A description of the biosis model to assess risk of bird collisions with wind turbines

Abstract

We describe the model of Biosis Propriety Limited for quantifying potential risk to birds of collisions with wind turbines. The description follows the sequence of the model's processes from input parameters, through modules of the model itself. Aspects of the model that differentiate it from similar models are the primary focus of the description. These include its capacity to evaluate risk for multidirectional flights by its calculation of a mean presented area of a turbine; its use of bird flight data to determine annual flux of movements; a mathematical solution to a typical number of turbines that might be encountered in a given bird flight; capacity to assess wind-farm configurations ranging from turbines scattered in the landscape to linear rows of turbines; and the option of assigning different avoidance rates to structural elements of turbines that pose more or less risk. We also integrate estimates of the population of birds at risk with data for numbers of their flights to predict a number of individual birds that are at risk of collision. Our model has been widely applied in assessments of potential wind-energy developments in Australia. We provide a case history of the model's application to 2 eagle species and its performance relative to empirical experience of collisions by those species. ß 2013 The Wildlife Society.KEY WORDS bird, collision, model, risk, turbine, wind energy.A number of mathematical models have been developed for the purposes of either describing the interaction of a bird with a wind turbine or to predict the risks of bird collisions with turbines (Tucker 1996a, b;Podolsky 2003Podolsky , 2005Bolker et al. 2006;Band et al. 2007). Tucker (1996a, b) and Band et al. (2007) detailed their models in the peer-reviewed literature. The collision risk model developed by Biosis Propriety Limited has been widely used to assess windenergy developments in Australia since 2002, but it has not previously been described in detail. Given high levels of interest in effects of wind turbines on fauna, we believe it is important for the model to be accessible.Our model provides a predicted number of collisions between turbines and a local or migrating population of birds. It has the potential to be modified to accommodate MonteCarlo simulation, although at its core it uses a deterministic approach. It is modular by design, and allows various customizations, depending upon the unique configuration of the wind facility and characteristics of the taxa modeled.The initial calculation involves species-specific parameters for speed and size of birds and specifications of the turbine, including its dimensions and rotational speed of its blades. Using these parameters, we derive the mean area of turbine presented to a bird in flight. This allows the model to accommodate flight approaches from any potential direction. Alternatively, unidirectional flights can be modeled by using the relevant turbine surface area presented to birds approaching from a given direction.Data for bird flights are collected ...

A Collision Risk Model to Predict Avian Fatalities at Wind Facilities: An Example Using Golden Eagles, Aquila chrysaetos

“…Bird minutes ( k ) are positive, whole numbered counts, allowing us to assume the data are distributed according to a Poisson distribution (e.g., [ 20 ]). From the conjugate family we chose a gamma distribution for the prior on λ , ensuring our estimate remains real-valued and positive and that the posterior on λ is also a gamma distribution.…”

“…The difficulty in prediction has led to a recognized need to better understand and anticipate the number of birds killed by collisions with operating turbines [ 17 ]. There are a number of different Collision Risk Models (hereafter referred to as CRM, e.g., [ 18 – 20 ]). Most existing methods of modeling predicted fatalities, however, do not incorporate uncertainty into their estimates and only provide point estimates from which to make management and conservation decisions.…”

Framework for Testing the Effectiveness of Bat and Eagle Impact-Reduction Strategies at Wind Energy Projects

“…Effective impact-reduction strategies will change the behaviors of target species such that passage rates, dwell time, and fatalities decrease. An effective deterrent will cause bats or eagles to turn away from the rotor-swept area of a turbine, and this behavioral shift, also often referred to as avoidance (Band, Madders, and Whitfield 2005;Chamberlain et al 2006;Smales et al 2013), can be quantified as another alternative metric to fatalities or passage rates, or preferably as a supplemental metric to fatality rates. Avoidance rates can be related to fatality rates to help understand whether and how a fatality-reduction strategy works.…”

A refinement of the Band spreadsheet for wind turbine collision risk allowing for oblique entry

“…This has led to the development of collision risk models (e.g. Tucker 1996a; Band et al 2007;Holmstrom et al 2011;Smales et al 2013). An advantage of such models is the ability to predict potential impacts of wind farm construction on bird mortality rates through pre-construction field surveys.…”