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THE WILSON JOURNAL OF ORNITHOLOGY • Vol 124. No. 3. September 2012 
TABLE 1. Distribution of fields, observation points, and observation time over five agroforestry systems in Tabasco. 
Mexico in 2008 and 2009. AA = animal agroforestry; AF = agroforest: LA = linear agroforestry; SA = sequential 
agroforestry: CT = crops under tree cover; min = minutes; * = transect count; all others - point counts. 
Rainy season 
Northern winds 
Dry season 
AD 
n fields 
n points 
Time (min) 
n fields 
n points 
Time (min) 
n fields 
n points 
Time Imin) 
Time (rain 
AA 
7 
9 
528 
7 
9 
540 
7 
9 
500 
1,600 
AF 
8 
8 
480 
8 
8 
480 
8 
8 
470 
1,462 
LA 
4 
4* 
325 
5 
5* 
311 
5 
5* 
338 
984 
SA 
4 
4 
238 
4 
4 
244 
4 
4 
240 
738 
CT 
7 
II 
666 
8 
12 
724 
7 
11 
658 
2.086 
All 
30 
36 
2,237 
32 
38 
2,299 
31 
37 
2.206 
6.870 
substantial rains. The dry season 
lasts from April 
with a fixed radius of 30 
m in all < 
classes of 
-- - --UWIIUMI IVIII|/VIUUIIV. 1.1 
(West et al. 1985). 
Tabasco had wide scale colonization and 
deforestation programs, and immigration in the 
second hall ot the 20th century. Farmers in 
deforested areas have established new agroforest¬ 
ry systems, which complement the traditional 
home gardens, cacao groves, and shifting cultiva¬ 
tion fields. Animal agroforestry is currently the 
most widely extended class of agroforestry 
systems. Agroforests, particularly home gardens, 
cover a small total area, but are the most frequent 
system and occur throughout the slate. Cacao 
groves, in the class of crops under tree cover, are 
irequent in selected areas. Shifting cultivation 
fields occur in the southern hills and mountains 
(Sanchez-Munguia 2000). 
Selection of Bird Monitoring Sites .—Selection 
of study sites was conducted in two stages. We 
traveled over primary and secondary roads in 
Tabasco, recorded the main characteristics of 500 
agroforestry fields selected at random, and 
assigned them to classes following Torquebiau 
(2000). We selected 32 fields, considering logis¬ 
tics, in which we placed 38 sampling points and 
transects, distributed over the agroforestry classes 
with the largest numbers of f ields and points in the 
most frequent classes, and smaller numbers in the 
sequential and linear classes (Table I). Spatial 
clustering of fields could not be avoided altogeth¬ 
er, but distance between fields was >2 km. and 
between points in the same field was >|00 m. 
Bird Monitoring and Groupings .—Bird counts 
were conducted in all three seasons: rainy season 
between 22 August and 27 October 2008, season 
of northern winds between 20 January and 24 
Feb.uaiy _009, and dry season between 30 March 
and 2 June 2009. We used the point-count method 
agroforestry systems, except for linear agroforest¬ 
ry systems where we used the linear transect 
method with a width of 30 m. We recorded all 
birds that used the system (foraging, perching 
etc.) during 30 min in the early morning and in 'he 
afternoon al each point. We listed birds recorded 
by family and species, and assigned them to 
foraging guilds, habitat preferences, and migrato¬ 
ry status following Howell and Webb (1995) 
and Hughes et al. (2002). We distinguished 13 
foraging guilds: scavengers, arboreal frugivores, 
granivores. bark-gleaning insectivores. foliage 
gleaning insectivores. arboreal insectivores/frugi- 
vores. terrestrial insectivores, sallying/sweeping 
insectivores, nectarivores/insectivores, omnivores, 
aquatics, piscivores, and raptors. Habitat prefer¬ 
ence categories were forest specialists, forest 
generalists (recorded most commonly in forest' 
and uncommonly in open areas and secoitdar) 
vegetation) following Howell and Webb (N^) 
and Hughes et al. (2002), open area specialists, 
and species occurring near water bodies. Migra¬ 
tory or resident status of species was also assign-’' 
based on the scientific literature. 
Data Treatment and Analysis.— We estimated 
Jacknife I total species richness using Estimate 
software (Colwell and Coddington 1994, Colv-eil 
2006) and calculated the efficiency of sampling 
by dividing die number of observed species b> 
estimated total species richness. We calculated 
dominance indices (Simpson), Shannon doers 1 : 
indices (H), Buzas and Gibson's evenness, and 
cquilability (Shannon diversity divided by in- 
logarithm of the number of taxa) for each point in 
each class of agroforestry systems in all sea* 1 t 
using PAST software (Hammer et al. 2001). Wo 
used ANOVA and Tukey’s HSD-tests when data 
were normally distributed (Shapiro-Wilks : tests' 
