Diet analysis and the assessment of plastic and other indigestible anthropogenic litter in the white stork pellets.

Pollution by anthropogenic litter is a major threat to global ecosystems. Seabirds are frequently used as environmental monitors of litter ingestion, but similar research is rare for terrestrial birds. Here, we focused on pellet analysis from 117 nests of an iconic bird of the Western Palearctic, the white stork (Ciconia ciconia), breeding in southern and southwestern Poland in a farmland landscape, far away from large dumps and landfills. We found that most prey items in the diet of white storks were invertebrates (particularly from orders Coleoptera, Orthoptera, and Hymenoptera) but vertebrate prey comprised most of the biomass. Further analysis revealed that anthropogenic litter was found in 22.7% of pellets (34.2% of breeding pairs) with plastic (8.4%) and cigarette filters (6.9%) being most prevalent. This study represents the first assessment through pellet analysis of the ingestion of anthropogenic litter by live wild storks in Poland and also by a migratory population of white storks. Our study indicates a potentially significant transfer of plastic and other anthropogenic material through terrestrial food webs.

Colour-assisted variation in elytral ICP-OES-based ionomics in an aposematic beetle.

Very little is known about how the elemental composition (ionome) of an insect cuticle varies as a result of different colouration. Using inductively-coupled plasma optical emission spectrometry (ICP-OES), we established ionomic profiles in microsamples of two adjacent regions of an insect cuticle with a contrasting colour pattern, namely, the black and orange regions of the elytra of the aposematic burying beetle Nicrophorus vespillo. The analysis revealed 53 elements (ranging in atomic weight from Na to Bi) occurring above the detection limit. The frequency of detectability of individual elements varied strongly, and only ten elements (Ba, Cu, Fe, K, Mg, Mn, P, Rb, Sb and Zn) were present in concentrations exceeding the detection limit in all the samples. The sum of concentrations of all elements in the orange regions of the elytra was 9% lower than in the black ones. The opposite distribution was displayed by the rare earth elements (REEs), the sum of which was 17% lower in the black elytral regions than in the orange ones. The concentrations of six elements were significantly higher in the black than in the orange regions: Al (by 97%), Cu (41%), Mn (14%), Na (46%), Se (97%) and W (47%). The concentrations of essential elements measured in both the black and orange regions exhibited very considerable variance: Ca (σ2 = 1834; 1882, respectively), K (145; 82) P (97; 76), Na (84; 53), Mg (24; 26) and Ba (9; 13). This, in part, could be attributed to individual differences, e.g. those resulting from the consumption of animal carcasses of different quality/chemical composition, but interference between elements and the consequent lowering of measurement quality are also possible. We highlight the fact that deeper insight into the basic relationship between insect colouration and variation in elemental composition requires micro-sampling of the homogeneous layers of an exoskeleton.

Supporting dataset and methods for body sizes and concentrations of chemical elements measured in elytra and abdomens of Stag Beetles Lucanus cervus.

The dataset presented in this data paper supports "Breaking down insect stoichiometry into chitin-based and internal elemental traits: Patterns and correlates of continent-wide intraspecific variation in the largest European saproxylic beetle" (Orlowski et al. 2020). Here we present the supplementary data and description of methods on the following: (1) mass of elytra and abdomens across 28 local Stag Beetle Lucanus cervus populations in Europe. (2) Population origin and coverage of six major land-cover types, including transport infrastructure, measured in three radii (500 m, 1000 m and 5000 m) around the sampling sites of these populations. (3) The relationship between the mass and concentrations of elements measured in abdomens and elytra in 28 Stag Beetle populations and major land-cover types around the sampling sites.

Breaking down insect stoichiometry into chitin-based and internal elemental traits: Patterns and correlates of continent-wide intraspecific variation in the largest European saproxylic beetle.

