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Abstract

The Henslow's Sparrow (Ammodramus henslowii) is a Maryland threatened species. It has gradually disappeared from Maryland except for the westernmost counties, where it uses the newly formed habitat of reclaimed strip mines. In 19891 discovered a small colony of these sparrows. I began to monitor that site, two other colonies, and to actively search for new colonies. From these observations I hypothesized that Henslow's Sparrows return to previous nesting sites, or nearby suitable sites, until vegetation becomes unfit for nesting purposes. To test this hypothesis I began a study with two objectives: (1) field visits to monitor known breeding populations and search for new colonies, and (2) a banding study to determine whether Henslow's Sparrows return to previous nesting sites or natal areas. I have discovered ten new colonies and monitored two previously occupied sites. Of these twelve sites, three colonies have disappeared due to succession and one was lost to pasturing of cattle. As of August 1998, eight sites were still occupied by breeding Henslow's Sparrows. I banded 87 Henslow's Sparrows from 1994 through 1997. Thirty-seven of these were adult males. None of the juvenile birds banded were subsequently captured. Of the seven breeding males banded in 1995, one adult male was recaptured in 1996. Four adult males banded in prior years were recaptured in 1997. This was the first documentation of breeding Henslow's Sparrows returning to their previous nesting site (Skipper 1998).

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