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Comprehensive Monitoring Plan for Snail Kites and Apple Snails in the Greater Everglades

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Project Investigators: Robert Fletcher, Wiley M. Kitchens, Christa Zweig

Project Personnel: Chris Cattau, Dan Cavanaugh, Ryan Dibler, Whitney Haskell, Ellen Robertson, Brian Jeffery, Rebecca Wilcox

Project Start Date: 2010 End Date: 2015



This project is to determine the relationship between hydrologic regimes, foraging patterns, habitat responses and kite demography and reproduction for the Southern Everglades.

The endangered snail kite (Rostrhamus sociabilis plumbeus) is a wetland-dependent raptor feeding almost exclusively on a single species of aquatic snail, the Florida apple snail (Pomacea paludosa). The viability of the kite population is dependent on the hydrologic conditions (both short-term and long-term) that (1) maintain sufficient abundances and densities of apple snails, and (2) provide suitable conditions for snail kite foraging and nesting, which include specific vegetative community compositions. Many wetlands comprising its range are no longer sustained by the natural processes under which they evolved (USFWS 1999, RECOVER 2005), and not necessarily characteristic of the historical ecosystems that once supported the kite population (Bennetts & Kitchens 1999, Martin et al. 2008). Natural resource managers currently lack a fully integrative approach to managing hydrology and vegetative communities with respect to the apple snail and snail kite populations.

At this point in time the kite population is approximately 1198 birds, down from approximately 4000 birds in 1999. It is imperative to improve our understanding hydrological conditions effecting kite reproduction and recruitment. Water Conservation area 3-A, WCA3A, is one of the 'most critical' wetlands comprising the range of the kite in Florida (see Bennetts & Kitchens 1997, Mooij et al. 2002, Martin et al. 2006, 2008). Snail kite reproduction in WCA3A sharply decreased after 1998 (Martin et al. 2008), and alarmingly, no kites were fledged there in 2001, 2005, 2007, or 2008. Bowling (2009) found that juvenile movement probabilities away (emigrating) from WCA3A were significantly higher for the few kites that did fledge there in recent years (i.e. 2003, 2004, 2006) compared to those that fledged there in the 1990s. The paucity of reproduction in and the high probability of juveniles emigrating from WCA3A are likely indicative of habitat degradation (Bowling 2008, Martin et al. 2008), which may stem, at least in part, from a shift in water management regimes (Zweig & Kitchens 2008).

Identifying areas of high habitat quality for snail kites is important for conservation and management (Garshelis 2000). Foraging success has often been assumed commensurate with high quality individuals (Schoener 1971) and high nesting success. Finding exact connections between energy acquisition (foraging) and habitat quality (fitness) is important for understanding how individual-level decisions transition to population-level phenomena (Real and Brown 1991). Given that conservation and management decisions focus on foraging behavior, with the implicit assumption that this will be related to habitat quality, understanding this relationship is needed for effective management.

Given the recent demographic trends in snail kite population, the need for a comprehensive conservation strategy is imperative; however, information gaps currently preclude our ability to simultaneously manage the hydrology in WCA3A ect to vegetation, snails,nd kites with respect to vegetation, snails, and kites. While there have been significant efforts in filling critical information gaps regarding snail kite demography (e.g., Martin et al. 2008) and variation in apple snail density to water management issues (e.g., Darby et al. 2002, Karunaratne et al. 2006, Darby et al. 2008), there is surprisingly very little information relevant for management that directly links variation in apple snail density with the demography and behavior of snail kites (but see Bennetts et al. 2006). The U.S. Fish and Wildlife Service (USFWS), the U. S. Army Corps of Engineers, and the Florida Fish and Wildlife Conservation Commission (FWC) have increasingly sought information pertaining to the potential effects of specific hydrological management regimes with respect to the apple snail and snail kite populations, as well as the vegetative communities that support them.

The following objectives of the proposed work are meant to directly address these critical gaps:

  1. To determine how hydrology, habitat quality, and prey density affect snail availability for foraging and nesting snail kites.
  2. To determine how snail availability affects kite foraging success, and nest and foraging site selection.
  3. To determine how snail availability affects nest success and recruitment.
  4. To determine the role of kite foraging success and nest and foraging site selection on nest success and recruitment.
  5. To determine areas of high kite foraging habitat quality and determine its relationship to hydrology and vegetation communities.

Work Plans



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Script last updated: 23 October 2018 @ 12:03 PM by THF. Record creator: KP. Record last updated by: KP.