key: cord-0316129-qgikyhf8
authors: Schalz, Sabrina; Horrod-Wilson, Warren D.; Chauhan, Keir
title: The Prevalence of Litter Foraging Among UK Birds Lessons Learned From A Citizen Science Project
date: 2021-11-19
journal: bioRxiv
DOI: 10.1101/2021.11.16.468840
sha: b10c0422dfcb3946eac08bf89b15bde740d10cdc
doc_id: 316129
cord_uid: qgikyhf8

Anthropogenic food sources, such as litter, are readily available to birds in urban areas. As an overly anthropogenic diet can have negative health consequences for wildlife, monitoring the frequency of foraging in litter compared to natural food resources can be an important component of wildlife conservation efforts. To understand how common litter foraging is among different bird species, we conducted a citizen science project with volunteers across the UK. Through this project, we also tried to engage people in birdwatching and bird surveys who would not normally participate in these activities. A particular focus was on recruiting respondents from underrepresented groups, and the methodology was designed to accommodate people without any background knowledge of birds. While we did not receive enough observations to draw conclusions about the litter foraging rates of different bird species across the UK, we report the submissions we received, as well as the demographic composition of the volunteer group. We successfully reached volunteers who did not participate in birdwatching or BTO bird surveys before, as well as some young volunteers, but were unsuccessful in reaching respondents from diverse socioeconomic backgrounds. We hope that the successes and failures of our methods reported here can be useful to others designing citizen science studies, so that birdwatching and volunteering for bird surveys will be equally accessible to all in the future.

Urbanisation and human presence have provided novel foraging opportunities for many bird species (Isaksson, 2018) : Carrion Crows (Corvus corone) have been found to aggregate in areas rich in anthropogenic food sources, such as waste disposal sites (Preininger et al., 2019) . House Sparrows (Passer domesticus) are more abundant in areas where there is access to rubbish containers, compared to areas where rubbish is stored underground or managed more effectively (Bernat-Ponce et al., 2021) . Feral pigeon (Columba livia) populations have become dependent on anthropogenic food sources, with a sharp decline in population sizes occurring during the COVID-19 circuit-breaker lockdown period in Singapore (Soh et al., 2021) . Other than waste disposal sites, birds generally forage in areas where human activity occurs, such as picnic areas (Kurosawa et al., 2003) , where they may directly take food from humans (Kurosawa 1999 , as cited in Kurosawa et al., 2003) .

But easy access to anthropogenic food comes at a cost: Innutritious diet has been linked to leucism in urban blackbirds (Turdus merula) (Izquierdo et al., 2018) . In urban Red-Winged Starlings (Onychognathus morio) nestlings fed a diet comprised of a higher proportion of anthropogenic food grew at a significantly slower rate compared to that of nestlings fed a higher proportion of naturally occurring food (Catto et al., 2021) . Adult birds who consumed a higher proportion of anthropogenic food had a significantly greater body mass compared to that of individuals which consumed a higher proportion of naturally occurring foods (Catto et al., 2021) . A study conducted on urban American Crow (Corvus brachyrhynchos) nestlings found that they had higher levels of cholesterol compared to their rural counterparts, though evidence as to whether cholesterol negatively or positively impacts avian life is mixed (Townsend et al., 2019) . Birds have also been observed to eat cigarette butts which contain toxic chemicals and plastics, which may consequently impact health and survival (Torkashvand et al., 2020) . Plastic has been found in the faeces of urban black vultures (Coragyps atratus) and turkey vultures (Cathartes aura), but almost none was found in that of Andean condors (Vultur gryphus), which avoid urban habitats (Balleko et al., 2021) .

Organisations such as the British Trust of Ornithology (BTO) are heavily reliant on the work of citizen scientists to get a national picture of our bird populations. Without continued involvement in their citizen science they would be unable to provide detailed analysis of changes to the UK's bird population. In doing so, the BTO has helped to establish a community around birding; whether that's working with bird observatories, supporting young people, or getting people outside and using their green spaces. Citizen science's impacts on mental health and wellbeing for many people and particularly those of young people is of paramount importance (White et al., 2019) . However, more work still needs to be done to encourage a more diverse population of birders participating in bird surveys and to ensure their safety when joining. Women, young people, people of colour, people without a background in higher education, and people in lower income households remain minorities within birding (US Fish & Wildlife Service, 2009 ).

