Bird density and marine mammal counts based on 7700 meter bins in southern California, 1999-2002

Tracklines and associated observations were mapped and analyzed using ArcMap (ESRI, Redlands, CA). GPS data were recorded in NAD27 map datum and projected to an USGS Albers Equal Area Conic map projection for presentation and subsequent density analyses. Concatenated GPS and observation data were then used to generate point and line coverages in ArcMap (ESRI, Redlands, CA). We designed a custom analytic tool using ArcMap Model Builder that allows for the construction and export of user-specified and effort-adjusted spatial binning of species observations along continuous trackines. For the purposes of this report, we calculated seabird density estimates and marine mammal counts along continuous 3.0-kilometer and 7.7-kilometer trackline segments (i.e., 3.0 kilometer and 7.7 kilometer bins). Therefore, marine bird densities (at 3-kilometer scale, for example) are based on a composite strip area ranging from 0.15 per kilometer squared (one observer on effort) to 0.30 per kilometer squared (two observers on effort). We made no effort to adjust densities such that they would be proportional to variations in the area of buffered transect strip bin (i.e., weighted offset variable). These data are associated with the following publication: Mason, J.W., McChesney, G.J., McIver, W.R., Carter, H.R., Takekawa, J.Y., Golightly, R.T., Ackerman, J.T., Orthmeyer, D.L., Perry, W.M., Yee, J.L. and Pierson, M.O. 2007. At-sea distribution and abundance of seabirds off southern California: a 20-Year comparison. Cooper Ornithological Society, Studies in Avian Biology Vol. 33. References- ESRI. ArcGIS Desktop: Release 10. Redlands, CA: Environmental Systems Research Institute.

本研究使用ArcMap（ESRI，加利福尼亚州雷德兰兹）对调查航迹（trackline）及关联观测记录进行了制图与分析。GPS数据采用NAD27大地基准面（NAD27 map datum）记录，并投影至美国地质调查局阿尔伯斯等面积圆锥投影（USGS Albers Equal Area Conic map projection），以用于成果展示与后续密度分析。拼接后的GPS与观测数据随后被用于在ArcMap（ESRI，加利福尼亚州雷德兰兹）中生成点、线地理要素覆盖集。本研究利用ArcMap模型构建器（Model Builder）开发了定制化分析工具，可实现沿连续调查航迹的物种观测数据的用户自定义、采样投入校正空间分箱（spatial binning），并支持结果导出。为满足本报告的研究需求，本研究沿连续的3.0千米与7.7千米调查航迹分段（即3.0千米、7.7千米空间分箱）计算了海鸟密度估算值与海洋哺乳动物种群数量。因此，以3千米尺度为例，海鸟密度的计算基于复合样带面积，其范围为每千米航迹对应0.15平方千米（单名在岗采样观测者）至0.30平方千米（两名在岗采样观测者）。本研究未对密度进行校正，使其与缓冲区样带分箱的面积变化成比例，即未引入加权偏移变量（weighted offset variable）。本数据集关联如下已发表文献：Mason, J.W.、McChesney, G.J.、McIver, W.R.、Carter, H.R.、Takekawa, J.Y.、Golightly, R.T.、Ackerman, J.T.、Orthmeyer, D.L.、Perry, W.M.、Yee, J.L. 与Pierson, M.O.，2007年。《加利福尼亚南部近海海鸟的海上分布与丰度：20年对比研究》，库珀鸟类学学会，《鸟类生物学研究》第33卷。参考文献——ESRI. 《ArcGIS Desktop 10.0 发行版》. 加利福尼亚州雷德兰兹：环境系统研究所。