Post-fledging Dispersal of Grasshopper Sparrows (ammodramus Savannarum) on a Restored Grassland in Maryland

—Little is known about the post-fledging period in most bird species, and almost nothing has been reported for the family Emberizidae, including New World sparrows. We report here, for the first time, the sizes (wing length and body weight) of, and the distances traveled by fledgling Grasshopper Sparrows within their hatch summer in a restored Atlantic Coastal grassland in Maryland. In the years 2002–2009, we recaptured 24.3% of the 799 banded nestlings in the grasslands at least once within their hatch year. Body weight was not correlated with wing length, wing length did not change with time of recapture, and the average fledgling gained weight by 14% in 100 days. Smaller than average birds were missing from late summer recaptures. As expected, the distance traveled increased significantly with time, but the average fledgling was recaptured 346 m from its nest. The average time of recapture was 33 days after fledging; the youngest recapture was 5 days after fledging and it dispersed a net 580 m from its nest; the longest and fastest distance recorded was 1,615 m from the natal nest in no more than 20 days; the longest recorded retention was 97 days by a local that moved a net distance of 753 m. We conclude that most fledglings in this population of Grasshopper Sparrows remain within their natal habitat for most of the months prior to their pre-formative molt, and that at least 1:4 of them survive at remarkably high rates. Received 13 July 2012. Accepted 13 November 2012.