The Wilson Journal of Ornithology 124(3 ):572-580. 2012 
THE COMPOSITION OF MIXED-SPECIES BIRD FLOCKS IN 
ALTO QUINDIO, COLOMBIA 
ENRIQUE ARBELAEZ-CORTES 1 -’ AND OSCAR H. MARIN-GOMEZ' 
ABSTRACT.—Mixed-species bird nocks are a prevalent characteristic of Andean avian communities. We describe the 
species composition of mixed-species bird flocks observed in a high mountain zone (3.000 to 3.450 m) of Quindio. central 
Andes Colombia. The total number of species observed in mixed-spccies Hocks was 42. and the mean number of species 
anc me ividuals per flock were 5.1 and I 1.5. respectively. Flock species composition was similar along the elevation 
gradient studied. Our observations suggest that five species (Margaromis sc/uamiger. Iridisomis rufivertex. Coniwstrm 
S'"',/- Stictopterus. and Difossa cyanca) could be nuclear species in the flocks. Received II August 
2011. Accepted 7 February 2012. 
Mixed-species bird flocks are heterospecific 
groups of individuals traveling and feeding togeth¬ 
er, and represent a prevalent characteristic of 
practically every terrestrial habitat in the tropics 
(Moynihan 1962, Powell 1985). The cohesion 
within any flock seems to result front attractions 
among their participants and not from the presence 
of clumped food resources (Moynihan 1962, Morse 
1977, Powell 1985). There are two general 
hypotheses to explain why birds may benefit from 
multispecies flocking. One is related to enhanced 
foraging and the other with reduction in predation 
pressure (Morse 1977. Jullien and Clobert 20(X), 
Sridhar et al. 2009). Species that participate in 
mixed-species bird flocks have been divided as 
nuclear or leaders in flocks and satellites or 
followers according to their role in cohesion of 
flocks and their relative position within them 
(Moynihan 1979, Powell 1985). Species with 
cohesive roles in mixed-species bird flocks could 
be niche constructors that are creating a complex 
social environment that shape their own ecology 
and that of other species (Harrison and Whitehouse 
2011 ). 
The Andes is a region with some of the most 
diverse and threatened bird faunas worldwide 
(Fjeldsa and Krabbe 1990), and mixed-species bird 
flocks represent a biologically important feature of 
their avian communities. These Andean flocks 
have large numbers of participating taxa. a high 
1 Programa de Lieenciaiura en Biologia y Kducacibi 
Ambiental, Facultad de Edueacion, Universidad del Quin 
dio. Armenia, Quindio. Carrera 15. Calle 12 N. Colombia 
Cun-en. address: Museo de Zoolog,a. Dcpartamcn.o d, 
Biologia Evolutiva, Faculiad de Ciencias and Posgrado ei 
Ciencias Biologicas, Universidad Nacional Autdnoma di 
Mexico. Mexico DC. Ciudad Universitaria 04510. Mexico 
Corresponding author; 
e-mail; enriquearbelaez@gmail.com 
frequency of occurrence, and usually contain 
Managers that seem to be involved in their overall 
cohesion (Moynihan 1979. Remsen 1985. Poulsen 
1996, Bohorquez 2003. Arbelaez-Cortes et al. 
201 la). I he bird species richness of the Andes is 
associated with many species occupying onh a 
narrow elevation band, promoting a dense vertical 
segregation of different species on their mountain¬ 
sides (Newton 2003). The patterns of bird com¬ 
munity changes along elevation gradients in the 
Andes have been studied (e.g., Terborgh 1977). but 
it has not been tested whether there are also 
changes in composition of mixed-species bird 
flocks. Switches in species with cohesive roles in 
mixed-species bird flocks at different elevations 
have been documented in New Guinea (Diamond 
1987). Our objectives are to: (I) describe the 
composition of mixed-species bird flocks in a high 
mountain zone of the central Andes of Colombia. 
(2) compare species composition along an eleva¬ 
tion gradient (3,000 to 3.450 m). and (3) focus on 
identifying species that could have the role of 
nuclear species important in cohesion of flocks. 
METHODS 
Study Area .—The area studied was in the Alto 
Quindio zone (Paynter 1997) in Salento municipality. 
Quindio Department, on the western slope of the 
central Andes of Colombia. The observations were 
made along an elevation gradient (04 37' 40” N. 75 
27' 04" W to 04 37' 13" N. 75 25' 19” W; 3,000- 
3,450 m: Fig. I) including both cloud forest and 
paramo vegetation (Arbelaez-Cortes et al. 201 lb). 
We visited the zone four times during September- 
October 2005 and April 2007 when conducting 
observations (82 hrs) above Estrella de Agua. The 
Paramo de Frontino and El Mirador-Estrella de Agua 
were explored by OHM-G in January 2006 (10 hrs) 
and April 2007 (29 hrs), respectively. 
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