Notes on Autumnal Trans-Gulf Migration of Birds

Abstract

Autumnal records of migrant land birds over the Gulf of Mexico have been reviewed by Lowery (Auk, 63, 1946:191-195) and more recently by Lowery and Newman (in press). Since there are actually far more records of land birds over the Gulf in spring than in fall, the following autumnal observations made aboard the Fish and Wildlife Service exploratory fishing vessel, the M/V may be of interest to students of bird migration. In the text that follows the figures in brackets refer to the positions of the Oregon indicated on the map, figure 1. On the afternoon of September 17, 1952, the Oregon was working at latitude 290 00' N., longitude 87' 55' W. [1], approximately 73 miles off the Alabama coast and 49 miles east by south of North Pass, Louisiana, the nearest land. At about 3: 10 p.m., a flight of twenty-two Common Nighthawks (Chordeiles minor) was observed heading south. The flight came near the vessel and one was shot for positive identification. The flight approached from astern and did not change course in passing the vessel. The nighthawks were flying from 20 to 30 feet above the water and drew abreast of the Oregon at a distance of 10 to 20 yards. Their air speed was not great and can be estimated at less than 30 miles per hour. The Oregon was traveling at 10 knots in the same direction as the birds and was quartering a southeast wind of 6 to 8 miles per hour. The flock did not change its course while under observation and disappeared in the south. The sky was partly cloudy but the visibility was good and the weather had been good on the preceding day. The same weather conditions prevailed about three hours later, 6:20 p.m., and about 27 nautical miles farther south at latitude 280 33', longitude 870 55' [2], when six nighthawks passed the Oregon, also headed south and flying at about the same height above the water.