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

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Frequently anticipated questions:

What does this data set describe?

Comprehensive Monitoring Plan for Snail Kites and Apple Snails in the Greater Everglades
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 and 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 1,218 birds (Cattau et al 2012), 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 and 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 (20098) 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 20098, Martin et al. 2008), which may stem, at least in part, from a shift in water management regimes (Zweig and 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, 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.
  1. How should this data set be cited?

    Kitchens, Wiley M., Fletcher, Robert, and Zweig, Christa, Unknown, Comprehensive Monitoring Plan for Snail Kites and Apple Snails in the Greater Everglades.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -81.6
    East_Bounding_Coordinate: -80.6
    North_Bounding_Coordinate: 27.6
    South_Bounding_Coordinate: 25.00000
    Description_of_Geographic_Extent: Greater Everglades and Everglades National Park, Florida, USA

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 2010
    Ending_Date: 2015
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: Maps and Data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

    2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.1. Longitudes are given to the nearest 0.1. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is World Geodetic System of 1984.
      The ellipsoid used is World Geodetic System of 1984.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.25722210088.

  7. How does the data set describe geographic features?

    Bird Information
    Information pertaining to the bird being observed (Source: Kitchens et al.)

    Reference number for the observed bird activity (Source: Kitchens et al.)

    Range of values

    Date of observation (Source: Kitchens et al.)

    Date in M/DD/YYYY format

    Location of observation (Source: Kitchens et al.)

    3BWCA 3B
    BCYBig Cypress National Preserve
    3A-YWCA 3A - Cypress
    3A-WWCA 3A - West
    3A-CWCA 3A Central
    3A-EWCA 3A - East

    Bird ID
    Bird band combination or sex/age description based on plumage (Source: Kitchens et al.)

    Sex & Age desciption

    Nest ID
    Current active nest number assocated with the individual of interest (Source: Kitchens et al.)

    Nest number assigned by researchers

    Foraging Bout Data
    Data recorded while observing bird foraging (Source: Kitchens et al.)

    Activity Code
    Describes bird activity (Source: Kitchens et al.)

    PSPerched with snail
    PMPerched with meat
    PSTPerched with stick
    HPHarassed on perch
    PNPerched on nest
    FLNon-foraging flight
    FSTFlying with stick
    FSFlying with snail
    SMFlying with meat
    AFAggressive flying
    DFDefensive flying
    CFCourtship flying
    ACCAttempted course capture
    CCSuccessful course capture
    ACPAttempted capture from perch
    CPSuccessful capture from perch
    LOSTLost visual of bird
    ENDend of observation period

    Time Start
    Start time of observed activity (Source: Kitchens et al.)

    Time in HH:MM:SS

    UTM X
    Northing location of data collection (the boat) (Source: Kitchens et al.)

    Northing value in meters

    UTM Y
    Easting location of data collection (the boat) (Source: Kitchens et al.)

    Easting value in meters

    Distance from the boat to activity location (perch, capture, etc.). Measured in meters and collected with a range finder. Three measurements taken (Source: Kitchens et al.)

    Range of values
    Units:meters (m)

    Bearing of bird with respect to the point of data collection (the boat). Measured in degrees and collected with a digital compass. Three measurements are taken. (Source: Kitchens et al.)

    Range of values

    Perch or foraging substrate/vegetation (Source: Kitchens et al.)

    Description of substrate/vegetation

    Snail fate
    After a snail is captured it's fate is recorded as either dropped, consumed (could be partial), or given to another kite (could be partial). The total of these three cells should equal 1 for each individual snail capture. (Source: Kitchens et al.)

    Snail drop
    Bird is observed dropping the snail (Source: Kitchens et al.)

    Range of values

    snail consumed
    Bird is observed consuming the snail (Source: Kitchens et al.)

    Range of values

    snail given to another
    Bird is observed giving the snail to another bird (Source: Kitchens et al.)

    Range of values

    Additional notes/observations (Source: Kitchens et al.)

    Free text notes

    Location Summary
    Summarizes the distance/bearing information and calculates the location of the activity (output in UTMs). (Source: Kitchens et al.)

    average dist
    Average distance the bird travels during the observed activity (Source: Kitchens et al.)

    Range of values

    SE Dist
    Standard error of the average distance (Source: Kitchens et al.)

    Range of values

    avg bear
    Average bearing of the bird during the observed activity (Source: Kitchens et al.)

    Range of values

    SE Bear
    Standard error of the average bearing (Source: Kitchens et al.)

    Range of values

    change x
    Change in northing location of the bird during the observed activity (Source: Kitchens et al.)

