Here we provide a general summary of the effort and species data generated during Iowa’s second Breeding Bird Atlas project (BBAII). This is meant to be an overview of the project; greater detail can be found in the individual species accounts.
Block Data
From 2008 to 2012 a total of 436 observers spent 10,644 hours during 7,465 visits for BBA II. During BBA II, all 791 blocks received some coverage with just 40 partially complete blocks (most were grid blocks) and 751 completed blocks. This compares to 152 noncovered blocks, 98 partially completed blocks, and 611 completed blocks during BBA I. Compared to BBA I we also had one less year of coverage and approximately 4,000 fewer hours of survey effort. With the advent of the Internet, however, we were able to focus annual atlas efforts more efficiently and minimize excessive coverage (>20 hours) for high interest sites. Effort was below expectations during the first three years, so the Steering Committee in 2010 began focusing field efforts in poorly surveyed parts of the state. This included sponsoring block-busting weekends and hiring trained atlassers to visit these areas in 2011 and 2012. As a result, atlas effort increased toward the end of the project. This fell short of the target of 20 hours per block (a total of 15,820 hours) but was still better than during BBA I. The average block had 74 species and 13.5 hours of effort during BBA II, compared to 74 species and 17 hours of effort in BBA I. See the Effort Summary for more detail.
Species Data
BBA II documented the presence of 196 species of birds in Iowa during the breeding seasons of the 5-year survey period (2008–2012). This evidence was based on 151,614 individual records that were submitted by all atlas participants combined. The list of species found during the BBA II project included 166 confirmed breeders, 16 probable breeders, 12 possible breeders, two observed without breeding evidence, and a few species that were reported but not considered realistic breeders in Iowa. The BBA II resulted in the addition of one species (Alder Flycatcher) to the list of Iowa breeding birds. The number of species per block was variable, although most blocks contained between 60 and 90 species with very few blocks recording >100 species. See the Project Overview, County Summary and Block Summary for details.
The results of BBA II revealed that Iowa’s breeding bird community has experienced significant changes in the 20+ years since the first atlas. The individual species accounts provide considerable detail on these changes on a species by species basis. Some of the patterns encompass groups of birds and are worth highlighting here by mentioning some successes The results of BBA II revealed that Iowa’s breeding bird community has experienced significant changes in the 20+ years since the first atlas. The individual species accounts provide considerable detail on these changes on a species by species basis. Some of the patterns encompass groups of birds and are worth highlighting here by mentioning some successes.
Wetland birds showed mixed patterns despite the increased wetland restoration efforts in the Des Moines Lobe region. Canada Goose solidified its breeding distribution statewide while Hooded Merganser continues to increase away from eastern Iowa and the wetlands of north-central and northwestern Iowa. Great Blue Heron was also detected more frequently with colonies now occurring statewide. Among the secretive marsh birds, Pied-billed Grebe, both bitterns, and Virginia Rail increased and are now more widely distributed on wetlands in the Des Moines Lobe. Forster’s Tern may have disappeared as a breeding bird, although Black Tern still persists in several locales. Marsh passerines like Marsh Wren, Swamp Sparrow, and Great-tailed Grackle all increased; the Yellow-headed Blackbird may have contracted its range to the Des Moines Lobe.
Among grassland birds both Sedge Wren and Henslow’s Sparrow saw huge increases as a result of grassland restoration efforts. Bobolink showed a similar pattern, especially in northern Iowa.
Among forest birds, the Red-shouldered Hawk and Pileated Woodpecker showed significant westward expansions, especially into south-central Iowa. Wood Thrush consolidated its breeding range, mainly in eastern and central Iowa. The southeastern warblers were mostly unchanged, except Kentucky Warbler, which increased in south-central Iowa. Among the nonnative species, Eurasian Collared-Dove is now widespread statewide whereas Eurasian Tree Sparrow has solidified its southeastern Iowa range; neither species was reported during the first atlas effort.