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Advances in the aquatic sciences
RESEARCH ARTICLE

A 6-year survey of plastic ingestion by aquatic birds in southern Portugal

Silvia Rao A , Katy R. Nicastro https://orcid.org/0000-0002-7071-141X A B C , María Casero D , Christopher D. McQuaid B and Gerardo I. Zardi https://orcid.org/0000-0001-8798-5794 B *
+ Author Affiliations
- Author Affiliations

A CCMAR-CIMAR – Associated Laboratory, University of Algarve, Campus de Gambelas, PT-8005-139 Faro, Portugal.

B Department of Zoology and Entomology, Rhodes University, Grahamstown, 6140, South Africa.

C Univ. Lille, CNRS, Univ. Littoral Côte d’Opale, UMR 8187, LOG, Laboratoire d’Océanologie et de Géosciences, Wimereux, France.

D Wildlife Rehabilitation and Investigation Centre (RIAS) – Associação ALDEIA, Ria Formosa Natural Park, Olhão, Portugal.

* Correspondence to: zardi73@yahoo.it

Handling Editor: Nicholas Davidson

Marine and Freshwater Research 73(4) 478-490 https://doi.org/10.1071/MF21221
Submitted: 9 July 2021  Accepted: 16 November 2021   Published: 22 December 2021

© 2021 The Author(s) (or their employer(s)). Published by CSIRO Publishing.

Abstract

Anthropogenic litter in the environment is pervasive globally. Of particular concern are plastics because of their ubiquity, longevity in the environment and lethal effects. Plastics affect organisms at most levels of biological organisation but, even in well studied animals like birds, we have limited insight into species-specific vulnerability or temporal trends of ingestion. We examined stomach contents of four aquatic bird species over more than 6 years in southern Portugal. Of the 462 individuals analysed, 22.7% had ingested anthropogenic litter, predominantly plastics, most of which were clear or white in colour. The white stork (Ciconia ciconia) exhibited the highest frequency of occurrence of anthropogenic litter (61.1%) and of plastics specifically (55.6%), whereas the yellow-legged gull (Larus michahellis) had the lowest (13.4% for both anthropogenic litter and plastics). Similar frequencies of occurrence were found for the northern gannet (Morus bassanus) (22 and 20.3%) and the lesser black-backed gull (Larus fuscus) (21.4 and 20.8%). The composition of the plastic ingested varied throughout the study period for each species, but with no clear temporal pattern. Our results revealed the ubiquity and frequency of occurrence of plastic ingestion as well as clear differences among species, providing a basis for long-term monitoring of litter ingestion.

Keywords: biodiversity, coastal lagoon, environmental monitoring, multispecies, plastic pollution, plastic debris, temporal trend.


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