Ecosystem Information

The Pacific and Yukon Region supports large populations of breeding seabirds. It is estimated that over 5.6 million breed at more than 500 locations along the coast (Rodway 1991). Seabirds are an integral part of coastal marine ecosystems. Monitoring programs conducted by Environment Canada's Canadian Wildlife Service at Haida Gwaii (Queen Charlotte Islands), Triangle Island, Desolation Sound and Georgia Basin (south coastal BC) provide population trend data (see map).

Between 1980 and 1986, the Canadian Wildlife Service (CWS) conducted inventories of nesting seabirds in Haida Gwaii to establish a baseline estimate of nesting seabird populations. Approximately 500,000 Ancient Murrelets presently nest on 31 islands in Haida Gwaii, representing almost all of the BC population and about half of the species' world population. Almost half (49%) of the Haida Gwaii population nest on four islands off Graham Island. Another 44% nest on 17 islands along the east coast of Moresby Island, mainly within Gwaii Haanas National Park Reserve, and the remaining 7% in 10 colonies along the rugged west coast of Moresby Island. Changes in Ancient Murrelet populations in Haida Gwaii have been variable among island populations. For example, at Helgesen Island they declined by 23% while at Lihou Island they increased by 9.5%. The graph below shows this variability at three large colonies that have been surveyed since 1980. Why some of these colonies have had declines is explained under the "why is it happening" section.

Source: Data is from Lemon and Gaston (1999). Note Langara Island data represents the number of active burrows. Biologists estimate the number of burrows in a colony by extrapolating the average burrow density, measured at several subplots, to the entire colony. Adjusting for the percentage of burrows in which breeding occurred provides an estimate of the breeding population in that particular year.

To investigate seabird population trends and their underlying causes elsewhere in coastal British Columbia, a monitoring station has been set up at Triangle Island, off northwest Vancouver Island. This monitoring station is run by CWS and the Centre for Wildlife Ecology at Simon Fraser University (SFU). The Triangle Island seabird colony is the largest in BC with the world's largest breeding population of Cassin's Auklet (1.1 million), and significant breeding populations of Rhinoceros Auklet (82,000), Tufted Puffins (52,000) and Common Murres (8,200) (Rodway 1991). Counts of active nesting burrows at permanent monitoring plots on Triangle Island did not detect long-term declines for Rhinoceros Auklet and Tufted Puffin populations but revealed a significant decline for Cassin's Auklet. This decline in burrow use by Cassin's Auklet is consistent with measures of low adult survival for the species on Triangle Island (Bertram et al. 2000).

In Desolation Sound, Marbled Murrelets have been studied since 1991 by CWS and Simon Fraser University. Unlike most seabirds, Marbled Murrelets nest solitarily or in loose associations, in old-growth forests up to 60 km from the ocean. This makes monitoring for this species more difficult than for other seabirds. After five years of intense banding, a survival estimate of 85% for Desolation Sound Marbled Murrelets was calculated, and the population is estimated at approximately 5,000 birds (Lougheed et al. 1998 and Cam et al. 2002). Data from nests found during radio-tracking allowed a preliminary estimate of breeding success of 40%. As time-series and sample sizes continue to grow, estimates will improve. Designated nationally as threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and red-listed by the BC government, the BC population constitutes about 20-30% of the total world breeding population. At this time there is insufficient data to indicate trends in the overall size of this population.

Although significant numbers of seabirds also winter along the coast of British Columbia, they are spread out and difficult to census. The National Audubon Society Christmas Bird Count, a limited time based survey (1 day/year) conducted by volunteers, show wide fluctuations in seabird numbers for the Georgia Basin. Of the three species best monitored by shore counts, the Common Murres have the greatest winter counts but are highly variable from year to year. The Marbled Murrelets counts indicate a build up to 1989 then dropping to lower numbers by early 2000. Pigeon Guillemot, the least numerous of the group by far, show wide count fluctuations, making it difficult to determine whether their numbers have declined in recent years.

Source: National Audubon Society (2002). The Christmas Bird Count Historical Results [Online]. Available http://www.audubon.org/bird/cbc [October 2002]. The number of birds are reported per party hour in order to standardize the data over time due to yearly fluctuations in participation and effort. Counts represent mostly shore observations from 13 circle count locations in the Georgia Basin of British Columbia. Some years not all counts were completed. See graph data for more details on the data, its calculations and a cautionary note on interpretation of counts.

Why is it Happening?

A wide variety of factors can affect seabird populations including disturbance, changes in key prey species, oil spills, toxic contaminants, overfishing, gillnet bycatch, predation and climatic conditions (Bertram 1995).

