Occurrence and notes on diet of Cassin's Auklet at Langara Island, British Columbia, 1970-1971.
Cassin's Auklet (Pytchorampus aleuticus) is among 5 species of nocturnal, burrow-nesting seabirds that historically nested on Langara Island and smaller nearby Cox Island, Queen Charlotte Islands (Haida Gwaii), British Columbia. Fork-tailed Storm-Petrel (Oceanodroma furcata), Leach's Storm-Petrel (O. leucorhoa), and Rhinoceros Auklet (Cerohinca monocerata) also previously nested there (Campbell and Garrioch 1979; Campbell and others 1990, 1992). Those 4 species were extirpated, likely due to the spread of introduced Black Rats (Rattus rattus) and Norway Rats (R. norvegicus) (Rodway 1991; Bertram 1995). The Ancient Murrelet (Synthliboramphus antiquus), the 5th species, still nests on Langara Island, but in greatly reduced numbers (Rodway and others 1994; Bertram 1995; Regehr and others 2007; Major and Jones 2011). Ornithologists who visited these islands between the early 1900s and mid-1960s documented extensive nesting and estimated numbers of birds, collected specimens, and studied the main predators (Drent and Guiguet 1961; also see Beebe 1960; Campbell 1968, 1969).
Early observations pointed to abundant nesting by Cassin's Auklets until at least 1948 on Langara Island and at least 1952 on Cox Island (Beebe 1960; Drent and Guiguet 1961). Campbell (1969) found a few Storm-Petrel burrows on Cox Island in 1966, but RW Nelson and KR Summers reported that the Tufted Puffin (Fratercula cirrhata) was the only burrow-nesting species remaining on Cox Island in 1971, and a field party from the British Columbia Provincial Museum (now Royal British Columbia Museum) confirmed the absence of Cassin's Auklet on Langara and Cox islands in 1977 (Rodway and others, in press). Cassin's Auklet was recorded nesting again on Langara Island in 2004 following rat eradication in 1995-1996 (Regher and others 2007). In this paper, our 1st objective is to add information on the status of Cassin's Auklet on these islands in the years 1970 and 1971, based on the results of nest searches as well as observations on the occurrence and abundance of Cassin's Auklets on surrounding waters. Our 2nd objective is to present information on breeding condition and diet of a small sample of Cassin's Auklets collected on the water at that time.
Searches for active nests of Ancient Murrelets and Cassin's Auklets were made by SGS at the following locations in 1970 and 1971 (Fig. 1): (1) slopes and summit of Cox Island (5 May 1971, and reports of a 2 August visit by KR Summers and RW Nelson); (2) west end and above the south-facing shoreline of Lucy Island (11 April 1971), although Cassin's Auklet had not been recorded nesting there (Drent and Guiguet 1961); (3) thorough searches, conducted over several weeks, of the slopes around Iphigenia Point (Ancient Murrelet colony A; see Sealy 1976) and slopes north of the former village of Dadens, and along the eastern shore north of Holland Point to the south end of Egeria Bay (colony B) in 1970 and 1971; and (4) searches of these slopes extended to McPherson Point (colony C) in 1971.
Opportunistic observations of Cassin's Auklets on the water were made from a pneumatic boat during trips mainly from Cloak Bay in the west to just beyond McPherson Point on the east coast of Langara Island and along the coast of Graham Island east of Gunia Point (Fig. 1). Boat trips were sporadic in 1970 (6 May to 10 July) but almost daily, weather permitting, in 1971 (17 March to 9 August). Eight individuals were collected opportunistically for diet analysis in 1971. Digestive tracts (developing gular pouches, proventriculi, and muscular stomachs) were dissected from 6 of the 8 birds. Prey items were stored and eventually sorted and identified following the keys and procedure outlined by Sealy (1975) in a study of diets of murrelets in the vicinity of Langara Island. Identities of all prey taxa were confirmed by specialists. The ventral thoracic and abdominal skin of each individual was examined for the presence of brood patches (Manuwal 1974). Each specimen was weighed to the nearest 0.1 g on a triple beam balance.
[FIGURE 1 OMITTED]
No Cassin's Auklet nests were discovered in 1970 and 1971 despite searches of extensive tracts of potential habitat on Cox and Langara islands, including some sites apparently used previously by this species (see Drent and Guiguet 1961). Ancient Murrelets were also absent from some previous nesting areas. Particularly disturbing was the abandonment of Ancient Murrelet nesting areas on the slopes north of Dadens and above the coastline north of Holland Point nearly to the headland at the south end of Egeria Bay (Fig. 1), which had been active only 4 y earlier (Campbell 1969). Although SGS conducted studies at 3 remaining Ancient Murrelet sites on Langara Island (colonies A-C, Sealy 1976), the numbers of nesting individuals of this species continued to decline in subsequent years (Rodway and others 1994; Bertram 1995), until today Ancient Murrelets nest in a single area, albeit one slowly expanding as the number of breeders increases following the 1995-1996 eradication of rats (Regehr and others 2007; Major and Jones 2011).
