Lost Bird-Years: Quantifying Bird Injuries in Natural Resource Damage Assessments for Oil Spills1

Abstract

Large oil spills routinely impact hundreds or even thousands of birds. In order to determine the compensation that responsible parties owe the public, trustee agencies typically examine the number of live and dead birds collected to estimate total bird mortality caused by the spill (Ford et al., 1987). In these natural resource damage assessments (NRDA), compensation is typically based upon the potential ecological benefits that flow from a restoration project. In the case of a bird kill, final compensation is based upon the cost of implementing a restoration project and not upon a dollar value per bird. The dominant paradigm for calculating compensatory restoration for bird injuries is Resource Equivalency Analysis (REA). This paper begins by providing a brief overview of REA when applied to birds. We then examine the REA implications of varying the level of mortality, baseline variability, and demographic variables in a simple population model that tracks both injured and baseline population levels. After finding no evidence that these factors necessarily produce short recovery times, we summarize two general approaches for calculating lost bird-years. We conclude that short recovery times (e.g., one-year) are unlikely for birds when using individual-based measures of injury. Further, we believe that recovery times may be much longer than currently calculated for situations where plausible "recovery mechanisms" cannot be defined.

Compensating white‐tailed eagle mortality at the Smøla wind‐power plant using electrocution prevention measures

“…The Discounted Bird Year metric allows for the summation of direct and indirect components of the debit and credit, accounts for disparity in age between injured and restored birds (Sperduto et al 2003, Zafonte and Hampton 2005), and assigns a higher weight to adult white‐tailed eagles than juveniles (8.73 vs. 7.16 Discounted Bird Years, see Appendices A and B, available online at http://www.onlinelibrary.wiley.com/). This is consistent with the ecological interpretation that older birds are more valuable to the population because they contribute to population growth and have a higher survival rate (a more sophisticated population model may better capture this difference, as noted below).…”

“…The debit relies on the single‐generation stepwise replacement model described in Zafonte and Hampton (2005). Ideally, we would model the recovery process based on assumptions about when the remaining non‐collided birds are able to compensate for the collided birds' productivity loss.…”

“…1). Previous studies have relied on Discounted Bird Years (Sperduto et al 2003), although Zafonte and Hampton (2005) discuss alternatives.…”

“…In theory, the debit could be very large if the population never recovers; however, we assume convergence of the 2 trajectories (“recovery date”; Fig. 1) based on recovery assumptions inherent in the stepwise replacement model (Zafonte and Hampton 2005). For example, for each 7‐year‐old white‐tailed eagle killed, we assume that by the time it would have died naturally (23 yr later), no more direct mortality losses occur.…”

Wind Power Compensation is not for the Birds: An Opinion from an Environmental Economist

“…Cole (2010) presents a quantitative, yet hypothetical EA case study to illustrate compensatory scaling in the case of White‐tailed Eagle (WTE) ( Haliaeetus albicilla ) collisions with wind turbines at the Smøla wind farm in Norway. The study, which follows the five‐step REMEDE process, considers the number of WTE collisions over time (past and projected losses), and quantifies the debit and credit using a “bird‐year” non‐monetary metric (Zafonte & Hampton 2005). This metric, which acts as a currency in measuring appropriate compensation, quantifies a bird's foregone life expectancy in years had it not collided with a turbine.…”