Printer Friendly

Decline of the Pelagic Cormorant in western Queen Charlotte Strait, British Columbia, 1975-2014.

Abstract--In July 2014, we conducted nest counts at 7 of 8 known breeding colonies of Pelagic Cormorants (Phalacrocorax pelagicus) in western Queen Charlotte Strait, British Columbia, to assess the current status of this population. Four nests were found on Dugout Rocks, the only known colony still used; 1 nest was found at Pine Island, a 9th (newly recorded) breeding location in the region. Total numbers of nests in this region declined 97% from 197 to 231 nests in 1975-1976, to 60 nests in 1982-1988, to 5 nests in 2014. Limited evidence suggests that Bald Eagle (Haliaeetus leucocephalus) disturbance and predation may be the main reason for this major decline in the cormorant breeding population. Historical population size of Pelagic Cormorants prior to the 1960s also may have been quite low, with breeding 1st recorded in this region in 1968, although little prior survey effort occurred. Population growth probably occurred in the 1960s and early 1970s to reach the population size noted during the 1st complete survey in 1975-1976, during a period of reduced impacts from eagles.

Key words: British Columbia, colony, nest, Pelagic Cormorant, Phalacrocorax pelagicus, roost, survey, trend

**********

Over the past 3 decades, declines in breeding population size of Pelagic Cormorants (Phalacrocorax pelagicus) have been noted in 2 areas of southern British Columbia. In the Strait of Georgia, nest numbers were 54% lower in 2000 (n = 1088) than in 1987 (n = 2356) (Chatwin and others 2002). At Barkley Sound, on the southwest coast of Vancouver Island, nest numbers were 85% lower in 1989 (n = 17) than in 1947-1975 (n = 170), with similar low nest numbers persisting in 2006-2007 (n = 26) (Vermeer and others 1992; Carter and others 2007). Three primary factors can account for reductions in nesting populations of Pelagic Cormorants over these wide areas: (1) Bald Eagle (Haliaeetus leucocephalus) disturbance and predation at breeding colonies; (2) changes in prey availability (Pelagic Cormorants feed primarily on bottom and midwater fish); and (3) human disturbance at breeding colonies (nests typically are placed on cliff ledges near the water, which can be disturbed by humans on the island or in boats near the island). However, at Seabird Rocks, near the entrance to Barkley Sound, unusual River Otter (Lontra canadensis) predation was confirmed in 2011 to be the factor responsible for colony loss (Carter and others 2012).

To further investigate the status of breeding populations of Pelagic Cormorants in southern British Columbia, we conducted a survey of breeding colonies in the western Queen Charlotte Strait region off northeastern Vancouver Island in 2014 and we collated available historical data in this region and neighboring areas to help assess changes in population size over time. Pelagic Cormorants were last surveyed in western Queen Charlotte Strait in 1982-1988, when decline was noted compared to 1975-1976 surveys, although details were not reported (Campbell and others 1990; Rodway 1991; Rodway and Lemon 1991a,b). After 1988, no further surveys of these remote colonies were conducted and nothing was known about their recent status, prior to our survey in 2014.

METHODS

2014 Survey

We surveyed 7 of 8 known colonies in the western Queen Charlotte Strait region (WQCS) in an approximately 50-km-long area between Dugout Rocks (51.3675[degrees]N; 127.806[degrees] W) and the Buckle Group (Bright Island) (50.9414[degrees]N; 127.656[degrees]W) (Fig. 1; Table 1). Due to time constraints, we were not able to conduct a survey at the 8th known colony at McEwan Rock. The 2014 survey was conducted on 8 and 9 July to match the approximate timing of the 1975-1976 and 1982-1988 surveys between early July and early August, although in 1976 some surveys were conducted in mid-June (Summers and Campbell 1978; Rodway and Lemon 1991a,b). The 2 northernmost colonies (Dugout Rocks and Ruby Rocks) were located up to 23 km north (straight-line minimum distance measurements using an online distance calculator) of Cape Caution (technically just north of Queen Charlotte Strait; Fig. 1). We added these 2 colonies to the 6 colonies in Queen Charlotte Strait proper to examine all known colonies in the WQCS geographic area (Fig. 1), which is separated by about 50-100 km from other known colonies at Blenheim Island, Deep Sea Bluff, Scott Islands, and Quatsino Sound (Drent and Guiguet 1961; Summers and Campbell 1978; Rodway and Lemon 1991a,b). Surveys were conducted by observing birds and nests with 8 x 40 power binoculars from a British Columbia Parks patrol vessel (Nahwitti Ranger; 8.5-m aluminum craft with twin Volvo Penta B4 225 hp inboard engines). This survey method reduced disturbance to breeding cormorants and other breeding seabirds from landing on islands and allowed us to efficiently survey widely-spaced small colonies in this region with limited time and funds. But because we did not land at these islands (as had been done in previous surveys), we could not discover carcasses or certain other information about predators, and we could not closely examine cormorant nest structures to best assess nesting stage. Each colony was circumnavigated at slow speeds (4 to 10 km/h) at a distance of about 100 m from shore, and all seabird nests and birds observed were counted. At nests, birds in incubation posture or standing in or beside nests were recorded. Plumages were recorded as "adult" (dark glossy contour feathers with or without white flank patches, 2-3+ y old) or "subadult" (brown contour feathers without white flank patches, 1-2 y old) (Pyle 2008; Hobson 2013). Due to time constraints, surveys were focused primarily on covering known Pelagic Cormorant colonies in this region, assuming that most or all colony locations had been identified through past surveys. Numbers of Glaucous-winged Gulls (Larus glaucescens), Black Oystercatchers (Haematopus bachmani), and Pigeon Guillemots (Cepphus columba) also were counted as the boat passed around islands with cormorant colonies, but nest numbers were not determined. Counts of gulls included birds in nesting habitats and at roosts. Counts of oystercatchers and guillemots included birds in nesting and intertidal habitats, on the water, or flying nearby. Limited information on other species was useful for assessing possible reasons for changes in the cormorant population.

