The Big Picture: Large-scale Summary of Population Change and Species Richness for Species Groups

This part of the Home Page provides an overall summary and discussion of large-scale patterns of bird species richness and population change (since 1966) for groups of North American birds.

Description of Methods

• Click here for a description of the methods and rationale for analysis of species groups
• Making the Species Richness Maps
  • These maps show the number of species in each group that were ever observed on individual BBS routes. Consequently, the maximum number of species on each maps is limited to the number of species in the species group. As with the relative abundance and trend maps, species richness maps are smoothed using inverse distancing.

    These maps are all underestimates of the actual species richness! Species are always "missed" on counts, hence these maps must be viewed as minimum estimates of richness. However, they do show the relevant regional patterns of species richness.

Species Group List

• Click here to view species lists for each group

Analysis of Percentage of Species with Positive Trends

Maps and Summaries for each Group

	Species Richness Map	Trend Map	Summary of Geographic Pattern
All Species	X	X	X
Breeding Habitat
Grassland Birds	X	X	X
Wetland Birds	X	X	X
Scrub/successional Birds	X	X	X
Woodland Birds	X	X	X
Urban Birds	X	X	X
Nest Type
Cavity-Nesting Birds	X	X	X
Open-cup Nesting Birds	X	X	X
Migration Form
Short-distance Migrant Birds	X	X	X
Permanent Resident Birds	X	X	X
Neotropical Migrant Birds	X	X	X
Nest location
Ground and Low Nesting Birds	X	X	X
Mid-story and Canopy Nesting Birds	X	X	X