Simplified Displacement model: Foraging Birds

• Main Author: Jared, Wilson
• Format: Article in Journal/Newspaper
• Language: English
• Published: Marine Scotland Science 2014
• Subjects: Birds, mammals and reptiles; Tay; Razorbill
• Online Access: https://dx.doi.org/10.7489/1678-1; https://data.marine.gov.scot/dataset/simplified-displacement-model-foraging-birds

This model, written in R, simulates the effects of offshore wind farms upon seabird foraging behaviour, and the ultimate consequences of this for adult and chick survival. The model has been designed for use with four specific proposed offshore wind farms in the Forth-Tay region, and for use with five specific species (guillemot, kittiwake, puffin, gannet and razorbill). Much of the code can be readily-applied to different species, wind farms and SPAs, but some will not fit. It was not designed to provide general code for modelling the effects of any wind farm in any geographical area : This simplified model includes three options for quantifying the magnitude of barrier effects. One option is to assume that they come from a normal distribution with mean 20 km and standard deviation 5 km; this corresponds to the way that barrier effects are specified in the full model. The remaining two options assume that the bird will incur an additional flight cost by flying around the wind farm rather than straight through it and quantify this additional cost by assuming that the wind farm is circular. The two options specify the radius of the circle in two ways: 1.To ensure that the set of bearings from the SPA that encounter the circle is the same that encounter the actual wind farm; or 2.To ensure that the area of the circle is the same as that of the actual wind farm GuillemotInput Files The model requires six input files; one file to provide species-specific information about the spatial distribution of the species within the region of interest, one file to provide parameter values for the model, and four files to provide meta-information. The four meta-information files contain: colonies.csv : locations of each colony (with columns ‘colony’, ‘longname’, ‘long’, ‘lat’) colonysize.csv : size of each colony, in terms of number of pairs (with columns ‘SPA’, ‘Colony’, ‘Guillemot’, ‘Razorbill’, ‘Kittiwake’, ‘Puffin’, ‘Gannet’). Note that SPAs may contain more than one colony. wfinfo.csv : locations, on the 0.5 x 0.5 km GEBCO grid, that are contained within the core and buffer regions for each wind farm. Columns are: ‘WFcode’, ‘Longitude’, ‘Latitude’. Ten options are currently used for WFcode: ‘IC-footprint’ (Inchcape footprint), ‘IC-buffer’ (Inchcape buffer), and so on for NnG, R3A, R3B and R3AB. wfstats.csv : summaries of the relationship between each wind farm and each SPA. Columns are: SPA, WindFarm, Dist, AngleMid, large.anglerange, large.radius, large.MAD, small.anglerange, small.radius, small.MAD. ‘Dist’ is the distance, in km, between the central colony of the SPA and the centre of the wind farm. The remaining columns refer to the sets of bearings from the SPA that would include the wind farm. The parameter.csv file contains parameter values to use in running the displacement model – an example is provided. Information is required for all rows and all species. The ‘Version’ column is used when performing sensitivity analysis, and should be left blank otherwise. Examples of the functions in use are available on MSI.