Patterns of Population Change in Birds

Summaries of Bird Population Change

The BBS has data from over 421 species of birds, covers most of North America, and has been going on for over 33 years. Summaries of the data are bound to be controversial, because they collapse information over species, space, or time. For example, it appears that rangewide, over the 31 years, about half (51.5%) of the species have increased, about what you would expect by chance. But, this apparent overall stability hides many increases and declines. Sorting out these patterns is difficult, and here we provide some tools for analyzing the patterns of population change.

Users can access:

Species group analyses:

Often, it is useful to group species that share some common feature. We group birds based on attributes such as breeding habitat, nest type, migration status, and nest location. If species in the group show consistent trends, and differ from species not in the groups, it suggests that the common feature could be influencing population change for the group. For more discussion on this, click here. For a listing of the species in each guild, click here

Percentage of Increasing Species by Group

Detailed Regional Analysis of Population Change

Maps of Population Change and Species Richness by Species Groups 1966 - 1996

Here are the maps that show you both where the species groups occur and the relative magnitude of population changes. The survey-wide percentage of species with positive trends are presented in parentheses, and ** indicates that the result is significantly different from 50%.

Breeding Habitat Species GroupspctN
Grassland Birds23.3%**N=28tend map  species richness map
Wetland/Open Water Birds66.5%**N=86tend map  species richness map
Scrub/Successional Birds39.6%N=86tend map  species richness map
Woodland Birds57.4%**N=133tend map  species richness map
Urban Birds28.3%N=14tend map  species richness map
Nest Type Species GroupspctN
Cavity Nesting61.0%N=62tend map  species richness map
Open-cup (Passerines and Cuckoos)43.0%N=184tend map  species richness map
Migration Status (Landbirds and Hawks)pctN
Permanent Resident55.3%**N=92tend map  species richness map
Short-distance Migrant46.1%**N=107tend map  species richness map
Neotropical Migrant46.3%N=136tend map  species richness map
Nest Location Species Groups (Passerines and Cuckoos)pctN
Ground or Low Nesting36.1%N=117tend map  species richness map
Mid-story or Canopy Nesting55.7%N=121tend map  species richness map
All SpeciespctN
all species51.5 N=421tend map  species richness map

Prepared by:
John R. Sauer
Patuxent Wildlife Research Center
11500 American Holly Drive
Laurel, Maryland 20708-4017 USA
Last updated 3 December 1999
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