a negative effect of birds on hunting but not on web-building spiders.     

Mesostigmatic mites associated with birds and mammals in Iran. A review

There are diverse relationships between mites and birds or mammals. These mites may play an important role in epizootics and in the perpetuation of some significant diseases. The purpose of this study is to revise the current knowledge of mesostigmatic mites occurring on birds, including their nests and mammals and their substrates, in Iran and to compare the results with other regions of the Palearctic ecozone. This study presents a revised list of 38 species of mesostigmatic mite occuring on birds (17 species) and mammals (24 species) or in their nests/substrates in Iran. Dermanyssus gallinae, Ornithonyssus sylviarum and Parasitus hyalinus were found on both birds and mammals. The species composition of mites reported in Iran was compared with other regions of the Palearctic ecozone. Parasites, specifically those from genera Dermanyssus, Ornithonyssus and Liponyssoides, may be hazardous to human health. Species from these genera were predominant among the reported mites.     

The conservation value of tree decay processes as a key driver structuring tree cavity nest webs in South American temperate rainforests

South American temperate rainforests, a global biodiversity hotspot, have been reduced to nearly 30% of their original extent and most remaining stands are being degraded. Cavity-nesting vertebrate communities are dependent on cavity-bearing trees and hierarchically structured within nest webs. Evaluating the actual degree of cavity dependence (obligate, non-obligate) and the preferred attributes of trees by cavity nesters is critical to design conservation strategies in areas undergoing habitat loss. During three breeding seasons (2010–2013), we studied the cavity-nesting bird community in temperate rainforests of Chile. We found the highest reported proportion of tree cavity nesters (n = 29 species; 57%) compared to non-cavity-using birds for any forest system. Four species were excavators and 25 were secondary cavity nesters (SCNs). Among SCNs, ten species were obligate and 15 were non-obligate cavity nesters. Seventy-five percent of nests of SCNs were located in cavities produced by tree decay processes and the remaining 25% were in cavities excavated mainly by Pygarrhichas albogularis and Campephilus magellanicus. Nest web structure had a low dominance and evenness, with most network interactions occurring between SCNs and large decaying trees. Tree diameter at breast height (DBH) was larger in nest-trees (57.3 cm) than in available trees (26.1 cm). Cavity nesters showed a strong preference for dead trees, both standing and fallen (58% of nests). Our results stress that retaining large decaying and standing dead trees (DBH > 57 cm), and large fallen trees, should be a priority for retention in forest management plans in this globally threatened ecosystem.     

Competition, predation and nest niche shifts among tropical cavity nesters: ecological evidence

I studied cavity-nesting birds in an undisturbed site in lowland Peru to determine the relative roles of competition and predation in favoring termitarium nesting over tree cavity nesting. Occupancy rates of both nest boxes and natural tree cavities near 2% suggest that competition for tree cavities is not favoring the use of termitaria. Artificial nests and bird nests in termitaria suffer significantly lower predation rates than similar nests in old tree cavities showing that predation is favoring the use of termitaria over old tree cavities. Bird nests in newly excavated tree cavities also show lower predation rates than older cavities suggesting that cavity age is more important than substrate (tree or termitaria) per se . This study suggests that nest predation has a greater influence than nest competition on life history evolution for many cavity-nesting birds.     

Factors influencing the appearance of spider (Araneae) and beetle (Coleoptera) assemblages in nests of great reed warbler Acrocephalus arundinaceus

The appearance of spider (Araneae) and beetle (Coleoptera) assemblages found in nests of great reed warbler Acrocephalus arundinaceus was studied, firstly to investigate breeding success and the amount of precipitation as potential factors which might affect the abundance and species richness of both groups. In addition, we compared the diversity of spider and beetle assemblages between nests found in different reed habitats, and considered the position of nests (above water or dry ground). In this study we selected five different randomly chosen reed habitats: two mining ponds, two small canals and one large canal. Great Reed Warbler nests were collected either shortly after fledging, or after the clutch had failed. Altogether, 12 species of spider and 19 species of beetle were collected. In both groups there was no significant difference in abundance between successful, lost and cuckoo-parasitized nests; however, there was a significant difference in species richness between the three nest categories in spider assemblages, which was not the case in beetle assemblages. The amount of precipitation did not affect beetle or spider abundance; only the species richness of spiders showed significant growth. Furthermore, we found no significant relationship between vegetation cover and the species richness and abundance of spiders and beetles. The diversity of both groups differed significantly according to reed habitat: beetle assemblages were most diverse by the large canal and spiders at the mining ponds.     

