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projects > comprehensive monitoring plan for snail kites and apple snails in the greater everglades > work plan

Project Work Plan

Department of Interior USGS GE PES
Fiscal Year 2012 Study Work Plan

Study Title: Comprehensive Monitoring Plan for Snail Kites and Apple Snails in the Greater Everglades
Study Start Date: 4/30/2012 Study End Date: June 30, 2013
Web Sites:
Location (Subregions, Counties, Park or Refuge): Total System
Funding Source: GE PES
Other Complementary Funding Source(s): U. S. Army Corps of Engineers
Funding History: FY10; FY11; FY12
Principal Investigator(s): Wiley Kitchens, Robert Fletcher, Christa Zweig
Study Personnel: Chris Cattau, Dan Cavanaugh, Eric Riddell, Kyle Pias, Rebecca Wilcox
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) 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 950 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 (2008) 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).

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 kite foraging habitat quality within foraging polygons and determine its relationship to hydrology and vegetation communities.

Specific Relevance to Major Unanswered Questions and Information Needs Identified: (Page numbers below refer to DOI Science Plan.)

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 3 of a 5 yr effort to determine the relationship between hydrologic regimes, habitat responses and kite demography and reproduction for the Southern Everglades.

Recent Products: Two Annual Reprots have been prepared detailing the status of the project to date.

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 track adult and juvenile kites using radio transmitters in order to
    1. define specific foraging and nesting polygons as indicators of habitat quality
    2. determine nest abandonment, success and recruitment as related to above
    3. 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, again as indicators of habitat quality.
    4. record movements among wetlands so that habitat quality in the donning and receiving sites can be assessed
  2. 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
  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., 2007c). 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 submitted a similar, complementary proposal to FWC through the aquatic habitat restoration and enhancement subgroup (AHRES) that would expand the scope of this proposed work to the Kissimmee-Chain-of-Lakes (KCOL).

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
FAX:
Task Status (proposed or active): Active
Task priority: High
Time Frame for Task 1: Continuing effort
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.

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 remaini9ng successive years of the study 2013, 2014, and 2015. To date (2011 and 2012), two 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: Determining the survival, movement probabilities, foraging polygons, snail capture rates, and nesting home ranges of kites.
Task Funding: USGS Priority Ecosystems Science
Task Leaders: Wiley Kitchens, Chris Cattau, Kyle Pias, and Christa Zweig
Phone: 352-846-0536
FAX: 352-846-0841
Task Status (proposed or active): Active
Task priority: High
Time Frame for Task 2: Continuing effort
Task Personnel: Kyle Pias, Christa Zweig, Dan Cavanaugh, Ellen Porter, Chris Cattau, Brian Reichert, and Rob Fletcher

Task Summary and Objectives :

  1. To track adult and juvenile kites using radio transmitters in order to
    1. define specific foraging and nesting polygons as indicators of habitat quality
    2. determine nest abandonment, success and recruitment as related to above
    3. 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, again as indicators of habitat quality.
    4. record movements among wetlands so that habitat quality in the donning and receiving sites can be assessed
  2. 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
  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

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

Field work

Using the proposed funds, we will capture, band, and equip up to 30 adult snail kites with radio transmitters each year (thus, we aim to deploy up to 90 transmitters over the course of the 3 year study). We will target kites in the southern end of their range (principally WCA3A), especially 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 trap and equip them). Throughout the year, all kites with active radio transmitters will be located biweekly at a minimum. From these data, we will estimate movement and survival probabilities, which can then be equated to habitat conditions sampled on the ground (e.g., hydrology, vegetative communities, snail densities (from P. Darby). While USACE funds will be used to pay for the aircraft flight time, funding from this proposed project will be directly applied to the transmitters and ground-level tracking efforts (see proposed budget), including conducting time activity budgets (TABs) of individual kites (see below).