[FIGURE 1 OMITTED]

Historical Data

Historical colony survey information for the WQCS region for 1975-1976 was obtained mainly from Campbell (1976) and Summers and Campbell (1978), and for 1982-1988 from Rodway and Lemon (1991a,b). Surveys in 1975-1976 and 1982-1988 covered all seabird species and included small boat surveys around islands, as well as landing on islands. To search for additional historical data prior to about 1980, we examined the British Columbia Seabird Colony Inventory (SCI) files located at the Royal British Columbia Museum (RBCM) in Victoria (referred to herein as RBCM-SCI, unpubl. data). These files also contain information from the British Columbia Nest Records Scheme. We also summarized post-1988 surveys of breeding Pelagic Cormorants in neighboring areas at Triangle Island (Rodway and others 2011), as well as at eastern and southwestern Queen Charlotte Strait and Quatsino Sound (HR Carter, unpubl. data). To further search for historical data, a literature review was conducted for WQCS and neighboring areas.

RESULTS

Western Queen Charlotte Strait--2014

A total of 5 Pelagic Cormorant nests were found at 2 colonies (1 known and 1 new) in WQCS in 2014 (Table 1). At the known colony at Dugout Rocks, 4 single nests were located within 3 deep clefts in the rock (Fig. 2): (#1) 1 adult standing in the nest; (#2) 1 adult standing in the nest and 1 adult standing beside the nest; and (#3) 1 adult in incubation posture on a nest, plus 1 adult standing in another nest in the same cleft. All nests were well-built and standing adults likely had small chicks or were incubating shortly before standing due to the presence of the survey boat. A total of 23 birds were noted at Dugout Rocks, including the 5 adults attending nests and 18 roosting birds (9 adults and 9 subadults). Roosting birds flushed during the survey, but most birds attending nests did not flush (only 1 adult standing beside a nest flushed). At the new breeding location at Pine Island, a single nest with 2 large chicks and an adult was hidden in a small cave (Fig. 3). Four other adults roosted nearby. Breeding at Pine Island had not been noted previously (Campbell 1976; Summers and Campbell 1978; Rodway and Lemon 1991a). At 6 other known colonies, no nests were noted. The coastlines of all colonies were checked thoroughly, but Dugout Rocks had deep clefts in the center of the rocks that could not be fully viewed from the boat and Storm Islands had narrow coves that we did not enter although most or all possible nesting habitats seemed to be visible. Nests at both Dugout Rocks and Pine Island appeared to contain either incubating adults or chicks, indicating that the timing of the survey was appropriate for near-maximum nest counts and that timing of breeding was similar to past surveys. At other colony locations without nests, we did not note: (1) any abandoned nests or areas of guano in nesting habitat that would have suggested earlier breeding; or (2) any persistent old nests that would have suggested breeding in recent years, although heavy winter rains in this region may wash away nests each year.

[FIGURE 2 OMITTED]

A total of 46 birds (35 adults and 11 subadults) were recorded at the 8 colonies (7 known and 1 new) surveyed. Small numbers (n = 18) roosted at 4 colonies without nests (Table 1). We also encountered 78 adults roosting on rocks with little or no nesting habitat at the outer entrances to Slingsby Channel (15 adults on a rock off Fox Islands) and Schooner Channel (19 adults on Town Rock and 44 adults on Elizabeth Rocks [Fig. 4]). All adults attending nests had visible white flank patches. Some roosting adults also had visible white flank patches, but it was difficult to determine if patches were present for many roosting adults during brief counts and some adults may have had faint white flanks that could not be easily observed.

