Page 46 - A bird’s-eye view of recreation - Rogier Pouwels

A bird's-eye view of recreation
100% 90% 80% 70% 60% 50% 40% 30% 20% 10%
0%
0 200
100 visitor groups per hour 25 visitor groups per hour
400 600 distance to path (m )
Figure 2. Schematic example of recreation impact on densities of nests of Curlew (Numenius arquata) (after Vos and Peltzer 1987).
Second, recreation has an impact on the escape behavior of animals like birds and mammals (Blanc et al. 2006, Gill 2007). The closer a visitor approaches, the higher the probability an animal will flee. Larger animals tend to flee at longer distances from an encounter with humans (Blumstein et al. 2005). Also the type of visitor and the way a visitor moves have effect on escape behavior. Ecotourists, hunters, browsers and visitors with dogs have a higher impact than cyclists or walkers. Unpredicted movement patterns of visitors and changes in speed or direction have a higher impact (Blanc et al. 2006). In periods when the escape behavior is an extra load on the scarce energy budgets of animals, recreation can have an impact on the survival of the animal or even the viability of the population. These periods are the winter, when food is scarce and energy costs are high (Gross-Custard et al. 2006, Stillman et al. 2007), and the spring, when energy budgets are directly linked to the number of offspring (Yalden and Yalden 1990, Murison et al. 2007, Langston et al. 2007). However, there is no guarantee that the behavioral response to disturbance is related to the population consequence, measured in terms of decreased reproduction or increased mortality (Gill et al. 2001). Birds exhibiting an escape behavioral response might actually be moving to alternative breeding or feeding sites (Stillmann et al. 2007). Stillmann & Goss-Custard (2002) document the seasonality of escape behavior for Oystercatchers. In late winter, when energy demands are higher and food quality is lower, Oystercatchers respond less frequently to disturbance. Individual based models, consisting of fitness-maximizing individuals, are one means of linking disturbance induced behavioral responses to population consequences (West et al. 2002, Stillmann et al. 2007).
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density compared to maximum