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Factors affecting the behavioural responses of whooper swans (Cygnus c. cygnus) to various human activities |
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| Authors: | Eileen C Rees Jennifer H Bruce |
| Institution: | a The Wildfowl and Wetlands Trust, Martin Mere, Burscough, Ormskirk, Lancashire L40 0TA, UK b The Wildfowl and Wetlands Trust, Slimbridge, Gloucester GL2 7BT, UK c 107 Hollows Avenue, Foxbar, Paisley PA2 0RD, UK |
| Abstract: | The effects of human activity on bird behaviour and distribution have been studied extensively in recent years, but variation in their response to disturbance is still poorly understood. Here, we analyse variation in the behaviour of wintering whooper swans Cygnus c. cygnus, to determine whether their susceptibility to human activity changes with time, location and the type of disturbance involved. Overall, the swans' feeding activity varied within and between years, and in relation to feeding site, but there was less variation in the amount of time spent alert. Disturbance frequency resulting from human activity was lower with increasing flock size and with increased distance to the nearest road or track. Distances that humans could approach before alerting the birds similarly varied with field characteristics (e.g. size and proximity to roads or tracks), and also with the type of disturbance involved. The distance at which >5% of the flock became alert because of human activity decreased with the number of previous disturbance incidents in the day, indicating that swans become less sensitive to disturbance events if daily disturbance frequency is high, but there was no evidence that habituation to disturbance persisted over longer periods. The time taken for the birds to resume undisturbed behaviour varied with the duration of the disturbance event, which in turn depended on the type of disturbance involved, with pedestrians alerting the birds for longer periods than vehicles and aircraft. Recovery rates following disturbance were also associated with field size, flock size and the proportion of the flock alerted. Feeding activity was influenced by a range of variables, including year, season, field location, crop type and the number of days that the flock had used the field (32.9% of variance in the data explained by these variables), with disturbance factors explaining an additional 4.9% of variance in the proportion feeding per hour. Conversely, alert activity was influenced mainly by disturbance events. The range of factors influencing the swans' feeding behaviour, and variability in their response to human activity, has implications for management programmes and for attempts to predict the effects of human activity on the birds at a local and larger scale. |
| Keywords: | Disturbance factors Feeding activity Alert response Recovery rates Spatial variation Temporal variation Whooper swans Cygnus c cygnus |
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