[FIGURE 3 OMITTED]

Black Oystercatchers were surveyed at 5 colonies, Glaucous-winged Gulls at 8 colonies, and Pigeon Guillemots at 9 colonies (Appendix). Numbers of Glaucous-winged Gulls were lower than would be expected from 1975-1976 and 1982-1988 nest counts (Summers and Campbell 1978; Rodway and Lemon 1991a,b). On the other hand, numbers of Black Oystercatchers and Pigeon Guillemots were similar to past surveys, with allowance for much variation in such counts. Seven Bald Eagles (hereafter eagles), including 5 adults and 2 juveniles, were noted on Bremner Islets, and a nest may have been hidden in the trees but was not visible from the boat. At the Naiad and Reid Islets, 2 adult eagles were present at each. Three eagles were noted at different locations around the Storm Islands. Eagles were not noted at Dugout Rocks and Ruby Rocks. A single River Otter was observed at the middle rocks of the Buckle Group between Bright Island and Herbert Island.

Western Queen Charlotte Strait--1862-1988

Pelagic Cormorants were 1st reported specifically from the WQCS region by Lord (1866 [Volume II]: 301) who referred to them as "... abundant about Fort Rupert [Hudson's Bay Company fort near Port Hardy]" when he visited the fort in October and November 1862. On 22 and 24 November 1862, 2 females (1 subadult) were collected at Fort Rupert, presumably during Lord's visit; H Moffat, chief trader at Fort Rupert, was listed as the collector of one but the other did not identify the collector. These specimens became part of the James Hepburn collection in Victoria which were sent to the University Museum of Zoology at Cambridge, United Kingdom, in 1870 (UMZC 10/Phal/3/r/3; 10/Phal/3/r/5). In 1929, Young (1930) observed Pelagic Cormorants at Pine Island between 30 May and about 18 June and reported that they bred in the area, although specific nests were not described at Pine Island, Tree Islets, or Storm Islands as noted for other seabirds in 1929. In 1968, breeding of Pelagic Cormorants in the WQCS was 1st documented when 6 nests were noted by RH Drent at the Reid Islets, but no other colonies were reported in WQCS until 1975-1976 (Drent and Guiguet 1961; Summers and Campbell 1978; RBCM-SCI, unpubl. data).

Six colonies with 197-231 nests were documented in WQCS during the 1st complete survey of seabird colonies throughout Queen Charlotte Strait and the north mainland coast of British Columbia in 1975-1976 (Table 2). Most of this range of nest numbers reflected 2 estimates at Bright Island: 52 nests on 11-12 July 1975 and 21 nests on 16 June 1976 (Summers and Campbell 1978). We could not determine if the 1976 count occurred prior to completion of nest building, so we treated it as a complete annual count. During the next set of surveys in 1982-1988, 5 colonies with 60 nests were noted, by combining single counts from 1982, 1987, or 1988 (Rodway and Lemon 1991a,b). Four of these colonies also had been noted in 1975-1976, and 1 new colony was found at McEwan Rock (Table 2). At 3 other colonies, nesting was not noted in 1982-1988 where it had been noted in 1975-1976.

[FIGURE 4 OMITTED]

Neighboring Areas

Scott Islands.--In 1909-1989, Pelagic Cormorant colonies were documented at Triangle Island, Sartine Island, Beresford Island, Lanz Island, and Cox Island (Carl and others 1951; Drent and Guiguet 1961; Vermeer and others 1976a,b; Rodway and others 1992, 2011; Carter and Sealy 2011). Only Triangle Island has been resurveyed periodically, mostly between 1968 and 1989. No surveys were conducted from 1990 to 2008; surveys did occur in 2009 and 2010 (Rodway and others 2011). Nest numbers fluctuated between 1968 and 1985 (n = 33-205), and then jumped to a maximum (n = 433) in 1989. Nest numbers fell by 23% between 1989 and 2009-2010 (n = 326-335), although the population still remained larger than in 1968-1985 (Rodway and others 2011).

Eastern Queen Charlotte Strait.--Only 1 colony has been reported from eastern Queen Charlotte Strait. Drent and Guiguet (1961) noted that A Menzies (physician and naturalist on Captain Vancouver's expedition) first reported a "shag" colony at Deep Sea Bluff, Simoon Sound, in 1792, likely the earliest known breeding record in British Columbia. In 1962, 53 nests were recorded (Summers and Campbell 1978), but this colony was not active when last surveyed in 1987 (Rodway and Lemon 1991a).

Southwestern Queen Charlotte Strait.--No colonies were reported prior to 1988 in the major chain of islands between Hope Island and the Gordon Islands in southwestern Queen Charlotte Strait (Fig. 1), and only 1 survey has been conducted since 1988. On 1-2 July 2009, HR Carter (unpubl. data) surveyed Pelagic Cormorant colonies in the Goletas Channel area in southwestern Queen Charlotte Strait. On 2 July, a new small cliff colony with 2 empty nests was found on Nigei Island, 0.9 km west of Boxer Point (50.8347[degrees]N; 127.664[degrees]W; Fig. 1).

