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Mixed-species flocks of birds have been studied for more than a century, but investigation efforts are historically unbalanced towards certain types of habitats, such as woodlands and lowland forests. Here we provide a first glance of bird flocks' patterns across different gradients in recent studies conducted within the Neotropics. We summarize a symposium where a series of independent studies that approached the topic, some of them making use of techniques that were seldom applied in previous decades in Neotropical systems. We discuss bird flocks' patterns across a latitudinal gradient, social network patterns in bird flocks' across elevational gradients in local and regional scale, and, finally, patterns of flocking response to different levels of human disturbance. Altogether, these studies offer a larger and diverse panorama of possible patterns of response and diversity of mixed-species flocks of birds in the Neotropical region, and provide a rich ground where future studies with bird flocks in the Neotropics may rely on.

The Alder (Empidonax alnorum) and Willow (E. trailli) flycatchers are cryptic species, and their distribution outside the breeding season is poorly known, owing mostly to identification difficulties. Our new records suggest that large numbers of Alder Flycatchers overwinter in rivers crossing the Chaco region and in the foothill forests of the Yungas of Argentina, significantly increasing their southern wintering range. Records in northern Argentina span 3 November to 23 March. Key habitat for overwintering Alder Flycatchers in Argentina included stands of palo bobo (Tessaria integrifolia) along the Rio Bermejo and tributaries, either in association with sparse shrubs of chilca (Baccharis salicifolia) or more rarely with canebrake (Gynerium sagittatum). Other habitats used were old shrubby ‘madrejones' with Tessaria scrub and sacha cafe (Sesbania virgata), very dense Baccharis salicifolia scrub next to flowing creeks in foothill Yungas and dry Chaco, and riparian forests dominated by palo flojo (...