Behavioural flexibility is an important way in which animals respond to changing environmental conditions. During winter, snow cover is an important seasonal refuge that provides thermal insulation and protects overwintering species from predators. However, snow depth and quality can be highly variable throughout winter, and it is unclear how species that use snow cover adjust their behaviour with changing winter conditions and in complex landscapes. During winter months, Ruffed Grouse Bonasa umbellus spend a large portion of time roosting in trees, understory, and in some cases, subnivean environments. Importantly, the ability to snow roost has been associated with reduced stress levels and increased overwinter survival. Across three winters, we studied the plasticity of roosting behaviour across a diversity of winter conditions and land cover types. In line with predictions, grouse were more likely to use snow burrows when snow was deep and powdery, and experienced warmer temperatures in snow roosts compared to other roost types. However, snow roosting behaviour did not vary strongly across land cover types, and grouse were not more likely to use snow burrows at colder temperatures, potentially because snow roosting may serve to protect grouse from predators regardless of winter weather conditions. Both the snow conditions necessary for snow roosting and the occurrence of snow roosting behaviour, were relatively rare during our 3-year study (only 3% of all roosts were snow burrows). Loss of winter refugia due to warming winters and declining snow cover may limit the use of behavioural flexibility for winter-adapted species to cope with environmental change.

Data were collected at Sandhill Wildlife Area in central Wisconsin. Individual Ruffed Grouse were radio-collared and their roosting behaviour was monitored for three winters: 2015-2016, 2016-2017, and 2017-2018. The dataset contained in “RuffedGrouseBehaviour_Dataset.csv” consists of roosting behaviour observations of individual grouse. We include all variables needed to run the multinomial analysis of roosting behaviour that is presented in the manuscript using the R script “RuffedGrouseBehaviour.R”.

To quantify the effect of roosting behaviour on temperatures experienced by grouse, we used temperature data recorded by iButton temperature sensors that were attached to grouse transmitters. For each roost observation of a grouse with an iButton, we extracted the median temperature from the bird’s iButton during the previous 12 hours, representing the temperature experienced by the grouse while at the roost. We then extracted the minimum temperature from the previous day from daily temperature rasters, and calculated the difference between the median grouse iButton temperature and the minimum ambient temperature. We used a generalized linear model with a Gaussian error distribution to model the effect of roosting behaviour on the difference in temperature between the median grouse iButton temperature and the minimum ambient temperature. Roosting behaviour was categorized as “snow roost”, “surface roost”, and “tree roost”. The dataset “Temperature_dataset.csv” contains the data necessary to run the generalized linear model. See manuscript for more details.

Program R is necessary to run the script "RuffedGrouseBehaviour.R"

Columns in the dataset “RuffedGrouseBehaviour_Dataset.csv”:

BirdName: a unique identifier for each individual Ruffed Grouse.

roostcat: a categorical variable describing roosting behaviour (“TREE”, “SURFACE”, “BOWL”, or “BURROW”). See manuscript for more details.

roostcover: a categorical variable describing land cover (“MF” = Mature Forest, “DC” = Dense Cover, “OP” = Open habitat, “SO” = Scrub Oak). See manuscript for more details.

Sdepth: snow depth at the roost site (cm), scaled.

Smintemp: minimum daily temperature (°C), scaled.

SJDate: modified Julian date where December 1^st = 1 and continues numerically through March 31^st of each year, scaled.

Stime: minutes from midnight, scaled.

Sden: Snow sink depth at the roost site (cm), scaled. Snow sink depth is an index of snow density. Larger values indicate more powdery snow.

Columns in the dataset “Temperature_dataset.csv”:

Temp_diff: the difference between the median grouse iButton temperature and the minimum ambient temperature.

RoostType: a categorical variable describing roosting behaviour (“TREE”, “SURFACE”, or “SNOW ROOST”).