The use of anthropogenic marine debris as a nesting material by brown boobies (Sula leucogaster)

Do birds select the plastics debris used for nest construction? A case study in a Mediterranean agricultural landscape

Plastic pollution is becoming a global problem due to its ubiquitous occurrence and the impacts detected for many species. However, the research about plastics in nests of terrestrial bird species has remained relatively overlooked in comparison to those devoted to marine ecosystems. Here we study the occurrence and patterns of use of anthropogenic material in nests of two passerine birds, the Eurasian magpie (Pica pica) and the European serin (Serinus serinus), breeding in an orange tree cultivation in Mediterranean Spain. Our results show that both species use extensively plastic debris as nest material; almost 71% of the European serin nests and 96% of nests of Eurasian magpies contained plastic debris. Furthermore, by analyzing the plastic debris availability in the agricultural landscape surveyed we confirmed a selection pattern in the two species. Thus, both species preferably select plastic filaments over other plastic debris. The Eurasian magpie does not select plastic based on size or color but the European serin avoid black plastics prefer smaller fragments in comparison to the average size available. Moreover, we suggest the apparent similarity of plastic filaments with the natural materials typically used by these species, as well as how they use the plastic in their nests could influence their selection behavior. More studies focused on terrestrial birds inhabiting human modified habitats could offer a deeper approach to how plastic debris interacts with wildlife in different ways.

Nesting material adaptation of native bird species with anthropogenic litter along an urbanization gradient in Pakistan

Rapid urbanization and associated waste generation have become a mounting ecological concern for wildlife, especially avian communities. Research has primarily focused on investigating the impacts of human activities on marine birds with comparatively less focus on terrestrial species that live in far more anthropized environments and are at significant risk. Our study has explored the abundance and characteristics of anthropogenic litter in 70 nests of four generalist bird species: Bank Myna (Acridotheres ginginianus), Common Myna (Acridotheres tristis), Black Kite (Milvus migrans) and House Crow (Corvus splendens), within the city of Lahore (Pakistan) and its surroundings, by determining and following an urbanization gradient. The overall frequency of litter occurrence (FLO%) for all the sampled nests was 89%. Over 80% of the recorded litter items consisted of plastic materials, primarily dominated by sheet-like plastics. There was a strong association between fabric and Black Kite nests, and metal and House Crow nests. Litter incorporation increased across the gradient from rural to urban habitats. The highest FLO% was found in nests sampled from waste dumping sites and urban sites (95%-100%), where anthropogenic influence was more intense. The high level of litter incorporation is potentially indicative of a species' adaptive response to urbanization, associated with the decline in natural nesting material and availability of anthropogenic litter. These findings highlight the need for strengthening the existing global database for terrestrial litter and its effect on wildlife and devising policy actions for better waste management and conservation of natural ecosystem balance.

Gulls as potential sentinels for urban litter: combining nest and GPS-tracking information

The production of urban waste has increased in the past decades leading to its mishandling. The effects on public health, economy, and wildlife that waste mismanagement can have are forcing governments to increase their efforts in detecting and mitigating the presence of waste. Identifying and monitoring sentinel species to assess the presence of urban litter could be a cost-effective option. Thus, analyzing the nest composition of yellow-legged gulls from an urban population inhabiting a very high populated city (Barcelona, Spain), and combining this information with accurate GPS tracking data, provides a potential tool to monitor the presence of marine and terrestrial litter over time. The results revealed the highest presence of debris in the nests of a seabird ever recorded. All the nests examined contained anthropogenic waste, with plastic items present in all of them. Crossing the nest composition with GPS tracking movements confirmed that the waste to build the nests was collected in the urban area and not in other environments surrounding the city. Then, the nest waste composition may be a good indicator of waste mismanagement and advise the municipalities to improve waste management and recycling strategies for the different types of litter. Using gulls breeding in cities as sentinel species and, in particular, the study of their nest composition, may provide essential data to decision-making stakeholders to adopt a One Health approach and help improve not only the environment's health but also the health of those who live in it.