In Haida Gwaii the main factor influencing Ancient Murrelet populations appears to be introduced mammals. For example, Langara Island murrelets sustained heavy predation from Norway and Black rats. All population estimates for colonies without introduced predators recorded increases in the breeding population ranging from 0.2 to 9.5% annually between 1980 and 1998 (Lemon and Gaston 1999). However, changes at colonies where introduced predators have been, or still are, present were all negative, with annual rates of decrease ranging from -1 to -23%. At Langara Island, approximately half of the 80,000+ burrows present in 1981 were gone by 1993. This colony may have supported as many as 200,000 breeding pairs earlier this century.

To address the declining seabird populations on Langara Island, the Canadian Wildlife Service began a rat eradication program in 1993. This program was based on methods used to exterminate pests from offshore islands in New Zealand, and was funded by compensation money from the Nestucca oil spill in 1989. As of 2002, there was no evidence of rats on the island. Unfortunately, the other islands with seabird colonies plagued by rats are very large (e.g. Lyell and Kunghit Islands) and eradication does not appear a realistic prospect at present.

In Haida Gwaii, between 1985 and 1995, the Ancient Murrelet population on Reef Island increased by almost 3% per year while the population on nearby East Limestone decreased by 1% per year (Lemon and Gaston 1999). Raccoons, another predator of seabirds, were present at East Limestone but no raccoons have been recorded on Reef Island. Raccoons were introduced to Haida Gwaii in the early 1940s because of their value as furbearers. However, they are able to cross stretches of open water. In the long term most of the Ancient Murrelet colonies could be affected if the raccoons expand unchecked.

Except for locations where there are introduced predators in Haida Gwaii, Ancient Murrelet colonies are stable or increasing. It is possible that population increases at certain islands reflect decreases at those islands with introduced predators. Young birds joining colonies may avoid those islands where predators are active, increasing recruitment to unaffected islands.

At Triangle Island, interannual variation in timing of breeding and reproductive success is tied to variation in oceanographic conditions, probably through effects on availability of key prey species throughout the breeding season. Some of the more important species are rockfish, sandlance and Pacific saury for species that feed themselves and their offspring on fish and other large items (including Rhinoceros Auklets, Tufted Puffins and Common Murres), and copepods for species that feed on smaller planktonic prey (such as Cassin's Auklets and Leach's Storm-petrels). There has been a general advancement in the timing of breeding at Triangle since the 1970s. This being most marked for the larger species, and is probably tied to a general increase in sea surface temperatures along much of the Pacific coast through this period. Both sea surface temperatures and air temperatures increased through the 20th century, and the 1990s had some of the highest values ever recorded.

Source: D. Bertram, CWS, Delta. 2002. Values are mean hatch dates (with 95% confidence intervals) for Cassin's Auklet, Rhinoceros Auklet and Tufted Puffin. Values for Common Murre are dates when nestlings were first observed.

There is compelling evidence that in years of warm ocean temperatures, the peak in availability of copepod prey for Cassin's Auklets occurs too early, so that reproductive success and chick growth rates are reduced (Bertram et al. 2001). The generally warmer conditions in recent years also may have caused a reduction in adult survival rates of Cassin's Auklets at Triangle Island (Bertram et al. 2000).

Source: Bertram, 2001. Growth rates for chicks of each species are expressed as anomalies from average growth rate for the period 1976 to 2001.

Throughout coastal BC, it is speculated that populations of Marbled Murrelets are declining due to the removal and fragmentation of old-growth forest, bycatch in gill net fisheries, recreational usage of the marine habitat, urban development and oil spills.

Marine pollution, such as oil spills and marine debris, may be having a large effect on some seabird populations. Environment Canada's Emergencies Section and the BC Oil Spill Workforce respond to spill events. In 1988, the Nestucca oil spill off the State of Washington coast killed an estimated 56,000 seabirds along the Washington and Vancouver Island coastline (Ford et al. 1991, Burger 1993). Marine spills continue to impact the BC coastline. Surveys conducted by the Department of Fisheries and Oceans estimate between 100,000 and 500,000 pieces of marine debris float in BC's coastal waters. In 1990, volunteers from BC Coastal Cleanup Campaign found that some beaches of the southern mainland and Vancouver Island had more than 1,000 pieces of debris per kilometre and that 77% of the debris was plastic or Styrofoam.

Why is it Significant?

Seabirds are conspicuous marine animals and studies of their population changes, breeding success and diets continue to increase our understanding of marine ecosystems (Furness and Greenwood 1993).

