Aggressive behavioural interactions between swans (Cygnus spp.) and other waterbirds during winter: A webcam-based study

• Published in: Avian Research
• Main Authors: Wood, KA, Ham, P, Scales, J, Wyeth, E, Rose, PE
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2020
• Subjects: Aggression; Agonistic behaviour; Bewick’s Swans; Intraspecifc versus interspecifc competition; Remote data collection; Waterfowl; Whooper Swans; Cygnus cygnus
• Online Access: http://hdl.handle.net/10871/126306; https://doi.org/10.1186/s40657-020-00216-7

This is the final version. Available on open access from BMC via the DOI in this record Availability of data and materials: The datasets generated and analysed during the current study are available from the corresponding author upon reasonable request. Background: Our understanding of any impacts of swans on other waterbirds (including other swans), and potential effects on waterbird community structure, remain limited by a paucity of fundamental behavioural and ecological data, including which species swans interact aggressively with and how frequently such interactions occur. Methods: Behavioural observations of aggression by swans and other waterbirds in winters 2018/2019 and 2019/2020, were carried out via live-streaming webcams at two wintering sites in the UK. All occurrence sampling was used to identify all aggressive interactions between conspecific or heterospecifics individuals, whilst focal observations were used to record the total time spent by swans on aggressive interactions with other swans. Binomial tests were then used to assess whether the proportion of intraspecific aggressive interactions of each species differed from 0.5 (which would indicate equal numbers of intraspecific and interspecific interactions). Zero-inflated generalized linear mixed effects models (ZIGLMMs) were used to assess between-individual variation in the total time spent by swans on aggressive interactions with other swans. Results: All three swan species were most frequently aggressive towards, and received most aggression from, their conspecifics. Our 10-min focal observations showed that Whooper (Cygnus cygnus) and Bewick's Swans (C. columbianus bewickii) spent 13.8 ± 4.7 s (means ± 95% CI) and 1.4 ± 0.3 s, respectively, on aggression with other swans. These durations were equivalent to 2.3% and 0.2% of the Whooper and Bewick's Swan time-activity budgets, respectively. Model selection indicated that the time spent in aggressive interactions with other swans was best-explained by the number of other swans present ...