Bird mortality due to the Deepwater Horizon oil spill: Reply to Sackmann & Becker (2015)

Abstract

Sackmann & Becker (2015; Mar Ecol Prog Ser 534:273-277, this volume) question assumptions we used to estimate bird mortalities from the 2010 Deepwater Horizon blowout in the northern Gulf of Mexico, recommending spill- and Gulf of Mexico-specific data, especially for estimating the probability of shoreline deposition of seabird carcasses killed at sea. The carcass drift and sinking study they recommend provides limited insight regarding shoreline deposition probability, because it fails to account for advection of tagged carcasses out to sea, the effects of tethering carcasses to buoyant floats, the time to abdominal cavity penetration by scavengers, or the very different conditions when the study was conducted in summer 2011 in comparison with the wind and current regime immediately following the blowout in spring 2010. Recognizing such limitations in studies of seabird carcass drift and sinking at sea, we think that the modeling approach we used, which provides parameter estimates primarily as uncertainty distributions rather than focusing on point estimates from single studies, more faithfully represents the state of knowledge supporting such estimates.