Counts of Ledge-Nesting Seabirds at Chagulak

AMNWR 04/21

LEDGE-NESTING SEABIRDS AT CHAGULAK ISLAND IN 2004

Photo by Martin Renner

G.Vernon Byrd, Jeffrey C. Williams, and Heather M. Renner

Key words: Aethia cristatella, Aleutian Islands, Chagulak Island, crested auklet, cormorant, kittiwake, murre, Phalacrocorax urile, Phalacrocorax pelagicus, Rissa brevirosrtris, Rissa tridactyla, seabird surveys

Alaska Maritime National Wildlife Refuge 95 Sterling Highway, Suite 1 Homer, Alaska 99603

November 2004

Cite as: Byrd, G.V., J.C. Williams and H.M. Renner. 2004. Ledge-nesting seabirds at Chagulak Island in 2004. U.S. Fish and Wildlife Serv. Rep. AMNWR 04/21.

EXECUTIVE SUMMARY

Chagulak Island is one of the largest seabird colonies in the Aleutian Islands Unit of the Alaska Maritime National Wildlife Refuge. Nevertheless, seabirds there have seldom been counted because Chagulak lies at the edge of Amukta Pass, an area known for strong currents and rough seas. The island is round with no protected bays, so opportunities for small boat surveys are restricted to a few days per summer. In July 2004, an opportunity occurred to conduct a nearshore boat survey to count and map the distribution of ledge-nesting seabirds. Breeding colonies at Chagulak had not previously been mapped and our counts were the first in more than 20 years there. We found 120 cormorants, more than 20,000 murres, and nearly 5,000 kittiwakes. Red-legged kittiwakes were discovered nesting at Chagulak for the first time. Numbers of murres and kittiwakes were slightly lower than those recorded previously, nevertheless, Chagulak remains one of the major breeding colonies of murres and kittiwakes in the Aleutian Islands.

INTRODUCTION

Chagulak Island, part of Alaska Maritime National Wildlife Refuge, is one of the largest breeding colonies of Northern Fulmar (Fulmarus glacialis) in the world with an estimated 450,000 birds. The steep and rugged 850 ha volcano never had foxes (Alopex lagopus) introduced like most of the other islands in the Aleutians, so its bird fauna has not been modified by invasive species. The lack of bays or other protected marine waters makes it a very difficult place to work, so only a few attempts have been made to count seabirds there. Previous work on Chagulak primarily consisted of surveys for the endemic Aleutian goose (Branta hutchensii leucopareia), since Chagulak is one of three sites with remnant breeding populations. In 1982, seabird populations were surveyed at Chagulak, but locations of breeding colonies were not delineated (E.P. Bailey and J.L. Trapp. 1986. A reconnaissance of breeding marine birds and mammals in the east-central Aleutian Islands—Kasatochi to the Island of Four Mountains—summer 1982, with notes on other species. Unpubl. U.S. Fish and Wildlife Service Report. In files, Alaska Maritime NWR, Homer, Alaska). These surveys were done primarily from small boats operated nearshore and all species were counted. Although noted for its immense fulmar population, Chagulak also contains significant populations of other nesting seabirds for which baseline data are needed to track changes over time.

In 2004, our objective was to map the distribution of ledge-nesting seabirds and conduct counts to characterize relative abundance of species for comparison with Bailey and Trapp (ibid). Also we wanted to sample productivity for cormorants and kittiwakes to compare with other sites in the Aleutians in 2004.

2 METHODS

Byrd, Williams, Marianne Kronk and Martin Renner conducted a coastline survey of Chagulak between 11:00-16:00 h on July 21, 2004 with an inflatable skiff operated within 10-50 m of the coastline. Transportation to the island and support during the surveys was provided by the refuge ship, M/V Tiglax. The seas were mostly calm and visibility was good. Cormorants and their nests were counted individually, and we made approximate counts (usually by blocks of 5 to 10) of all murres and kittiwakes except for the high density area near the southwest point of the island which we photographed and counted later. For that section, overlapping digital photographs were pasted together in Adobe Photoshop. Areas that were redundant were marked and excluded from the count. Heather Renner then electronically placed a small dot on each bird. Separate layers were created for murres and kittiwakes. The individual counting layers were exported as a grayscale GIF file and analyzed using ImageJ, a freeware Java image processing and analysis tool available at http://rsb.info.nih.gov/ij/. ImageJ returned a count of individual dots in each layer which represented the count of birds. Colony locations were approximately mapped on a hand-drawn enlarged chart of Chagulak. Existing published charts of the island are inaccurate and our map better reflects the islands coastline shape. Productivity was estimated for cormorant and kittiwake pairs by recording the contents of a sample of nests that we could see well from the water. Notes were made on all species opportunistically encountered (see Appendix A).