The first aim of this study was to examine the frequency of foraging in anthropogenic resources such as litter and food waste across the UK, and across different species. Understanding the prevalence of litter foraging along the urban-rural gradient, as well as potential differences between species, is an important component of wildlife conservation work. The second aim was to develop a survey that is accessible to volunteers from the general public who don't have any previous knowledge about birds. Projects such as this can help engage more people with the natural world, and in particular the birds in front of their doorsteps. While not necessarily collecting much usable data and not a solution to other deterring factors such as racism, sexism, and financial constraints, this project seeks to help engage underrepresented groups by reducing the barrier of required prior knowledge and prior established contact with the bird community through our design of the questionnaire and use of recruitment channels. Recruitment of a citizen science sample not only provides the opportunity to engage different communities in bird watching, but it also presents the opportunity to educate people and encourage behavioural change initiatives (Van Noordwijk et al., 2021) , such as reduced rates of littering. We focused on reaching groups currently underrepresented in birdwatching, in particular with regards to age and socioeconomic backgrounds.

Participants (N = 55) were UK residents (see demographic summary under 4.2). A total of 254 clicks on the survey link were recorded.

To reach a diverse and large group of potential participants, we used a variety of communication channels for recruitment. Emails sent to approximately 1,000 community groups across the UK interested in conservation was the most successful method. Twitter 

The survey was presented online in Qualtrics from 26 th June to 26 th August 2021 (see questionnaire in appendix A). A common barrier in citizen science bird surveys is that most require bird ID skills (personal observation). We designed the questionnaire in a way that it requires no previous knowledge of birds so that more people without a background in birding could participate. Demographic questions were included to evaluate the success levels of reaching respondents from different backgrounds. Respondents were also asked to make up a username for themselves so that we could track multiple participations. The survey was approved by the Middlesex Psychology Ethics Committee and all participants gave informed consent before beginning the survey.

3.3 Analysis 61 responses were included in the analysis. Two observations had been excluded as they had taken place outside the UK. Blue tit, great tit, robin, goldfinch, greenfinch, sparrow, and thrush were pooled into the umbrella term "Garden bird". Mallard, goose, jackdaw, rook, siskin, treecreeper, and green woodpecker were excluded from the group analysis as there was only one observation of each, but their data is reported in appendix B (see table 1 29 birds were spotted handling human food, 32 handling nature food. Human foods included bread, fish heads and leftovers, while natural foods included a discarded apple, commercial bird food and nuts. While these items were provided by humans, they are indiscernible from naturally found apples, seeds and nuts and were therefore counted as natural. Bread and fish leftovers do not naturally occur in the corresponding habitats (though there is obviously some overlap between human and natural foods, since humans also consume the latter and don't rely exclusively on processed foods).

There were considerable differences between species groups: garden birds, blackbirds and starlings were rarely reported to take human food, while crows and gulls mostly took human food, and magpies and pigeons took a combination of natural and human foods (see figure 1 ). Those species preferring human food sources had more diverse foraging locations while those relying exclusively or almost exclusively on natural foods were almost entirely seen in gardens (see figure 2 ). Across species, the foraging locations between human foods and natural foods only differed with regards to human food coming from bins and natural foods coming from bird feeders instead. Both food types were equally distributed with regards to the other locations (provided by a person, found on the ground). Only crows, magpies, pigeons and gulls were reported to forage in bins.

29 participants self-reported their gender as female, 22 as male, one as non-binary and three did not specify. The mean age of respondents was 51.7 (SD = 19.5, 2 participants did not report their age, see figure 3 ). Four respondents participated multiple times. One respondent changed their answer from "never birdwatching" to "birdwatching less than once a month" in their second participation.

13 respondents made use of the option to use common names for birds instead of their species name (such as "seagull"). Another person described the appearance of a bird instead of naming it.

45 respondents self-identified as British, one as Caribbean, one as British-Caribbean, one as Black British, one as Dutch, one as European, and one as Polish. Most volunteers had completed either college or a university degree and have a yearly household income of £20,000 to £40,000 (see figure 4 ). Most volunteers chose the most negative ranking for their opinion about litter (N = 39), the least negative ranking reported being a 6 out of 10. Noticing litter and being around others who litter was also common (see figure 6 ). 

Given the small sample of observations we received, we cannot draw broad conclusions about the frequency of litter foraging in different UK regions and species. We therefore chose to only report the observations submitted. It should however be noted that the species reported to consume human food in place of naturally occurring food were consistent with previous research (Palacio, 2019) : Urban exploiters such as Gulls, Crows and Pigeons were found to be foraging in diverse habitats and predominantly eating human food in place of naturally occurring foods in more than half of the observations submitted for those species. Gulls were observed to exclusively forage and consume human food in place of natural food. Garden birds, Magpies, Starlings, and Blackbirds were reported to consume human food to a much lower degree, and in the case of the Blackbird not at all. These species were also observed foraging in areas such as gardens and parks, as opposed to streets. Although these species relied to a greater degree on naturally occurring foods, in this study we included food items which could also be provided by humans, such as nuts on bird feeders, as natural food.