Stoichiometric, trophic and ecotoxicological data have traditionally been acquired from patterns of variation in elemental traits of whole invertebrate bodies, whereas the critical issue of the extracellular origin of some portion of elements, such as those present in ingested food and internal organs, has been ignored. Here we investigated an unexplored, yet crucial, question relating to whether, and to what degree, metals from two major body fractions: exoskeleton (elytra) and internal (body organs with gut material present in abdomens), are correlated with each other in wild populations of the largest European saproxylic insect, the Stag Beetle Lucanus cervus, and how metals from these two fractions vary with insect size and local habitat conditions. We examined the continent-wide variation in the concentrations of 12 chemical elements (Ca, Mg, K, Na, Mn, Fe, Zn, Cu, As, Cd, Pb and Ni) measured in the elytra and abdomen of specimens from 28 populations inhabiting an urban-woodland habitat gradient across the species' entire distributional range from Spain to Russia. Across populations, elemental concentrations (except Ni and Pb) were 2-13 times higher in abdominal samples than in elytra, and the magnitude of these differences was related to both insect size and local habitat conditions. Smaller individuals from both woodland and urban habitat tended to have higher concentrations of trace elements (Zn, As, Cd, Pb and Ni). The concentration of only six elements (Mg, K, Na, Mn, Cd and Ni) was correlated in the elytra and abdomen at the individual and population levels, implying a limitation to the broader applicability of elytra as a surrogate for internal elemental pools. We highlight that in non-feeding adult saproxylic beetles, minerals, acquired during the larval stage, may be concentrated in the large quantities of residual body fat.

Supporting dataset for elemental traits of plant-invertebrate food web components of oilseed rape fields.

This dataset is provided in support of the paper "Edge effect imprint on elemental traits of plant-invertebrate food web components of oilseed rape fields" (Orlowski et al., 2019). Supplementary data are given on the following: (1) the full taxonomic list of invertebrates (n = 12 916) classified into food guilds and functional groups, which were sampled in 34 oilseed rape fields in SW Poland in spring 2015; (2) concentrations of 12 chemical elements measured in invertebrates; (3) the relationships between abundance and percentage (%) in the community of major invertebrate groups, and habitat variables; (4) the statistical tests comparing the concentrations of chemical elements between the different groupings of organisms; (5) the relationships between the elemental traits of oilseed rape plant samples and major functional invertebrate groupings or main taxonomic insect groups, and the habitat variables of oilseed rape fields.

Edge effect imprint on elemental traits of plant-invertebrate food web components of oilseed rape fields.

Of fundamental importance for the functioning of a community is the flow of energy and elements through its components. However, the question of how (if at all) the edge effect of habitats can drive elemental traits of organisms has hitherto been largely neglected issue in ecosystem ecology at the community level. We quantified the abundance of invertebrates and measured the elemental composition (K, Na, Ca, Mg, Cu, Zn, Fe, Mn, As, Cd, Co and Pb) of 15 different organisms within the plant-invertebrate food web (plant - oilseed rape pests/herbivores - pollinators = wild bees - saprovores - predators - parasitoids) sampled in 34 fields of a key bioenergy crop that is an exceptionally strong biodiversity driver, the oilseed rape. Then these were related to the individual field edge habitat features (including typically anthropogenic ones like dirt and tarred roads) measured within a 100 m radius around the invertebrate sampling sites. Our study showed that elemental traits of the plant-invertebrate food web components in oilseed rape crops varied owing to the habitat specificity determined at the relatively small spatial scale of an individual field, and that the elemental traits of these organisms differed from both an inter- and an intra-guild perspective. The major mechanistic explanation for most of these relationships seems to derive from the secondary gut content effect. Determining one single state for the homeostatic/stoichiometric regulation of chemical elements in invertebrates based on the application of whole-body metal concentrations is in principle impossible, because of the unknown noise caused by the inclusion of extracellular portions of metals in the analysis. It is thus imperative to develop consistent principles for assessing elemental traits of organisms that are based on highly sensitive and high-throughput analytical methods for the ionomic profiling of microsamples at the organ, tissue, cellular or even sub-cellular levels.

Linking land cover satellite data with dietary variation and reproductive output in an opportunistic forager: Arable land use can boost an ontogenetic trophic bottleneck in the White Stork Ciconia ciconia.

