.--Studies of migrants in Ontario and of specimens from throughout the range show that adult (AHY = after hatching year) Least Flycatchers (Empidonax minimus) migrate south an average of about 38 days in advance of the immatures (HY -- hatching year). Median "autumn" migration dates for AHY Least Flycatchers are 22July (with the middle 90% of the records spanning the period 11 July- 13 August) at Long Point, Ontario, and 3 August for spec- imens collected in the southern United States. Arrivals of AHY Least Flycatchers in Mexico and Central America start in early and mid-August, respectively. The corresponding dates for HY Least Flycatchers are 29 August (90% from 17 August to 13 September) at Long Point, 9 September in the southern U.S., and mid-September for arrivals in Mexico and Central America (Hussell, J. Field Ornithol. 51:65-71, 1980; 52:97-111, 1981; 53:223- 234, 1982). These data indicate a minimum migration time between Ontario and Mexico of about 25 days for both age classes. A recent recovery in Mexico of a Least Flycatcher banded in Ontario is consistent with this view of the autumn migration of the species. The bird was banded by N. Garber at Long Point Bird Observatory (LPBO), Ontario, 42ø30'N, 80ø00'W (SE corner of 10' block containing the site), on 17 August 1982. It was aged HY on the basis of its incom- pletely pneumatized skull and broad buff wing bars; its wing chord was 62 mm, and it weighed 11.9 g. Sex was unknown because the wing chord length was in the overlap range. On this date it would be among the earliest 5% of HY migrants at Long Point (Hussell 1981). The bird was found 32 days later, on 18 September 1982, at Las Rosas, Chiapas, Mexico (approximately 16ø20'N, 92'20'W). The recovery date is within the week following the first appearance of HYs in Mexico: the earliest HY specimen in Mexico was taken on 11 September (Hussell 1980). The recovery locality is 3135 km S 24.9øW of Long Point, which indicates a minimum average daily flight of 98 km. Distance travelled and migration speed increase to at least 3700 km and 116 km/day, however, if a westward route around the Gulf of Mexico was followed, as appears to be indicated by specimen records. Because banding and recovery dates may not represent departvre and arrival dates, migration speed may have been even faster than this. Only two other Least Flycatchers have been recovered south of 35øN and only one of those was either banded or recovered during autumn migration. The latter was an HY bird banded by D. Bordner on 7 September 1966 at Island Beach, New Jersey, 39'50'N, 74'00W, and shot at Filomeno Mata, Veracruz, Mexico, on an unknown date in December 1966 (Foy, Bird-Banding 47:214-230, 1976). Thanks to R. B. H. Smith, LPBO, for providing data on the recovery reported here, to K. Klimkiewicz, Bird Banding Laboratory, U.S. Fish and Wildlife Service for confir- mation of the recovery record, and to C. Hyslop, Migratory Birds Branch, Canadian Wildlife Service for information on other Least Flycatcher recoveries. This note is a contribution of the Long Point Bird Observatory and is Ontario Ministry of Natural Resources, Wildlife Research Section Contribution No. 83-10.--D^wD J. T. HUSSELL, Wildlife Research Section, Ontario Ministry of Natural Resources, P.O. Box 50, Maple, Ontario LOJ IEO, Canada. Received 30 Sept. 1983; accepted 27 Oct. 1983.