Table 5.—Maximum Nightly Densities at Stations with More Than One Night of Observation
| Observation Station | March | April | May |
| Mexico | |||
| Tamps.: Tampico | 5,500 | 63,600 | |
| Yuc.: Progreso | 31,600 | ||
| United States | |||
| Fla.: Winter Park | 6,200 | ||
| Ga.: Athens | 2,600 | ||
| Thomasville | 3,900 | ||
| Iowa: Ottumwa | 15,300 | 54,600 | |
| Kans.: Lawrence | 51,600 | 5,400 | |
| Ky.: Louisville | 17,000 | 8,400 | |
| Murray | 16,400 | ||
| La.: Baton Rouge | 6,200 | ||
| Mansfield | 4,900 | 5,200 | |
| Oak Grove | 13,600 | 5,800 | |
| Miss.: Rosedale | 6,800 | 5,800 | |
| Mo.: Columbia | 1,400 | 10,300 | |
| Okla.: Stillwater | 2,700 | 1,900 | 3,000 |
| Tenn.: Knoxville | 15,200 | 9,000 | |
| Memphis | 3,600 | 7,900 | 7,000 |
| Tex.: College Station | 6,200 | 13,200 |
Fig. 34. Stations at which telescopic observations were made in 1948.
Gulf Migration: A Review of the Problem
In view of the controversy in recent years pertaining to migration routes in the region of the Gulf of Mexico (Williams, 1945 and 1947; Lowery, 1945 and 1946), the bearing of the new data on the problem is of especial interest. While recent investigations have lent further support to many of the ideas expressed in my previous papers on the subject, they have suggested alternative explanations in the case of others. In the three years that have elapsed since my last paper dealing with Gulf migration, some confusion seems to have arisen regarding the concepts therein set forth. Therefore, I shall briefly re-state them.
It was my opinion that evidence then available proved conclusively that birds traverse the Gulf frequently and intentionally; that the same evidence suggested trans-Gulf flights of sufficient magnitude to come within the meaning of migration; that great numbers of birds move overland around the eastern and western edges of the Gulf; that it was too early to say whether the coastal or trans-Gulf route was the more important, but that enough birds cross the water from Yucatán to account for transient migration in the extreme lower Mississippi Valley; and, that, in fair weather, most trans-Gulf migrants continue on inland for some distance before coming to land, creating an area of "hiatus" that is usually devoid of transient species. I tried to make it emphatically clear that I realized that many birds come into Texas from Mexico overland, that I did not think the hordes of migrants normally seen on the Texas coast in spring were by any means all trans-Gulf migrants. I stated (1946: 206): "Proving that birds migrate in numbers across the Gulf does not prove that others do not make the journey by the coastal routes. But that is exactly the point. No one has ever pretended that it does." Although some ornithologists seem to have gained the impression that I endorse only the trans-Gulf route, this is far from the truth. I have long held that the migrations overland through eastern Mexico and southern Texas on one hand, and the over-water flights on the other, are each part of the broad movement of transients northward into the United States. There are three avenues of approach by which birds making up the tremendous concentrations on the Texas coast may have reached there: by a continental pathway from a wintering ground in eastern and southern Mexico; by the over-water route from Yucatán and points to the southward; and, finally, by an overland route from Central America via the western edge of the Gulf. As a result of Louisiana State University's four-year study of the avifauna in eastern Mexico, I know that migrants reach Texas from the first source. As a consequence of my studies in Yucatán of nocturnal flight densities and their directional trends, I strongly believe that migrants reach Texas from this second source. As for the third source, I have never expressed an opinion. I am not prepared to do so now, for the reason that today, as three years ago, there is no dependable evidence on which to base a judgment one way or another.
Western Gulf Area