Determining how the progressive loss of resources due to agricultural intensification and habitat degradation affect individual fitness and population persistence is a matter of urgency. Here we explored three major questions in order to extend knowledge of the relationship between reproduction rate, diet and energy intake in White Storks Ciconia ciconia based both on our own analysis of pellets and landscape properties sampled in 52 nests in south-western Poland, and published literature data. (1) How many individual prey items are needed to meet the daily energy requirements of nestlings over the brood rearing period? (2) How do the dietary patterns vary under different habitat conditions and what is the spatial scale responsible for these relationships? (3) Is reproductive output related to variations in landscape traits, and is diet variability related to intraspecific competition resulting from colonial breeding? In our estimation, the energy requirements of nestlings during the brood rearing period showed that the most profitable invertebrate prey items were Orthoptera and earthworms. Owing to the nestlings' gape-size constraint (precluding consumption of vertebrate prey items of the size of Common Voles), these most likely comprise the staple diet enabling survival during the first 20 days of life. The total energy content across all the pellets was a simple function (a negative correlation) of %arable land within a distance of 5 km around the nests. White Storks from nests of high-productivity pairs (with 3-4 fledglings and less %arable around) consumed equal %biomasses of invertebrate and vertebrate prey, while invertebrates prevailed in the diet of the low-productivity pairs. Our results suggest that a two-level ontogenetic trophic bottleneck may explain the low productivity of White Stork pairs in simplified landscapes with predominant arable land use. As a result of this, parent birds are unable to satisfy the growing energy demands of nestlings (1) by gathering a sufficient volume of abundant small-sized prey (early nestlings) and (2) by delivering energetically more profitable vertebrate prey at the time of the diet switch.

Data exploration on diet, and composition, energy value and functional division of prey items ingested by White Storks Ciconia ciconia in south-western Poland: Dietary variation due to land cover, reproductive output and colonial breeding.

The dataset presented in this data paper supports "Linking land cover satellite data with dietary variation and reproductive output in an opportunistic forager: Arable land use can boost an ontogenetic trophic bottleneck in the White Stork Ciconia ciconia" (Orlowski et al. 2019) [1]. Analysis of data on diet and prey composition based on an investigation of 165 pellets of White Storks Ciconia ciconia sampled from 52 nests showed that their diet was based primarily on 'eurytopic prey' (embracing taxa from grassland and a variety of non-cropped habitats), the biomass contribution of which in the diet was disproportionately (3-4-fold) higher than the percentage of available corresponding habitats. Similarly, prey items from water/wetland sites prevailed over the availability of corresponding habitats. The opposite pattern characterized prey taxa from arable habitats and forests, the contribution of which was lower than the availability of the corresponding habitats. The total energy content per pellet (calculated by summing the energy content of all individual prey items across one specific prey group) was the most strongly correlated with the biomass of Orthoptera, thereafter with that of mammals, other vertebrates, earthworms and other invertebrates, but not with the biomass of Coleoptera. White Storks from nests of low productivity pairs (i.e. with 1-2 fledglings) consumed a significantly (up to two-fold) higher biomass of Coleoptera, Orthoptera and all invertebrates, which also translated into a higher total biomass and a higher total energy content compared to the diet of high-productivity pairs (i.e. with 3-4 fledglings). Our data, in particular those relating to energy content in a variety of invertebrate taxa, and their body mass and functional division in terms of habitat preferences should be useful for other researchers to calculate energy budgets of predatory animals living in agricultural landscapes in Europe.

Effect of Brood Age on Nestling Diet and Prey Composition in a Hedgerow Specialist Bird, the Barred Warbler Sylvia nisoria.

The composition and quality of food provided to nestling birds influence their growth and development and offers key insight into the ecological requirements of birds. One bird species whose feeding ecology is poorly understood is the Barred Warbler (Sylvia nisoria), which utilizes semi-natural shrubby vegetation in agroecosystems. Because Barred Warbler nestlings vary greatly in body mass we hypothesised that diet and prey properties (size, diversity, taxonomic composition, and chitin content and resulting body hardness and digestibility) would differ as the nestlings aged. We quantified the diet based on faecal analysis, sampling faecal sacs from the nestlings pooled into three age classes: 2-3 days old, 4-6 d old, and 7-9 d old. Nestlings were provided a wide diversity of food and a strong relationship existed between food characteristics and nestling age. The youngest nestlings (2-3 d old) had the lowest values of each dietary characteristic (diversity, number and total biomass of prey, and individual prey weight), that were significantly lower than the oldest nestlings (7-9 d old). Nestlings aged 4-6 d exhibited intermediate dietary characteristics. Differences in dietary composition of the six major food types showed marked differences between the individual broods and age categories. Percentages of the number and biomass of soft-bodied prey were highest in the diet of 2-3 d and 4-6 d old nestlings, and decreased with increasing age, whereas the opposite trend was observed in the percentage of intermediately and heavily chitinised prey. Parent Barred Warblers probably preferentially select soft-bodied prey for the youngest nestlings, and satisfy the greater energy demands of the older ones by providing them with a greater variety of prey containing more chitin, as well as plant food. The provisioning of less-readily digestible prey to older nestlings suggests that as the quality of food decreases the quantity increases, implying that the youngest nestlings may be physiologically limited as regards their ability to digest more heavily chitinised prey.

