Abstract
Two pairs of species (Tyrannus verticalis and T. vociferans, Sayornis nigricans and S. saya) were selected for a study of competitive relationships among sympatric species of birds in the Trans-Pecos region of Texas. Field studies were conducted during June-August 1969 and May-August 1970, with supplemental observations in November 1970 and May 1971. The objective of the study was to learn how the resources of the area were divided among the four species. Specifically the geographical and ecological distribution, nesting habits, food composition and feeding behavior were to be determined for each species. Interactions involving these species were also recorded. While the kingbirds (Tyrannus) studied were geographically sympatric, there was considerable ecological segregation. T. verticalis occupied elevations less than 4000 feet and vociferans predominated above 4000 feet. Associated with elevational differences were those of habitat type. The desert shrub and farmland habitat types were typically occupied by verticalis, whereas vociferans was more abundant in the pine-oak-juniper, grassland and riparian habitat types. ...
Ohlendorf, Harry Max (1971). Competitive relationships among selected species of flycatchers (Tyrannidae) in Trans-Pecos Texas. Doctoral dissertation, Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -172559.