The Effect of Wind Exposure on the Web Characteristics of a Tetragnathid Orb Spider

Studies on spiders in their natural habitats are necessary for determining the full range of plasticity in their web-building behaviour. Plasticity in web design is hypothesised to be important for spiders building in habitats where environmental conditions cause considerable web damage. Here we compared web characteristics of the orb spider Metellina mengei (Araneae, Tetragnathidae) in two different forest habitats differing in their wind exposure. We found a notable lack of differences in web geometry, orientation and inclination between webs built along an exposed forest edge and those built inside the forest, despite marked differences in wind speed. This suggests that M. mengei did not exhibit web-building plasticity in response to wind in the field, contrasting with the findings of laboratory studies on other species of orb spiders. Instead, differences in prey capture and wind damage trade-offs between habitats may provide an explanation for our results, indicating that different species employ different strategies to cope with environmental constraints.     

Seasonality,habitat type and locality influenced bird assemblage structure in Nigeria

This is the first report of the avian assemblage in the study area of Dutse, Nigeria. In addition to recording bird species, the effects of season, dominant vegetation structure, locality and anthropogenic activities on bird abundance, species richness and diversity were investigated. Using the point transect method, 264 points on 48 km of transect were used to count birds between 06:30 and 11:00 from August 2015 to February 2016. A total of 122 bird species of 41 families were recorded. Highest bird species richness was recorded in Warwade, highest abundance in Model, and highest diversity in Malamawa. The dry season and woodland habitat showed higher bird species richness, abundance and diversity than the wet season and shrubland habitat. Tree density was more important in increasing bird abundance than shrub density. Small-scale anthropogenic activities and habitat modification, such as farming, grazing, wood removal and human interference did not appear to have impacted the birds; however, loss of high tree-density woodland habitats may pose a major threat to the bird community in Dutse. The presence of birds of concern in the area suggests the need for conservation efforts of avifauna and as well as the forested habitats in Dutse.     

Effects of ant competition and bird predation on the spider assemblage of a citrus grove

Characterizing intraguild interactions is key to improving understanding of food webs because they are major forces in the structuring of communities. Spiders are generalist predators with intermediate positions in the food web that establish intraguild interactions with ants and birds, which respectively compete with and prey on them. Research has also found interactions between birds and ants, potentially resulting in non-additive effects of both groups on arthropod assemblages, although studies of their combined impacts with tests for multiple-predator effects are scarce. We thus aimed to discern the relative effect of ants and birds on the spider assemblage of a citrus grove. We used a split-plot design to factorially exclude these groups over 2 years, preventing ants reaching the canopies by placing sticky bands around tree trunks, and birds by enclosing groups of trees in cages. We sampled spiders from the canopies (beating) and the ground (pitfalls) every 3 months, and we identified them to species. We found a strong influence of ants on the canopy spider assemblage, mainly through a negative effect on the families Araneidae and Theridiidae. Since spiders’ weights from ant-excluded and control trees were similar, these results suggest interference competition of ants on spiders rather than competitive exploitation. Bird exclusion did not affect the spider assemblage, contrasting with other studies reporting a marked predatory pressure of birds on spiders; nor were there any non-additive effects of ants and birds. Our findings show that spider assemblages are not uniformly affected by intraguild competitors.     

Bark-dwelling spider assemblages (Araneae) in the boreal forest: dominance,diversity, composition and life-histories

We collected spiders from tree-bark, foliage and litter habitats in deciduous and conifer dominated stands in NW Alberta (Canada) to define these assemblages and consider their conservation significance. To establish habitat associations, we used Indicator Species Analysis (ISA) together with a species dominance metric (DV′) newly proposed here. Of the 116 species collected, 78 were collected from bark. Results support categorizing 16 species as true bark-dwellers, 16 as facultative bark-dwellers and 46 as accidental bark-dwellers or species of unknown association. Species that were strong indicators of particular microhabitats in analyses restricted to bark habitats lost their indicator value when foliage and ground habitats were also considered, suggesting that bark habitats are critical for specific life-history functions. Clubiona canadensis Emerton 1980, Callobius nomeus (Chamberlin 1919), Pocadicnemis americana Millidge 1976 and Enoplognatha intrepida (Sørensen 1888) were the most common bark-dwelling species but their dominance varied among forest cover-types and trapping techniques. Collecting period, forest cover-type, habitat, and trapping technique were generally important environmental variables influencing composition of bark-dwelling assemblages. Although less important in structuring assemblages, tree status (dead or alive) and decay class were important for particular species. Bark habitats are crucial for boreal forest spider assemblages and must be considered central to maintenance of spider diversity.     

