. Bonner zoologische Monographien. Zoology. JAHN. BIRD COMMUNITIES OF THE ECUADORIAN CHOCO dition, they should have been detected in less samples than core territories of the same species. Once the number of core and peripheral territo- ries is known, it has to be determined how many of them were recorded during 'valid' samples (see above). Subsequently, the factor v by which the average DTD |l, has to be increased in order to ob- tain an estimate for the effective DTD might be calculated as follows:. with T representing all territorial species considered in the analysis, t, the total number o
. Bonner zoologische Monographien. Zoology. JAHN. BIRD COMMUNITIES OF THE ECUADORIAN CHOCO dition, they should have been detected in less samples than core territories of the same species. Once the number of core and peripheral territo- ries is known, it has to be determined how many of them were recorded during 'valid' samples (see above). Subsequently, the factor v by which the average DTD |l, has to be increased in order to ob- tain an estimate for the effective DTD might be calculated as follows:. with T representing all territorial species considered in the analysis, t, the total number of central and marginal territories found for species i, and ct the number of core territories of species i detected during Valid1 samples. The factor v represents an average value for all territorial species sharing an equal number of valid samples and should be smaller for nocturnal and crepuscular species than for diurnal taxa. Potential problems with the applicability of this formula may arise from the enormous intraspecific and interspecific differences in the detectability of territorial breeding birds, making an unbiased dif- ferentiation between core and peripheral territories difficult. Once the factor v has been determined, estimates for the effective DTD fa can be derived: where u; is the average DTD of species i. Sub- sequently, the effective 'detection areas' (DAs) should be calculated using the following equation: Ä, = (2Lp,/) + (jt [ij) where A; is the estimated effective detection area of species i, and L the transect length. Deviating from the method used for the calculation of the population data for transects MNT1 and MNT2, I also add here the area surveyed beyond the two transect ends, which corresponds to a circle with the radius ji,. This should be done only when the positions of the birds were accurately mapped also at the transect ends, , when the improved transect-mapping form was employed (p. 104, Guidelines for an optimized transect-mapping protoc
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