Preface
In 1986, the Missouri Department of Conservation commenced an ambitious statewide survey to determine the distribution of Missouri's breeding bird species-the Missouri Breeding Bird Atlas Project. The department's ornithologist, James D. Wilson, initiated the project and about 50 dedicated birders participated in the first year's effort. As word spread among the birding community, more people volunteered to be Atlasers, enough to survey 1207 breeding bird atlas blocks.
During the second year, the Department of Conservation hired Brad Jacobs, a 1986 block surveyor, and Jim and Brad worked together on the many tasks associated with data management, volunteer workshops, special survey weekends, newsletters and block surveys. The Atlas Project took much of the authors' time, including seven years of field work and four years of data analysis and writing. Sharon Hoerner skillfully handled volunteer communications and coordination, and the day-to-day tasks that kept this project on target.
This report would not have been possible without the help of more than 400 dedicated volunteer birders who contributed more than 21,000 hours to advance our understanding of Missouri birds. Their efforts have given us a benchmark set of data from which to compare future bird studies and to monitor changes in bird distribution. Other bird species information that was collected during the Atlas Project, including relative abundance, breeding season phenology and brood parasitism heightened our understanding of Missouri's birds.
The Department of Conservation is pleased to make the Missouri Breeding Bird Atlas available for scientists, land managers, students, birders and interested citizens.
Introduction
Figure 1. U.S. Geological Survey 7.6 Minute Quadrangles with Expanded Survey Blocks A-F
The Missouri Breeding Bird Atlas Project, conducted from 1986 through 1992, sought to document the status and distribution of the bird species that breed in Missouri. The primary goal was to develop a distributional map for each species that depicts as accurately as possible its true breeding range in the state. The resultant information was intended to: 1) provide baseline data against which future changes in the status and distribution of Missouri's breeding birds could be measured, 2) determine the location of rare species, 3) identify significant habitats and 4) develop a factual database to assist environmental planners in making wise decisions about resource use in Missouri. During the process of collecting the distributional and status information, data were also obtained on species' abundance, breeding phenology and Brown-headed Cowbird brood parasitism.
The Atlas Project relied on the cooperation and participation of 438 field surveyors (primarily volunteers), who recorded 21,577.7 hours collecting data during the seven-year period. Additional benefits of the project were the heightened awareness of Missouri's summer bird life and the cooperative spirit that developed among birders and scientists statewide. This project highlighted the value of volunteer-based bird population monitoring.
Methodology
Sampling Procedure
Data collection was conducted using a sampling process, established by the North American Ornithological Atlas Committee, wherein one survey area was designated within each of the 1,210 United States Geological Survey 7.5-minute quadrangles that encompass Missouri. Survey areas, termed blocks, were established by dividing each 7.5-minute quadrangle into sixths and then randomly selecting one of these sixths (fig. 1). Each block contains approximately 25 square kilometers. The random selection process ensured no habitat bias. Blocks bisected by the state's border were surveyed only if more than 50 percent of the block fell within Missouri. Of the 1,210 established blocks, 1,207 were actually surveyed. The 7.5-minute quadrangles and blocks are listed in Appendix A.
Figure 2a. Atlas Project Field Data Card
Block Assignments
Atlas surveyors, termed Atlasers, typically received their block assignments by contacting the Missouri Department of Conservation and designating a region that was convenient or that they believed had interesting bird potential. They were provided with a packet containing field cards (fig. 2a, 2b) that listed the assigned block's name and number, a topographic map and a county map detailing the block, a Missouri Breeding Bird Atlas Project Handbook and calling cards and a vehicle sign to inform landowners and passersby about the project. While most block assignments were given before the breeding season each year, some assignments were made as late as midsummer with the understanding that the survey of the block could continue in the following year. Blocks usually were assigned to one surveyor at a time, with reassignments made when an Atlaser was unable to complete a block.
Figure 2b. Atlas Project Field Data Card
Breeding Criteria and Codes
The North American Ornithological Atlas Committee's Standardized Breeding Code Criteria were used to classify species (fig. 3). Codes were arranged on the field card from less to greater certainty of breeding within three main categories: possible, probable and confirmed breeding. Possible and probable categories required observations that occurred within "safe dates," a period when migrants of that species are expected to be absent from Missouri. Within safe dates, occurrence in suitable habitat alone provided elementary evidence that the species was potentially breeding in the block. Safe dates established for each species were listed following the species' name on the field card. Confirmed observations were recorded on the field card regardless of safe dates.