Predators at bird nests in a northern hardwood forest in New Hampshire

ABSTRACT.   Nest predation is the primary cause of nest failure in most passerine birds, and increases in nest predation associated with anthropogenic habitat disturbance are invoked as explanations for population declines of some bird species. In most cases, however, the identity of the nest predators is not known with certainty. We monitored active bird nests with infrared time-lapse video cameras to determine which nest predators were responsible for depredating bird nests in northern New Hampshire. We monitored 64 nests of 11 bird species during three breeding seasons, and identified seven species of predators during 14 predation events. In addition, we recorded two instances of birds defending nests from predators and, in both cases, these nests were ultimately lost to predation. These results contrast with other studies in terms of the relatively high proportion of nests depredated by raptors and mice, as well as the absence of any predation by snakes. The diverse suite of predators in this and other studies is likely to confound our understanding of patterns of nest predation relative to fragmentation and habitat structure.     

Predation of <Emphasis Type="Italic">Halyomorpha halys</Emphasis> (Hemiptera: Pentatomidae) from Web-Building Spiders Associated with Anthropogenic Dwellings

The brown marmorated stink bug, or Halyomorpha halys, is an invasive pest in North America and Europe that causes severe agricultural damage and nuisance problems for homeowners; and it is originally from China, Taiwan, and the Republic of Korea. While the natural enemy community of H. halys has been evaluated in several agroecosystems, it has not been examined where H. halys overwinters in anthropogenic structures. The aims of the current study were to evaluate 1) whether spider webs commonly found in the home and yard can successfully ensnare H. halys, 2) whether entanglement resulted in consumption by spiders inhabiting the webs, and 3) how frequently H. halys becomes entangled in webs under ambient conditions. To accomplish this, adult H. halys were introduced into webs in and near anthropogenic structures in West Virginia and Maryland, United States, and the behavior of spiders was observed for 5-min intervals at 0, 1, 2, and 24 h after introduction. In addition, a survey of webs was performed to determine the frequency with which spiders naturally capture H. halys inside buildings and in the landscape. Overall, the study found seven spider families in anthropogenic structures. Adult H. halys that were introduced into the webs of Theridiidae, Pholcidae, or Agelenidae had a greater than 50% chance of being ensnared and consumed. Adult H. halys were found naturally most often in webs of Theridiidae. Webs with a funnel or cob web architecture had the greatest probability of ensnaring H. halys, while those with orb structures resulted in the fewest caught. In the wild, 13–20% of spider webs contained dead H. halys. Our results suggest that spiders may be an important contributing factor for mortality of H. halys at overwintering sites, and spiders in or outside homes may help reduce nuisance problems caused by H. halys.     

Diptera in Nests of the Fieldfare <Emphasis Type="Italic">Turdus pilaris</Emphasis> in Moscow City

The composition of dipterans inhabiting fieldfare nests in a big city was studied for the first time, based on material collected soon after chick fledging. Larvae of 21 species belonging to 14 families were found, including saprophages, necrophages, and predators (Scatopsidae, Ceratopogonidae, Phoridae, Chloropidae, Anthomyiidae, etc.), and also Protocalliphora azurea (Fallén, 1816) (Calliphoridae) and Neottiophilum praeustum (Meigen, 1826) (Neottiophilidae) known as bloodsucking ectoparasites of nestlings. Larvae of P. azurea (up to 121 per nest) were found in both early (April–May) and late (May–June) nests. Larvae of N. praeustum (up to 299 per nest) were recorded only in late nests. The two species occurred both separately and jointly in one nest, with N. praeustum dominating numerically. The seasonal differences in the development of these two parasitic species may account for their high abundance in such ephemeral habitats. Larvae of Trypocalliphora braueri (Hendel, 1901), a subcutaneous parasite of nestlings of many bird species, were not found in the fieldfare nests. A key to the larvae of the three fly species parasitizing nestlings in European Russia is given.     

