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Tuesday, January 30 • 2:40pm - 3:00pm
SYMPOSIA-08: Challenges of Wetland Restoration Monitoring--If You Build It Will They Come, If They Come Will You Know It?

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AUTHORS. Robert J. Gates, Ohio State University; Jacob Straub, University of Wisconsin Stevens Point; Michael Brasher, Ducks Unlimited, Inc.; John Coluccy, Ducks Unlimited, Inc.

ABSTRACT. Wetland conservation projects are monitored to measure waterbird population responses to habitat change, assuming that abundance is affected by habitat quality.  Food energy is assumed to be primarily limiting for non-breeding waterfowl, although non-food factors also affect abundance.  Regardless, duck use-days are typically assumed to be positively related to availability of food energy.  We tested this assumption by estimating food energy and duck use-days in wetlands in northwestern Ohio during fall and spring 2001-2004 and on 6 sites in IL, WI, OH, and MI during springs 2006-2007.  Higher levels of duck use-days were observed at sites with more food energy, although abundant food did not guarantee high rates of duck use at individual locations.  Distributions of duck use-days and food energy were right-skewed and were correlated only when duck use-days were plotted on the log scale.  Transforming food energy to the log scale linearized this relationship.  Hurdle models revealed a positive linear relationship between log(duck use-days) and log(food energy).  Hurdle models estimated probabilities of false zeroes (habitat suitable but not used by ducks), which ranged from 0.15 to 0.60.  We concluded that food energy positively influenced duck abundance but other factors constrain the capacity of migrating ducks to track food resources.  Separate processes likely determine occupancy and use rates on occupied sites.  Our results showed that waterfowl occupancy and abundance do not consistently align with expectations of habitat quality as measured by food energy, despite evidence for an overall positive relationship.  This poses a problem for monitoring if the goal is to evaluate population response to habitat change.  These concerns may be addressed with analytical approaches such as we applied.  We discuss the implications of our findings for monitoring population response to wetlands restoration and enhancement. 

Tuesday January 30, 2018 2:40pm - 3:00pm CST