Arbelaez-Cortes and Marin-Gomez • MIXED-SPECIES BIRD I-LOCKS 
579 
TABLE 2. Extended. 
B. monuma 
6 (0.967) 
2(0.151) 
1 (0.041) 
6 (0.286) 
3 (0.442) 
5 (0.604) 
2 (0.233) 
6(0.174) 
4(0.291) 
3 (0.459) 
H. superciliaris 
7 (0.747) 
8 (0.015) 
0 (0.007) 
2 ( 0 . 221 ) 
4 (0.47) 
5 (0.447) 
5 (0.37) 
4 (0.42) 
3 (0.504) 
1 (0.287) 
2 ( 0 . 66 ) 
H. venicalis 
7 (0.475) 
7 (0.034) 
2 (0.291) 
3 (0.574) 
5 (0.307) 
5 (0.307) 
5 (0.248) 
4 (0.334) 
3 (0.429) 
2 (0.673) 
3 (0.276) 
4 (0.059) 
M. slicmpterus 
7 (0.476) 
7 (0.034) 
3 (0.574) 
5 (0.371) 
2 (0.332) 
7 (0.008) 
1 (0.132) 
4 (0.335) 
6 (0.008) 
2 (0.674) 
3 (0.277) 
2 (0.549) 
2 (0.49) 
P. boissoneauti 
5 (0.621) 
4 (0.49) 
4 (0.328) 
3 (0.623) 
5 (0.098) 
4 (0.288) 
3 (0.537) 
1 (0.18) 
2 (0.64) 
2 (0.588) 
1 (0.461) 
2 (0.485) 
3 (0.139) 
1 (0.57) 
I). cyanea 
2 (0.077) 
4 (0.378) 
2 (0.474) 
5 (0.068) 
2 (0.516) 
3 (0.483) 
2 (0.048) 
1 (0.243) 
2 (0.606) 
2 (0.516) 
3 (0.163) 
2 (0.416) 
1 (0.635) 
4 (0.016) 
1 (0.687) 
U. slolznianni 
5 (0.3) 
3 (0.565) 
4 (0.152) 
0 (0.052) 
0 (0.062) 
2 (0.621) 
5 (0.020) 
0 (0.073) 
0 (0.138) 
0 (0.186) 
1 (0.608) 
0 (0.248) 
0 (0.285) 
0 (0.285) 
0 (0.326) 
0 (0.373) 
them: large intraspecific groups (mean number ol 
individuals per flock = 1.9 to 3.3). However, 
these attributes were not exclusive ol these five 
species. Thus, other species could also be nuclear 
in the study zone because we did not observe 
these five potential nuclear species in all flocks. 
This nuclear role is based mainly on qualitative 
data and a precise definition needs turlher 
quantitative or experimental approaches (e.g., 
Goodale and Kotagama 2005). We did not find 
differences in the composition of mixed-species 
bird flocks along the elevation gradient, but some 
of the potential nuclear species dittered between 
elevations bands. For example, the Golden- 
crowned Tanager was mainly observed in the 
higher elevation band while the Masked Flower- 
piercer was recorded principally in the lower 
band. These differences are related with changes 
in elevation and habitat where the species occur 
(Fjeldsa and Krabbe 1990). as has been docu¬ 
mented for mixed-species bird flocks in New 
Guinea (Diamond 1987). However, switches in 
those species with cohesive roles in mixed-species 
bird flocks along an elevational gradient deserve 
further attention. 
ACKNOWLEDGMENTS 
Universidad del Quindio (Viccrrectoria de Investigaciones i 
provided financial support for held work in ihe tirst slage ol 
this project. We especially acknowledge Oscar Baena-Tovar 
and J. C. Ospina-Gonzalez for help during some field tnps. A. 
G. Navarro-SigUenza. C. E. Braun, and two anonymous 
referees made valuable comments that improved this 
manuscript. EAC thanks CONACyT-Mexico for a graduate 
studies scholarship (# 210543) during writing of this paper. 
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