Landbird monitoring 2016 annual report: Channel Islands National Park

Hall, Linnea; Larramendy, Peter; Power, Paula

Channel Islands National Park has monitored landbirds as part of their long-term ecological monitoring program since 1993. The program seeks to determine the long-term trends in species composition, distribution and abundance of both native and nonnative landbird species on the islands. For the 2016 monitoring year, a total of 9 line transects (3 on Santa Barbara Island, 1 on East Anacapa Island, and 5 on San Miguel Island) and 338 out of 346 point count sites (33 on Santa Barbara Island, 8 on Anacapa Island, 112 of 120 on Santa Cruz Island, 145 on Santa Rosa Island, and 40 on San Miguel Island) were counted using distance-based sampling methods by staff with the Western Foundation of Vertebrate Zoology. All data were entered into the park’s landbird monitoring database and subsequently verified, validated and certified. Data summaries were generated in Program R. In 2016, 64 landbird species were counted, with the 10 most commonly detected landbirds parkwide being, in descending order, Spotted Towhee, Song Sparrow, Western Meadowlark, Orange-crowned Warbler, Horned Lark, Bewick’s Wren, White-crowned Sparrow, House Finch, Common Raven, and Chipping Sparrow. Birds exhibiting decreased detections were Song Sparrow and Western Meadowlark on Anacapa Island, and Allen’s Hummingbird on Santa Cruz Island. Species exhibiting increased detections were Rock Wren (on Anacapa and Santa Barbara), White-crowned Sparrow (on Anacapa, Santa Barbara, Santa Cruz, and San Miguel); Horned Lark (on Santa Barbara); House Finch, Orange-crowned Warbler, and Rufous-crowned Sparrow (on Santa Cruz); Spotted Towhee (on Santa Cruz and Santa Rosa); and Song Sparrow and Western Meadowlark (on Santa Rosa). Species richness graphs were summarized for each island. These graphs can be used to determine whether species are appearing on or disappearing from the islands, however, these results must be interpreted with caution since the present evaluation only relied on a simple assessment of detections. Trends in bird numbers are better revealed by analyses of densities, such as through distance analyses (i.e., Coonan et al. 2015, Coonan et al. 2011b) to account for differences in detection rates. Notable findings on each island for 2016 were: 1. Anacapa Island: 24 species have been counted since 1993; 10 were counted in 2016, with no new vagrant species observed. 2. Santa Barbara Island: 46 species have been counted since 1993; 18 were counted in 2016. Golden-crowned Sparrow and House Finch appears to be increasing. Bewick’s Wren was the only new vagrant observed, but Burrowing Owl, Sharp-shinned Hawk, and Spotted Towhee also showed back up for the second or third time on the island, as did Short-eared Owl, which hadn’t been detected since 2007. 3. San Miguel Island: 69 species have been counted since 1993; 21 were counted in 2016. Rufous-crowned Sparrow was detected for only the second time in 2016, and Rufous Hummingbird was detected for the first time in 2016. 4. Santa Rosa Island: 70 species have been detected since 1994; 40 were detected in 2016. Eurasian Collared Dove and European Starling, both nonnative to the islands, occur infrequently on the island but were detected in both 2015 and 2016. American Robin, Black-throated Gray Warbler, and Cooper’s Hawk were detected for the first time in 2016, and Hermit Warbler was detected for only the second time since 1998. 5. Santa Cruz Island: 64 species have been counted since 2013; 53 were counted in 2016. Black-headed Grosbeak was detected every year but 2016. American Goldfinch, Brewer’s Blackbird, and a Prairie Falcon were detected for the first time in 2016. Across all five islands, eight vagrant bird species were newly recorded in 2016, and 10 were recorded in 2016 for only the second time. Non-native birds were counted on only two of the five islands: Eurasian Collared Dove and European Starling on Santa Rosa, and European Starling on Santa Cruz. However, sightings of non-native species, including ......

Landbird monitoring 2016 annual report: Channel Islands National Park

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