Multi-year model with only a single survey each year

questions concerning analysis/theory using program PRESENCE

Multi-year model with only a single survey each year

Postby dbuhl » Thu Sep 19, 2019 10:05 pm


I have 4 years of data with only a single survey each year. I have both occupancy and abundance for each survey. I also have several covariates that are measured at each survey. Can I run a multi-season model with only one survey per season, and obtain estimates of occupancy, detection, extinction, and colonization?

Thank you.
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Re: Multi-year model with only a single survey each year

Postby jhines » Mon Sep 23, 2019 1:15 pm


With only 1 survey per season, it's impossible to estimate occupancy and survey-specific detection probabilities as you have more parameters than data. If you assume detection probability constant over surveys, then you can get estimates of occupancy/colonization/extinction and detection. This is a pretty strong assumption and if not true, could lead to biased estimates of occupancy/col/ext, and/or incorrect model effects on those parameters. A slightly better model would assume detection varies by a survey covariate like "effort" (or anything which might be related to detection). This is still a strong assumption which would require justification if used.

My point is that it's possible to do something with this type of data, but it has the potential to give very misleading results. Having replicate surveys each season eliminates the need to make those strong assumptions.

Jim H.
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