Colonial seabirds are among the few common vertebrates in which it is possible to get a reasonable estimate of global as well as regional populations. This makes them valuable for monitoring long-term changes in marine ecosystems related to the effects of global climate change, periodic El Niño events, over-fishing and pollution.

Marbled Murrelets are unique seabirds since they nest almost exclusively in old-growth forest. Population trends in Marbled Murrelet reproductive success would then also reflect, to some extent, the health of terrestrial ecosystems in BC.

These monitoring programs are also important in assessing whether seabird populations are being sustained at desirable levels. Under Canada's Committee on the Status of Endangered Wildlife (COSEWIC), one species, Marbled Murrelet, is listed as threatened and another species, Ancient Murrelet, is listed as special concern. Of the fourteen seabird species and two subspecies that breed in British Columbia, six are provincially red-listed, four blue-listed and three are stable or increasing. Three species are not known well enough to be rated.

Status of seabird species breeding in British Columbia.
Species	Estimated numbers	Status	Comments
Leach's Storm-Petrel	1,400,000	trends unknown	status unknown
Fork-tailed Storm-Petrel	400,000	trends unknown	status unknown
Double-crested Cormorant	4,000	blue-listed by BC	breeding restricted to Strait of Georgia
Brandt's Cormorant	200	red-listed by BC	irregular breeder
Pelagic Cormorant - has 2 subspecies	9,000	the pelagicus subspecies red-listed by BC - other subspecies is stable	widespread coastal breeder
Glaucous-winged Gull	58,000	increasing
Common Murre	9,000	red-listed by BC	scarce breeder, mostly on Triangle Island.
Thick-billed Murre	20	red-listed by BC	at southern limit of range
Marbled Murrelet	66,000	threatened as per COSEWIC & red-listed by BC	listed due to threats of nesting habitat loss from logging of old growth forests.
Ancient Murrelet	540,000	special concern as per COSEWIC & blue-listed by BC	impacted by rat and raccoon predation
Horned Puffin	60	red-listed by BC	at southern limit of range
Tufted Puffin	78,000	blue-listed by BC	severe reproductive failure at Triangle Island 1994-98. No evidence for population decline.
Cassin's Auklet	2,700,000	blue-listed by BC	Triangle Island population is declining.
Rhinoceros Auklet	720,000	stable	some reproductive failure at Triangle Island. No evidence for population decline.
Pigeon Guillemot	9,000	trends unknown	scattered; difficult to census

Source: Canadian Wildlife Service. 1999. Red-listed species by the BC government are any indigenous species or subspecies (taxa) considered to be extirpated, endangered, or threatened in British Columbia. Extirpated taxa no longer exist in the wild in British Columbia, but do occur elsewhere. Blue-listed species by the BC government are particularly vulnerable to human disturbance and are at risk but not extirpated, endangered or threatened.

What is Being Done?

The Canadian Wildlife Service (CWS) management plan for seabirds takes a proactive approach. Ongoing monitoring provides information on the status of seabird species and identifies threats to their populations and to their habitats. For example, within Gwaii Hannas National Park Reserve representative monitoring plots have been permanently marked and mapped out on three of the large colonies of Ancient Murrelets (Ramsay, George and Rankine Islands). Repeat counts within these plots at 5 year intervals will measure the status of the breeding population of those colonies and provide population trend data.

In 1999, the Canadian Wildlife Service also entered into a partnership with Bird Studies Canada to conduct the BC Coastal Waterbird Survey. The monthly survey will assess changes in the number and distribution of coastal waterbirds including seabirds in BC. During each survey volunteers systematically cover over 200 standarized shoreline sites. To view some recent results (1999/2000), or to participate in the survey visit www.bsc-eoc.org/regional/bccwaterbirds.html.

As part of the Canadian Wildlife Service research into understanding population trends, regular sampling of seabirds for contaminants is carried out under the CWS National Seabird Monitoring Program. Samples of eggs of three seabird species representing coastal (Double-crested Cormorants), continental shelf (Rhinoceros Auklet) and offshore habitats (Leach’s Storm Petrel) are collected at 4 year intervals. These analyses will allow any significant trends in contaminant levels to be measured, causes identified and actions taken.

Where healthy levels of seabirds are not being maintained the Canadian Wildlife Service takes appropriate population intervention measures. These measures can include securing habitats, promoting stewardship, or regulating predator species such as rats and raccoons.

CWS is also involved in a cooperative program to prevent the spread of raccoons in Haida Gwaii and is involved with Bird Studies Canada in Beached Bird Surveys in BC to assess background levels of chronic oiling of seabirds and other marine animals.

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What is Happening?

Why is it Happening?

Why is it Significant?

What is Being Done?