Table A1.

Fixed effect predictor variables for each model in the set of twenty models fitted separately to data from each of the four political units, in order to identify the best-supported model(s) describing inter-annual variation in numbers of observation events across the equal-area hexagonal grid cells into which each political unit was divided. An “X” within a column indicates that this predictor variable was included in the model described by a row within this table. The fixed effect predictor “CalYr” is a continuous variable that describes monotonic changes across the calendar years in each moment of the distribution (i.e. mean, variance, and skewness) “COVIDYr” is a 2-value categorical variable that indicates whether the calendar year was 2020; this predictor functions to allow the moment of distribution to deviate in 2020 from the longer-term trend described by “CalYr”. All models converged, except for fitting of models for Portugal; here, 3 models failed to converge^a.

Model number	Mean		Variance		Skewness
	CalYr	COVIDYr	CalYr	COVIDYr	CalYr	COVIDYr
1	X
2	X	X
3	X		X
4	X	X	X
5	X		X	X
6	X	X	X	X
7	X				X
8	X	X			X
9	X				X	X
10	X	X			X	X
11	X		X		X
12	X	X	X		X
13	X		X		X	X
14	X	X	X		X	X
15	X		X	X	X
16	X	X	X	X	X
17	X		X		X	X
18	X	X	X		X	X
19	X		X	X	X	X
20	X	X	X	X	X	X

^aModels # 13, 17 and 20 did not converge when fitted to the data from Portugal.