Habitat and Population Evaluation Team
Midwest Region

Targeting the Small Wetlands Acquisition Program (SWAP) in Minnesota

The purpose of the SWAP is the conservation of small wetlands and associated upland habitats in the conservation of breeding waterfowl, while providing collateral benefits to migrant waterfowl and other species of wetland and grassland dependant migratory birds. HAPET has developed a set of tools for targeting the acquisitions of Waterfowl Production Areas (WPAs) and conservation easements.  The tools enable managers to assess the potential population benefits of the conservation of every 40 ac parcel within Minnesota’s Wetland Management Districts (WMDs) for

  • Wetland restoration and protection, based on
    • Integrity of the existing wetland complex
    • Predicted landscape-scale nest success; and
  • Grassland restoration and protection, based on
    • Landscape-scale duck pair potential (accessibility to upland nesting hens)
    • Contribution to a Type I Grassland Bird Conservation Area

To develop these criteria in a spatial context, we developed and applied a series of models.
Integrity of the existing wetland complex Characteristics of wetland complexes affect the functionality of individual wetlands they encompass, particularly for species that use small wetlands.  Logistic models predicting probability of wetland use based on the wetland complex within a 2 mi radius and wetland size were developed for a suite of dabbling duck and diving duck species and black terns using 10 years of 4 mi2 survey data.  For each species, wetland size was fixed at 2 ac and models were applied to wetland data modified from the National Wetlands Inventory.  Individual species data were then merged to assess the relative potential of 2 ac wetlands, in their existing wetland complex context, to support multiple species.  This composite data layer was interpreted as an index to existing wetland complex integrity.
Predicted nest success – It is not desirable to restore wetlands for waterfowl in landscapes where nests have a low probability of hatching.  Nest success was predicted as a function of the amount of grass in the landscape using the following function.  This model was applied to a digital data layer of percent grass in a 2 mi radius (described elsewhere).  The index for wetland complex integrity and nest success were each rescaled from 0-100 and summed to develop an index to priority for wetland restoration and protection (likewise, rescaled from 0-100).
Duck pair potential – This is a thunderstorm “map” of access of upland nesting waterfowl hens to existing or potential grassland habitat.  The derivation of this data layer is described elsewhere on this web site.
Contribution to a Type I GBCA – The acres needed to create a Type I GBCA was an intermediate product of the GBCA delineation process (described elsewhere).  Acres needed were subtracted from 640 ac (the minimum area of the Type I GBCA) as an index to grassland patch size and blockiness (greater being better for both). 

Duck pair potential and contributions to a Type I GBCA were each rescaled from 0-100 and summed to develop an index to priority for grassland restoration and protection (likewise, rescaled from 0-100).

Lastly, composite indices of priority for wetland restoration/protection and grassland restoration/protection were summed to create an overall SWAP priority index (rescaled to 100).  An Excel spread sheet of a legal description and the raw data and derived indices for every 40 ac parcel in Minnesota’s WMDs was developed and distributed to WMDs.  Managers are advised to use either the wetland restoration/protection priority score, the grassland restoration/protection priority score, or the overall SWAP priority score, depending on the nature of the proposed acquisition or management actions.


Cry of the Marsh
Strategic Habitat Conservation
Last updated: December 9, 2009