Figure 4: Temporal changes in the frequency of the brown morph in Finland on different scales.

(a) Historical data on colour morph frequencies in the early century (1911–1945) and mid-century (1946–1980) based on skins from the Zoological museum collection (University of Helsinki). Each symbol represents the mean frequencies of seven 5-year periods (± s.e.m.). (b) Frequency of the brown morph in the study population based on captured breeding birds between 1981 and 2008. Shown are mean annual frequencies of the brown morph in 5-year periods (±s.e.m.). (c) Nationwide population frequency of brown individuals based on all breeding birds ringed or recaptured by amateur ringers in Finland and colour scored as either grey or brown. Symbols are as in b. Total sample size is given along the x axis. The method of scoring colour morphs in a and b (filled diamonds) differs from the method used in c (filled dots), such that the averages and slope of the trend are not directly comparable, although the direction is.