Quatsino Sound.--Breeding was first reported at the south end of the Quatsino Sound area at Solander Island in 1954 (Guiguet 1955). Vermeer and others (1992) noted similar nest numbers between 1975 (w = 771; Campbell 1976; Summers and Campbell 1978) and 1988 (n = 731), with much lower numbers in 1989 (n = 186), partly due to a food shortage, as well as differences in survey methods at Solander Island (Rodway and others 2011). Only 1 survey of breeding Pelagic Cormorants has been conducted since 1988. In 2012, HR Carter (unpubl. data) found a new Pelagic Cormorant colony on the mainland cliffs 0.25 km NW of Kains Island (50.4458[degrees]N; 128.041[degrees] W; Fig. 1) that contained 14 nests attended by 33 birds on 26 May and 92 empty nests (apparently abandoned, no birds present) on 24 July. At the nearby Gillam Islands (nesting recorded in 1988; Rodway and Lemon 1990), no nesting was found in 2012, but 3 roosting birds were noted on 26 May and about 200 on 24 July.

DISCUSSION

Timing and Degree of Decline (1975-2014)

After the 2nd set of surveys in 1982-1988, declines in nesting numbers of Pelagic Cormorants in WQCS were first reported compared to 1975-1976 counts (Campbell and others 1990; Rodway 1991; Rodway and Lemon 1991a,b). In 1975-1976, 197 to 231 nests were found in WQCS, compared with only 60 nests in 1982-1988, reflecting 70 to 74% lower numbers (see Table 2). In 1978, JB Foster and T Carson noted 1 active and 2 empty nests at Tree Islets (lower than the 7 nests in 1975), but none at Bright Island (versus 21-52 nests in 1975-1976) (Summers and Campbell 1978; RBCM-SCI, unpubl. data). This information suggested that decline was progressing in the late 1970s. Most change in total nest numbers between 1975-1976 and 1982-1988 resulted from 89% lower nest numbers at the largest colony at Dugout Rocks and 71 to 88% lower numbers at the 2nd largest colony at Bright Island. In addition, a change in colony locations apparently occurred. At Reid Islets, Storm Island, and Tree Islets, nests were recorded in 1975-1976 but not in 1986-1987. Alternatively, at Bremner Island and McEwan Rock, nests were recorded in 1982 but not in 1975. Based on similar numbers of birds and proximity of these 5 locations, it appeared that, between 1976 and 1982, some birds may have moved from Reid Islets and Storm Islands to Bremner Island and McEwan Rock.

A 92% reduction in numbers of nests occurred between 1982-1988 (n = 60) and 2014 (n = 5), assuming that McEwan Rock also did not have any nests in 2014 (like other nearby colonies in this area). Dugout Rocks numbers were 97% lower in 2014 than in 1976. However, the 18 roosting birds at Dugout Rocks in 2014 may suggest that: (1) some adults may have not built nests; (2) progeny from past years may have attended the colony prior to future breeding (assuming some philopatry); or (3) roosting cormorants were not associated with the colony and were merely feeding in this area. Ruby Rocks and Bright Island were no longer active colonies in 2014. Reid Islets, Storm Islands, Tree Islets, and Bremner Island remained inactive in 2014, as in the 1980s. While 40 non-nesting birds (29 in adult and 11 in subadult plumages) were noted roosting at known colony locations, another 78 birds in adult plumage were found roosting away from colonies. We suspect that most or all non-nesting birds originated from other areas outside WQCS and birds in adult plumage likely were 2- to 3-y-old birds (not yet of breeding age or condition). The few nests found on the 2014 surveys could not account for this number of pre-breeders derived from WQCS colonies. The few birds observed in subadult plumage may reflect small numbers of chicks produced in WQCS in recent years (which is consistent with low nest numbers found in 2014), but we also had some difficulty with detecting darker-brown plumages (especially second-year birds) at greater distances from the boat (Pyle 2008; Hobson 2013).

We consider that patterns of colony use by breeding Pelagic Cormorants in WQCS between 1975 and 2014 are most consistent with a major population decline and do not merely represent interannual variation. To establish full confidence in assessing population changes, it is desirable to collect data annually at all colonies or at least have more than 1 y of data to establish population levels in each decade, because numbers of cormorant nests can be highly variable across years (Carter and others 1984, 2007; Rodway and others 2011). However, the remote nature of the WQCS region and few funds available for seabird population monitoring have prevented gathering more than 1 y of data in each decade at most of these colonies. Although the single year of surveys in 2014 may not have detected peak breeding numbers in WQCS (either within that year or in relation to recent years), we did not note any empty abandoned nests from 2014 or persistent nests from previous years, suggesting that we did not miss peak nesting numbers due to earlier timing of breeding or low breeding in 2014. Local shifts of breeding birds between known colonies within the WQCS, that appeared to occur between 1975-1976 and 1982-1988 surveys, did not appear to occur between 1982-1988 and 2014 surveys. However, the single nest at the new breeding location at Pine Island may have reflected a local shift of a few birds associated with the nearby Tree Islets colony that was active in 1975-1978, although this nest was difficult to detect in 2014 and breeding at this location may have been missed during past surveys.