    Range of values
    Units:meters (m)

    change y
    Change in easting location of the bird during the observed activity (Source: Kitchens et al.)

    Range of values
    Units:meters (m)

    bird utm x
    Northing location of the bird activity (Source: Kitchens et al.)

    Range of values
    Units:meters (m)

    bird utm y
    Easting location of the bird activity (Source: Kitchens et al.)

    Range of values
    Units:meters (m)

  8. What biological taxa does this data set concern?

    Taxonomic_Keyword_Thesaurus: None
    Taxonomic_Keywords: multiple species
    Taxonomic_Keywords: animals
    Taxonomic_Keywords: invertebrates
    Taxonomic_Keywords: snails
    Taxonomic_Keywords: birds
    Taxon_Rank_Name: Kingdom
    Taxon_Rank_Value: Animalia
    Taxon_Rank_Name: Phylum
    Taxon_Rank_Value: Chordata
    Taxon_Rank_Name: Subphylum
    Taxon_Rank_Value: Vertebrata
    Taxon_Rank_Name: Class
    Taxon_Rank_Value: Aves
    Taxon_Rank_Name: Order
    Taxon_Rank_Value: Accipitriformes
    Taxon_Rank_Name: Family
    Taxon_Rank_Value: Accipitridae
    Taxon_Rank_Name: Genus
    Taxon_Rank_Value: Rostrhamus
    Taxon_Rank_Name: Species
    Taxon_Rank_Value: Rostrhamus sociabilis
    Applicable_Common_Name: Snail Kite
    Applicable_Common_Name: Milan des marais
    Taxon_Rank_Name: Phylum
    Taxon_Rank_Value: Mollusca
    Taxon_Rank_Name: Class
    Taxon_Rank_Value: Gastropoda
    Taxon_Rank_Name: Subclass
    Taxon_Rank_Value: Prosobranchia
    Taxon_Rank_Name: Order
    Taxon_Rank_Value: Architaenioglossa
    Taxon_Rank_Name: Family
    Taxon_Rank_Value: Ampullariidae
    Taxon_Rank_Name: Genus
    Taxon_Rank_Value: Pomacea
    Taxon_Rank_Name: Species
    Taxon_Rank_Value: Pomacea paludosa
    Applicable_Common_Name: Florida applesnail
  9. What special analytical tools are available to help me understand this data set?

    Tool 0 of 1
    Program R Statistical Software

    How to obtain this tool:

    How to access the tool:

    Tool_Access_Instructions: Program R is available at http://www.r-project.org/

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

    • Wiley M. Kitchens
    • Robert Fletcher
    • Christa Zweig

  2. Who also contributed to the data set?

    Organization: University of Florida

    Organization: Florida Fish and Wildlife Cooperative Research Unit

    Individual: Phil Darby, University of West Florida

  3. To whom should users address questions about the data?

    Wiley M. Kitchens
    P.O. Box 110485
    Gainesville, FL 32611-0485

    (352) 392-1861 (voice)
    (352) 392-1707 (FAX)

Why was the data set created?

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

To determine how hydrology, habitat quality, and prey density affect snail availability for foraging and nesting snail kites.

To determine how snail availability affects kite foraging success, and nest and foraging site selection.

To determine how snail availability affects nest success and recruitment.

To determine the role of kite foraging success and nest and foraging site selection on nest success and recruitment.

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

How was the data set created?

  1. What methods were used to collect the data?

    Method 0 of 1
    Type: Field

    We focus our foraging observations on breeding snail kites. Upon locating a nest, we randomly assigned one tending adult (either the male or female) as the focal individual. We then revisited nests on multiple occasions to perform foraging observations of the focal individual, returning every three to four days as long as the nest had not failed or fledged young. Since many focal individuals were unmarked, we used the presence of an adult of the proper sex (dimorphic plumage) at respective nests to uniquely identify focal individuals. If the focal bird was at the nest site upon our arrival, we initiated a 60-minute observation period immediately. If the focal bird was not at the nest upon our arrival, we waited for it to return to the nest to confirm its identity then started a 60-minute observation period when the bird next left the nest. We recorded the length of time (to the nearest second) of pertinent activities (e.g., course hunting, prey handling, perching, flying, sitting on nest). We recorded spatial locations of perches, snail capture points, and attempted capture points using a rangefinder and digital compass, and we identified the dominant vegetation type at each of these points. We also collected submersed and emergent vegetation at snail capture points using 0.5 m2 quadrats. After identifying and sorting plant samples to the species level, we counted the number of stems and took the wet weight for each species in the sample.


