Table 1 Variable names and descriptions and associated hypotheses
From: Rodent-avoidance, topography and forest structure shape territory selection of a forest bird
Hypothesis | Variable | Description | Breeding | Control | Abandoned |
|---|---|---|---|---|---|
Forest structure | |||||
Ground variables | Cover of herb layer a | Percentage of ground covered by vegetation < 0.5 m, visually estimated | 24.2, 10.9–42.6 | 14.8, 6.4–32.0 | 25.5, 12.2–29.2 |
Number of tussocks b | Number of grass and sedge tussocks | 325.5, 122.8–653.5 | 40.0, 3.0–216.0 | 28.5, 0–310.8 | |
Number of bushes c | Number of bushes > 0.5 m height and number of young trees with dbh < 8 cm | 38.5, 17.8–70.8 | 69.0, 12.0–246.0 | 34.0, 6.8–137.8 | |
Tree variables | Number of trees c | Number of trees with dbh > 8 cm | 16.5, 13.0–22.0 | 13.0, 10.0–17.0 | 11.0, 7.8–14.5 |
Number of trees branched < 4 m c | Number of trees with branches below 4 m | 10.0, 6.0–14.0 | 7.0, 4.0–11.0 | 5.5, 3.8–10.3 | |
Number of trees branched < 10 m c | Number of trees with branches below 10 m | 13.0, 9.0–18.0 | 9.0, 6.0–13.0 | 7.0, 6.0–12.0 | |
Tree dbh d | Average dbh of all trees with dbh > 8 cm | 26.0, 22.3–30.0 | 31.0, 26.0–36.0 | 27.5, 24–37.5 | |
Tree species diversity e | Shannon’s index of diversity based on tree species and dbh data | 1.2, 0.7–1.5 | 0.9, 0.7–1.3 | 0.9, 0.6–1.2 | |
Sky visibility d | Percentage of sky visible (see “Estimation of sky visibility” section) | 13.0, 9.0–19.0 | 14.0, 10.0–19.0 | 10.5, 9.0–21.8 | |
Proportion beech e | Number of beech trees divided by total number of trees | 43.2, 20.3–59.3 | 50.0, 29.2–69.6 | 52.3, 33.3–58.5 | |
Proportion other deciduous trees e | Number of deciduous trees except beech divided by total number of trees | 31.7, 18.6–47.1 | 25.0, 14.3–50 | 41.4, 18.6–53.1 | |
Proportion conifers e | Number of coniferous trees divided by total number of trees | 13.1, 0–31.7 | 0, 0–29.4 | 0, 0–15.4 | |
Rodent-avoidance | Rodent numbers | Number of rodents captured in the 25 traps per territory or control area | 8.0, 0–15.8 | 13.0, 4.0–22.0 | 7.0, 1.0–13.3 |
Anthropogenic disturbance | Distance to paths f | Distance to paths, i.e. trails regularly used by humans | 48.0, 15.0–75.8 | – | 37.5, 25.8–45.5 |
Distance to forest edge f | Distance to edge of forest | 148.5, 102.8–237.8 | 153.0, 72.0–224.0 | 98.5, 60.8–148.5 | |
Topography | Elevation f | Elevation in m above sea level | 698, 656–931 | 699, 610–920 | 575, 548–740 |
Aspect d | Measured in degrees (o) with a compass in the centre of each 50-m2-square | 174, 144–204 | 171, 127–227 | 162, 109–307 | |
Slope steepness d | Measured in degrees (o) with a compass in the centre of each 50-m2-square | 31.5, 27.0–37.0 | 26.0, 21.0–33.0 | 21, 16.8–23.5 | |