Structured and unstructured citizen science: Seven decades of expanding bird populations in central Ontario, Canada

摘要: Abstract Citizens’ observations of wildlife offer a wealth information. Such data, however, may be prone to biases or inaccuracies — in particular, the over-reporting novel species and under-reporting common mundane species. Few studies have assessed relationship between unstructured structured using long-term data. We compared 69 years voluntary bird sightings, recorded regular publication Peterborough Field Naturalists (PFN), 1948-2016, systematic Christmas Bird Counts (CBC; during winter) Breeding Surveys (BBS; spring) central Ontario, Canada. focused on seven that had expanded their ranges into area: Northern Cardinal ( Cardinalis cardinalis ), House Finch Haemorhous mexicanus Purple purpureus Red-bellied Woodpecker Melanerpes carolinus Wild Turkey Meleagris gallopavo Canada Goose Branta canadensis American Robin Turdus migratorius ). For each species, we first record, annual number relative abundance from PFN record CBC BBS. anticipated naturalists’ accounts would more sensitive arrival but underestimate as became common. In general, our results agreed with these predictions. 11 12 cases, naturalists detected well advance BBS average by 1½ decades (range: 5–33 years). The correlations (PFN) (CBC BBS) data were variable; most weak negative. found significant negative for two (winter) (spring), (winter), positive correlation rarest (spring). surmise novelty underlies rarity increases likelihood reporting non-professionals. conclude are valuable detecting they inconsistent, even inverse, indicators expanding once established.