Nest-box occupancy data for flying squirrels

Data describes occupancy (1=precence, 0=absence) of flying squirrels in nest boxes. BCODE= name of nest box. ID = a unique combination of box name and census year. Ural owl and goshawk columns describe modelled predation risk from these predators at the nest box site, see article for methods. h1...h27 refer to different land use classes and their combinations as in Table 1 of the research article. _200m and _1km means area (square meters) of that habitat within 200 meters and 1km from nest box, respectively. s (for example h17_200ms) refers to standarized amount of that habitat, see methods

Predation risk landscape modifies flying and red squirrel nest site occupancy independently of habitat amount

<div><p>Habitat choice often entails trade-offs between food availability and predation risk. Understanding the distribution of individuals in space thus requires that both habitat characteristics and predation risk are considered simultaneously. Here, we studied the nest box use of two arboreal squirrels who share preferred habitat with their main predators. Nocturnal Ural owls (<i>Strix uralensis</i>) decreased occurrence of night-active flying squirrels (<i>Pteromys volans</i>) and diurnal goshawks (<i>Accipiter gentilis</i>) that of day-active red squirrels (<i>Sciurus vulgaris</i>). Unexpectedly, the amount of preferred habitat had no effect on nest box use, but, surprisingly, both squirrel species seemed to benefit from close proximity to agricultural fields and red squirrels to urban areas. We found no evidence of trade-off between settling in a high-quality habitat and avoiding predators. However, the amount of poor-quality young pine forests was lower in occupied sites where goshawks were present, possibly indicating habitat specific predation on red squirrels. The results suggest that erecting nest boxes for Ural owls should be avoided in the vicinity of flying squirrel territories in order to conserve the near threatened flying squirrels. Our results also suggest that flying squirrels do not always need continuous old forests, and hence the currently insufficient conservation practices could be improved with reasonable increases in the areas left untouched around their nests. The results of this study demonstrate the importance of taking into account both habitat requirements and predation risk as well as their interactive effects when modeling the occupancy of threatened animal species and planning their conservation.</p></div

Spruce cone crop data

Data describes estimates of Norway spruce cone crop (unit: cones per tree, calculated from trees in research forests) in three different areas, Ullava, Oravainen and Maalahti, surrounding the red squirrel study area in Kauhava, Finland

Nest box occupancy data for red squirrels

Data describes nest box occupancy of red squirrels. 1= presence, 0=absence. BCODE= name of the box. ID= unique combination of box name and census year. Goshawk and Ural owl columns describe modelled predation risk from these predators at the nest box site, see methods in research article. h1...h27 refer to land use classes as in Table 1 of the article. _300 and _2500 m refer to the area of each land use class within 300 meters and 2.5 kilometers from the nest box in square meters. Ending 's' (h8_300ms) refers to the standardized area. TimePeriod describes the slightly different detection probability before and since 2006

Land use classes, their combinations and abbreviations.

<p>Land use classes, their combinations and abbreviations.</p

Summary of flying squirrel models.

<p>Summary of flying squirrel models.</p

Young pine forest has a negative effect on nest box occupancy by arboreal squirrels.

<p>The effect of standardized amount of young pine forest (A) within buffers of 200 m and 1 km on flying squirrel occurrence in nest boxes, and (B) within buffers of 300 m and 2.5 km on red squirrel occurrence in nest boxes.</p

Increasing area of field first increases and eventually decreases occurrence of squirrels.

<p>The effect of standardized amount of agricultural field (A) within buffers of 200 m and 1 km on flying squirrel occurrence in nest boxes, and (B) within buffers of 300 m and 2.5 km on red squirrel occurrence in nest boxes.</p

The presence of main avian predator decreases nest-box occupancy by flying and red squirrels.

<p>The effect of (A) Ural owl (kernel height) on occurrence of flying squirrels and (B) goshawk (kernel height) on occurrence of red squirrels in nest boxes based on models at small and large spatial scale.</p

Red squirrels benefit from human settlement, and nest boxes in mature and old spruce forests are more likely to be occupied when spruce cone crop is abundant.

<p>The effect of (A) standardized amount of built areas within buffers of 300 and 2.5 km on red squirrel occurrence in nest boxes and (B) the effect of spruce cone crop on the estimated coefficient of mature spruce forest, i.e. the interaction between cone crop and spruce forest on red squirrel occurrence.</p