Marine litter pollution of breeding colony and habitat use patterns of Black-tailed gulls in South Korea

Marine litter can affect the survival of the breeding population in seabird colonies. In this study, five 5 m × 5 m quadrats were installed at a Black-tailed gull (Larus crassirostris) breeding colony on Nan Island to collect marine litter and regurgitated pellets, from which the types, sizes, and quantities of marine litter were identified. Global positioning system (GPS) devices were attached to five adult gulls to investigate their major foraging habitats during the breeding period. Eighty-two pieces of marine litter were found, of which 74.4 % were related to fishing; all pellets contained fishing-related marine litter. Over half of the foraging habitats included fishing areas (ports and fish farms). This study is the first to quantitatively demonstrate the exposure of breeding colonies of Black-tailed gulls, the most dominant Korean seabird, to marine litter pollution during the breeding period; the birds forage predominantly in fishing areas close to their breeding colonies during this period.

The influence of seabirds on their breeding, roosting, and nesting grounds: a systematic review and meta-analysis

Seabird species worldwide are integral to both marine and terrestrial environments, connecting the two systems by transporting vast quantities of marine-derived nutrients and pollutants to terrestrial breeding, roosting, and nesting grounds via the deposition of guano and other allochthonous inputs (e.g., eggs, feathers). We conducted a systematic review and meta-analysis and provide insight into what types of nutrients and pollutants seabirds are transporting, the influence these subsidies are having on recipient environments, with a particular focus on soil, and what may happen if seabird populations decline. The addition of guano to colony soils increased nutrient levels compared to control soils for all seabirds studied, with cascading positive effects observed across a range of habitats. Deposited guano sometimes led to negative impacts, such a guanotrophication, or guano-induced eutrophication, which was often observed where there was an excess of guano or in areas with high seabird densities. While the literature describing nutrients transported by seabirds is extensive, literature regarding pollutant transfer is comparatively limited, with a focus on toxic and bioaccumulative metals. Research on persistent organic pollutants and plastics transported by seabirds is likely to increase in coming years. Studies were limited geographically, with hotspots of research activity in a few locations, but data were lacking from large regions around the world. Studies were also limited to seabird species listed as Least Concern on the IUCN Red List. As seabird populations are impacted by multiple threats and steep declines have been observed for many species worldwide, gaps in the literature are particularly concerning. The loss of seabirds will impact nutrient cycling at localised levels and potentially on a global scale as well, yet it is unknown what may truly happen to areas that rely on seabirds if these populations disappear.

Comparing methods for monitoring nest debris using silver gulls as a case study

Global plastics production is increasing exponentially and contributing to significant pollution of the marine environment. Of particular concern is ingestion and entanglement risks for marine wildlife, including when items such as rope are incorporated into nest structures. These events are commonly documented using photographic and visual surveys, and each presents a number of challenges and benefits for species conservation and monitoring. Here we compare an invasive (i.e., removing debris from nests) and non-invasive (i.e., photographs) sampling method for quantifying nest debris using the silver gull (Chroicocephalus novahollandiae) as a case study. Overall, 17 debris items were detected in 9% of gull nests. While the use of photographs to monitor nest debris is increasingly popular, the invasive method detected one additional debris item not identified using photography. We therefore recommend caution for nest debris and other monitoring programs where identifying small or cryptic items may require a high level of skill.

Anthropogenic debris in Kelp Gull and other seabird nests in northern Patagonia, Argentina

Anthropogenic debris is used as nesting material by many seabirds and may result in negative impacts. We assessed the frequency of occurrence of debris (>5 mm) in Kelp Gull (Larus dominicanus) nests at six locations along 2400 km of the Argentine coast, at different distances from urban centres, and in nests of other seven seabird species nesting syntopically. Frequencies in Kelp Gull nests were in general relatively low, ranging between 3.3 and 37.5%, and differed significantly among colonies. No relationship was found between frequency and distance to urban centres. Debris were recorded with frequencies of less than 19.2% in nests of Olrog's Gulls (L. atlanticus), Dolphin Gulls (L. scoresbii), Imperial Cormorants (Leucocarbo atriceps) and Magellanic Penguins (Spheniscus magellanicus), but not in nests of Neotropical Cormorants (Nannopterum brasilianus), Rock Shags (Leucocarbo magellanicus) and Southern Skuas (Catharacta antarctica). This information obtained along a wide coastal sector provides a baseline for future monitoring.

