- A fragment is a patch of habitat that is broken up by less suitable habitat
- Many species of mammals and birds cannot maintain viable populations in small habitat patches, fragmentation may lead to extinctions.
- There are two hypotheses for fragmentation ecology
o The first states that species richness increases with area, so patches that are larger should have more species in them
o The second states that population abundance will increase with area, so that animals and plants in small patches will suffer more mortality, or have lower reproductive rates, than individuals in larger patches
- Fragmentation of large blocks of habitat into smaller blocks can reduce reproductive and survival rates of birds and condemn some species to extinction
- In eastern Northern America wood thrushes are a common nesting bird. Nesting success of the wood thrush is reduced in smaller fragments as the nests are more easily predated.
- When large blocks of habitat are broken up into smaller pieces, some species are lost, but other generalists or weedy species may colonize.
- The studied species in western North America may have been a predator bird, such as an Eagle, and predated vulnerable species.