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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123, No. 3, September 2011 
FIG. 1. Mexico and Central America indicating location of field site in the Sierra de Los Tuxtlas, Mexico. 
it is now a mosaic with a high percentage of 
pasture, fence rows, and isolated trees (Dirzo and 
Garcia 1992). Andrle (1964) estimated that 50% 
of the region was forested in 1962; by 1986 15% 
of forests remained (Winker et al. 1990, Dirzo and 
Garcia 1992), and in 1994 only 7-10% of the 
region was forested (Winker 1997). The remain¬ 
ing forest is primarily in the highlands and is 
scarce below 500 m above sea level (Rappole et 
al. 1994). 
Our Field site is on the southern edge of the 
700-ha Estacion de Biologia Los Tuxtlas (18 34' 
30" N, 95 04’ 20" W) operated by the Instituto de 
Biologia at the Universidad Nacional Autonoma 
de Mexico. The field station protects one of the 
few remaining large tracts of lowland evergreen 
forest in the region. The climate is hot and wet 
with a mean annual temperature of 25 C (Soto 
and Gama 1997). Annual precipitation is 4.5- 
4.9 m with a short drier season from March to 
May (Soto and Gama 1997). Our netting site was 
on the edge of the Estacion in primary and 
second-growth forests -150 m above sea level. 
The exact netting site was used previously by 
Winker (1995a), and we placed nets as precisely 
as possible in the same net lanes. Canopy heights 
in the primary forest ranged from 30 to 35 m 
(Ibarra-Manriquez et al. 1997). Second growth 
areas had variable canopy heights from 3 to 20 m 
Data Collection. —Thirty-six standard nylon 
mist nets (12 X 2.6 m, 30 and 36 mm mesh) 
were placed 30 m apart in primary and second- 
growth forest and operated (weather permitting) 
during daylight hours. The outer rows of nets 
encompassed an area of -1.8 ha. Effort was 
concentrated in the morning and evening. Nets 
were open for 8,395 net hrs between 21 February 
and 27 April 2003 and for 2,312 net hrs from 5 to 
29 April 2004. We placed captured birds in light 
cloth bags and brought them to a central 
processing area. Birds were banded, wing chord 
and tail lengths were measured to the nearest 
0.1 mm using vernier calipers, and birds were 
weighed to the nearest 0.1 g using Pesola spring 
scales. Fat scores were assigned following Helms 
and Drury (1960). 
Data Analyses. —T-tests were used to examine 
gross differences in overall condition (mass/wing 
chord X 100) between years. We pooled data 
from both field seasons because only Hooded 