Reasons for Decline

While evidence for decline of breeding Pelagic Cormorants in WQCS since 1975 is reasonably compelling, mechanisms causing this decline are less well understood. We suspect that Bald Eagle disturbance and predation may be the main reason for this decline, based on indirect evidence including: (1) restricted use of protected nesting habitats in rock clefts-caves at Dugout Rocks and Pine Island by cormorants in 2014--previous larger numbers of active nests were not restricted to limited rock cleft-cave habitats, suggesting reduced predation by Bald Eagles in the past--the remnant population in Barkley Sound in 2006-2007 also was found in similar nesting habitats that provided some protection from avian predators (Carter and others 2007); (2) widespread presence of eagles at Bremner Islets, Naiad Islets, Reid Islets, and Storm Islands in 2014, and presence, nesting, and predation of seabirds (although not cormorants) by eagles at these and other nearby WQCS islands in 1975-1976 and 1982-1988 (Rodway and Lemon 1991a,b); and (3) apparent decline in Glaucous-winged Gulls, which are commonly preyed upon by eagles, at the same islands between 1982-1988 and 2014, although populations of other marine bird species not heavily preyed upon by eagles (such as Black Oystercatchers and Pigeon Guillemots) did not change to a great extent. Most eagle impacts on nesting cormorants likely occurred during the period of greatest decline in the 1970s and 1980s, but direct observations of eagle impacts were not reported during surveys in 1975-1976 and 1982-1988 (Summers and Campbell 1978; Rodway and Lemon 1991a,b). In such a remote area as WQCS, a lack of direct observations is not surprising, given small colonies that may be targeted by eagles over short periods of time and surveys that were conducted over only a few days (often relatively late in the breeding season) each decade.

The timing and pattern of cormorant and gull decline in WQCS were generally consistent with an increase in eagle abundance. Since the 1990s, population levels of eagles have remained higher than in previous decades, and eagle predation and disturbance at seabird colonies in the Strait of Georgia have increased (Blight 2012; Hipfner and others 2012; T Chatwin and H Carter, unpubl. data). Decline in the WQCS Pelagic Cormorant population in the 1970s and 1980s may have reflected a rebound in eagle numbers in the WQCS during these decades, but we are not aware of eagle studies that have demonstrated such a rebound in this area. Given 1st recorded breeding by Pelagic Cormorants in the WQCS region in 1968, rapid growth of the nesting population also appeared to occur in the 1960s and early 1970s during a period of potentially reduced eagle abundance, although we also are not aware of eagle studies that demonstrated lower numbers in the WQCS region at this time. Breeding Pelagic Cormorants were documented much earlier (1792-1954) at neighboring colonies around the WQCS survey area (Carl and others 1951; Guiguet 1955; Drent and Guiguet 1961; Carter and Sealy 2011) and likely provided colonists for the WCQS region when eagle numbers were reduced in the 1950s and 1960s, even though small numbers may have long bred in the WQCS region prior to 1968 given recorded occurrence since the 1860s. Increases in Pelagic Cormorant populations occurred in the Strait of Georgia between the 1910s and 1950s, partly due to reduced impacts from seabird harvesting by First Nations peoples, although eagle numbers also were reduced during this period (Pearse 1956; Drent and Guiguet 1961). At Triangle Island, low or no apparent impacts on Pelagic Cormorants from breeding eagles and Peregrine Falcons (Falco peregrinus) did not reflect any major changes in eagle or falcon abundance over time, but likely did reflect the great abundance of other preferred eagle and falcon prey, especially hundreds of thousands of Cassin's Auklets (Ptychoramphus aleuticus; Beebe 1960; Rodway and others 2011). With limited available information, we were not able to detect any changes in numbers of Pelagic Cormorants breeding in neighboring areas that may have resulted from breeding adults moving away from the WQCS region during the period of decline. Rodway and others (2011) speculated that some birds from WQCS or Quatsino Sound may have moved to Triangle Island, potentially accounting for the high count in 1989, but such movements have not been well documented in Pelagic Cormorants, adults may have remained in the WQCS region without breeding, and the high count at Triangle Island can be explained in other ways.