Comparing photography and collection methods to sample litter in seabird nests in a coastal archipelago in the Southwest Atlantic

Different methods are used to quantify and classify litter in seabird nests, such as the collection method (CM) and the photography method (PM). We compared the CM and PM in 195 brown booby (Sula leucogaster) nests breeding in a coastal archipelago in the state of Rio de Janeiro, Brazil. Photographs recorded 109 litter items in 44 nests (23% of nests), compared to 416 litter items in 82 nests (42%) by the CM. Pairwise comparison showed a significant difference in the variety and amount of litter items per nest, which was greater for CM (2.1 ± 1.1 categories, 2.13 ± 4.8 items) than for PM (1.5 ± 0.8 categories; 0.56 ± 1.6 items), in addition to a significant difference in the overall litter composition. The CM has been the most often used method to date. Although PM underestimates the amount and frequency of litter, we encourage its use when litter is abundant in nests and for threatened species.

A standardised method for estimating the level of visible debris in bird nests

Unlike records of plastic ingestion and entanglement in seabirds which date back to the 1960s, the literature regarding debris in bird nests is comparatively limited. It is important to identify standardised methods early so that data are collected in a consistent manner, ensuring that future studies can be comparable. Here, we outline a method that can be applied to photographs for estimating the proportion of visible debris at the surface of a nest. This method uses ImageJ software to superimpose a grid onto a photograph of a nest/s. The number of cells with and without debris are then counted. Our proposed method is repeatable, straightforward, and accessible. We optimised the method to estimate the level of visible debris in Northern Gannet (Morus bassanus) nests, however, with some modification (i.e., adjustment of grid cell size), it could be applied to other seabird species, and terrestrial birds, that incorporate debris within nests.

Measuring nest incorporation of anthropogenic debris by seabirds: An opportunistic approach increases geographic scope and reduces costs

Data on the prevalence of anthropogenic debris in seabird nests can be collected alongside other research or through community science initiatives to increase the temporal and spatial scale of data collection. To assess the usefulness of this approach, we collated data on nest incorporation of debris for 14 seabird species from 84 colonies across five countries in northwest Europe. Of 10,274 nests monitored 12% contained debris, however, there was large variation in the proportion of nests containing debris among species and colonies. For several species, the prevalence of debris in nests was significantly related to the mean Human Footprint Index (HFI), a proxy for human impact on the environment, within 100 km of the colony. Collecting opportunistic data on nest incorporation of debris by seabirds provides a cost-effective method of detecting changes in the prevalence of debris in the marine environment across a large geographic scale.

First evidence of anthropogenic debris in nests of the Kelp Gull (Larus dominicanus) from a small semi-desert Argentinean coastal ecosystem

Here, we present the first findings of anthropogenic debris (AD) used as nest material by the Kelp Gull (Larus dominicanus) on a small semi-desert coastal ecosystem in northern Argentine Patagonia. Anthropogenic debris was found in ca. 40% of the 259 active nests, with an average of 2.80 ± 2.60 items per nest (n = 126) with >1 item recorded in >50% of surveyed nests containing debris. The average weight of AD per nest was 4.58 ± 12.74 g; the heaviest debris item weighed 82.58 g. Fragmented plastics were more abundant than unbroken items. Plastic followed by paper dominated the fraction of AD, with flexible plastic items dominating at both sites (nests: 97%, adjacent beach: 82%). Mega-sized plastics (>10 cm in length) and white/clear debris prevailed at both gull nests and the adjacent beach; fisheries and recreational activities were identified as the main sources of AD.

Seabird breeding islands as sinks for marine plastic debris

Seabirds are apex predators in the marine environment and well-known ecosystem engineers, capable of changing their terrestrial habitats by introducing marine-derived nutrients via deposition of guano and other allochthonous inputs. However, with the health of the world's oceans under threat due to anthropogenic pressures such as organic, inorganic, and physical pollutants, seabirds are depositing these same pollutants wherever they come to land. Using data from 2018 to 2020, we quantify how the Flesh-footed Shearwater (Ardenna carneipes) has inadvertently introduced physical pollutants to their colonies on Lord Howe Island, a UNESCO World Heritage site in the Tasman Sea and their largest breeding colony, through a mix of regurgitated pellet (bolus) deposition and carcasses containing plastic debris. The density of plastics within the shearwater colonies ranged between 1.32 and 3.66 pieces/m² (mean ± SE: 2.18 ± 0.32), and a total of 688,480 (95% CI: 582,409-800,877) pieces are deposited on the island each year. Our research demonstrates that seabirds are a transfer mechanism for marine-derived plastics, reintroducing items back into the terrestrial environment, thus making seabird colonies a sink for plastic debris. This phenomenon is likely occurring in seabird colonies across the globe and will increase in severity as global plastic production and marine plastic pollution accelerates without adequate mitigation strategies.

