GENERAL INFORMATION

Title of Dataset: Spatial predictions of scoter nesting location arrivals

Date of data collection: Scoter satellite telemetry tracking data collected between 1999 - 2019. Snowmelt data downloaded from the National Oceanic and Atmospheric Administration (NOAA) National Snow & Ice Data Center's Ice Mapping System (IMS) snow cover maps in February 2022.   

Geographic location of data collection: Canadian boreal shield, taiga shield, and low-Arctic tundra; Alaska

Information about funding sources that supported the collection of the data: 
	This study received funding from the Bureau of Ocean Energy Management (BOEM) through IAA #M12PG00005 with the U.S. Fish and Wildlife Service (USFWS), the Sea Duck Joint Venture, and Environment and Climate Change Canada, with additional support from the Department of Energy (DOE), the Bailey Foundation, and the USFWS.

METHODOLOGICAL INFORMATION

We generated spatial predictions of scoter arrival timing across the breeding range using annual snowmelt data and model-based arrival date predictions. The model included species, wintering origin, age class, sex, and snow-free date as fixed effects. We estimated black, surf, and white-winged scoter breeding ranges by drawing a 100 km buffer around the Taiga and Hudson Plains ecoregions and extending this polygon to include PTT-estimated breeding locations along the Alaskan coast. For prediction, we overlaid the prediction area with a hexagonal grid. IMS snow cover data had a spatial resolution of 24 km; we thus generated grids within which each hexagon had an apothem (i.e., distance from the hexagon centre to side) of 24 km. Using annual snowmelt rasters from 2010 to 2020, we generated a new raster showing mean snowmelt date for the last 11 years. We then determined mean snow-free date within each hexagonal grid cell. Finally, we predicted arrival dates for black, surf, and white-winged scoters using each hexagon’s estimated average snow-free date and by holding wintering origin at Atlantic, age at adult, sex at male, and year and animal identity at 0. 

DATA-SPECIFIC INFORMATION FOR: Dataset_2

File has tabs labelled: BLSC, SUSC, and WWSC, which contain arrival date predictions for black, surf, and white-winged scoters, respectively.

Number of variables: 6

Number of cases/rows: BLSC = 23392, SUSC = 23392, WWSC = 23392

Variable List: 
	- hexID: identifier for each individual hexigon within hexagonal grids overlaying each species breeding range
	- lon: longitudinal location of each hexagon's corners (some hexIDs have more than 6 corners due to hexagons being cropped at breeding range edges) - coordinate projection = +proj=aea +lat_0=40 +lon_0=-96 +lat_1=50 +lat_2=70 +x_0=0 +y_0=0+datum=NAD83 +units=m +no_defs   
	- lat: latitudinal location of each hexagon's corners (some hexIDs have more than 6 corners due to hexagons being cropped at breeding range edges) - coordinate projection = +proj=aea +lat_0=40 +lon_0=-96 +lat_1=50 +lat_2=70 +x_0=0 +y_0=0+datum=NAD83 +units=m +no_defs
	- order: order in which coordinates should appear for plotting
	- snowmelt: mean snowfree date from 2010 to 2020 within each hexagon  
	- arrival: model-predicted scoter arrival dates at nesting locations within each hexagon