Despite the lack of nesting, low numbers of Cassin's Auklets in breeding condition (Table 1) were encountered in waters in the months during which nesting was recorded in the earlier decades (Drent and Guiguet 1961). Birds observed or collected from 25 March through 23 April 1971 were identified as after hatch year (AHY) or after second year (ASY), respectively (Table 1). Between 24 April and 17 July 1971, 1 AHY Cassin's Auklet was recorded, whereas on 1 and 3 June 1970 "a few flocks" and 1 AHY were recorded, respectively (Table 1). That neither of the 2 females collected in late March and April 1971 had laid was confirmed by the absence of post-ovulatory follicles, and none of the 6, males or females, had developed brood patches that are generally functional in birds that lay eggs early in the season, but not in all late-breeding Cassin's Auklets (Manuwal 1974). Some of the ASY birds were up to 35 g heavier than March and April means (about 175 g) of Cassin's Auklets breeding in California (Manuwal and Thoresen 1993).
Although isolated pairs of Cassin's Auklet may have nested on Langara Island or Cox Island in 1970 or 1971, it is likely that many of the adults and juveniles encountered originated from colonies off the west coast of Graham Island, such as Frederick Island (53[degrees]93"02"N, 133[degrees]20'09"W), or southeast Alaska, such as Forrester Island (54[degrees]48"10"N, 133[degrees]31'37"W). Breeding Cassin's Auklets forage on the edge of the continental shelf during the breeding season in British Columbia and are rarely seen near colonies during the day (Vermeer and others 1985; Rodway and others 1994; Boyd and others 2008).
Hatch-year (HY) Cassin's Auklets were recorded only after mid-July (Table 1), which coincided with dates of nest departure reported for Frederick Island (Vermeer and others 1985; Rodway and others 1994) and with approximate fledging dates in the days when Cassin's Auklets still nested abundantly on Langara Island and Cox Island (Drent and Guiguet 1961).
Gular pouches (see Speich and Manuwal 1974) of the 4 ASY birds taken between 29 March and 18 April 1971 yielded prey, whereas the tracts of 2 HY individuals taken on 17 and 20 July were empty (Table 2). Percent occurrence of 84 prey items was tallied (Table 2), of which 92% were of 2 species of euphausiid shrimp, Thysanoessa spinifera (16%) and Euphausia pacifica (76%). Each of 3 stomachs yielded 1 polychaete (1 approximately 15 mm long; 2 approximately 25 mm long), previously unrecorded in the diet of Cassin's Auklet. In addition to a single species of calanoid crustacean, at least 2 species of amphipod were identified. A 3rd taxa of amphipod, which could be identified only to genus, was taken by 1 of the 3 females collected on 29 March 1971 (Table 1). EL Bousfield and CT Shih, then of the National Museums of Canada, Ottawa, attempted to identify the specimen, but Bousfield commented (in litt. 24 December 1971) that one of the specimens of Parathemisto "... is represented only by the anterior portion (head and peraeon) and has given us a great deal of difficulty in identification. It is a large species (estimated to be over 15 mm in total body length) and with many of the characteristics of the arctic P. libellula (Brandt). We have also consulted [ornithologist] Dr. Earl Godfrey on this interesting problem. Since the nearest known records of P. libellula are from the Bering Sea, more than a day's flight for a Cassin's Auklet, that would probably be moving north [Bousfield's emphasis] from its wintering grounds along the US coast in March, and the amphipod specimen is in such good state of preservation that it could not be more than 2-3 hr in digestion, we can only conclude that the specimen is an aberrant form of P. japonica, a common large N[orth] Pacific species ([hybridized] with libellula?) or a new species ..." Additional material was not available and nothing further was ascertained regarding the identity of this specimen.
Data from this small sample reflected the importance of euphausiids in the diet of Cassin's Auklets during the early part of the breeding season, as in Ancient Murrelets foraging off Langara Island before fish assumed greater importance later in the breeding season (Sealy 1975). This extends the information obtained from prey delivered to chicks on nearby Frederick Island (Vermeer and others 1985) and at other colonies in British Columbia (Carl and others 1950; Vermeer 1981,1984; also see Hipfner 2008). It is not known, however, whether prey were taken near Langara Island or farther offshore (see Vermeer and others 1985; Boyd and others 2008). If Cassin's Auklets continue to re-establish a nesting population on Langara Island (see Regehr and others 2007), prey fed to chicks may be determined at this site.
