Declines in Populations of Peregrine Falcons and Their Seabird Prey at Langara Island, British Columbia

Nelson, R. Wayne; Myres, M. T.

doi:10.2307/1367687

Cited by 25 publications

(31 citation statements)

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“…This large fishing fleet had the potential to cause mass mortality of seabirds and may have contributed significantly to the decline of Ancient Murrelets on Langara prior to the 1970s. Nelson and Myres (1976) hypothesized that the decline of Ancient Murrelets onLangara may have resulted from reductions in the zooplankton upon which the birds feed. They reasoned that "Either biocides have affected plankton (probably via the Davidson Current flowing north from California), or an anomalous intrusion of warm water near the British Columbia coast for most of 1957-71 has reduced the supply of plankton" (Nelson & Myres 1976; see also Nelson 1976).…”

Section: Commercial Fishing Operationsmentioning

confidence: 99%

“…Nelson and Myres (1976) hypothesized that the decline of Ancient Murrelets onLangara may have resulted from reductions in the zooplankton upon which the birds feed. They reasoned that "Either biocides have affected plankton (probably via the Davidson Current flowing north from California), or an anomalous intrusion of warm water near the British Columbia coast for most of 1957-71 has reduced the supply of plankton" (Nelson & Myres 1976; see also Nelson 1976). Gaston (1992) argued that it is unlikely that pesticides or oceanographic changes caused a consistent decline in zooplankton production in the region.…”

Section: Commercial Fishing Operationsmentioning

confidence: 99%

“…Beebe (1960), who studied Peregrine Falcons on Langara from 1952 to 1958, stated that "... the entire fringe forest seems to be one continuous colony, extending to all parts of the island that I know, from Cloak Bay around to Langara Point." Signs that colony extent had diminished were evident in 1970, when Sealy noted (cited in Nelson & Myres 1976) that the colony near Dadens, which was "riddled with burrows" in 1966 (Campbell 1969), had been abandoned. In retrospect, Sealy estimated 80,000 to 90,000 pairs of Ancient Murrelets in 1971 (Vermeer et al 1984).…”

Section: Introductionmentioning

confidence: 99%

“…Total counts of occupied Peregrine Falcons nests on Langara indicate that numbers declined from about 21-23 pairs in the early 1950s to 5-6 pairs during -1973(Nelson & Myres 1976. Their numbers have since remained roughly constant (Nelson 1990).…”

Section: Introductionmentioning

confidence: 99%

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The Roles of Introduced Rats and Commercial Fishing in the Decline of Ancient Murrelets on Langara Island, British Columbia

Bertram

1995

Conservation Biology

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I examined the decline of Ancient Murrelets (Synthliboramphus antiquus), a small, burrow‐nesting seabird, at Langara Island. The island’s seabird colony was historically one of the largest colonies of Ancient Murrelets in British Columbia—perhaps in the world—with an estimated 200,000 nesting pairs. I reviewed historical information and compared the results of surveys from 1981 and 1988 that employed the same census protocol. The extent of the colony, a potential index of population size, declined from 101 ha in 1981 to 48 ha in 1988. Burrow density increased during the same period, however, suggesting that the colony bad consolidated. In 1988, the population estimate was 24,200 ± 4000 (S.E.) breeding pairs compared to 22,000 ± 3700 in 1981. in 1988, 29% of the burrows that were completely searched contained bones of Ancient Murrelets. Bones were most common in burrows located in abandoned areas of the colony and were least common where burrow occupancy was high. The discovery of adult Ancient Murrelets killed in their burrows by introduced rats, combined with the high proportion of burrows with bones, suggests that rats (Rattus rattus and R. norvegicus) have contributed significantly to the decline of the population. In addition, the presence and activities of a salmon‐fishing fleet in the 1950s and 1960s may also be linked to the decline of the Langara Ancient Murrelet population during that period because these fisheries are known to have caused heavy mortality through fatal light attraction and drowning in gill nets. The combined effects of ongoing predation by introduced rats and—to a lesser extent—previous, episodic fishery‐induced mortality are probable causes for the population decline.

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Section: Commercial Fishing Operationsmentioning

confidence: 99%

Section: Commercial Fishing Operationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Roles of Introduced Rats and Commercial Fishing in the Decline of Ancient Murrelets on Langara Island, British Columbia

Bertram

1995

Conservation Biology

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“…There were no other fish remains among about 3,000 food items identified at Peregrine nests in north-east Scotland (Weir et al, in prep,), and I have only one record from this region of a Peregrine attempting to take prey from the water. However, Nelson and Myres (1976) stated that the North American race F.p.pealii did so when hunting small auks (Alcidae) over the sea. St John (1888) obtained a a fine young Peregrine from a shepherd on the upper Findhorn (Scotland), which had been fed on trout since taken from the nest.…”

Section: A J Prater British Trust Formentioning

confidence: 99%

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et al. 1979

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Organochlorine contaminants in seabird eggs from the Pacific coast of Canada, 1971?1986

Elliott¹,

Noble²,

Norstrom³

et al. 1989

Environ Monit Assess

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Eggs were collected from seven seabird species at colonies on the British Columbia coast from 1983 to 1986 and analyzed for organochlorine contaminants. Total PCB levels (wet weight) were highest in double-crested cormorants (Phalacrocorax auritus) from the Fraser estuary (2.91 mg kg(-1)) and the Strait of Georgia (3.79 mg kg(-1)). Highest DDE levels were in fork-tailed storm-petrels (Oceanodroma furcata) from the Queen Charlotte Islands (1.68 mg kg(-1)). Organochlorine levels were generally lower in eggs from the mid 1980s than in those collected in the early 1970s. Organochlorine levels in Pacific alcids and hydrobatids foraging in offshore locations were compared to those in the same or ecologically similar species from the Canadian Atlantic coast. DDT- and HCH-related compounds were higher in Pacific populations while levels of dieldrin, oxychlordane, and HCB were generally lower. With the exception of β-HCH, levels of all measured organochlorines were lower in cormorants breeding in the Fraser River estuary than in cormorants from the St. Lawrence River estuary on the Atlantic coast.

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Declines in Populations of Peregrine Falcons and Their Seabird Prey at Langara Island, British Columbia

Cited by 25 publications

References 0 publications

The Roles of Introduced Rats and Commercial Fishing in the Decline of Ancient Murrelets on Langara Island, British Columbia

The Roles of Introduced Rats and Commercial Fishing in the Decline of Ancient Murrelets on Langara Island, British Columbia

Short Notes

Organochlorine contaminants in seabird eggs from the Pacific coast of Canada, 1971?1986

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