Data from the US Geological Survey's Breeding Bird Survey, National Audubon Society's Christmas Bird Count, nestbox monitoring programs (Smallwood et al. 2009), and Raptor Population Index (migration counts), collectively indicate long-term declines of American Kestrel populations in numerous regions of North America.
The map below illustrates model-estimated average % annual population change, based on Breeding Bird Survey (BBS) data, for Bird Conservation Regions (BCRs), which were developed by the North American Bird Conservation Initiative and are based on similar bird communities, habitats, and resource management issues.
|Bird Conservation Region|
|5||Northern Pacific Rainforest|
|6||Boreal Taiga Plains|
|8||Boreal Softwood Shield|
|12||Boreal Hardwood Transition|
|14||Atlantic Northern Forest|
|16||Southern Rockies/Colorado Plateau|
|17||Badlands and Prairies|
|19||Central Mixed-grass Prairie|
|21||Oaks and Prairies|
|22||Eastern Tallgrass Prairie|
|23||Prairie Hardwood Transition|
|25||West Gulf Coastal Plain/Ouachitas|
|26||Mississippi Alluvial Valley|
|27||Southeastern Coastal Plain|
|30||New England/Mid-Atlantic Coast|
|33||Sonoran and Mojave Deserts|
|34||Sierra Madre Occidental|
Selecting a BCR will produce a graph showing the BCR’s model-estimated average number of American Kestrels counted per BBS route (24.5 mi/39.2 km) per year, typically from the late 1960s to 2010, depending on data availability.
Solid line represents model-estimated, route-level average abundance per year, and dashed lines represent 95% credible intervals for the averages.
N: number of BBS survey routes within BCRs that provided the data for estimates of abundance and population change.
λ (Greek letter Lambda): model-estimated average % annual population change. Parenthesized values represent the 95% credible interval for λ. Generally, if the 95% credible interval does not overlap zero (indicated by red or green graphs), then we can have a higher level of confidence in the trend’s reality, whereas credible intervals that overlap zero and are less reliable are indicated by orange graphs.
% population change is a simple ratio of average abundance estimates for 1966 and 2010.