Breeding status of Cassin's auklet (Ptychoramphus aleuticus) and Rhinoceros auklet (Cerorhinca monocerata) on Castle Rock National Wildlife Refuge, Del Norte County, California.

Graduation Date

2010

Document Type

Thesis

Program

Other

Program

Thesis (M.S.)--Humboldt State University, Natural Resources: Wildlife, 2010

Committee Chair Name

Richard T. Golightly

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Auklets, Humboldt State University -- Theses -- Wildlife, Rhinoceros auklet, Breeding status, Ptychoramphus aleuticus, Castle Rock, Seabirds, Cassin's auklet, Thermal imaging, Cerorhinca monocerata

Abstract

Breeding population estimates of the Cassin's Auklet (Ptychoramphus aleuticus) and Rhinoceros Auklet (Cerorhinca monocerata) on Castle Rock National Wildlife Refuge are hindered by nocturnal colony activity and burrow-nesting habits. Additionally, Castle Rock cannot be physically accessed during the breeding season because of disturbance to nesting seabirds. A remotely controlled thermal-imaging video camera was installed on the island and was used to observe auklets during the 2007 breeding season. I estimated burrow entrance occupancy and the total number of auklet nest sites to assess the status of Cassin's and Rhinoceros Auklets breeding on the eastern half of the island. The total number of nest cavities available to auklets during the breeding season was estimated by a post-season burrow count and a sub-sample of burrow entrances were examined to determine the mean number of nest sites per burrow entrance. Approximately 69.6% of auklet burrow entrances were occupied by Rhinoceros Auklets and 4.3% of burrow entrances were occupied by Cassin's Auklets during the 2007 breeding season. The post-season count of auklet burrow entrances was 1126 over an area of approximately 3 hectares and led to a total of 1013 nest sites. I estimated 43 and 705 breeding pairs of Cassin's and Rhinoceros Auklets, respectively, were on the island in 2007.

https://scholarworks.calstate.edu/concern/theses/8049g726x

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