RESULTS

Distribution of Ledge-Nesting Seabirds

We recorded the locations of 19 breeding locations of ledge-nesting seabirds and two locations for concentrations of breeding crested auklets on Chagulak in July 2004 (Fig. 1). The largest concentration of ledge-nesting seabirds was on the southwestern point of the island in area 15 (Table 1, Fig. 1).

Figure 1. Map of Chagulak showing locations of ledge-nesting seabird (indicated by numbers) and crested auklet (Crea) breeding colonies.

4 Table 1. Counts of kittiwakes and murres at colonies on Chagulak Island, July 21, 2004.

Sectiona Black-legged Kittiwake Red-legged Kittiwake Murreb 1 0 0 100 2 0 0 900 3 0 0 70 4 0 0 20 5 0 0 30 6 0 0 50 7 0 0 100 8 70 0 100 9 0 0 410 10 320 0 480 11 0 0 400 12 150 0 350 13 25 0 300 14 756 13 3126 15c 2547 5 9343 16 598 0 2155 17 0 0 1285 18 94 0 175 19 213 0 545 Totals 4,773 18 20,539 aSee figure 1 for locations of colonies referred to in this table bBoth thick-billed and common murres were present but the species could not be separated in many cases during the survey, so they are combined in this table. cBlack-legged kittiwakes and murres in section 15 were counted from digital photographs in this segment

Counts

Cormorants—We recorded 33 nests of red-faced cormorants (Phalacrocorax urile) and we saw about 55 birds. For pelagic cormorant (P. pelagicus), we recorded 18 nests and 65 birds. Two nests had chicks present but no adults, so we could not identify them to species. Few subadult birds were noted.

Kittiwakes—We counted about 4,773 black-legged kittiwakes (Rissa tridactyla) (Table 1, Fig. 1), and we discovered the presence of red-legged kittiwakes (R. brevirostris)at Chagulak for the first time; 18 birds and 5 nests.

Murres—We counted 20,539 murres at Chagulak (Table 1). Only about 5% of the murre chicks had hatched and the remainder were on eggs. Thick-billed murres (Uria lomvia) appeared to be more abundant than common murres (Uria aalge), but both species were present.

Pigeon Guillemot—Although we were not specifically looking for this species, we counted 41 guillemots (Cepphus columba) during our shoreline survey of ledge- nesters.

Reproductive Success

Cormorants—About 31 of 33 red-faced cormorant nests we observed were still active at the time of our survey (Table 2), although nests that failed early may have lost most of the nest material and gone undetected. Of the active nests in which we could determine the exact number of chicks, 3 nests had one chick, 9 had two, and 4 had three chicks. For pelagic cormorants, 16 of 18 nests were still active during our survey. For nests with known contents, 1 had a single chick, 3 had two chicks, and 3 had three chicks (Table 2).

Kittiwakes—We sampled 315 black-legged kittiwake nests that we could see fairly clearly from the small boat. About 16% did not have eggs or chicks, but the others were still active at the time of our survey (Table 2). In nests where exact brood sizes were recorded, 1 chick broods were most common; 126 with one chick compared to only 15 with two chicks. We found 5 red-legged kittiwake nests. Three were had no eggs or chicks and two had single chicks (Table 2).

