Edge Effects

1
Edge Effects Ecological Traps

• Build upon population growth models, source-sink
  dynamics
• Contrast edge population dynamics at the edge and
  core
• Evaluate how selection for edge and core habitat
  affects population persistence

2
Edge Effects Traps

• Not all habitat is created equal
• E.g. Bobolinks nest in grasslands and in
  hayfields
• When harvested early, breeding success is
  lowered dramatically
• Densities as high or more
• Ecological trap

3
Edge Effects Traps

• So what is an ecological trap?
• Most organisms occur in both high and low quality
  habitats (recall S-S dynamics)
• However, low quality habitat does not immediately
  confer trap status
• It needs to be a sink and preferred
• E.g. 40 of habitat is hay yet contains 60 of
  bobolinks

4
Edge Effects Traps

• Edges are defined as borders between two
  different habitat types
• Core habitat is defined as habitat that is
  buffered some distance from an edge
• Birds sometimes occur in higher densities at the
  edge, possibly because of increased niches and
  higher food
• However, they frequently have higher BP and
  mortality rates

5
Edge Effects Traps

• Habitat edges have long been hypothesized as
  ecological traps for songbirds

6
Edge Effects Traps

• In this exercise, you will model an organism that
  that breeds in edge and core habitats, where each
  habitat type has its own, unique reproductive and
  survival parameters
• All individuals in core habitat will have one
  specific rate while those in edge will have
  another specific rate