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Is it possible to do some accounting for imperfect detection within only one temporal visit? For example, an entomologist may have only a few hours to visit each of several small volcanic islands in the Aleutians, during which time he wishes to collect as many species as possible. He decides to take ten non-overlapping sweep net samples on each island, all standardized by time and area to the best of his ability. He brings the vials back to his lab and identifies the species in every sample, yielding a vector of ten presence/absence observations for each species on each island.

Can occupancy methods be applied to such data to estimate occupancy and detection probability for these species over this set of islands? In this case the definition of the "season" is temporally very short; the "revisits" are spatially separated, not separated in time. Of course the parameter estimates of occupancy and detection would not be applicable outside of the short temporal window in which the collector worked on the islands, but could it be valid within this time?

Matthew,

Under certain circumstances it is possible to estimate detection with only a single visit. Subhash Lele at the University of Alberta has been working on such methods and has several papers in the works and software for doing the estimation. In short, a critical requirement is that there must be appropriate covariates that influence detection and occupancy (i.e., detection and occupancy cannot be constant), and the there must be at least some covariates that influence either detection or occupancy, but not both. And, it is best to have many sites and plenty of variation in the covariates. Subhash says feel free to contact him (slele@ualberta.ca) for papers and software if you would like to pursue this route further.

Glenn