| POSSIBLE CODES | BREEDING EVIDENCE |
|---|---|
| 0 | Species observed in block, but not in breeding habitat. (These are not mapped. Please see page 2 under Breeding Criteria and Codes.) |
| X | Species heard or seen in breeding habitat within safe dates. |
| PROBABLE CODES | BREEDING EVIDENCE |
|---|---|
| S | Seven singing males detected in one visit. |
| P | Pair observed in suitable breeding habitat within safe dates. |
| T | Territorial behavior or singing male present at same location, on at least two different days, a week or more apart. Territoriality can be presumed from defensive encounters between individuals of the same species, or by observing a male singing from a variety of perches within a small area. |
| C | Courtship or copulation observed. This includes displays, courtship feeding and birds mating. |
| N | Visiting probable nest site. Primarily applies to hole-nesters. This code applies when a bird is observed visiting the site repeatedly, but no further evidence is seen. |
| A | Agitated behavior or anxiety calls from adult. Parent birds respond to threats with distress calls or by attacking intruders. |
| Z | Nest building by wrens or excavation by woodpeckers. Both groups build dummy or roosting nests. |
| CONFIRMED CODES | BREEDING EVIDENCE |
|---|---|
| NB | Nest building (except wrens and woodpeckers) or adult carrying nesting material. |
| PE | Physiological evidence of breeding based on bird in the hand. |
| DD | Distraction display; including injury-feigning. |
| UN | Used nest found. |
| FL | Recently fledged young or downy young. This includes dependent young only. Young cowbirds begging for food confirm both the cowbird and the host species. |
| FS | Adult bird seen carrying fecal sac. |
| FY | Adult carrying food for young. |
| ON | Occupied nest presumed by activity of parents: entering nest holes and staying, parents exchanging incubation responsibility, etc. |
| NE | Nest with eggs or eggshells on ground. Cowbird eggs in nests confirm both the cowbird and the host species. |
| NY | Nest with young seen or heard. A cowbird chick in a nest confirms both the cowbird and the host species. |
Based on breeding evidence observed in the field, volunteers inserted the appropriate code in the possible, probable or confirmed column on a field card. The date associated with the highest level of breeding evidence was entered in the column following the code. Survey dates, times of day and number of hours spent during each visit were recorded. Comments on Brown-headed Cowbird brood parasitism or other observations were placed in the notes section.
Species recorded only by the "O" code under possible breeding were not included on the Atlas Project distribution maps. Because these species were not in breeding habitat, it was considered unlikely they were breeding in that block.
Asterisked Species
Unusual or difficult-to-distinguish species were asterisked on the field card, indicating that a completed verification form was required to document the sighting. Species recorded that were not printed on the field card also required a completed verification form.
Coverage Goals
The Missouri Breeding Bird Atlas Project sought to record evidence of breeding for the majority of species present within each block. A minimum standard of coverage was necessary in every block in order for Atlas Project maps to show meaningful patterns of distribution. Atlasers were instructed to search their block's area and habitat thoroughly enough to be reasonably certain that they had recorded most of the species expected to be nesting. Field tests and other atlas projects had indicated that 15 hours of field work was the optimal amount of time needed to record 75 percent of the species present in the block. Depending on habitat diversity, this level of coverage would typically record 50-70 species for the block. Atlasers sought to place 25 percent of the species in the possible breeding category, 50 percent in the probable category and at least 25 percent in the confirmed category. Once these approximate levels were reached, volunteers were encouraged to start a new block in the interest of spreading coverage evenly among the blocks.
The Missouri Breeding Bird Atlas Handbook instructed Atlasers to visit their assigned blocks in various months because bird species vary seasonally in ease of detection. Atlasers were encouraged to use June as the primary month for building a species list, and July and August as optimal months to record birds in the probable and confirmed categories. Figure 4 depicts the frequency of various breeding codes from April through August. The handbook recommended early morning and evening as the most productive periods but also asked Atlasers to visit their blocks at night to record nocturnal species. Hours spent per block are compiled in Appendix A and graphically illustrated in figure 5.
Block-Busting
Within the first two years of the Atlas Project, it became apparent that blocks in the vicinity of Kansas City, St. Joseph and St. Louis were being assigned more rapidly and receiving more complete coverage than blocks elsewhere in the state. To promote coverage in under-surveyed regions, special Atlasing events, termed "Block-Busting" weekends, were held in 1990, 1991 and 1992 during the height of the breeding season. Atlasers were invited to work together in these regions to accomplish at least cursory coverage of these blocks. Blocks covered by Block-Busting are noted in Appendix A.