  2. From what previous works were the data drawn?

  3. How were the data generated, processed, and modified?

    Date: Unknown (process 1 of 1)
    The spatial points were used to calculate 95% kernel polygons using ABODE in ArcGIS 9.3. Home ranges were only calculated for birds with more than two observation periods and more than 10 spatial points. These polygons and the associated foraging points were provided to Dr. Phil Darby, and he used the throw-trap method (Darby et al. 1999) to estimate the snail density for each polygon in 2011. A foraging rate was calculated for each foraging bout that a kite made as the number of captures made per the minutes of foraging flight. A foraging bout was considered to start when the bird started foraging flight (head downward searching for snails), and was ended when either a capture was made or the bird ceased foraging flight. The relationship between snail density and snail capture rate was evaluated using a generalized linear mixed model (GLMM) with a binomial error distribution and a logit link, including individual bird as a random effect. The relationship between snail density and home range area (log-transformed) was evaluated using a GLM with a gamma error distribution and a log link. GLM analyses were performed in SAS 9.2. We analyzed biomass and abundance data for all submerged and emergent vegetation for each kite foraging point. To account for high densities of low biomass species and high biomass of low density species, we relativized the foraging habitat data using an index, importance value (IV), which is calculated by: IV for species i = ((Rdi + Rbi)/2)*100, where Rdi is the relative density of species i and Rbi is the relative biomass of species i. Relative measures are the sum of biomass or density of species i divided by the sum of biomass or density of all species within each sample. We performed a hierarchical cluster analysis on the IV data with a Sorenson distance measure and flexible beta of -0.25 in PC-ORD (McCune and Mefford 1999). To choose how many clusters were present during the study period, we ran an indicator species analysis (ISA) (Dufrêne and Legendre 1997) to prune the cluster dendrogram.

  4. What similar or related data should the user be aware of?

    Bennetts, R.E. & W.M. Kitchens, 1997, The demography and movements of snail kites in Florida: Technical Report 56, 169pp, U.S. Geological Survey/Biological Resources Division, Florida Cooperative Fish and Wildlife Research Unit, Gainesville, FL.

    Bennetts, R.E. & W.M. Kitchens, 1999, Within year patterns of snail kite survival in Florida: Journal of Field Ornithology 70(2):268-275.

    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, A., 2009, Effects of habitat degradation on monthly movements of juvenile snail kites.

    Other_Citation_Details: MS Thesis
    Cattau, C.E., B. Reichert, W. Kitchens, R. Fletcher Jr., J. Olbert, K. PIas, E. Robertson, R. Wilcox and C. Zweig, 2012, Snail Kite Demography Annual Report: U.S. Geological Survey, Florida Cooperative Fish and Wildlife Research Unit, Universtiy of Florida, Gainsville, FL.

    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., R.E. Bennetts, and H.F. Percival, 2008, Dry down impacts on apple snail demography: implications for wetlands water management.: Wetlands 22:204-214.

    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. & Oli, M.K, 2011, Relative importance of natural disturbances and habitat degradation on snail kite population dynamics: ESR 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.

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

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

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

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

    Researchers performed instrument calibrations and spot checked data and spreadsheet macros for outliers.

  2. How accurate are the geographic locations?

    Before each survey period a reference point is calculated with the field equipment (range finder, GPS and digital compass). This point can then be used later to correct location data points.

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    All years are represented but not all sights are represented each year (collection location depends on the activity of the birds each season)

  5. How consistent are the relationships among the observations, including topology?

    Not applicable

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None
Cite primary authors and database when using or publishing these data.

  1. Who distributes the data set? (Distributor 1 of 1)

    Heather S. Henkel
    U.S. Geological Survey
    600 Fourth Street South
    St. Petersburg, FL 33701

    727-502-8028 (voice)
    727-502-8182 (FAX)

  2. What's the catalog number I need to order this data set?

  3. What legal disclaimers am I supposed to read?

    The data have no explicit or implied guarantees.

  4. How can I download or order the data?

Who wrote the metadata?

Last modified: 24-Jan-2014
Metadata author:
Heather S. Henkel
U.S. Geological Survey
600 Fourth St. South
St. Petersburg, FL 33701

727-502-8028 (voice)
727-502-8182 (FAX)

Metadata standard:
FGDC Biological Data Profile of the Content Standard for Digital Geospatial Metadata (FGDC-STD-001.1-1999)

Generated by mp version 2.9.26 on Fri Jan 24 13:39:36 2014

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Last updated: 23 December, 2016 @ 01:49 PM (KP)