Eastern monarch population trends (fall):

  • Highlighted subregion: Northcentral. This is where most breeding occurs for eastern summer populations. Northeast is another important breeding zone.
  • Season: Fall (8/16-10/31). Seasons are defined by monarch activity
  • Featured program(s):
    • Cape May: A peninsula at the tip of New Jersey
    • Peninsula Point: In Michigan’s upper peninsula
    • Both sites serve as a funneling point for migrating monarchs. Routes are surveyed daily in the fall and raw scores are the average number of monarchs seen per hour
00.250.50.751199319951997199920012003200520072009YearRelative abundance IndexProgramsFall Northeast (Cape May)Fall Northcentral (Peninsula Point)

All trend graphs show “relativized” abundance indices.  This means that “raw” scores that measure some index of abundance are transformed so the highest value in the series is equal to 1, and all other values are then relative to the highest value.  This allows scores to be overlaid among programs so that yearly dynamics can be compared.  The “raw” score measured varies and is described separately for each program.  The length of the time series (start and end year) vary depending on how long the programs have run and how much data we have received from each program.