Direct or indirect evidence of non-eagle factors that could have caused or contributed to decline of nesting Pelagic Cormorants in WQCS is lacking. River Otter or American Mink (Neovison vison) predation may have affected certain WQCS colonies, but without landing on islands to search for evidence of presence (such as scat, paths through vegetation) or predation (such as seabird carcasses), we could not gather evidence to investigate this possibility. Human disturbance is infrequent in the relatively remote breeding locations in WQCS which have been largely protected in the Duke of Edinburgh Ecological Reserve since 1988. Diet and prey availability for Pelagic Cormorants in WQCS has not been studied, although they are known to feed on a broad range of midwater and bottom fish species mainly in nearshore waters (Hobson 2013), possibly making them less sensitive to variation in the availability of individual prey species. At the better-studied Triangle Island (with breeding eagles and falcons and with little human disturbance) in 1968-2010, the breeding population of Pelagic Cormorants stayed at relatively high levels, but with great annual variation (n = 33-433 nests), suggesting that prey resources in the Scott Islands had not declined greatly over time (Rodway and others 2011). In parts of California, without eagle impacts and usually with little human disturbance, some populations of Pelagic Cormorants (for example, South Farallon Islands) have declined in recent decades (Warzybok and Bradley 2011; McChesney and others 2013), while others (for example, San Miguel Island) have not changed greatly over the same period (Carter and others 2008). Long-term prey changes in the California Current likely contribute to declines in Pelagic Cormorant breeding populations in certain areas of California. The WQCS region off northeastern Vancouver Island is part of an estuarine system at the north end of the California Current and south end of the Alaska Current, where prey resources can differ from outer coast waters and less variation in prey availability may occur. However, changes in prey availability have occurred for Glaucous-winged Gulls in the Strait of Georgia, also an estuarine system (Blight 2012; Blight and others 2015). More work is needed to examine the diet of Pelagic Cormorants (for example, using regurgitations from roost sites) in the WQCS region and other parts of southern British Columbia for assessing possible changes in prey availability over time.

ACKNOWLEDGEMENTS

British Columbia Parks provided funding for the 2014 survey and Carter Biological Consulting provided in-kind support. Vessel support aboard the Nahwitti Ranger was provided by British Columbia Parks, with excellent captains J Spowart and D Jack. E Carter assisted 2009 and 2014 surveys. L Halpin assisted the 2012 survey at 2 colonies in Quatsino Sound. T Chatwin (British Columbia Ministry of Forests, Lands and Natural Resource Operations; FLNR) greatly assisted with fund raising and project planning. Figure 1 also was kindly prepared by L Sinclair (FLNR). L Kennes kindly assisted access to the British Columbia Seabird Colony Inventory files housed at the Royal British Columbia Museum (Victoria, British Columbia). M Lowe and M Brooke graciously assisted access to H Carter to examine specimens at the University Museum of Zoology at Cambridge (UMZC) in 2015. Carter Biological Consulting provided funding and equipment for 2009 and 2012 surveys. H Carter also was fortunate to assist surveys of seabird colonies in Queen Charlotte Strait in 1976 when working for the British Columbia Provincial Museum (now Royal British Columbia Museum), under the direction of W Campbell and C Guiguet. Valuable comments were provided by reviewers P Capitolo and J Adkins.

LITERATURE CITED

Beebe FL. 1960. The marine peregrines of the northwest Pacific coast. Condor 162:145-189.

BLIGHT L. 2012. Glaucous-winged Gulls Larus glaucescens as sentinels for a century of ecosystem change --long-term trends in population, diet, and egg production in North America's Salish Sea [dissertation], Vancouver, BC: University of British Columbia. 218 p.

Blight LK, Drever MC, arcese P. 2015. a century of change in Glaucous-winged Gull (Larus glaucescens) populations in a dynamic coastal environment. Condor 117:108-120.

* CAMPBELL RW. 1976. Sea-bird colonies of Vancouver Island area. Victoria, BC: British Columbia Provincial Museum [map].

Campbell RW, Dawe NK, Mctaggart-Cowan I, Cooper JM, Kaiser GW, McNall MCE. 1990. The birds of British Columbia. Vol. 1, Nonpasserines: Introduction, loons through waterfowl. Victoria, BC: Royal British Columbia Provincial Museum. 514 p.

Carl GC, Guiguet CJ, Hardy GA. 1951. Biology of the Scott Island group, British Columbia. In: Report of the Provincial Museum of Natural History and Anthropology for the year 1950. Victoria, BC: King's Printer, p B21-B63.

* Carter H, Whitworth D, Hebert P, Koepke J, Capitolo P, McChesney G, McIver W, Ochikubo Chan L, Pierson M, Hebshi A, Martin P. 2008. Status of breeding seabirds in the San Miguel Island group, California. Victoria, BC: Carter Biological Consulting; Davis, CA: California Institute of Environmental Studies. 131 p.

Carter HR, Sealy SG. 2011. Earliest breeding records of storm-petrels in British Columbia, 1909-1927: Triangle Island, Tree Islets, Cox Island, Cleland Island, Lepas Bay Islands, and Tian Islets. Wildlife Afield 8:167-194.

Carter HR, Hobson KA, Sealy SG. 1984. Colony-site selection by Pelagic Cormorants (Phalacrocorax pelagicus) in Barkley Sound, British Columbia. Colonial Waterbirds 7:25-34.

