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Vol. 49 No. 3, 2010
Effective Point-Count Duration for Estimating Bird Species’ Richness in Chilean Forest
Pablo M. Vergara1,*, Jaime E. Jiménez2, and Roberto P. Schlatter3
1Departamento de Ingeniería Geográfica, Universidad de Santiago de Chile, Av. Lib. B. O’Higgins 3363, Santiago, Chile
2Laboratorio de Vida Silvestre, Universidad de Los Lagos, Casilla 933, Osorno, Chile
3Instituto de Zoología, Facultad de Ciencias, Universidad Austral de Chile Casilla 567, Hotel Isla Teja, Valdivia, Chil
Pablo M. Vergara, Jaime E. Jiménez, and Roberto P. Schlatte (2010)
When point counts are used to assess species richness or diversity,
optimizing the allocation of sampling effort requires that the
effective point-count duration be determined that optimizes the species
detection rate at each point. In this study, we used species
accumulation functions to estimate the effective point-count duration
in 6 different Chilean forests. An effective point-count duration
was dependent upon forest habitat, the type of accumulation function,
and travel time. The effective count durations predicted by 2
different species accumulation functions, the linear dependence and
Clench models, increased with increasing travel time. For short
travel times (≤ 10 min), effective count durations were ≤ 5 min and
slightly shorter than count durations required to reach 80% of the
function asymptote. For long travel times (20-30 min), effective
count durations were about 7 min, but shorter than count durations
required to reach 90% of the function asymptote. These results
show that for travel times of 5 min, the use of effective count
durations can result in 50% more points. Effective count
durations are suggested when a survey is focused on assessing species
richness and the presence of common or conspicuous species.
Key words: Bird richness, Chilean forests, Effective count duration, Point count.
*Correspondence: Tel: 56-2-7182227. E-mail:pablo.vergara@usach.cl
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