Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
  High-Bandwidth Version
Search Evolution  
 
Click to return to the Evolution Home Page
darwin change extinction survival sex humans religion
Darwin    
   
Origin of Species

Intro | Storm | Pollenpeepers' New Homes | Windsor Island | Warwick Archipelago | Gallery

As you will see, pollenpeeper populations on Windsor Island, like the mainland, will show relatively minor changes over time. Populations will continue to occupy niches similar to those they occupied before the storm, since there are few opportunities to move into other niches. Follow along to explore what happens to the Windsor Island pollenpeepers.

Windsor Island: 5 Million Years Ago

Highlight

  • A new wave of immigrants is blown in by storm.

Pollenpeeper changes

  • The pollenpeeper population increases 400 percent -- from 50 to 200 -- as birds are blown from the mainland to Windsor Island, five miles to the eastf.
  • Immediately following the storm, immigrants assimilate into the local population; individuals from each population are indistinguishable from one another.
  • As the population grows, pollenpeepers slowly begin to expand their range inland from their coastal habitat.

Habitat

  • The island receives more rainfall than the coastal mainland; consequently, it is much more lush.

Food

  • Seeds
Some seeds available
  • Insects
Many insects available
  • Flowers
Few nectar flowers available

Competition

  • When the newest pollenpeepers arrive on Windsor Island, there are few other species present to compete with them for resources. Competition remains low during this time period.

Predators

  • Many predators threaten these pollenpeepers

Windsor Island: 4 Million Years Ago

Highlight

  • Two new species of finch arrive.

Pollenpeeper changes

  • There is very little change in the appearance of the beaks of Windsor pollenpeepers.
  • Head plumage of Windsor pollenpeepers slowly becomes redder than that of mainland peepers.
  • Occasional immigrants -- four or five per year -- arrive on Windsor Island from the coastal mainland.

Habitat

  • The habitat remains wet and lush across the island during this time period.

Food

  • Seeds
Some seeds available
  • Insects
Many insects available
  • Flowers
Few nectar flowers available

Competition

  • Two new species of finch arrive on the island during this time period and begin to compete with pollenpeepers for food resources. This only provides significant pressure infrequently, in years when food availability is low.

Predators

  • Many predators threaten these pollenpeepers

Windsor Island: 3 Million Years Ago

Highlight

  • Birds develop redder heads and move inland.

Pollenpeeper changes

  • The head plumage of the pollenpeepers, especially the males, continues to grow redder.
  • There is no apparent change in beak size and shape during this time period.

Habitat

  • Overall, pollenpeeper habitat does not change significantly. Pollenpeepers begin to use their habitat differently, however, as a portion of the population moves from the coast into the wetter, denser island interior.

Food

  • Seeds
Some seeds available
  • Insects
Many insects available
  • Flowers
Few nectar flowers available

Competition

  • Pollenpeepers that move inland feed on the same insects as two other species of insect-eating birds. Insect larvae are plentiful, though, and there is still very little competition among the birds.

Predators

  • Many predators threaten these pollenpeepers

Windsor Island: 2 Million Years Ago

Highlight

  • Some residents move back to the mainland.

Pollenpeeper changes

  • There is little change in the morphology of Windsor pollenpeepers during this period.
  • Population density of pollenpeepers along the coastal habitats on Windsor has reached a peak.
  • Each year, at least a dozen or more pollenpeepers leave Windsor Island, bound for the mainland coast. Nearly as many disperse from the mainland to Windsor, though, so the population remains stable.

Habitat

  • The habitat remains lush and tropical during this period.

Food

  • Seeds
Some seeds available
  • Insects
Many insects available
  • Flowers
Few nectar flowers available

Competition

  • Competition among pollenpeepers for foraging and nesting resources, especially along the coast, reaches a peak due to the highest population density to date.

Predators

  • Many predators threaten these pollenpeepers

Windsor Island: 1 Million Years Ago

Highlight

  • A new wave of immigrants from the mainland invade Windsor.

Pollenpeeper changes

  • Pollenpeepers from the mainland's northern coast disperse to Windsor Island in increasing numbers. The new immigrants have slightly longer, narrower beaks than the native Windsor pollenpeepers.
  • Movement and interbreeding between Windsor Island and mainland pollenpeeper populations becomes more frequent. The mainland birds with their longer bills are better adapted and more successful at finding food on Windsor Island; through interbreeding they pass their genes and longer, narrower beaks on to the population as a whole.

Habitat

  • The habitat remains lush and tropical. Seed-producing grasses are increasingly displaced by trees and shrubs during this time period.

Food

  • Seeds
Few seeds available
  • Insects
Many insects available
  • Flowers
Few nectar flowers available

Competition

  • Competition among birds along the coast becomes intense, favoring individuals with longer, narrower beaks.

Predators

  • Many predators threaten these pollenpeepers

Windsor Island: Present

Highlight

  • Short, blunt beaks become obsolete.

Pollenpeeper changes

  • Pollenpeepers move regularly between Windsor Island and the mainland; the two populations interbreed.
  • There is a trend toward longer, narrower beaks within both populations.

Habitat

  • Grass seeds become rare and unreliable as a food resource. The tropical environment supports an abundance of insects. Pollenpeepers become better adapted at finding and using this rich food resource.

Food

  • Seeds
Few seeds available
  • Insects
Many insects available
  • Flowers
Few nectar flowers available

Competition

  • The reduction in seed availability and the presence of birds that are better adapted for insect-eating pushes short, blunt beaks from the population.

Predators

  • Many predators threaten these pollenpeepers

-> Explore pollenpeeper evolution on the Warwick Archipelago

Intro | Storm | Pollenpeepers' New Homes | Windsor Island | Warwick Archipelago | Gallery

  related web activities  
   
Darwin's Diary
Delve into Darwin's secret inner world.
 
 
Coral Reef Connections
Dive in and learn why this beautiful world is so fragile.
 
 
All in the Family
Test your skills at judging who's who on the tree of life.
 
   
Sex and the Single Guppy
Learn how exhibitionism has an evolutionary payoff.
 
 
related topics  
 
Adaptation and Natural Selection  
 
Evolution of Diversity  
 
Deep Time/History of Life  
 
 
       
         
Videos Web Activities Site Guide About the Project FAQ Glossary Site Map Feedback Help Shop