Data from: Hide and seek in vegetation: time-to-detection is an efficient design for estimating detectability and occurrence

1. Ecology and conservation require reliable data on the occurrence of
animals and plants. A major source of bias is imperfect detection, which,
however, can be corrected for by estimation of detectability. In
traditional occupancy models, this requires repeat or multi-observer
surveys. Recently, time-to-detection models have been developed as a
cost-effective alternative, which requires no repeat surveys and hence
costs could be halved. 2. We compared the efficiency and reliability of
time-to-detection and traditional occupancy models under varying survey
effort. Two observers independently searched for 17 plant species in 44
100 m2 Swiss grassland quadrats and recorded the time-to-detection for
each species, enabling detectability to be estimated with both
time-to-detection and traditional occupancy models. In addition, we gauged
the relative influence on detectability of species, observer, plant height
and two measures of abundance (cover and frequency). 3.Estimates of
detectability and occupancy under both models were very similar. Rare
species were more likely to be overlooked; detectability was strongly
affected by abundance. As a measure of abundance, frequency outperformed
cover in its predictive power. The two observers differed significantly in
their detection ability. 4. Time-to-detection models were as accurate as
traditional occupancy models, but their data easier to obtain; thus they
provide a cost-effective alternative to traditional occupancy models for
detection-corrected estimation of occurrence.