Effects of recreational disturbance on the foraging behaviour of waders on a rocky beach
S. Fitzpatrick, B. Bouchez
1998
Bird Study
B ecause of the tidal restrictions on their foraging, disturbance of waders and waterfowl by human activities during their feeding periods might have potentially serious effects on their ability to acquire sufficient food for their needs. This is particularly important at times of the year when energy demands are high, for example in midwinter, on migration and during moult. 1 Disturbance can cause a reduction in food intake in several ways: the presence of people leads to increased vigilance
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... foraging waders and to a decrease in the proportion of time devoted to feeding, 2-4 the birds may stop foraging altogether and they may leave the foraging site, 5,6 perhaps changing to a less profitable site at which they have a lower food intake rate. 7 In addition to this reduction in food intake, energy expenditure can be increased by avoidance behaviour, particularly if the birds fly away. The combination of these effects may produce serious deficits in the daily energy budget of the disturbed birds, 8 or necessitate extra compensatory foraging, for example, at night. 9 The summer seasonal peak of human recreational use of beaches coincides with one of the times of peak energy demands for waterbirds, during the postbreeding migration and subsequent moult. 10 In this study, the types and extent of human recreational disturbances on a beach and their effects on the foraging behaviour of three species of wader (Oyster-catcher, Curlew and Redshank) were studied during June-August 1996, with the aim of assessing the relative impacts of differing types and locations of human activity in the vicinity of the beach on the waders' foraging rates. Bird Study (1998) 45, 157-171 Oystercatcher Haematopus ostralegus, Curlew Numenius arquata and Redshank Tringa totanus reacted in a variety of ways to human disturbance. They delayed arrival and departed earlier when disturbed. Vigilance (scan rates) increased with the vigour of human activity and the birds were more vigilant in the higher shore zones, but there was no corresponding decrease in food searching (peck rates). Prey capture rates of Oystercatcher and Curlew apparently increased with moderately close human disturbance. Undisturbed birds may not have been foraging at maximum rates and rested periodically during the low tide period. Characteristic avoidance behaviour elicited by disturbance differed between the species; Curlew and Redshank typically stopped feeding and, if they left, flew away, whereas Oystercatcher walked away. This difference may be related to plumage crypsis. Flight distances of all species were very low. Habituation may be an important response to regular but benign disturbance, reducing the disturbance-induced decrease in feeding time to a level which may be compensated for, at least in summer, within the normal low-tide foraging period.
doi:10.1080/00063659809461088
fatcat:j72slawkorfi3ebzc5qxnsmxbm