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 Plan for Reducing Mottled duck X Mallard Hybridization

 Attachment A of a Report to Commissioners, May 15, 2002, 
Reducing Mallard Releases

I.       Background Information

A.   Conservation Plan – The Conservation Plan for the Florida Mottled Duck (Florida Fish and Wildlife Conservation Commission 1999) sets forth a population management objective as follows:  “Maintain the most recent five-year average estimate of mottled duck breeding population density at or above 0.7 birds/km2 within the currently surveyed area, or at or above the current level as determined by a revised survey.”  One of the specified strategies for achieving this objective is to minimize interbreeding and hybridization between mottled ducks and mallards by (1) identifying and implementing mechanisms to reduce hybridization including distributing public information materials describing the problem, why it is occurring, and how it can be reduced, (2) evaluating or developing techniques to identify hybrids, and (3) periodically assessing the proportion and distribution of hybrids in the population.  This plan functions as a sub-plan of The Conservation Plan for the Florida Mottled Duck and provides more detailed strategies and tasks for reducing hybridization.

B.     Need for Action – Feral mallards pose a major threat to the conservation of Florida’s endemic mottled duck (Anas fulvigula fulvigula) because the two closely related species interbreed, resulting in fertile, hybrid offspring.   Florida’s mottled duck is nonmigratory, is genetically distinct from mottled ducks occurring elsewhere in the country, and occurs only in peninsular counties of the state.  Their existence is threatened by interbreeding with feral mallards and by rapid changes in Florida’s landscape, mostly resulting from agricultural and urban development.  The mottled duck is a defining member of the unique suite of wildlife species characteristic of the prairie ecosystem of southern Florida.  An estimated 5% of Florida's mottled duck population exhibits hybrid characteristics, based on wing plumage.  This is a minimum estimate of the proportion of the population that is hybridized because many mallard genes are not expressed visibly.  Worldwide, mallard-type species repeatedly have been partially or, perhaps in one case, completely hybridized out of existence by introduced mallards.   As illustrated by the decline and loss of these other similar species, mallard x mottled duck hybridization can be a devastating problem, and a comprehensive strategy is needed to address it.  Unless the release of mallards in Florida is stopped, mallard genetic introgression into the mottled duck population will continue to increase, possibly to the demise of Florida’s mottled duck.

II.    Plan

A.   Objective:  Develop techniques to identify hybrids

1. Strategy:  Develop technique to distinguish hybrids by genotype
    
a) Task – Collect additional tissue samples from mallards and hybrids
    
b) Task – Contract with genetics lab to develop technique

2.  Strategy: Develop technique to distinguish hybrids by phenotypic characteristics

     a) Task – Use genetic technique to identify known hybrids and identify plumage characteristics that distinguish hybrids from either species
     b) Task – Develop key or field guide to identifying hybrids by phenotypic characteristics for use during banding and at hunter check stations

B. Objective:  Assess proportion and distribution of hybrids in population

1. Strategy:  Obtain current estimate of proportion of population that are hybrids

2. Strategy:  Identify geographic problem areas

3. Strategy:  Implement periodic sampling of population to measure temporal change in hybridization rate

     a) Task– Obtain tissue from museum specimens and compare to current genetic makeup of mottled duck population to measure any previous temporal change toward more mallard-type genes
    
b) Task – Design sampling scheme
     c) Task – Periodically sample population

C.  Objective:  Identify and implement mechanisms to reduce hybridization

1. Strategy:  Learn about the sources of mallards being released

     a) Task – Conduct survey of farm-and-feed-type of stores and pet stores
    
b) Task – Conduct informal survey of commercial mallard breeders
    
c) Task – Investigate possible data bases and other sources of information concerning the number of mallards brought into the state, means of transport, and disposition

2. Strategy:  Develop and implement communications plan (i.e., marketing and public relations strategy)
     a) Tasks – (See Attachment C, Integrated Communications Plan)

3. Strategy:  Recommend rule changes to curb mallard releases

     a) Task – Prohibit release of mallards on private hunting preserves
     b) Task – Review other potential regulatory mechanisms for addressing the problem

4. Strategy:   Investigate animals to be purchased for pets and for ornamental purpose as alternatives 
     a) Task - investigate feasibility of producing sterile mallards     b) Task

b)           Task – Investigate feasibility of developing a supply of captive-reared mottled ducks

5.     Strategy:  Facilitate direct control of mallard populations where feasible

a)     Task – Obtain from U.S. Fish and Wildlife Service a permit to allow for lethal control

b)     Task – Develop strategy for implementing permit

c)     Task – Implement permit

6.     Strategy:  Provide for the release of captive-reared mottled ducks on private hunting preserves

a)     Task – Recommend rule change to establish guidelines for release of mottled ducks from private hunting preserves

b)     Task – Support industry efforts to have federal regulations changed that restrict release of captive-reared mottled ducks on private hunting preserves

c)     Task – Assess requirements for establishing a captive program

d)         Task – Permit the capture and keeping of wild mottled ducks or their eggs

e)          Task – Assist as necessary and feasible with taking wild mottled ducks or eggs to establish captive flock and, if necessary, obtain pertinent federal permit

f)            Task – Ensure genetic purity of brood stock through regulation and inspection

g)          Task – Ensure to the extent possible through regulation and enforcement that released birds are disease-free

h)            Task– Assess impact of captive-reared and released mottled ducks on wild mottled duck population and monitoring programs

(1)  Require that preserves provide daily records of bird numbers released and harvested
(2)  Estimate annual and seasonal (post-season until annual mottled duck population monitoring) survival rates of released birds
(3)  Periodically estimate band reporting rates for wild mottled ducks to assess potential of mottled duck releases to bias band recovery dataP
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