Carter HR, Hebert PN, Clarkson PV. 2007. Decline of Pelagic Cormorants in Barkley Sound, British Columbia. Wildlife Afield 4:3-32.

Carter HR, Burger AE, Clarkson PV, Zharikov Y, Rodway MS, Sealy SG, Campbell RW, Hatler DF. 2012. Historical colony status and recent extirpations of burrow-nesting seabirds at Seabird Rocks, British Columbia. Wildlife Afield 9:13-48.

Chatwin TA, Mather MH, Giesbrecht TD. 2002. Changes in Pelagic and Double-crested Cormorant nesting populations in the Strait of Georgia, British Columbia. Northwestern Naturalist 83:109-117.

Drent RH, Guiguet CJ. 1961. A catalogue of British Columbia sea-bird colonies. Victoria, BC: British Columbia Provincial Museum Occasional Paper, No. 12. 173 p.

Guiguet CJ. 1955. Solander Island. In: Provincial Museum of Natural History and Anthropology Report for the year 1954. Victoria, BC: Queen's Printer, p B16-B18.

Hipfner JM, Blight LK, Lowe RW, Wilhelm SI, Robertson GJ, Barrett RT, Anker-Nilssen T, Good TP. 2012. Unintended consequences: How the recovery of sea eagle Haliaeetus spp. populations in the northern hemisphere is affecting seabirds. Marine Ornithology 40: 39-52.

Hobson KA. 2013. Pelagic Cormorant (Phalacrocorax pelagicus). In: Poole A (editor). The birds of North America online. Ithaca, NY: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/ bna/species/282.

Lord JK. 1866. The naturalist in Vancouver Island and British Columbia. Volumes I and II. London, UK: Richard Bentley.

* McChesney GJ, Carter HR, Bechaver CA, Rhoades SJ, Bradley RW, Warzybok PM, Golightly RT, Capitolo PJ. 2013. Seabird breeding population sizes within the North Central Coast Study Region of the California Marine Life Protection Act Initiative, 2010-2012. In: McChesney GJ, Robinette D, editors. Baseline characterization of newly established marine protected areas within the North Central California Study Region--seabird colony and foraging studies. Fremont, CA: US Fish and Wildlife Service, San Francisco Bay National Wildlife Refuge Com plex; Petaluma, CA: Point Blue Conservation Science, p 78-110.

Pearse T. 1956. Changes in breeding populations of pelagic birds in the Gulf of Georgia, BC. Murrelet 37:22-23.

Pyle P. 2008. Identification guide to North American birds. Part II. Anatidae to Alcidae. Point Reyes Station, CA: Slate Creek Press. 835 p.

Rodway MS. 1991. Status and conservation of breeding seabirds in British Columbia. In: Croxall JH, editor. Seabird status and conservation: A supplement. International Council of Bird Preservation Technical Publication No. 11. p 43-102.

Rodway MS, Lemon MJF. 1990. British Columbia seabird colony inventory: Report #5--West coast Vancouver Island. Delta, BC: Canadian Wildlife Service, Pacific and Yukon Region, Technical Report Series No. 94. 87 p.

Rodway MS, Lemon MJF. 1991a. British Columbia seabird colony inventory: Report #8: Queen Charlotte Strait and Johnstone Strait. Delta, BC: Canadian Wildlife Service, Pacific and Yukon Region, Technical Report Series No. 123. 82 p.

Rodway MS, Lemon MJF. 1991b. British Columbia seabird colony inventory: Report #7: Northern mainland coast. Delta, BC: Canadian Wildlife Service, Pacific and Yukon Region, Technical Report Series No. 121. 182 p.

Rodway MS, Lemon MJF, Summers KR. 1992. Seabird breeding populations in the Scott Islands on the west coast of Vancouver Island, 1982-1989. In: Vermeer K, Butler RW, Morgan KH, editors. The ecology, status, and conservation of marine and shoreline birds on the west coast of Vancouver Island. Occasional Paper, Canadian Wildlife Service, No. 75. p 52-59.

Rodway MS, Summers KR, Hipfner JM, van Rooyen JC, Campbell RW. 2011. Changes in abundance and distribution of Pelagic Cormorants nesting on Triangle Island, British Columbia, 1949-2010. Wildlife Afield 8:147-166.

* Summers KR, Campbell RW. 1978. Natural history theme study of bird and mammal habitats of Canada's Pacific coast and adjacent coastal waters. Ottawa, ON: Parks Canada, Project C1632--Contract 76-198. 238 p.

Vermeer K, Manuwal DA, Bingham DS. 1976a. Seabirds and pinnipeds of Sartine Island, Scott Island group, British Columbia. Murrelet 57:14-16.

Vermeer K, Summers KR, Bingham DS. 1976b. Birds observed at Triangle Island, British Columbia, 1974 and 1975. Murrelet 57:35-42.

