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Project Work Plan

Department of Interior USGS GE PES
Fiscal Year 2014 Study Work Plan

Study Title: Comprehensive Monitoring Plan for Snail Kites and Apple Snails in the Greater Everglades
Study Start Date: 6/30/2014 Study End Date: 6/30/2015
Location (Subregions, Counties, Park or Refuge): Total System
Funding Source: GE PES
Funding History: FY10; FY11; FY12; FY13
FY14 USGS funding:
Principal Investigator(s): Robert Fletcher, Wiley Kitchens, and Christa Zweig
Supporting Organizations: U. S. Army Corps of Engineers, U. S. Fish and Wildlife Service
Associated / Linked Studies: Demography and Movement of Snail Kites

Overview & Objective(s): 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 with respect 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.

Specific Relevance to Major Unanswered Questions and Information Needs Identified:

This study supports several of the projects listed in the DOI science plan (specifically: Water Conservation Area 3 Decompartmentalization and Sheetflow Enhancement) by (a) examining the linkages between snail kite nesting and productivity and snail densities; (b) documenting the areas and vegetation communities used by breeding snail kites; and (c) examining the linkages between apple snail densities and snail kite foraging behavior.

The study supports the Water Conservation Area 3 Decompartmentalization and Sheetflow Enhancement project (DECOMP; p. 76) as it helps fill the gaps in baseline information regarding snail kite habitat condition, nesting, and productivity (p. 79).

The study supports the Combined Structural and Operational Plan project (CSOP and Mod Waters; p. 80) as it will (1) generate information regarding the vegetative communities that are tied to both snail kite nesting and foraging and apple snail densities as well as the potential effects of differing apple snail densities on snail kite nesting and productivity (p. 82)

Status: This work plan details a continuing study. This is Year 5 of a 5 yr effort to determine the relationship between hydrologic regimes, foraging patterns, habitat responses and kite demography and reproduction for the Southern Everglades.

Recent Products: Three Annual Reports have been prepared detailing the status of the project to date (4th will be submitted June 2014).

Planned Products: Annual Reports with a Final Report at the end of 2015.

WORK PLAN

Scope of work

To meet the aforementioned objectives, we propose the following:

  1. To determine the effects of hydrologic conditions, snail capture rates (and snail density estimates from P. Darby), and vegetative community structures on nest success, nest productivity, recruitment, and movement
  2. Observe breeding and non-breeding adult and juvenile snail kites foraging in the greater everglades ecosystem to establish links between foraging behavior and nest success.
    1. conduct time-activity-budget and record searching times, flying times, handling times, snail captures and attempts, distances to captures, and vegetative communities of captures for snail captures.
    2. determine nest abandonment, failure, success and recruitment as related to above individuals
  3. To characterize vegetation communities within kite foraging areas with links to our previous intensive sampling sites to provide general recommendations for hydrologic alterations to maintain or improve kite nesting and foraging habitat

The proposed studies would be greatly facilitated by the volume of work and data already accumulated in our kite and vegetation studies in the Everglades over the past 10 years. Additionally this proposed project would benefit from an "economy of scale" provided by our on-going studies funded by the USACE for range-wide demographic, movement, and habitat studies. This effort already maintains much of the infrastructure and expertise required to conduct the research proposed here (see Bennetts & Kitchens, 1997; Martin et al., 2007). In addition, we maintain a field quarters and lodging in 2 travel trailers in Big Cypress National Preserve. We also manage a fleet of trucks and airboats that can be used to conduct the proposed field work. The funding requested here mainly covers the additional personnel and operating expenses necessary to fulfill the objectives of this proposal. We have also conducted a similar, complementary study funded by FWC through the aquatic habitat restoration and enhancement subgroup (AHRES) that expands the scope of this proposed work to the Kissimmee-Chain-of-Lakes (field work conducted 2010-2011).

Title of Task 1: Integrated Synthesis of Existing Data
Task Funding:
USGS Priority Ecosystems Science
Task Leaders: Rob Fletcher, Chris Cattau
Phone: 352-846-0632
Task Status (proposed or active): Active
Task priority: High
Task Personnel: Rob Fletcher, Chris Cattau

Task Summary and Objectives:

The Florida Cooperative Fish and Wildlife Research Unit (Coop) has monitored the snail kite population since 1992 and has a wealth of range-wide demographic data. We will synthesize existing data regarding snail kite demography, snail density, vegetation, and hydrology. In addition, we will use current data collection methods to tighten and refine our understanding of linkages of existing data. Dr. Rob Fletcher will lead this effort. He is already working closely with all potential parties to ensure seamless integration of existing data sets, which will maximize our ability to interpret potential linkages outlined in Figure 1. This synthesis will require truly collaborative partnerships among all parties for interpretation and analysis.

