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

Abstract

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 for Whooper Swans, and an interactive effect of time of day and winter of observation for Bewick’s Swans. However, the relationship between swan numbers and Whooper Swan aggression times was not strong (R2 = 19.3%). Conclusions Whilst swans do exhibit some aggression towards smaller waterbirds, the majority of aggression by swans is directed towards other swans. Aggression focused on conspecifics likely reflects greater overlap in resource use, and hence higher potential for competition, between individuals of the same species. Our study provides an example of how questions relating to avian behaviour can be addressed using methods of remote data collection such as live-streaming webcams.

Seasonal and diel activity patterns of the endangered taiga bean goose (Anser fabalis fabalis) during the breeding season, monitored with camera traps

“…In this study, a variety of bird and mammal species were recorded, such as potential predators (large and medium-sized mammals such as the wolverine, Gulo gulo, Eurasian lynx, Lynx lynx, and red fox, Vulpes vulpes) and competitors (whooper swan, Cygnus cygnus). Whooper swans are territorial, defending a nest site not only against conspecifics, but also showing aggression towards other species [49]. The increased whooper swan population is suggested to be one potential reason for the decline of the taiga bean goose population [11,50], but this is mostly based on anecdotal evidence with long-term studies lacking.…”

Web-based citizen science as a tool in conservation research: A case study of prey delivery by the Lesser Spotted Eagle

“…However, surprisingly little research has used data from webcams [ 9 ]. Examples include behavioural studies [ 9 – 11 ] and studies of breeding biology [ 12 , 13 ]. Although webcams at nests can potentially provide detailed information on species diets, few studies have used this approach [ 14 ].…”

Assessing trade-offs in avian behaviour using remotely collected data from a webcam

“…In this study, we used remote behavioural observations made via a live-streaming webcam to investigate the trade-offs in avian behaviour. Webcams have become a valuable tool in the study of animal behaviour, as they allow behavioural observations to be made without disturbance to focal individuals and without the need for researchers to be physically present at study sites [11][12][13][14][15]. We selected two common waterbirds as our focal species, the mute swan (Cygnus olor) and whooper swan (Cygnus cygnus).…”