Vermeer K, Morgan KH, Ewins PJ. 1992. Population trends of Pelagic Cormorants and Glaucouswinged Gulls nesting on the west coast of Vancouver Island. In: Vermeer K, Butler RW, Morgan KH, editors. The ecology, status, and conservation of marine and shoreline birds on the west coast of Vancouver Island. Occasional Paper, Canadian Wildlife Service, No. 75. p 60-64.

* Warzybok PM, Bradley RW. 2011. Status of seabirds on Southeast Farallon Island during the 2011 breeding season. Petaluma, CA: PRBO Conservation Science.

Young CJ. 1930. A study of the Rhinoceros Auklet and other birds in British Columbia, 1929. In: Report of the Provincial Museum of Natural History for the year 1929. Victoria, BC: King's Printer, p F16-F19.

Submitted 13 February 2015, accepted 15 July 2015.

Corresponding Editor: D Max Smith.

* Unpublished
APPENDIX. Counts of Black Oystercatchers, Glaucous-winged
Gulls, and Pigeon Guillemots at breeding colonies in western
Queen Charlotte Strait, British Columbia, in 2014.

                       Black       Glaucous-winged    Pigeon
Colony Name        Oystercatcher        Gull         Guillemot

Dugout Rocks             3               120            17
Ruby Rocks               8          30 (160) (a)        14
Bremner Islets           6                7              0
Tremble Island           0                0           17 (b)
Naiad Islets             2               125             3
Reid Islets              0               30              5
Storm Islands            0             55 (50)        10 (c)
Tree Islets              0               30             24
Pine Island              0                0             56
Bright Islandd           2               42             11
Herbert Islandd          0                0             10
Total                   21            439 (210)         167

(a) For gulls, birds counted in nesting area, with roosting
birds in parentheses.

(b) At Tremble Island (51.0966[degrees]N; 127.503[degrees]W;
see Fig. 1), adults were observed flying out of 4 apparent
nest holes as we passed around the island. Pigeon Guillemots
had not been previously reported breeding at this location,
although it is not clear if it was surveyed in the past.

(c) Low count compared to past surveys may have reflected
rough sea conditions during the survey, or decline.

(d) Bright Island and Herbert Island occur within the Buckle
Group colony.


Harry R Carter

Carter Biological Consulting, 1015 Hampshire Road, Victoria, BC V8S 4S8 Canada; carterhr@shaw.ca

Erica L McClaren

British Columbia Parks, West Coast Region, 1812 Miracle Beach Drive, Black Creek, BC V9J 1K1 Canada
TABLE 1. Counts of Pelagic Cormorant nests and birds at
breeding colonies in western Queen Charlotte Strait, British
Columbia, 8-9 July 2014. Colonies are listed in north to
south order (see Fig. 1).

                           Adults
                          attending   Roosting   Roosting    Total
Colony Name       Nests     nests      adults    subadults   birds

Dugout Rocks        4         5          9           9        23
Ruby Rocks          0         0          2           2         4
Bremner Islets      0         0          2           0         2
Naiad Islets        0         0          2           0         2
Reid Islets         0         0          0           0         0
Storm Islands       0         0          0           0         0
Tree Islets         0         0          0           0         0
Pine Island         1         1          4           0         5
Bright Island       0         0          10          0        10
Total               5         6          29         11        46

TABLE 2. Pelagic Cormorant nest counts at breeding colonies
in western Queen Charlotte Strait, British Columbia, in
1975-1976 (Campbell 1976; Summers and Campbell 1978), 1982-
1988 (Rodway and Lemon 1991a,b), and 2014 (this study).

                                  Nests

Colony Name        1975-1976    1982-1988   2014

Dugout Rocks          148          18         4
Ruby Rocks             8            6         0
Bremner Islets      -- (a)         16         0
McEwan Rock            0           14        --
Reid Islets            7            0         0
Storm Islands         6-9           0         0
Tree Islets            7            0         0
Pine Island            0          0 (b)       1
Bright Island        21-52          6         0
Total             197-231 (c)      60       5 (d)

(a) Dash indicates colony not surveyed.

(b) Rodway and Lemon (1991a) reported a bird flying out
from a cliff but it may have been roosting.

(c) Assumes no nests at Bremner Islets.

(d) Assumes no nests at McEwan Rock.
COPYRIGHT 2016 Society for Northwestern Vertebrate Biology
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2016 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Carter, Harry R.; McClaren, Erica L.
Publication:Northwestern Naturalist: A Journal of Vertebrate Biology
Article Type:Report
Geographic Code:1CBRI
Date:Mar 22, 2016
Words:6257
Previous Article:A blind-test comparison of the reliability of using external morphology and echolocation-call structure to differentiate between the Little Brown Bat...
Next Article:River Otter (Lontra canadensis) food habits in a Washington coast watershed: implications for a threatened species.
Topics:

Terms of use | Privacy policy | Copyright © 2019 Farlex, Inc. | Feedback | For webmasters