Review of habitats occupied by <Emphasis Type="Italic">Urocoras longispinus</Emphasis>: a little-known spider species,and responses to grassland management

The main objective of this paper is to report habitat occupancy, naturalness status and phenology of Urocoras longispinus (Chyzer and Kulczyński 1897), a little-known spider species. Sampling was conducted in Natura 2000 habitats of the Mátra Mountains, and four disturbed mainroad verges in Hungary between 2012 and 2015. We recorded 356 adult specimens active throughout the year, but abundance was highest in autumn. In the Mátra Mountains shrub removal negatively affected the abundance of U. lonsgspinus: the species preferred shaded habitats. The intensity of mowing maintenance caused changes in the species’ abundance in mainroad verges: the number of individual spiders increased as a result of both without maintenance and enhanced maintenance. We conclude that U. longispinus is a stenochronous spider species which lives in both human-disturbed and undisturbed habitats. However, the nature of the disturbance influenced the abundance of this species to varying degrees.     

Using Bloodmeal Analysis to Assess Disease Risk to Wildlife at the New Northern Limit of a Mosquito Species

The historically southeastern mosquito species Culex erraticus has over the last 30 years undergone a marked expansion north. We evaluated this species’ potential to participate in local disease cycles in the northeastern USA by identifying the vertebrate sources of blood in Cx. erraticus specimens from New Jersey. We found that the majority of bloodmeals (92.6%) were derived from birds, followed by 6.8% from mammals (of which half were human), and a single amphibian bloodmeal from a spring peeper (0.56%). Medium- and large-sized water birds from the order Pelecaniformes made up 60.4% of the bird species and 55.9% of all identified hosts. This group of birds is known enzootic hosts of arboviruses such as eastern equine encephalitis virus, for which Cx. erraticus is a competent vector. Additionally, we screened blooded mosquitoes for avian malaria parasites and identified three different lineages of Plasmodium, including what may represent a new Plasmodium species (likely a wetland bird specialist) in bloodmeals from Green Herons, a Great Egret, and a Double-Crested Cormorant. Our results support the utility of mosquito bloodmeals as sources of information about circulating wildlife pathogens and reveal the potential of range-expanding species to intensify local zoonoses and bridge enzootic pathogens to humans.     

Characteristics of body mass growth in semialtricial and altricial bird species during the nestling period

The dynamics of body mass growth were studied in nestlings of 22 semialtricial and altricial bird species based on materials collected in seven regions of Russia in the years 1976–2013. The bird species belong to four orders and 13 families. The results of the study indicate the nonuniform growth of nestlings in different bird species. Of the species investigated, only seven were found to reach or exceed the mass of adult birds. Over the nestling period, the nestlings of open-nesting species, such as the hooded crow (Corvus cornix), rook (Corvus frugilegus), magpie (Pica pica), fieldfare (Turdus pilaris), song thrush (Turdus philomelos), and goldfinch (Carduelis carduelis), do not reach the weight of adult birds and their growth continues after they leave the nest. In closed-nesting species, only the nestlings of the barn swallow (Hirundo rustica) reach or exceed the definitive mass, whereas the nestlings of the jackdaw (Corvus monedula), starling (Sturnus vulgaris), wryneck (Jynx torquilla), tree sparrow (Passer montanus), and great tit (Parus major) continue to grow after leaving the nest. The body mass of birds on the day of their hatching and before their departure from the nests and the mass of adult birds depend on the nesting type, duration of the nestling period, size groups of species, and their definitive size. The average specific growth rate of body mass and its maximum values for different species are also associated with these factors. The maximum specific growth rate in small-sized and medium-sized bird species was observed on the 0–1st days of life; in large bird species, on the 2nd–4th days. The specific growth rate did not depend on the type of nesting, but it was inversely related to the duration of the nestling period and the definitive sizes of birds.     

Steeplebushes conquer the countryside: influence of invasive plant species on spider communities (Araneae) in former wet meadows

Central European wet meadows are diminished by abandonment of cultivation measures, drainage, pollution, intensive agriculture and climate change during the last decades. In addition, original wet meadow communities can be threatened by immigrating neophytes. Typical invasive species in wet meadows are the steeplebushes Spiraea tomentosa and Spiraea douglasii, but their impact on the indigenous arthropod fauna is unknown. The present study therefore investigates Spiraea-induced changes in ground- and herb dwelling spiders in Spiraea sites, uncultivated meadows with interspersed Spiraea sp. and mowed meadows without Spiraea sp. using pitfall traps and sweep netting. Light intensity, vegetation height and coverage differed significantly between the Spiraea sites and the mowed meadows. In consequence, the activity density of ground-dwelling spiders was much lower in the Spiraea sites and their habitat preferences differed significantly from the two meadow types. Species preferring forests and forest edges were more abundant in invaded sites whereas specimens preferring open habitats decreased. Although the vegetation height and coverage of mowed meadows and cultivated meadows did not differ remarkably, uncultivated meadows contained less spiders of open dry habitats whereas forest species increased. In contrast, differences between herb dwelling spider assemblages of the three habitat types were not significant. Based on the results of the project, the risk of steeple bush invasion and management methods of wet meadows are discussed.     