Citizen science aims to educate and engage individuals from all backgrounds, whilst raising awareness of and solving real world issues, such as climate change and littering (Gura, 2013; Van Noordwijk et al., 2021) . In this study, we aimed to engage individuals from a broad range of ethnic and socioeconomic backgrounds in bird watching. We were partially successful in this endeavour: In our sample gender was well balanced, approximately half the respondents were not already engaged in regular birdwatching and almost none of the participants have been involved with the British Trust of Ornithology (BTO) before. 14 participants made use of the option to enter common names for birds in place of species names, which was added to increase accessibility. 10 volunteers were under the age of 30, six of them 18 or younger.

However, our goal of reaching respondents from diverse socioeconomic backgrounds was unsuccessful, as only three of the 55 participants were people of colour and the majority of those that participated had a middle-class income and university degree. Having a sample which lacks diversity in citizen science means that individuals from non-white backgrounds miss out on opportunities to develop scientific knowledge and understanding (Brouwer & Hessels, 2019) as we failed to reach them. Improvement to our recruitment methodologies are needed to capture individuals from a variety of background, such that scientific knowledge and skills can be shared with individuals from all ethnic and socioeconomic backgrounds.

We were unable to track individual changes in the perception of birds and litter over time as only four respondents participated multiple times. Repeated participation may be facilitated through questionnaires which capture the necessary information in as few questions as possible.

Additionally, data capture forms should be made as convenient as possible, so that participants are more inclined to participate multiple times in the same data collection effort (Pandya, 2012) .

While this citizen science study did not achieve a sufficiently large sample to draw broad ecological conclusions, it was successful in reaching and engaging some volunteers new to birdwatching and bird surveys. We hope this report of the successes and failures of our project can be useful in the planning of future citizen science studies. 10. 

Plastic ingestion and dispersion by vultures may produce plastic islands in natural areas

Effect of replacing surface with underground rubbish containers on urban House Sparrows Passer domesticus. Urban Ecosystems

Increasing research impact with citizen science: The influence of recruitment strategies on sample diversity

Pulses of anthropogenic food availability appear to benefit parents, but compromise nestling growth in urban red-winged starlings

Urban metal pollution explains variation in reproductive outputs in great tits and blue tits

A meta-analysis indicates reduced predation pressure with increasing urbanization

Urban herring gulls use human behavioural cues to locate food

Street smart: faster approach towards litter in urban areas by highly neophobic corvids and less fearful birds

Citizen science: amateur experts

Impact of urbanization on birds

Factors associated with leucism in the common blackbird Turdus merula

Urbanisation and nest building in birds: a review of threats and opportunities

Knowledge gain and behavioral change in citizen-science programs

The life of Jungle Crows (Corvus macrorhynchos) in Inokashira Park

Diet of jungle crows in an urban landscape

Successful city dwellers: a comparative study of the ecological characteristics of urban birds in the Western Palearctic

Escape behaviour of birds provides evidence of predation being involved in urbanization

Urban habitats and feeders both contribute to flight initiation distance reduction in birds

Urban exploiters have broader dietary niches than urban avoiders

A framework for engaging diverse communities in citizen science in the US

Waste disposal sites as all-youcan eat buffets for carrion crows

The establishment of an urban bird population

Air pollution impacts on avian species via inhalation exposure and associated outcomes

Contrasting effects of the COVID-19 lockdown on urban birds' reproductive success in two cities

The evolution of food caching by birds and mammals

Restricted human activities shift the foraging strategies of feral pigeons (Columba livia) and three other commensal bird species

Littered cigarette butt as a well-known hazardous waste: a comprehensive systematic review

Urbanization and elevated cholesterol in American Crows

Birding in the United States: A Demographic and Economic Analysis Addendum to the 2006 National Survey of Fishing, Hunting, and Wildlife-Associated Recreation

Creating positive environmental impact through citizen science

Spending at least 120 minutes a week in nature is associated with good health and wellbeing

What bird did you see? You can give the exact name (such as "Carrion crow"), the broad name (such as "crow"), or describe what it looks like

What did the bird eat

Where there any other birds? a. Yes, and they looked like my bird (how many other birds?)

Yes, but they looked different than my bird (how many other birds

Did you notice any other behaviour, such as fighting, feeding other birds, singing

On what date and at what time did you see the bird?

Where in the UK did you see the bird? You can answer with the postcode, location name (e.g. name of the city, park or forest), or with

Other (please specify) BTO volunteer?

We are very grateful to all volunteers who have participated in this survey and submitted their observations. We are also thankful for the help we received in distributing this survey, as well as the feedback we have received from Dawn Balmer, Amanda Mead, Kirsty Neller, and Tom Dickins during the early planning stage and the development of the questionnaire.