A model to assess the use of nest exclosures for local population recovery of the western snowy plover (Charadrius alexandrinus nivosus)

In Humboldt County, nest exclosures have been used from 2001 to 2006 as a management tool in the recovery of the local population of western snowy plovers (Charadrius alexandrinus nivosus). Due to a sudden increase in adult mortality in 2006, the use of nest exclosures was abandoned. To assess the efficacy of nest exclosures, a mathematical model was constructed using a system of ordinary differential equations to calculate the change in the population. The model showed nest exclosures to be effective in increasing egg survival. The model also showed that an increase in adult mortality would counteract the increase in egg survival. A change in adult survival was shown to have approximately twice the effect on the population as an equal change in egg survival. Therefore, nest exclosures, under that condition, are not beneficial for the recovery of the population and should only be used with great caution.