Acknowledgments.--Data presented here were derived ancillary to doctoral research by SGS on seabird ecology conducted on and near Langara Island out of the University of Michigan, Ann Arbor. Important assistance in the field was received from RW Nelson, A Nelson, NL Sealy, KR Summers, and personnel of the Marine Division of the Ministry of Transport (Prince Rupert, British Columbia) and Prince Rupert Fishermen's Cooperative Association. A base for field operations was established on the site of the former village of Dadens with permission granted by the Haida Band Council of Masset. E Brunton confirmed identifications of euphausiids, and EL Bousfield and CT Shih identified the amphipods. Funding was provided by the Canadian National Sportsmen's Show, Frank M Chapman Fund (American Museum of Natural History), Society of Sigma Xi, and a block grant from the National Science Foundation awarded to the Museum of Zoology, University of Michigan. MSR conducted surveys in the Langara Island area, funded by the British Columbia Provincial Museum (now Royal BC Museum) in 1977 and by the Canadian Wildlife Service in 1981 and 1986. The reviewers, RW Nelson and KR Summers, offered comments on the manuscript. The map was prepared by CloverPoint Cartographies (Victoria, BC), with assistance from K Henkelman and E Hillier.
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Department of Biological Sciences, University of Manitoba, Winnipeg, MB R3T 2N2 Canada; email@example.com (SGS); Wildwing Environmental Research, Box 47, Gold Bridge, BC V0K 1P0 Canada; firstname.lastname@example.org (MSR). Submitted 30 April 2015, accepted 27 July 2015. Corresponding Editor: Robert Hoffman.
TABLE 1. Specimens and observations of Cassin's Auklets near Langara Island, British Columbia, 1970-1971. Date Observations/specimens Locality 1970, June 1 a few flocks 8 km east of Langara Island 1970, June 3 1 AHY (1) Near Cox Island 1971, March 25 1 ASY (1), [male] 1 km west of Pillar Bay (left testis, 7.1 X 2.6 mm), 168.8 g (2,3) 1971, March 29 aggregation of ~200 5 km east of Cohoe Point individuals 1971, March 29 1 ASY, [female] 3 km east of Cohoe Point (largest follicle, 2.5 mm), 190.4 g (3) 1971, March 29 1 ASY, [male] 3 km east of Cohoe Point (9.8 x 5.2 mm), 205.5 g (3) 1971, March 29 1 ASY, [female] 3 km east of Cohoe Point (3.1 mm), 210.4 g (3) 1971, April 10 4 AHY 2 km east of Gunia Point 1971, April 18 1 ASY, [male] 6 km east of Cohoe Point (15.6 X 6.4 mm), 211.7 g (3) 1971, April 23 1 ASY, [male] 1.6 km east of Andrews (15.6 X 6.7 mm), Point 196.8 g 1971, May 5 1 AHY 2 km east of Lucy Island 1971, July 17 1 HY (1-3) Parry Passage 1971, July 17 1 HY, [male] 1 km east of Gunia Point (3.5 x 0.9 mm), 120.6 g (3,4) 1971, July 18 1 HY Egeria Bay 1971,July 20 1 HY, [female] East of Cohoe Point (<1 mm), 144.4 g (3) 1971, July 22 3 HY (4) Egeria Bay 1971, July 23 1 HY (4) Parry Passage 1971, July 24 4 HY (4,5) Cloak Bay 1971, July 26 1 HY (4) Parry Passage 1971, July 28 2 HY (4) Solide Passage (1) Aged as AHY = after hatch year, ASY = after second year, HY = hatch year. (White irides of AHY and ASY birds, dark eyes of HY individuals [see Emslie and others 1990].) None of the ASY specimens possessed a brood patch. (2) University of Manitoba Zoology Museum (UMZM 1172). (3) Digestive tract removed for diet analysis. (4) Individuals observed closely enough to discern dark irides and fresh plumage. (5) Feeding in a mixed-species flock (see Sealy 1973). TABLE 2. Percentage occurrence of 84 prey items dissected from incompletely developed gular pouches of 4 ASY Cassin's Auklets, Langara Island, 29 March to 20 July 1971 (see also Table l).1 Number Prey categories and species (% occurrence) Calanoida Calanus pacificus 1 (1.2) Amphipoda Parathemisto pacifica 1 (1.2) Parathemisto spp. 1 (1.2) Hyperoche medusarum 1 (1.2) Euphausiacea Thysanoessa spinifera 13 (15.5) Euphausia pacifica 64 (76.2) Polychaeta Unidentified spp. 3 (3.6) Total number of prey 84 (1) Digestive tracts of the 2 HY birds were empty.
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|Title Annotation:||GENERAL NOTES|
|Author:||Sealy, Spencer G.; Rodway, Michael S.|
|Publication:||Northwestern Naturalist: A Journal of Vertebrate Biology|
|Date:||Mar 22, 2016|
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