Limited catching bias in a wild population of birds with near‐complete census information

Abstract

Animal research often relies on catching wild animals; however, individuals may have different trappability, and this can generate bias. We studied bias in mist netting, the main method for catching wild birds. The unusually high resighting rate in our study population—house sparrows (Passer domesticus) on Lundy Island (England)—allowed us to obtain accurate estimates of the population size. This unique situation enabled us to test for catching bias in mist netting using deviations from the expected Poisson distribution. There was no evidence that a fraction of the birds in the population consistently remained uncaught. However, we detected a different bias: More birds than expected were captured only once within a year. This bias probably resulted from a mixture of fieldworkers sometimes ignoring rapid recaptures and birds becoming net shy after their first capture. We had sufficient statistical power with the available data to detect a substantial uncaught fraction. Therefore, our data are probably unbiased toward catching specific individuals from our population. Our analyses demonstrate that intensively monitored natural insular populations, in which population size can be estimated precisely, provide the potential to address important unanswered questions without concerns about a fraction of the population remaining uncaught. Our approach can help researchers to test for catching bias in closely monitored wild populations for which reliable estimates of population size and dispersal are available.

Winter territory prospecting is associated with life‐history stage but not activity in a passerine

“…The main method was mist‐netting but we also captured some birds inside nest‐boxes and with funnel walk‐in traps. Our population shows very limited, close to no resighting bias (Simons et al ); using this information we can exclude possible trapping biases (Archard and Braithwaite , Michelangeli et al ). After capture, each bird was introduced into a 2 m high dome‐shaped camping tent with five sides (each side measuring 2.74 m width at the floor) that contained two artificial trees made of plastic and bamboo.…”

Slicing: A sustainable approach to structuring samples for analysis in long‐term studies

“…House sparrows are a relatively long‐lived species (on Lundy: mean lifespan is 3.5 ± 1.4 SE , maximum lifespan is 9 years; Schroeder, Burke, Mannarelli, Dawson, & Nakagawa, ). The Lundy population has been systematically studied since 2000 and the adult population size varies between years (Simons, Winney, Nakagawa, Burke, & Schroeder, ). Immigration to and emigration from the island is low (0.5% of recruits; Schroeder et al, ), with an annual resighting probability of 0.91–0.96 (Simons et al, ).…”

“…The Lundy population has been systematically studied since 2000 and the adult population size varies between years (Simons, Winney, Nakagawa, Burke, & Schroeder, ). Immigration to and emigration from the island is low (0.5% of recruits; Schroeder et al, ), with an annual resighting probability of 0.91–0.96 (Simons et al, ). This closed island population on Lundy thus provides precise ages and life‐history data for all individuals.…”

Heritability and social brood effects on personality in juvenile and adult life‐history stages in a wild passerine

“…Behavioural and genetic data were collected from the Lundy Island house sparrow population, Lundy Island, UK, where breeding and survival have been comprehensively monitored since 2000 (Nakagawa et al ., ; Schroeder et al ., ). This population has extremely low rates of immigration and emigration, and high resighting probabilities (Simons et al ., ), so the survey has a very limited bias. A large proportion of nestlings were cross‐fostered on the day after hatching (Winney et al ., ).…”