Measuring nest incorporation of anthropogenic debris by seabirds: An opportunistic approach increases geographic scope and reduces costs. O’Hanlon, N.J., Bond, A.L., Masden, E.A., Lavers, J.L. & James, N.A. 2021 Marine Pollution Bulletin. doi: 10.1016/j.marpolbul.2021.112706 VIEW
Despite all the media around plastic pollution and the push for initiatives to reduce it, the amount of plastics produced globally is forecast to continue to increase. Therefore, large amounts of plastic waste will continue to enter the environment, including our oceans, unless substantial interventions are put in place to reduce production, improve waste management systems and recover plastics from the environment (Borrelle et al., 2020).
Seabirds are currently facing a multitude of threats and separating the population-level effects of plastics from other threats is difficult. Seabirds are also sentinels of our oceans, and so can help us evaluate the effectiveness of initiatives to reduce plastics in the marine environment. Therefore, collecting data on anthropogenic debris (hereafter debris) in seabird nests can not only help us identify species where entanglement from incorporated debris might be a risk, but also to detect changes in the amount of debris in an area related to local and national action, or lack of action, in reducing plastic pollution.
In a recent study, we found that the frequency of Northern Gannet nests containing incorporated threadlike plastics was related to the extent of fishing activity in the vicinity of the colony, as well as the age of the colony (O’Hanlon et al. 2019; see previous #theBOUblog post on this). But what about other seabird species? To what extent do they incorporate debris in their nests, and does this reflect the amount of debris in the surrounding marine environment?
Recording debris incorporated into seabird nests is relatively straight-forward and non-invasive. Therefore to obtain as many data as possible from a wide range of species and locations we put out a request to seabird researchers, wardens and ringers to collect information on debris incorporated into seabird nests, or not, during routine activities at colonies they were visiting.
Figure 1 Location of seabird colonies where data were collected on anthropogenic debris incorporated into nests between 2016 and 2020.
Thanks to this collective effort between 2016 and 2020, 10,274 nests were monitored of 14 seabird species from 84 different colonies, largely in the UK but also in the Faroe Islands, Iceland, Norway, Svalbard and Sweden (Figure 1). Of these 10,274 nests, 1199 (12%) contained debris, however, there was large variation among species and colonies, and in the number of nests and colonies that were monitored per species (Figure 2). Focusing on the species where a relatively large sample size of colonies and nests were monitored, Herring Gulls Larus argentatus (13 colonies, 1728 nests) and European Shags Phalacrocorax aristotelis (26 colonies, 1243 nests) had the highest frequency of occurrence of nests containing debris (26% and 25% of all monitored nests, respectively). By contrast, from 3681 Black-legged Kittiwake Rissa tridactyla nests being monitored, at 33 colonies, only 4% of nests contained debris (Figure 3). Surprisingly, the Atlantic Puffin Fratercula arctica had the highest overall frequency of occurrence of nests containing debris, with 67% of nests containing debris, however only 130 nest crevices in three colonies were monitored (two in Norway and one in Svalbard).
Figure 2 Boxplot highlighting among-species group differences in the frequency of occurrence (%) of anthropogenic debris incorporated into nests across colonies. Points represent raw data at the species-colony level. Sample sizes of nests monitored for each species are shown at the top of each boxplot.
From a sub-sample of nests where data on the type of debris incorporated in nests were also recorded, threadlike and sheet plastics were the most incorporated items of debris. We also found that for the shags and gulls colonies located in areas with higher mean Human Footprint Index (a proxy for human impact on the environment taking into account population density, human land use, infrastructure and human access; WCS & CIESIN, 2005) contained a greater proportion of nests containing debris. This indicates that the large gulls and European Shag, which incorporate a range of debris types into their nests, reflect local levels of plastic pollution in the vicinity of their colonies and would likely make good sentinels.
A major benefit of requesting information of nest incorporation of debris from those already visiting seabird colonies was that we obtained a large amount of data from a wide range of species, over a large geographical area, that we could not have collected on our own. So a massive thank you to everyone who contributed data! We calculated that if I had visited all these colonies independently it would have cost over £18,000 (including travel and accommodation but not researcher costs) and involved travelling a minimum of 21,600 km, with associated carbon emissions of 3.76 metric tons. It would also have taken a considerable amount of time, not only in travelling but in planning the logistics to access all the colonies.
Figure 3 Most Kittiwake colonies monitored contained no or few nests containing anthropogenic debris. However, there were a few exceptions, with two colonies having 31% and 49% of nests containing debris: Dunbar Harbour on the east coast of the UK, and an oilrig in the North Sea, pictured here. © Signe Christensen-Dalsgaard
There are several limitations to this approach, including spatio-temporal biases in data collection. However, to help answer the grand challenges in marine plastic pollution research, opportunistic data obtained from robust, easily implemented methods are beneficial to increase our understanding of entanglement risk of seabirds at the nest and to assess the efficiency of actions to reduce plastic pollution in the environment. The prevalence of debris of different types, from consumer and fishery related sources, in many of the seabird colonies included in this study, emphasises further the need to reduce the production and consumption of plastics and for improved waste management infrastructure to prevent these items entering the environment and being available as nesting material, or being ingested.
Top right: Threadlike debris in the nest of a European Shag Phalacrocorax aristotelis. © Nina O’Hanlon
Borrelle, S.B., Ringma, J., Law, K.L., Monnahan, C.C., Lebreton, L., McGivern, A., Murphy, E., Jambeck, J., Leonard, G.H., Hilleary, M.A., Eriksen, M., Possingham, H.P., Frond, H. De, Gerber, L.R., Polidoro, B., Tahir, A., Bernard, M., Mallos, N., Barnes, M., Rochman, C.M. 2020. Predicted growth in plastic waste exceeds efforts to mitigate plastic pollution. Science 1518: 1515–1518. VIEW
O’Hanlon, N.J., Bond, A.L., Lavers, J.L., Masden, E.A., James, N.A. 2019. Monitoring nest incorporation of anthropogenic debris by Northern Gannets across their range. Environmental Pollution 255: 113152. VIEW
WCS & CIESIN. 2005. Last of the Wild Project, Version 2 (LWP-2): Global Human Footprint Dataset (IGHP). NASA Socioeconomic Data and Applications Center (SEDAC), Palisades, NY. VIEW