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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123, No. 3, September 2011 
longer at the site to accomplish a long overwater 
flight. If a direct overwater route is followed from 
Los Tuxtlas by any of our study species, two 
possible destinations are Galveston, Texas and 
Mobile. Alabama, which are each 1,150 km from 
the Sierra de Los Tuxtlas. Our calculations, based 
on Tucker (1974) and Nisbel et al. (1963), 
indicate that individuals of the study species 
varied in the distances they are capable of flying 
from the site. For no taxa did the average 
individual carry sufficient fuel reserves for a 
single trans-gulf flight (Tables 7, 8: Fig. 4). No 
greater proportion of the populations of trans-gulf 
migrants was capable of making such a flight than 
taxa with coastal or dual migration strategies 
(Table 8). This provides strong inference that 
birds were generally not crossing the Gulf of 
Mexico directly from the Isthmus of Tehuantepec 
on the night following their capture, and that this 
stopover site is used more for short-distance 
movements than as a staging site for long 
movements (Warnock 2010). These estimates 
assume calm wind conditions across the Gulf of 
Mexico. The proportion of individuals capable of 
the flight might increase substantially with a tail 
wind. 
TABLE 8. Number of sampled individuals and 
estimated proportion of the population with sufficient fuel 
to fly 1,150 km in still air from the Sierra de Los Tuxtlas 
Mexico to Galveston. Texas using fat-free mass < 1). (from 
Odum in Dunning 1993). and (2) from zero fat score 
individuals as a base. 
* of individuals t ot popikw 
Species I 2 1 
Empidonax spp. 
NA 
0 
NA 
0.0 
Gray-cheeked Thrush 
2 
2 
3.5 
35 
Swainson's Thrush 
35 
18 
11.0 
5.7 
Wood Thrush 
3 
3 
2.6 
2.6 
Gray Catbird 
0 
0 
0.0 
0.0 
Magnolia Warbler 
2 
1 
5.1 
2.6 
Kentucky Warbler 
12 
7 
9.0 
5.3 
Hooded Warbler* 
23 
0 
13.5 
0.0 
Worm-eating Warbler 
12 
7 
15.4 
9.0 
Yellow-breasted Chat 
NA 
0 
NA 
0.0 
Ovenbird 
2 
0 
2.9 
0.0 
Painted Bunting 
NA 
0 
NA 
0.0 
Indigo Bunting 
13 
1 
8.3 
0.6 
The dramutic difference between the two methods may be a result of the 
substantial difference between the average fat-free masses of the two techniques 
in a relatively small species (1.32 g). 
