survey design is essential to estimate population size reliably, especially for
endangered species. Dupont’s lark Chersophilus
duponti, one of the most endangered passerines in Europe, has been
monitored using diverse counting methods. This variation in the methods
employed may have a significant effect on the estimates of population sizes.
The present study compares four methodologies cited in the literature as having
been used for Dupont’s lark censuses: the Finnish line transect (25 m inner
belt width), line transect (500 m inner belt width, a specific application of
the transect method developed for the second national census of the species in
Spain), mapping and point counts methods. We also determined the adequate
number of visits needed to detect a reliable number of territories by the
mapping method and analysed the effect of census month on the number of males recorded in line transects. According to our results,
we consider that the mapping method, based on four visits, is the most adequate
methodology for monitoring the species. However, for surveys in large areas the
use of the line transect method during May and June may be more affordable. Although
census date did not have a significant effect on the number of males recorded
by line transect surveys, a larger number of males were indeed detected during
May and June. Thus, censuses carried out in March may lead to greater
underestimation of population sizes. Nonetheless, the best date for counting
Dupont’s Lark may differ for populations located at lower altitude. Point
counts and Finnish line transects should not be used for counting the species,
since both overestimate population sizes by about 35%, according to the mapping
method and line transect results.
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