Article: Daily variation in activity and flock size of two parakeet species from southeastern Brazil.

Psittacids are wide-ranging birds usually occurring in large flocks, making direct density estimates of parrots difficult. Researchers often are obliged to rely on indirect methods to estimate their abundances (see Terborgh et al. 1990, Pizo et al. 1995). These estimates are based on the number of flocks contacted in a given period (average encounter rate) and on the mean flock size of the species considered. However, both measures can vary on a daily basis (Blake 1992, Cannon 1984, Chapman et al. 1989), implying that parrot counts should be concentrated in a given period of the day to save time and to ensure a more realistic estimate (Blake 1992). Some attempts have been ...

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