A metapopulation of wood thrushes is found in an area of the Midwest.Individual thrush populations exist in forest patches interspersed with farm fields.Monitoring over several years showed several types of populations:
I.Populations with negative birth rates that went extinct
II. New populations that occasionally formed in previously bare patches
III. Populations with positive birth rates that maintained population equilibrium
Which of these types would be considered source populations, and which would be considered sink populations?

Question

A metapopulation of wood thrushes is found in an area of the Midwest.Individual thrush populations exist in forest patches interspersed with farm fields.Monitoring over several years showed several types of populations: 
I.Populations with negative birth rates that went extinct
II. New populations that occasionally formed in previously bare patches
III. Populations with positive birth rates that maintained population equilibrium
Which of these types would be considered source populations, and which would be considered sink populations?

Quizplus · Accepted Answer

Sink populations are those with negative population growth that require influxes of individuals from source populations to maintain viability. Both populations with negative birth rates that went extinct (Type I) and new populations that occasionally formed in previously bare patches (Type II) fit this definition and are likely sink populations. Populations with positive birth rates that maintained population equilibrium (Type III) could act as source populations, providing individuals to maintain or establish sink populations. Therefore, I and II are likely sink populations, while III might be a source population.

A Metapopulation of Wood Thrushes Is Found in an Area