Vocal Activity as a Low Cost and Scalable Index of Seabird Colony Size

• Published in: Conservation biology Vol. 28; no. 4; pp. 1100 - 1108
• Main Authors: BORKER, ABRAHAM L, MCKOWN, MATTHEW W, ACKERMAN, JOSHUA T, EAGLES‐SMITH, COLLIN A, TERSHY, BERNIE R, CROLL, DONALD A
• Format: Journal Article
• Language: English
• Published: Hoboken, NJ Blackwell Scientific Publications 01-08-2014; Blackwell Publishing Ltd; Wiley Periodicals Inc; Wiley-Blackwell
• Subjects: Acoustics; adaptive management; Animal communication; Animal nesting; Animal populations; Animal, plant and microbial ecology; Animals; Applied ecology; Aves; Aves marinas; bioacoustics; bioacústica; Biological and medical sciences; Bird nesting; Birds; breeding; breeding sites; Charadriiformes - physiology; Colonialism; Conservation biology; Conservation of Natural Resources - methods; Conservation, protection and management of environment and wildlife; Contributed Papers; Fundamental and applied biological sciences. Psychology; General aspects; manejo adaptativo; monitoreo; monitoring; Monitoring costs; nesting; nests; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; Population Density; population indices; San Francisco; Sea birds; seabirds; Sensors; Sound; Sterna; Sterna forsteri; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Vocalization, Animal; wildlife; Wildlife conservation; wildlife management; índices de población; San Francisco; INE, USA, California, San Francisco Bay; Marine animal; Costs; population indices; Sound production; bioacoustics; adaptive management; Activity; monitoring; Vertebrata; seabirds; Surveillance; Colony; Aves; Adaptation; Environmental protection; monitoreo; manejo adaptativo; índices de población; Aves marinas; bioacústica
• ISSN: 0888-8892; 1523-1739
• DOI: 10.1111/cobi.12264

Although wildlife conservation actions have increased globally in number and complexity, the lack of scalable, cost‐effective monitoring methods limits adaptive management and the evaluation of conservation efficacy. Automated sensors and computer‐aided analyses provide a scalable and increasingly cost‐effective tool for conservation monitoring. A key assumption of automated acoustic monitoring of birds is that measures of acoustic activity at colony sites are correlated with the relative abundance of nesting birds. We tested this assumption for nesting Forster's terns (Sterna forsteri) in San Francisco Bay for 2 breeding seasons. Sensors recorded ambient sound at 7 colonies that had 15–111 nests in 2009 and 2010. Colonies were spaced at least 250 m apart and ranged from 36 to 2,571 m². We used spectrogram cross‐correlation to automate the detection of tern calls from recordings. We calculated mean seasonal call rate and compared it with mean active nest count at each colony. Acoustic activity explained 71% of the variation in nest abundance between breeding sites and 88% of the change in colony size between years. These results validate a primary assumption of acoustic indices; that is, for terns, acoustic activity is correlated to relative abundance, a fundamental step toward designing rigorous and scalable acoustic monitoring programs to measure the effectiveness of conservation actions for colonial birds and other acoustically active wildlife. La Actividad Vocal como un Índice Escalable y de Bajo Costo del Tamaño de Colonia de las Aves Marinas