Habitat Conservation Plans (HCPs) commonly facilitate habitat conservation on private land in the United States, yet the effectiveness of individual HCPs is rarely evaluated. Here, we assess the effectiveness of a high-profile HCP created by a lumber company to protect old-growth forests used for breeding by Marbled Murrelets (Brachyramphus marmoratus) on private land. We used 17 years of HCP-monitoring data to compare trends in murrelet occupancy and inland counts between private HCP areas and public reference areas over time. Based on occupancy models applied to audio-visual survey data, average occupancy was higher in public reference areas (0.85; 85% confidence intervals [CI]: 0.79–0.90) than in private HCP areas (0.46; 85% CI: 0.38–0.54). Numerically, trends in occupancy were slightly positive in public areas ( = 1.01; 85% CI: 0.94–1.08) and slightly negative in private areas ( = 0.97; 85% CI: 0.87–1.06), but CI did not preclude stable occupancy on both ownerships. Based on generalized linear mixed models applied to inland radar survey data, murrelet counts in private HCP areas (least-squares [LS] mean = 8.7; 85% CI: 6.2–12.2) were lower than those in public reference areas (LS mean = 14.8; 85% CI: 10.1–21.7), but CI overlapped. Murrelet counts declined by 12–17% annually on both ownerships over the study period based on the top model, but a closely competing interactive model suggested more rapid declines in public reference (14–20%) than in private HCP (10–15%) areas. Both models indicated that murrelet counts were negatively related to sea surface temperature, suggesting that warm ocean conditions negatively affect murrelet breeding effort. Collectively, these results suggest that while HCP habitat may be lower quality than public reference areas, the HCP has likely not exacerbated ongoing declines of murrelets in the region. This work highlights the importance of including reference areas when evaluating conservation policies.

中文翻译：

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评估森林栖息地保护计划对受威胁海鸟 Marbled Murrelet 的有效性

栖息地保护计划 (HCP) 通常促进美国私人土地上的栖息地保护，但很少评估单个 HCP 的有效性。在这里，我们评估了由一家木材公司创建的备受瞩目的 HCP 的有效性，该 HCP 旨在保护用于在私人土地上饲养 Marbled Murrelets (Brachyramphus marmoratus) 的古老森林。我们使用了 17 年的 HCP 监测数据来比较私人 HCP 区域和公共参考区域之间 murrelet 入住率和内陆数量的趋势。根据应用于视听调查数据的入住率模型，公共参考区域的平均入住率（0.85；85% 置信区间 [CI]：0.79-0.90）高于私人 HCP 区域（0.46；85% CI：0.38-0.54） ）。从数值上看，公共区域的入住率趋势略微积极（= 1.01；85% CI：0.94-1。08）和在私人区域略有负面（= 0.97；85% CI：0.87-1.06），但 CI 并不排除两种所有权的稳定入住。根据应用于内陆雷达调查数据的广义线性混合模型，私人 HCP 区域的 murrelet 计数（最小二乘 [LS] 平均值 = 8.7；85% CI：6.2-12.2）低于公共参考区域（LS 平均值 = 14.8；85% CI：10.1–21.7），但 CI 重叠。根据顶级模型，在研究期间，两种所有权的 Murrelet 计数每年下降 12-17%，但一个竞争激烈的交互模型表明，公共参考 (14-20%) 比私人 HCP (10-15%) 下降更快) 领域。两种模型都表明海鱼数量与海面温度呈负相关，这表明温暖的海洋条件会对海鱼的繁殖工作产生负面影响。集体，这些结果表明，虽然 HCP 栖息地的质量可能低于公共参考区域，但 HCP 可能并未加剧该地区 murrelets 的持续下降。这项工作强调了在评估保护政策时包括参考区域的重要性。