Estimates of Adult Survival, Capture Probability, and Recapture Probability: Evaluating and Validating Constant-effort Mist Netting

Nur, Nadav; Geupel, Geoffrey; Ballard, Grant

We evaluate the use of capture-recapture data gathered with constant-effort mist-netting to infer adult survival, comparing estimates obtained using the program SURGE with direct observations on color-banded individuals. In addition, we determined capture probability of breeding adults in relation to several factors such as distance from nest to nearest net. Data were collected as part of a long-term, on-going study of species breeding at the Palomarin Field Station, Point Reyes National Seashore, concentrating on Wrentits. Capture probability of breeding Wrentit adults was strongly related to distance from nest to nearest and, independently, to the number of intervening territories between nest and net. In addition, females (and their mates) laying early in the season were less likely to be caught than those laying later. Breeding adults whore nests were more than 200m from the closest mist net were rarely caught. Most adults caught were transient individuals, not holding local breeding territories, Territory-holders were caught repeatedly; non-territory holders were not. Recapture probability of territory-holders in the following year (if alive) was estimated at 71%, but only at 5% for those not holding local territories. Survival of Wrentit breeding adults was estimated to be 57%, which was slightly below estimates based on re-sightings (59% to 64%). However, survival estimated on the basis of capture-recapture of all adults (ignoring territorial status) was only 38%. We suggest that, in the absence of information regarding territorial status, survival analyses be restricted to individuals caught at least twice in a season. This is an effective method for screening out transient individuals.

Estimates of Adult Survival, Capture Probability, and Recapture Probability: Evaluating and Validating Constant-effort Mist Netting

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