The use of anthropogenic debris as nesting material by the greater thornbird, an inland-wetland-associated bird of South America

Plastic pollution has become a globally pressing environmental issue. In birds, plastic may cause harm by entangling or ingestion when used for nesting. The use of anthropogenic nesting material has so far been mostly studied in birds of terrestrial or marine habitats, but there are yet very few reports for inland water-associated birds. The aim of this study is to better understand the extension and magnitude of the use of anthropogenic debris as nesting material by the greater thornbird (Phacellodomus ruber), a bird species preferably nesting in river floodplain wetlands in South America. We found that P. ruber uses disproportionally large quantities of plastic debris as nesting material (more than 90% of some nest chambers is plastic). This occurred even if ample vegetation (commonly used as soft material) was available. Most of the artificial nesting material was derived from wrapping material released into the environment. We suggest that this species has the potential to indicate vulnerable areas to plastic pollution associated with urban waste mismanagement.

Understanding individual and population-level effects of plastic pollution on marine megafauna

Plastic pollution is increasing rapidly throughout the world’s oceans and is considered a major threat to marine wildlife and ecosystems. Although known to cause lethal or sub-lethal effects to vulnerable marine megafauna, population-level impacts of plastic pollution have not been thoroughly investigated. Here, we compiled and evaluated information from peer-reviewed studies that reported deleterious individual-level effects of plastic pollution on air-breathing marine megafauna (i.e. seabirds, marine mammals, and sea turtles) worldwide, highlighting those that assessed potential population-level effects. Lethal and sub-lethal individual-level effects included drowning, starvation, gastrointestinal tract damage, malnutrition, physical injury, reduced mobility, and physiological stress, resulting in reduced energy acquisition and assimilation, compromised health, reproductive impairment, and mortality. We found 47 studies published between 1969 and 2020 that considered population-level effects of plastic entanglement (n = 26), ingestion (n = 19), or both (n = 2). Of these, 7 inferred population-level effects (n = 6, entanglement; n = 1, ingestion), whereas 19 lacked evidence for effects (n = 12, entanglement; n = 6, ingestion; n = 1, both). However, no study in the past 50 yr reported direct evidence of population-level effects. Despite increased interest in and awareness of the presence of plastic pollution throughout the world’s oceans, the extent and magnitude of demographic impacts on marine megafauna remains largely unassessed and therefore unknown, in contrast to well-documented effects on individuals. Addressing this major assessment gap will allow researchers and managers to compare relative effects of multiple threats—including plastic pollution—on marine megafauna populations, thus providing appropriate context for strategic conservation priority-setting.

Density and composition of surface and buried plastic debris in beaches of Senegal

Debris poses a series of problems to marine life and human well-being. However, estimates of density and characteristics of debris found on beach surfaces and buried in the sand are patchy on a global scale and absent for West Africa. Here we investigate the density of surface and buried debris accumulated in two beaches with contrasting levels of urbanisation in Senegal, West Africa. We also describe type, colour, weight, size, and possible source of the 1766 items collected. The average density of debris buried at a depth of 10 cm (48.75 items/m²) was 25 times higher than that observed at the surface (1.92 items/m²). Plastics accounted for 97.62% of the items. Plastic bags and clothing plastic were the most common types, whereas white and transparent were the most common colours. Most items originated from mixed sources, i.e. beach users and land-based sources (51.30%). Debris density in the urbanised site was 20 times higher than that in the non-urbanised site. Debris density can, therefore, be largely underestimated when sampling only on the beach surface. Our study provides the first findings for future research on beach debris in Senegal.

Characterization of anthropogenic materials on yellow-legged gull (Larus michahellis) nests breeding in natural and urban sites along the coast of Portugal

Anthropogenic materials are a persistent pressure on ecosystems, affecting many species. Seabirds can collect these materials to construct their nests, which may modify nest characteristics and cause entanglement of chicks and adults, with possible consequences on breeding success. The incorporation of anthropogenic materials in nests of seabird species that breed in both natural and urban environments, such as gulls, is poorly known. Here, we characterize and compare anthropogenic materials incorporated in yellow-legged gull (Larus michahellis) nests from two natural and two urban breeding sites across their Portuguese breeding range and during 2 consecutive years. Anthropogenic materials were found in 2.6% and 15.4% of gull nests from natural locations and in 47.6% and 95.7% of nests from urban breeding sites. No differences were found on hatching success between urban and natural breeding colonies. A significantly higher number of anthropogenic materials were found in the largest and more populated urban breeding colony, which on average included items of a greater mass but smaller size than items from the other three colonies. The higher incorporation of anthropogenic materials in urban locations could be a consequence of a lower access to natural nest construction materials and higher availability of anthropogenic debris. The quantity and diversity of anthropogenic materials incorporated in gull nests from urban locations indicate a need for improved debris management in urban settlements.