In order to address objectives 3 and 4, radio-telemetry data from both juvenile and adult snail kites will be used to estimate the monthly survival and movement probabilities in response to snail availability. As outlined in the Figure 1, snail availability, actualized in capture rates can be described as a product of snail density, vegetation community structure and localized water stage levels. These data are critical to understanding how resource availability may be limiting reproduction and recruitment.

We will conduct TABs on radioed and non-radioed snail kites, including breeding adults and non-breeding adults and juveniles. Radio tagging will allow us to identify and follow individual birds beyond the area immediately adjacent to their nests and/or regular foraging areas. This will allow us to test assumptions about the distance from nests that kites typically forage. Additionally, little is known about the movements of kites after a failed nesting attempt, and transmitters will allow the tracking of birds even if large movements occur (during nesting, after young fledge or after a nest failure). Also, it will be valuable to know if birds abandon a nesting area and move to a new wetland unit. For these long distance movements, transmitters are essential.

Once a radioed kite is located via airboat, we will conduct a TAB. TABs will be of two durations: two-hour and day-long. During the TABs we will record the number of snails captured, 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 will be used in the estimation of foraging polygons. The GPS points where prey captures occur will be used to guide site selection for sampling snail densities. We will also identify the vegetative community within a representative sample of the foraging polygons based on capture rates of the associated TABs.

During the breeding season, we will conduct TABs on all radioed breeding kites, as well as on non-radioed breeding kites if the sample size needs to be increased. We will collect approximately 90 two-hour and six day-long TABs on breeding adults each year. We will conduct TABs on radioed juveniles during the breeding and non-breeding seasons. We will collect approximately 90 two-hour and six day-long TABs on juveniles each year. Finally, we will also conduct TABs on radioed non-breeding adults during the breeding and non-breeding seasons. We will collect approximately 90 two-hour and six day-long TABs on these birds each year.

These data will be used to estimate foraging polygons using a kernel-density estimator. Locations of the capture sights and polygons will be provided to P. Darby et al. A sub-sample will be used to estimate snail densities within the foraging polygons. Snail densities and TAB data will be integrated for analysis in order to address Objective 1. We will model capture rates as a function of snail densities, and then we can use capture rates to estimate snail densities where snail sampling cannot be conducted.

Data Analysis

Home ranges will be primarily calculated using a kernel density estimator (KDE), and/or minimum convex polygons (MCP's). The exact parameters of these analyses will depend on the nature of the data collected. A sample KDE calculation based on actual activity points from a nesting female on Lake Toho is shown in Fig. 4. By combining home range calculations with vegetation data, the habitat matrix that exists within the kite's home range can be quantified. These calculations can be compared to nest success, productivity, and recruitment. Selection of this habitat matrix can also be determined by randomly selecting areas that are a comparable size to a kite home range, and quantifying the matrix within these random areas.

Snail densities within each kite's home range will be estimated and effect of snail density on nest success, nest productivity, and recruitment will be tested. Snail sampling will be conducted through a separate contract with the University of West Florida (Phil Darby, P.I.).

Time activity budget data will also be quantified, and we will compare capture rates and provisioning rates among vegetative communities and among a range of snail densities, we will also compare capture rates to nest success, nest productivity, recruitment, and survival.

Specific Task Product(s): Progress will be reported annually in the form of status reports June 30 of the remaini9ng successive years of the study 2013, 2014, and 2015. To date (2011 and 2012), two 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 3. Vegetation sampling
Task Funding: USGS Priority Ecosystems Science
Task Leaders: Wiley Kitchens, Kyle Pias, and Christa Zweig
Phone: 352-846-0536
FAX: 352-846-0841
Task Status (proposed or active): Active
Task priority: High
Time Frame for Task 2: Continuing effort
Task Personnel: Kyle Pias, Christa Zweig, Dan Cavanaugh, Ellen Porter, Chris Cattau, Brian Reichert, 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 polygons defined by the intense radio 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 in press). 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.