Figure 3
Distribution of disease incident reports (DIRs) in Eurasian blackbirds (Turdus merula) from Great Britain, June -November inclusive, 2019 (A; n = 56) and 2020 (B; n = 120). Red circles represent DIRs consistent with neurological disease; orange circles represent DIRs involving blackbirds exhibiting signs of generalised ill health; white circles represent all other morbidity and/or mortality DIRs (removing categories where USUV could reasonably be excluded as the cause i.e. avian pox, nestling mortality, beak and plumage abnormality); red triangle denotes site of confirmed USUV infection. Green circle (A, 2019) indicates statistically significant cluster of reports, accounting for heterogeneity in blackbird population density. Hatched circle (B, 2020) indicates statistically significant cluster of reports, accounting for spatial heterogeneity in surveillance effort by using number of sites from which passerine DIRs were submitted in each county (yellow) and for heterogeneity in blackbird population density (green); clusters are of identical size and location. Map created with Google Earth Pro. Version 7.3.3.7699 (2020) (https://www.google.com/intl/en_uk/earth/versions/#earth-pro).