Confidence intervals and sample size for estimating the prevalence of plastic debris in seabird nests

Evidence is accumulating about the impacts of plastics on marine life. The prevalence of plastics in seabird nests has been used as an indicator of levels of this pollutant in the ocean. However, the lack of a framework for defining sample sizes and errors associated with estimating the prevalence of plastic in nests prevents researchers from optimising time and reducing impacts of fieldwork. We present a method to determine the confidence intervals for the prevalence of debris in seabird nests and provide, for the first time, information on the prevalence of these items in nests of the Hartlaub's gull Larus hartlaubii, the African penguin Spheniscus demersus, the great white pelican Pelecanus onocrotalus, and the white-breasted cormorant Phalacrocorax lucidus in South Africa. The method, based on observations and resampling simulations and tested here for nests of 12 seabird species from 15 locations worldwide, allows for straightforward hypothesis testing. Appropriate sample sizes can be defined by combining this method with a Bayesian approach. We show that precise estimates of prevalence of debris in nests can be obtained by sampling around 250 nests. Smaller sample sizes can be useful for obtaining rough estimates. For the Hartlaub's gull, the African penguin, the great white pelican, and the white-breasted cormorant, debris were present in 0.75%, 3.00%, 6.41%, and 25.62% of the respective nests. Our approach will help researchers to determine errors associated with the prevalence of debris recorded in seabird nests and to optimise time and costs spent collecting data. It can also be applied to estimate confidence intervals and define sample sizes for assessing prevalence of plastic ingestion by any organism.

Using photographs to record plastic in seabird nests

The incidence of plastic in seabird nests can be used to track changes in the amounts of marine debris, but large sample sizes are needed for accurate estimates. Surveys of active nests cause disturbance to breeding birds, so we need an efficient way to sample nest plastics. Photographs of brown noddy Anous stolidus nests at Ducie Atoll, southeast Pacific Ocean, allowed rapid characterisation of plastic use with limited disturbance, and showed selection for blue-green items. Plastic was more prevalent in noddy nests at Ducie Atoll (97%) than at Inaccessible Island, South Atlantic Ocean (41%), despite lower debris densities at Ducie. Differences in nesting habitat and the resultant availability of natural nesting material drive this difference in plastic loads. Using photographs to record plastic in seabird nests reduces disturbance to breeding birds and might decrease the risk of missing cryptic debris items. Photographs also provide a permanent record of pollution levels.

Marginal presence of plastic in nests of yellow–legged gulls (Larus michahellis) in the southeastern Bay of Biscay

Nest entanglement and consumption of plastics can be a cause of mortality in chicks of various seabird species. As plastic debris may be chosen as a source of nesting material, evaluation of its presence and contribution to nest building in seabird colonies is important. Here, we determined the contribution of anthropogenic debris to nest construction by a yellow–legged gull Larus michahellis population that largely depends on refuse tips to forage. Two colonies within the southeastern Bay of Biscay, Spain, were sampled in 2019. One of the colonies was in Getaria, where no debris was found in nests, and the second was in Ulia, where 40 % of the nests had some kind of artificial material. In all cases, however, this debris comprised less than 5 % of the nests’ area. Among the studied nests, we found one had a piece of fabric, five had pieces of rope, and 20 had pieces of flexible plastic packaging. These results contrast with other seabird species that face problems of conservation due to the increasing use of plastic for nesting. With the low prevalence of artificial debris (chiefly plastic) in nests found in this study, mortality due to debris entanglement or ingestion is unlikely.

The prevalence and source of plastic incorporated into nests of five seabird species on a small offshore island

There is little evidence documenting the prevalence of plastic nest incorporation for different seabird species and populations, and even less detailing the source of such debris as nesting material. This study presents a baseline dataset on the presence of plastic in the nests of five seabird species on Lady Isle, Scotland using a novel and repeatable methodology for quantifying plastic incorporated into nests. Plastic was found in 24.5% to 80% of nests of all species. We analysed pellets of regurgitated material and the spatial distribution of herring gull nests containing plastic in the context of the tide and nesting habitat. Differences in the types of plastic found in pellets and nests suggests that plastic incorporated into herring gull nests was not derived at foraging sites and likely collected from the local environment. Targeted beach cleans before the breeding season could help minimise the quantity of plastic available to herring gulls.

