The Texas Breeding Bird Atlas Project was modeled after the breeding bird atlases which began in England in 1968 and which were later conducted in Europe, Canada, New Zealand, and a number of states and counties in the United States. The TBBA Project spanned 5 breeding seasons (1 March 1987 -29 February 1992). It was a cooperative effort of Texas A&M University (Dept. of Wildlife and Fisheries Sciences), local Audubon Societies, conservation groups, and individuals. Over 200 volunteers gathered data on the breeding behaviors of over 350 species of birds during the TBBA Project.
The state’s large size (267, 339 sq. miles) required that the size of the atlasing unit be relatively large. The atlasing unit chosen was the USGS 7.5-minute quadrangle. Each quadrangle is 1/64th of a latilong (a square of one degree of latitude by one degree of longitude). Texas spans 12 degrees of latitude and 14 degrees of longitude and contains over 5,000 quadrangles. Data were gathered from at least one out of every four quadrangles. In order to produce a map with discrete data points, the mapping unit was a block of 4 quadrangles (or a square 15-minutes on a side). Each data point on a TBBA range map represents at least one, but more likely several, record(s) for that 4-quadrangle block.
A bird was recorded as a Possible, Probable or Confirmed breeder depending on the evidence observed. Possible evidence included “species observed in suitable habitat during the breeding season” and “singing male present in suitable habitat during the breeding season”. Probable evidence of breeding included “multiple singing males in one quadrangle on one visit”, “pair observed”, “territory maintained”, “courtship behavior or copulation”, “visiting probable nest site”, and “agitated behavior or anxiety calls from adult birds”. The most certain category of evidence, Confirmed, required that the observer see “nest building”, “distraction displays”, “an occupied nest or a recently used nest identifiable to species”, “adults carrying food or fecal sacs”, “nests with eggs or nests with young” ,”recently fledged young” or to note “physiological evidence of breeding on a bird in hand”.
Approximately 92,000 records were collected and entered into the database. By 1995, preliminary maps had been generated from these records. These maps were made available to researchers investigating Texas birds and to individuals wishing to serve as authors of the species accounts. Authors were found for more than half of the species and artwork was donated to illustrate almost all of the species. But the rapid explosion of information technology and the World Wide Web made traditional publication of the maps and species accounts less and less satisfactory. Thus the decision was made to produce a website for the Texas Breeding Bird Atlas as a means to disseminate the range maps and accompanying texts. All of the species found to show evidence of breeding have been mapped and the maps are available here. Just click on Range Maps. Written accounts (and artwork) will be placed on the website on an account by account basis as soon as the permissions have been secured.