by Robert McFarlane, Houston Bird Survey Coordinator
With three summer (June) and three winter (January) Houston Bird Surveys now completed, mapping the survey results is providing ecological clues regarding urban birds and their more reticent rural counterparts. Four thrushes have been reported in our surveys.
American Robins are a common winter migrant found nearly everywhere in Harris County, penetrating deep into the inner city (the blue and green squares on the map). These birds are the Eastern American Robin, Turdus migratorius migratorius. Once they have departed for their northern breeding grounds, robins become rather uncommon. Left behind is the resident subspecies, the Southern American Robin, Turdus migratorius achrusterus, our nesting robin. These birds have a more restricted distribution in Harris County (the red and green squares on the map). They are found inside of Loop 610, west and southwest of downtown, stretching just past the Galleria area. Another cluster is found in the northwest, beyond Beltway 8. They appear to require a particular habitat that is not associated with a rural-suburban-urban gradient.
Eastern Bluebirds are uncommon but widespread in Harris County in both summer and winter. The map clearly reveals that they do not penetrate inside of Beltway 8. Some habitat requisite is clearly missing in the urbanized area.
The Wood Thrush is a rare nesting species, appearing only on the Hewlett-Packard Campus and Jesse Jones Park in summer, and the Houston Arboretum and one point southeast beyond Beltway 8 in winter. This species requires a relatively large patch of woodlands for nesting. It formerly nested on the 17 acre Edith Moore Sanctuary but it has not been seen there for the past three summers. Species can go extinct in small patches of habitat. How long will it take for a venturesome juvenile to rediscover the sanctuary?
The Hermit Thrush is a common (?) winter migrant that has been found inside Beltway 8 and Loop 610. It will apparently accept woodland understory habitat wherever it finds it.
