Population trends of birds of open farmland and of farmyards and thicket:
The figure shows two trends.
1. Population trends of open farmland birds.
2. Population trends of farmyard and thicket.
Each of these two trends is divided into three time periods.
1. 1900 to 1960 based on little data.
2. 1960 to 1990 based on more data.
3. 1990 to 2024 based on standardized observations.

The last period contains the average index figures and a trend line calculated through them starts at 100 in 1990.

The progression is broadly as follows.
1. Birds from open farmland start at 194 for the period around 1915 and 226 around 1950. This group then drops from 214 in 1960 to 106 in 1990. The trend line from 1990 shows a further decrease from 100 to 31 (in 2023) .
2. Birds of yards and shrubs. 1915: 244; 1950: 170. After that the decline continues from 141 in 1960 to 78 in 1986. After that there is a short period of some increase. In 1990 the average index is 103. The trend line from 1990 onwards is relatively flat. In 2024 the trend value is 93.