Projecting population dynamics of the snail kite in relation to hydrology using an individual-based model.
Mooij, Wolf*,1, 1 Netherlands Institute of Ecology, Nieuwersluis, Utrecht, The Netherlands
ABSTRACT- The Florida snail kite is an endangered raptor that occurs as a closed population of about 2000 birds in the wetlands of Southern and Central Florida. This study aims at exploring the viability of the Florida snail kite population under various drought regimes in its wetland habitat. The population dynamics of snail kites are strongly linked with the hydrology of the system due to the dependence of this bird species on one exclusive prey species, the apple snail, which is negatively affected by a drying out of habitat. Based on empirical evidence, it has been hypothesised that the viability of the snail kite population critically depends not only on the time interval between droughts, but also on the spatial extent of these droughts. A system wide drought is likely to result in reduced reproduction and increased mortality, whereas the birds can respond to local droughts by moving to sites where conditions are still favourable. This study explores the implications of this hypothesis by means of a spatially-explicit individual-based model. There are two specific aims of the model. The first aim is to explore in a factorial design the dynamics of the kite population in relation to two scale parameters, the temporal interval between droughts and the spatial correlation between droughts. These analyses showed that high drought frequencies led to reduced numbers of kites. Also, habitat degradation due to prolonged periods of inundation led to lower predicted numbers of kites. The second aim is to project the future population dynamics of the snail kite for a given set of hydrological scenarios provided by the South Florida Water Management District. The model could clearly discriminate among scenarios in terms of the expected population growth rate of snail kite in Southern and Central Florida.
Key words: Everglades, spatially-explicit, conservation, droughts
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