Variable contribution of functional prey groups in diets reveals inter- and intraspecific differences in faecal concentrations of essential and non-essential elements in three sympatric avian aerial insectivores: a re-assessment of usefulness of bird faeces in metal biomonitoring.

Aerial insectivores through their insect diet can contribute to biotransfer of elements across habitats. We investigate the relationship between dietary composition as expressed by the contributions of six functional invertebrate prey groups (primarily of agriculturally subsidised invertebrates characteristic of agricultural areas in temperate regions of Europe) and concentrations of essential (Na, K, Ca, Mg, Fe, Cu, Zn, Mn, Co) and non-essential (As, Cd, Pb) elements of environmental concern in the faeces of nestlings of three species of avian aerial insectivores - Common Swift Apus apus, Barn Swallow Hirundo rustica and House Martin Delichon urbicum - which breed sympatrically and use apparently similar resources of flying insect prey. There were significant differences between the species for 7 of the 12 elements (Ca, Zn, Cu, Co, As, Pb, Cd); these differences were attributable to the variable dietary composition, even though the concentrations of the elements varied enormously between the faecal samples from the individual species. Partial correlation analysis between the biomass (expressed in mg dry weight) of the six functional prey groups and faecal concentrations of elements showed the highest number of significant relationships for toxic metals (As, Pb and Cd). The results of the General Regression Model explaining faecal element concentrations revealed the different explanatory power of the effects of PCA (of six functional prey groups) dietary scores. A significant fit of GRM was obtained for 7 elements (Na, Mg, Fe, Mn, As, Pb, Cd) for Barn Swallows, 2 elements (Cu, As) for House Martins and 1 element (Mn) for Common Swifts. Overall, the results confirmed our predictions that the biomass of consumed coprophilous taxa and insects from crop habitats was positively correlated with the faecal concentrations of toxic elements. Unexpectedly, however, the faecal samples (primarily those of Common Swifts) that contained many oil-seed rape insect pests had lower Ca, Pb and Cd levels and a higher As level. Our study implies that the cross-boundary transfer of contaminants, primarily non-essential elements, by aerially foraging birds through the considerable accumulation of their faeces has potential consequences for the local biogeochemical cycle and environmental quality.

Functional invertebrate prey groups reflect dietary responses to phenology and farming activity and pest control services in three sympatric species of aerially foraging insectivorous birds.

Farming activity severely impacts the invertebrate food resources of farmland birds, with direct mortality to populations of above-ground arthropods thorough mechanical damage during crop harvests. In this study we assessed the effects of phenological periods, including the timing of harvest, on the composition and biomass of prey consumed by three species of aerial insectivorous birds. Common Swifts Apus apus, Barn Swallows Hirundo rustica and House Martins Delichon urbica breed sympatrically and most of their diet is obtained from agricultural sources of invertebrate prey, especially from oil-seed rape crops. We categorized invertebrate prey into six functional groups, including oil-seed rape pests; pests of other arable crops; other crop-provisioned taxa; coprophilous taxa; and taxa living in non-crop and mixed crop/non-crop habitats. Seasonality impacted functional groups differently, but the general direction of change (increase/decrease) of all groups was consistent as indexed by prey composition of the three aerial insectivores studied here. After the oil-seed rape crop harvest (mid July), all three species exhibited a dietary shift from oil-seed rape insect pests to other aerial invertebrate prey groups. However, Common Switfts also consumed a relative large quantity of oil-seed rape insect pests in the late summer (August), suggesting that they could reduce pest insect emigration beyond the host plant/crop. Since these aerially foraging insectivorous birds operate in specific conditions and feed on specific pest resources unavailable to foliage/ground foraging avian predators, our results suggest that in some crops like oil-seed rape cultivations, the potential integration of the insectivory of aerial foraging birds into pest management schemes might provide economic benefits. We advise further research into the origin of airborne insects and the role of aerial insectivores as agents of the biological control of crop insect pests, especially the determination of depredation rates and the cascading effects of insectivory on crop damage and yield.