Diagram showing conceptual model of environmental and biological variables affecting key demographic parameters of the snail kite populatio
Figure 1. Conceptual model of environmental and biological variables affecting key demographic parameters of the snail kite population. [larger image]

To interpret the role that snails and hydrology play on the demography of snail kites, we will quantify relationships of snail density, as estimated by Dr. Darby and his lab, with snail foraging and capture rates. This will be crucial for interpreting the relationship between snail density and availability to kites, and for hindcasting snail density data that has been collected since the 1990's with measures of spatio-temporal variation in snail availability. This linkage will be primarily estimated with data collected for this proposal (see below). We will also use existing data to re-analyze spatio-temporal relationships of measured snail densities to hydrologic variation. Finally, we will link snail capture rates to reproductive success. With these linkages established, we will able to better understand the role that hydrology and snail availability has played, and continues to play, on the biology of snail kites. For each of these issues, Bayesian hierarchical models will be developed (Royle and Dorazio 2008). Bayesian hierarchical models have the potential to link observation models (i.e., the data we collect) with process models (i.e., the data/process we wish to understand). In addition, another major advantage of these models is that this approach allows for rigorous interpretation of uncertainty in our knowledge about the system, including both measurement and process uncertainty. As a consequence, these modeling efforts will provide both rigorous estimates of linkages and the associated uncertainty with linkages.

When possible, we will also use quantile regression methods for interpreting the limiting role of snails on snail kite demography. Quantile regression is particularly useful for understanding the potential for limiting factors, because this method identifies upper (or lower) bounds on relationships (Cade and Noon 2003). Unlike typical least-squares regression that fits models based on the conditional mean of response variables, quantile regression allows for assessing potential limiting relationships by estimating relationships of the median or specified quantiles (e.g., upper 95% quantile).

This task is critical to the information required to populate the Individually-based species model EVERKITE.

Specific Task Product(s): Progress will be reported annually in the form of status reports June 30 of the remaining successive years of the study 2014, and 2015. To date (2011, 2012 and 2013), three reports have been delivered summarizing progress to date. This task is vital to the continued integration of historic and current information. Given the ever evolving consequences of habitat degradation and the behavioral adaptation of the kites to compensate for less that optimal habitat conditions, we face a continuing challenge to resolve demographic responses to a continually changing environment. For example, the population has been decimated by half twice in the past two decades, shifted its reproductive range, and currently become dependent on exotic snails. All these add facets to the complex protocols required to tease out demography responses.

Title of Task 2: Determine if links between kite foraging behavior and breeding success exist
Task Funding: USGS Priority Ecosystem Science
Task Leaders: Rob Fletcher, Wiley Kitchens
Phone: 352-846-0632
FAX: 352-846-0841
Task status (proposed or active): Active
Task Priority: High
Task Personnel: Dan Cavanaugh, Ryan Dibler, Whitney Haskell, Chris Cattau, Ellen Robertson, Brian Jeffery, Rebecca Wilcox

Task Summary and Objectives:

  1. To observe adult and juvenile kites to:
    1. evaluate foraging behaviors of breeding and non-breeding individuals
    2. determine nest abandonment, success and recruitment as related to the above
    3. conduct time activity budgets (TABs) and record search times, flying times, handling times, snail captures and attempts.
    4. collect vegetation samples from a random selection of successful capture locations
  2. To determine the effects of hydrologic conditions and vegetative community structures on foraging behavior through time.
  3. To use the above information to determine if there are any links between foraging behavior and breeding success. Also attempt to link various foraging parameters with individual-level demography (nestling quality, number of nestlings fledged) and site-level demography (active nests per season, successful nests per season) as an assessment of habitat quality.

