Seabird Population Transect Surveys

Seabirds are long-lived, upper trophic level predators that are integral components of marine ecosystems. Marine protected areas (MPAs) can provide both direct and indirect benefits to seabirds. Direct benefits involve reducing the direct interactions seabirds have with humans such as from fisheries and recreational activities. Indirect benefits involve reducing competition with humans for prey resources. As the abundance of prey increases within and adjacent to MPAs, seabirds may benefit as more abundant prey resources lead to increases in their productivity and population sizes. We monitored four coastally breeding seabirds that feed largely on juvenile and other small fishes in nearshore habitats (Brandt’s cormorant, pelagic cormorant, western gull, and California least tern) and one shorebird that feeds on rocky intertidal invertebrates (black oystercatcher). We collected data on baseline population size, productivity, foraging rates, and rates of human-caused disturbance inside and outside of three MPA clusters: Gull Island SMCA, Painted Cave SMCA and Scorpion SMR (Santa Cruz Island); Point Vicente SMR and Abalone Cove SMCA (Palos Verdes); and Cabrillo SMR, South La Jolla SMR/SMCA, and Matlahuayl SMR (San Diego). California least tern diet composition data were collected inside and outside of MPAs including Bolsa Chica Basin SMCA, Bolsa Bay SMCA, Batiquitos Lagoon SMCA, and Tijuana River Mouth SMCA. The long-term objectives of our monitoring are to 1) document how seabirds are using coastal and nearshore habitats in relation to a sample of newly established MPAs within the SCSR and 2) develop seabirds as tools to investigate changes in fish and invertebrate populations inside and outside of SCSR MPAs. Data presented here focus on baseline population size, for both roosting and breeding seabirds.

海鸟为长寿命的上层营养级捕食者，是海洋生态系统不可或缺的组成部分。海洋保护区（Marine Protected Areas, MPAs）可为海鸟提供直接与间接双重效益：直接效益指减少海鸟与人类的直接交互，例如渔业活动及休闲娱乐带来的干扰；间接效益则指降低海鸟与人类对猎物资源的竞争。随着海洋保护区内部及周边区域的猎物丰度提升，海鸟可从中获益——更充足的猎物资源将推动其繁殖生产力与种群规模增长。

本研究监测了5类鸟类：4种主要以近岸生境中的幼鱼及其他小型鱼类为食的沿海繁殖海鸟，即勃兰特鸬鹚、海鸬鹚、西美鸥与加州小燕鸥；以及1种以潮间带岩相无脊椎动物为食的滨鸟，即黑蛎鹬。研究人员收集了三类保护区集群内及周边区域的基线种群规模、繁殖生产力、觅食速率及人为干扰率数据，三类保护区集群分别为：圣克鲁兹岛的古尔岛SMCA、彩绘洞SMCA与斯科皮翁SMR；帕洛斯弗迪斯的文森特角SMR与鲍鱼湾SMCA；以及圣地亚哥的卡布里略SMR、南拉霍亚SMR/SMCA与马特拉韦尔SMR。此外，研究人员还收集了加州小燕鸥在包括博尔萨奇卡盆地SMCA、博尔萨湾SMCA、巴蒂基托斯潟湖SMCA与提华纳河河口SMCA在内的海洋保护区内外的日粮组成数据。

本监测项目的长期目标为：1）记录海鸟如何利用沿海与近岸生境，以响应SCSR内新建的一批海洋保护区样本；2）将海鸟作为研究工具，探究SCSR海洋保护区内外的鱼类与无脊椎动物种群变化。本文呈现的数据聚焦于栖息与繁殖海鸟的基线种群规模。