Impact of avian and arthropod predation on lepidopteran caterpillar densities and plant productivity in an ephemeral agroecosystem

Abstract.  1. Most studies evaluating the combined impact of spiders and other predators on herbivore densities in agroecosystems have focused primarily on their trophic connections with invertebrate predators (e.g. carabids, chrysopids); however linkages among spiders and vertebrate predators may also help structure the population dynamics of insect herbivores. A field experiment was conducted to examine the impact of avian and spider predation on lepidopteran caterpillar densities and plant productivity within a Brassica agroecosystem.
2. Arthropod abundance, leaf-chewing damage, and final plant productivity associated with broccoli, Brassica oleracea L. (var. italica ), were recorded for four treatments: (1) bird present but spiders removed; (2) both birds and spiders present; (3) birds excluded, spiders present; and (4) birds and spiders both excluded.
3. Densities of Artogeia rapae L. (Lepidoptera: Pieridae) and Trichoplusia ni Hübner (Lepidoptera: Noctuidae) large caterpillars and post feeding stages were reduced significantly by bird predation. The abundance of large caterpillars was also reduced on spider-inhabited plants during early plant growth; however the assemblage of birds and spiders did not suppress caterpillar densities more significantly than either predator alone.
4. Plants protected by birds, spiders, and birds plus spiders sustained less folivory attributable to leaf chewing caterpillars than check plants. Plant productivity was also greater for predator-protected plants than check plants.
5. Although spiders and parasitoids were responsible for some of the mortality inflicted upon lepidopteran caterpillars, it was concluded that in this study system, birds are the most important natural enemies of folivores.     

<Emphasis Type="Italic">Salmonella</Emphasis> in Wild Birds Utilizing Protected and Human Impacted Habitats,Uganda

As human populations in Africa expand, humans encroach and modify wildlife habitats for farming, fishing, tourism, or settlement. Anthropogenic activities in shared environments may promote transmission of zoonotic pathogens between humans, domestic animals, and wildlife. Between July 2012 and February 2014, we evaluated Salmonella prevalence, serovars, genotypes, and antibiotic resistant phenotypes in resident and migratory birds utilizing human-impacted habitats in northwestern Lake Victoria and protected habitats in Queen Elisabeth National Park. Salmonella occurrence in the urban environment was assessed by sampling storm-water and wastewater from a channel that drains Kampala City into Lake Victoria. Salmonella was detected in 4.3% pooled bird fecal samples, and 57.1% of environmental samples. While birds in impacted and protected areas shared serovars, the genotypes were distinct. We found distinct strains in birds and the environment suggesting some strains in birds are host adapted, and strains circulating in the environment may not necessarily disseminate to birds. Conversely, birds in both impacted and protected areas shared strains with the urban environment, suggesting Salmonella disseminates between impacted environments and birds across sites. Overall, more strains were observed in the urban environment compared to birds, and poses risk of Salmonella reemergence in birds and transmission across species and space.     

Spiders provide important resources for an endangered lizard

Conservation management requires knowledge of how a target species interacts with other species. Some relatively common species can modify the environment to the advantage of rarer, endangered species. Thus, local enhancement of those common species can positively influence remaining populations of the rarer species. The endangered pygmy bluetongue lizard Tiliqua adelaidensis inhabits burrows that are constructed by lycosid and mygalomorph spiders. We recorded 490 burrows in a 1 ha plot at the end of one season, and then observed at regular intervals the formation and loss of burrows, and the changes in occupancy status of each burrow over the next season. We found spiders in 94% of all newly constructed burrows and deduced that they had built the burrows. We found no evidence that lizards dug new burrows or deepened existing burrows. The numbers of both lizards and spiders in the burrows declined over the spring and summer, with lizards moving from their burrows more often early in the season than later. However, there was no strong trend for lizards to replace spiders in burrows. In fact, lizards tended to occupy deeper burrows than spiders, suggesting little negative impact of lizards on spiders. However, spiders had a positive impact on lizards by providing the refuge burrows central for lizard survival. Although lizards readily accept artificial burrows, long-term conservation for the lizards must include viable spider populations to maintain a supply of suitable burrow refuges.