Work to be undertaken during the proposal year and a description of the methods and procedures:

Field Work

Using a portion of the proposed funds, we will observe breeding and non-breeding, adult and juvenile snail kites. We will target kites in the southern end of their range (principally WCA3A), prioritizing those that are likely to breed, as identified by courtship or nest building behavior. (Note that while the focus of this proposal is the southern portion of the kites' range, specifically WCA3A, the distribution of kites during the given year will ultimately dictate where we can observe them. Thus observations may also take place in Everglades National Park (Frog City), WCA3B and Big Cypress National Preserve.) Throughout the year, a sample of kites utilizing WCA3A and the southern Everglades will be observed. Individuals associated with known nests will be observed biweekly throughout the duration of the nest. From these data and data available form a broader mark/re-sight study, we will be able to link specific foraging behaviors to nests with known fates (failed or successful and if successful how many young fledged and of what weight).

Once a kite is located via airboat, we will conduct a TAB. TABs will consist of observation periods lasting one-hour in duration. During the TABs we will record the number of snails captured, capture mode, searching times, handling times, feeding rates, and other pertinent behaviors to foraging and nesting. GPS points will be taken at perches and at successful and failed capture points. These GPS locations can be used to look at foraging from a spatial context. These points will be used to calculate average capture distance from nest, and provide insight into where favored foraging (assumed to be superior foraging habitat) sites exist. We will also identify the vegetative community within a representative sample of the breeding bird's foraging habitat based on capture points of the associated TABs.

Data Analysis

Data will be analyzed throughout the duration of the project but an emphasis will be placed on data analysis once the field work has been completed. Field work will end when snail kites cease breeding and vegetation work is complete, approximately the end of 2014. Data actively collected during this project will be analyzed in conjunction with data collected by the Florida Cooperative Fish and Wildlife Research Unit (Coop) snail kite population monitoring program (as mentioned in task 1). This data set will provide us with information on snail kite demography and movement (since 1992) to synthesize with the extensive foraging data collected over the duration of this project.

Foraging behavior will be quantified by time spent foraging (search time), search tactics (foraging mode), foraging speed (movements per hour), capture rate (successful captures per minute), nestling provisioning rate, distance to foraging point from nest, and capture success ratio. Demographic parameters at the individual- and site-level will be evaluated using fledgling weight, number of fledglings produced, number of active nests and number of successful nests. General linear models will be used to look at the effect of the various foraging parameters on demographic parameters. Hydrologic information from the EDEN database will be utilized during analysis. A series of mixed models will be used to look at the how foraging behavior changes though time and is affected by nest stage, hydrology and other covariates.

Specific Task Product(s): Progress will be reported annually in the form of status reports June 30 of the remaining year of the study 2015. To date (2011, 2012 and 2013), three reports have been delivered summarizing progress to date, a forth will be submitted in June 2014. This task is vital to the continued integration of historic and current information. Given the ever evolving consequences of habitat degradation and the behavioral adaptation of the kites to compensate for less that optimal habitat conditions, we face a continuing challenge to resolve demographic responses to a continually changing environment. For example, the population has been decimated by half twice in the past two decades, shifted its reproductive range, and currently become dependent on exotic snails. This task in particular will explore the importance of individual foraging behavior (energy acquisition) and its effect on population level processes (demography) which will help inform managers to the importance of conducting studies on snail kite foraging.

Title of Task 3. Vegetation sampling
Task Funding: USGS Priority Ecosystems Science
Task Leaders: Rob Fletcher, Wiley Kitchens, Christa Zweig,
Phone: 352-846-0536
FAX: 352-846-0841
Task Status (proposed or active): Active
Task priority: High
Budget and Time Frame for Task 2: See Task 1
Task Personnel: Christa Zweig, Dan Cavanaugh, Ryan Dibler, Chris Cattau, and Rob Fletcher

Task Summary and Objectives:

To characterize vegetation communities within kite foraging areas with links to our previous intensive sampling sites to provide general recommendations for hydrologic alterations to maintain or improve kite nesting and foraging habitat.

