U. S. Fish and Wildlife Service, Division of Migratory Bird Management, 3020 State University Drive East, Modoc Hall, Suite 2007, Sacramento, CA, 95819, USA.
U.S. Fish and Wildlife Service, Natural Resource Damage Assessment and Restoration Program, 1011 E Tudor Rd, MS 361, Anchorage, AK, 99503, USA.
Environ Monit Assess. 2020 Mar 17;191(Suppl 4):816. doi: 10.1007/s10661-019-7924-z.
We estimated detection probabilities of bird carcasses along sandy beaches and in marsh edge habitats in the northern Gulf of Mexico to help inform models of bird mortality associated with the Deepwater Horizon oil spill. We also explored factors that may influence detection probability, such as carcass size, amount of scavenging, location on the beach, habitat type, and distance into the marsh. Detection probability for medium-sized carcasses (200-500 g) ranged from 0.82 (SE = 0.09) to 0.93 (SE = 0.04) along sandy beaches. Within sandy beaches, we found that intact/slightly scavenged carcasses were easier to detect than heavily scavenged ones and did not find strong effects of location on the beach on detection probability. We estimated detection rate for each combination of scavenging state, carcass size, and position along sandy beaches. In marsh edge habitats, detection ranged from 0.04 (SE = 0.04) to 0.86 (SE = 0.10), with detection rates rapidly increasing from small (< 200 g) to medium carcass sizes and leveling off between medium and extra-large (> 1000 g) carcasses regardless of vegetation type (Spartina or Phragmites). Carcasses of all sizes were generally harder to locate in Spartina-dominated marshes than in Phragmites-dominated ones. A subset of the data for which we could adequately assess the effect of distance into the marsh indicated that detection rates generally declined the farther a carcass was into marsh vegetation. Based on power analyses, our ability to identify predictors that influence detection rates would be higher with larger numbers of carcasses, greater numbers of search trials per carcass, or more balanced sampling distributions across predictor values.
我们估计了墨西哥湾北部沙质海滩和沼泽边缘栖息地中鸟类尸体的检测概率，以帮助建立与深海地平线石油泄漏相关的鸟类死亡率模型。我们还探讨了可能影响检测概率的因素，例如尸体大小、腐肉量、海滩位置、栖息地类型和向沼泽内部的距离。在沙质海滩上，中等大小（200-500 克）的尸体的检测概率范围为 0.82（SE=0.09）至 0.93（SE=0.04）。在沙质海滩内，我们发现完整/轻微腐肉的尸体比严重腐肉的尸体更容易被发现，而且没有发现海滩位置对检测概率有强烈影响。我们估计了每个腐肉状态、尸体大小和沙质海滩位置组合的检测率。在沼泽边缘栖息地，检测概率范围为 0.04（SE=0.04）至 0.86（SE=0.10），无论植被类型（互花米草或芦苇）如何，从小（<200 克）到中等大小的尸体检测率迅速增加，并在中等和特大（>1000 克）尸体之间趋于平稳。所有大小的尸体在互花米草占主导地位的沼泽中通常比在芦苇占主导地位的沼泽中更难找到。我们对一部分数据进行了充分评估，结果表明，随着尸体进入沼泽植被的距离越来越远，检测率通常会下降。基于功效分析，如果有更多的尸体、每个尸体的搜索试验次数更多，或者在预测值上的采样分布更加平衡，我们识别影响检测率的预测因子的能力将会更高。
