British Columbia Seabird Colony Inventory

This data set includes the locations of all known seabird colonies along the coast of British Columbia, and provides a compilation of the population estimates of seabirds breeding at those colonies since 1980, and historical estimates prior to 1980 for some colonies. It does not include an estimate of the numbers of juvenile birds or non-breeders in the population.

The rationale for developing this inventory was the recognized need for a product that could assist with: coastal zone and conservation area planning; emergency response to environmental emergencies and identifying areas of potential interactions between seabirds and anthropogenic activities. In addition, the data used to develop the document provides a baseline to compare with future seabird population estimates in order to measure the impacts of shifts in composition, abundance and/or distribution of prey, and climatic and oceanographic changes. The database is not a substitute for on-site surveys usually required for environmental assessment.

Here we present data on the breeding colony population estimates of the 15 species of seabirds (including two storm petrels, three cormorants, one gull and nine alcids) and one shorebird (Black Oystercatcher Haematopus bachmani) that breed on the coast of British Columbia. Over 5.5 million colonial birds are currently estimated to nest at 627 sites, based on surveys primarily conducted in the 1980’s. Five species (Cassin's Auklets Ptychoramphus aleuticus, Fork-tailed Storm-petrels Oceanodroma furcata, Leach's Storm-petrels Oceanodroma leucorhoa, Rhinoceros Auklets Cerorhinca monocerata, and Ancient Murrelets Synthliboramphus antiquus) comprise the vast majority of that population, although Glaucous-winged Gulls (Larus glaucescens) and Pigeon Guillemots (Cepphus columba) nest at the most sites. Marbled Murrelets (Brachyramphus marmoratus), which nest on the mossy limbs of mature and old-growth trees within the coastal forests, are not included in this database, due to their dispersed nesting habit.

The population estimates presented in this database are compiled from the results of several surveys. Many of the seabird breeding colonies in British Columbia have been known for more than 50 years, but because of the remoteness of the sites, visits to them have been rare. The majority of the data are the results of a comprehensive inventory of colonial nesting seabirds along the British Columbia coastline conducted between 1980 and 1989 by the Canadian Wildlife Service of Environment and Climate Change Canada. The goal of that program was to establish baseline estimates of breeding seabird populations in BC using standardized survey techniques to allow future comparisons and monitoring of those populations. A few colonies on small remote islands were not visited during that survey. Therefore, for some colonies the most current population estimates are from the first complete survey of the BC coastline, carried out by the Royal British Columbia Museum in the mid 1970’s. That survey identified colony sites and provided rough assessments of the population sizes of breeding seabirds.

Since 1989, surveys have been conducted on some alcid, cormorant and gull colonies along the BC coast, and results have been included in the dataset (data entry ongoing). As well as data from Canadian Wildlife Service surveys, we have attempted to obtain recent data from all other sources including Parks Canada, the Ministry of Forests, Lands, Natural Resource Operations and Rural Development, the Bamfield Marine Station and the Laskeek Bay Conservation Society.

Since 2000, inventories of nesting Black Oystercatchers have been conducted in some regions of the coast by Parks Canada and partners (Gulf Islands National Park Reserve, Pacific Rim National Park Reserve, and Gwaii Haanas National Park Reserve) and results have been included in the dataset (data entry ongoing). A long time series of nesting Black Oystercatcher data collected by Laskeek Bay Conservation Society in the Laskeek Bay area of the East Coast of Moresby Island has also been included in this dataset.