Work to be undertaken during the proposal year and a description of the methods and procedures:

We will collect vegetation data within a representative sample of the foraging area defined by the intense tracking of individual kites during both the non-breeding and nesting season of the kites in WCA3A, 3B, and Northeast Shark Slough. The intent is to define or characterize successful and non-successful foraging habitats and their associated or major driving force environmental conditions. To further the work that has been done by Bennetts et al (2006), we will be able to link these habitat samples to our intensive vegetation sampling communities for which we already have an understanding of contributing environmental variables (Zweig 2008, Zweig and Kitchens 2008, Zweig and Kitchens 2014). These linkages to our large-scale vegetation database will allow us to infer the vegetation communities present and the hydrologic conditions that affect them. This reduces the need for intensive vegetation sampling and additional hydrologic data and monitoring, greatly decreasing cost and time involved. From these links we will be able to make recommendations for hydrologic alterations to maintain or improve kite foraging habitat, and thus the snail kite behaviors and demographic parameters associated with habitat quality.

Product: Final Report Delivery Date: June 30, 2015

Literature Cited

Bennetts, R.E. and W.M. Kitchens. 1997. Population dynamics and conservation of snail kites in Florida: the importance of spatial and temporal scale. Col. Waterbirds 20:324-329.

Bennetts, R.E. and W.M. Kitchens. 2000. Factors influencing movement probabilities of a nomadic food specialist: proximate foraging benefits or ultimate gains from exploration? Oikos 92:1-9.

Bennetts R.E., P.C. Darby, and L.B Karunaratne. 2006. Foraging patch selection by snail kites in response to vegetation structure and prey abundance and availability. Waterbirds 29:88-94

Bowling, C.A. 2009. Effects of habitat degradation on monthly movement of juvenile snail kites. Master Thesis, University of Florida, Gainesville, Fla.

Cade, B. S. and B. R. Noon. 2003. A gentle introduction to quantile regression for ecologists. Frontiers in Ecology and the Environment 1:412-420

Darby, P.C., R. E. Bennetts, S. J. Miller, and H. F. Percival. 2002. Movements of Florida apple snails in relation to water levels and drying events. Wetlands 22:489-498

Darby, P.C., Bennetts, R.E. and H.F. Percival. 2008. Dry down impacts on apple snail demography: implications for wetlands water management. Wetlands 28:204-214.

Garshelis, D.L. 2000. Delusions in Habitat Evaluation: measuring use, selection, and importance. Pp. 111-164 in: Research Techniques in Animal Ecology: Controversies and Consequences (L. Boitani and T.K. Fuller, eds.). Colombia University Press, New York, NY.

Karunaratne, L.B., P.C. Darby, and R.E. Bennetts. 2006. The effects of wetland habitat structure on Florida apple snail density. Wetlands 26:1143-1150

Martin, J., J.D. Nichols, J. E. Hines, and W. M. Kitchens. 2006. Multiscale patterns of movement in fragmented landscapes and consequences on demography of the snail kite in Florida. Journal of Animal Ecology 75(2): 527-539.

Martin, J., Kitchens, W.M., Cattau, C.E. and Oli, M.K. 2008. Relative importance of natural disturbances and habitat degradation on snail kite population dynamics. Endangered Species Research 6: 25-39.

Mooij, W.M., R.E. Bennets, W. M. Kitchens, and D. L. DeAngelis. 2002. Exploring the effect of drought extent and interval on the Florida snail kite: interplay between spatial and temporal scales. Ecological Modelling 149: 25-39.

Real, L.A. and J.H. Brown. 1991. Foundations in Ecology: classic papers with commentaries. The University of Chicago Press. Chicago, IL.

RECOVER. 2005. The RECOVER team's recommendations for interim targets for the Comprehensive Everglades Restoration Project. c/o U.S. Army Corps of Engineers and South Florida Water Management District, West Palm Beach.

Royle, J.A. and R.M. Dorazio. 2008. Hierarchical Modeling and Inference in Ecology. Academic Press, Amsterdam.

Schoener, T.W. 1971. Theory of feeding strategies. Annual Review of Ecological Systems. 2, 369-404

USFWS. 1999. South Florida multi-species recovery plan. US Fish and Wildlife Service, Department of the Interior, Atlanta, GA, USA.

Zweig, C.L. 2008. Vegetation ecology of an impounded wetland: Information for landscale-level restoration. Dissertation, University of Florida, Gainesville, Fla.

Zweig, C.L. and W.M. Kitchens. 2008. Effects of landscape gradients on wetland vegetation communities: information for large-scale restoration. Wetlands 28: 1086-1096.

Zweig, C. L. and W. M. Kitchens. 2014. Reconstructing historical habitat data with predictive models. Ecological Applications 24:196-203.


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