Species Assessment
The science behind bird conservation
The first step in the conservation planning process is a status
assessment of each species throughout its range and annual cycle.
Four basic factors affect a species' vulnerability:
- Habitat threats
- Declining populations
- Small population size
- Limited distribution
To evaluate a spcies' conservation needs, ornithologists use the following six criteria. The most vulnerable species (highest priority) are those with a combination of small and declining populations, limited distributions, and deteriorating habitats.
- Population Size: total number of adult individuals in the planning unit
- Breeding Distribution: geographic extent of a species’ breeding range
- Non-breeding Distribution: geographic extent of a species’ non-breeding range
- Threats to Breeding: conditions that threaten the ability to survive and successfully reproduce in breeding areas
- Threats to Non-breeding: conditions that threaten the ability to survive over the non-breeding season
- Population Trend: direction and magnitude of changes in population size over the past 30 years
Similar-seeming birds often have different conservation priorities. Consider these three thrushes:
The Bicknell's Thrush (top photo), with its tiny world distribution and
population, as well as severely threatened winter habitat, is among the
most threatened North American landbirds.
The Wood Thrush (center photo) has a much larger breeding distribution
and population, however a small and threatened winter range and
declining population trend nevertheless warrant its inclusion on the
Partners In Flight Watch List.
The very large population and range size of the Hermit Thrush (bottom
photo), combined with low threats and increasing population, make this
species one of the least vulnerable of North American landbirds.