Incidence of anthropogenic material in Sula leucogaster nests in a distant archipelago of Brazil

Anthropogenic debris has been affecting fauna in different ways. We investigate the frequency of anthropogenic material in nests of a brown booby (Sula leucogaster) colony in the Saint Peter and Saint Paul Archipelago (SPSPA), Rio Grande do Norte, Brazil in February 2015 and November 2016. The items were classified according to type (threadlike plastic, sheet plastics, hard fragments, foamed synthetics and miscellaneous) and color. In 2015, a total of 30 anthropogenic items were found in 20.4% of the nests. In nests containing debris, miscellaneous items were found in 73.6% of nests. White/clear was the most common color, 52.6% of nests containing debris had items of this color. In 2016, 45 anthropogenic items were observed in 13.3% of the nests. Threadlike plastic was found in 59.2% of nests. Blue/purple was the most common color (55.5%). Even far from the Brazilian coast, the S. leucogaster colony has been affected by marine pollution.

Trace element concentrations in feathers from three seabird species breeding in the Timor Sea

Mobile marine predators, such as seabirds, are frequently used as broad samplers of contaminants that are widespread in the marine environment. The Timor Sea off remote Western Australia is a poorly studied, yet rapidly expanding area of offshore development. To provide much needed data on contamination in this region, we quantified trace element concentrations in breast feathers of three seabird species breeding on Bedout Island. While adult Masked Boobies Sula dactylatra exhibited some of the highest concentrations, values for all species were below toxicology thresholds for seabirds and were comparable to those reported in other closely related species. The low concentrations detected in the birds provide a valuable baseline and suggest that the local marine environment around Bedout is in relatively good condition. However, careful monitoring is warranted in light increasing anthropogenic activity in this region.

Monitoring nest incorporation of anthropogenic debris by Northern Gannets across their range

Anthropogenic marine debris is a recognised global issue, which can impact a wide range of organisms. This has led to a rise in research focused on plastic ingestion, but quantitative data on entanglement are still limited, especially regarding seabirds, due to challenges associated with monitoring entanglement in the marine environment. However, for seabird species that build substantial surface nests there is the opportunity to monitor nest incorporation of debris that individuals collect as nesting material. Here, we monitored nest incorporation of anthropogenic marine debris by Northern Gannets (Morus bassanus) from 29 colonies across the species' range to determine a) the frequency of occurrence of incorporated debris and b) whether the Northern Gannet is a suitable indicator species for monitoring anthropogenic debris in the marine environment within their range. Using data obtained from visual observations, digital photography and published literature, we recorded incorporated debris in 46% of 7280 Northern Gannet nests, from all but one of 29 colonies monitored. Significant spatial variation was observed in the frequency of occurrence of debris incorporated into nests among colonies, partly attributed to when the colony was established and local fishing intensity. Threadlike plastics, most likely from fishing activities, was most frequently recorded in nests, being present in 45% of 5842 nests, in colonies where debris type was identified. Comparisons with local beach debris indicate a preference for threadlike plastics by Northern Gannets. Recording debris in gannet nests provides an efficient and non-invasive method for monitoring the effectiveness of actions introduced to reduce debris pollution from fishing activities in the marine environment.

Can the Atlantic ghost crab be a potential biomonitor of microplastic pollution of sandy beaches sediment?

The objective of the present study was to test whether the Atlantic ghost crab Ocypode quadrata is a reliable biomonitor of microplastic (MP) pollution of beach sediments. To test the hypothesis (H1) that the sediment is the main source of MP ingestion, the proportion of MP types (hard plastic, microfibers, pellet, soft plastic, and extruded polystyrene foam) in the gut content was compared with that on the strandline. The types of MPs in the gut content and sediment had similar proportions; black (~49%) and blue (~45%) microfibers were responsible for this similarity (55%), hence confirming H1. However, the second hypothesis (H2) that prevalence of MP in the gut content is related to its density on beach with distinct urbanization degree was not accepted. These results indicate that high trophic plasticity of the ghost crab and, consequently, multiple-sources of contamination may interfere with its use as a biomonitor of MP pollution.