6 Table 2. Indices of productivity for cormorants and kittiwakes at Chagulak Island, July 21, 2004.

Status of Nestsa RFCOb PECO BLKI RLKI

No egg or chick 2 (06)c 2 (11) 51 (16) 3 Adult Presentd 5 (15) 6 (33) 87 (28) 1 chick 3 (09) 1 (06) 126 (40) 2 1+ chick 7 (21) 1 (06) 36 (11) 2 chicks 9 (27) 3 (17) 15 (05) 2+ chicks 3 (09) 2 (11) 3 chicks 4 (12) 3 (17)

Total 33 18 315 5

aSome nests contents could not be seen clearly so we used “+” where appropriate to record the number of chicks in nests bRFCO = red-faced cormorant, PECO = pelagic cormorant, BLKI = black-legged kittiwake, RLKI = red-legged kittiwake cproportion of total in parentheses. dadult sitting tight on nest, probably had small chick or late egg.

DISCUSSION

There has been no previous attempt to map specific locations of ledge-nesting seabird colonies at Chagulak, but Bailey and Trapp estimated the number of ledge-nesters seen on the entire island. They estimated approximately 25,000 murres were present in July 1982, slightly more than we saw at there in 2004 (Table 3). Bailey and Trapp also counted slightly more kittiwakes in 1982 than we found in 2004. Numbers of cormorants were similar between the two counts, although the species composition was different, with more red-faced and less pelagic cormorants in 2004.

Apparently cormorants and black-legged kittiwakes were having a relatively successful year in 2004 based on chick production, and the marine ecosystem may have been highly productive. Alan Springer, Univ. of Alaska, Fairbanks, noted large numbers of the zooplankton, Neocalanus cristatus, washed up on the beach at Chagulak probably indicating they were abundant in the nearshore marine waters.

7 Table 3. Comparisons of counts of cormorants, kittiwakes, and murres at Chagulak Island between 1982 and 2004.

Species 1982 2004

Red-faced Cormorant 10 55 Pelagic Cormorant 106 65 Black-legged Kittiwake 6000 4773 Red-legged Kittiwake 0 18 Common and Thick-billed Murre 24700 20539 Pigeon Guillemot 170 41

8 APPENDIX A. Annotated List of Species Observed at Chagulak in 2004

Laysan Albatross. Phoebastria albatrus: One adult was seen within 100 m of the beach.

Northern Fulmar. Fulmarus glacialis: No chicks were seen during our survey on July 21, but lots of birds were incubating eggs. Dozens of birds were seen feeding by pecking something, probably euphausiids, on the water surface.

Red-faced Cormorant. Phalacrocorax urile: Chicks were mostly at least half-grown based on their size.

Pelagic Cormorant. Phalacrocorax pelagicus: Chicks ranged from very small to probably nearly half-grown.

Peregrine Falcon. Falco peregrinus: Two pairs were seen.

Rock Sandpiper. Calidris ptilocnemis : At least 5 were seen on offshore rocks.

Red-necked Phalarope. Phalaropus lobatus: One bird was seen nearshore.

Glaucous-winged Gull. Larus glaucescens: Gulls were very common, and chicks were seen on beaches. Chicks ranged from very young to up to approximately 30 days old.

Black-legged Kittiwake. Rissa tridactyla. Most chicks were large enough to be seen well even if adults were present. Dozens of kittiwakes were seen pecking something, probably euphausiids, on the water surface, and euphausiids were the primary prey in kittiwake regurgitations according to Alan Springer. Ticks were common on birds captured for research by Alan Springer.

Red-legged Kittiwake. Rissa brevirostris. Red-legged kittiwakes were discovered nesting at Chagulak for the first time. It is unknown whether a small population has existed there before and gone unnoticed.

Common Murre. Uria aalge: This species was far less common than thick-billed murre based on the murres we could see well enough to identify to species. Ticks were noticed on birds captured for research by Alan Springer.

Thick-billed Murre. Uria lomvia: At least a few had just hatched chicks, most seemed to be in incubating posture at the time of our survey.

Pigeon Guillemot. Cepphus columba: At least one bird was seen carrying fish.

Ancient Murrelet. Synthliboramphus antiquus: Several pairs were seen near shore in the morning.

9 Cassin’s Auklet. Ptychoramphus aleuticus: A freshly killed bird was found.

Parakeet Auklet. Aethia psittacula: Alan Springer counted at least 500 in nearshore water near colony 18 (Fig. 1), and we saw hundreds, possibly low thousands, mostly within 50 m of shore, particularly off large boulder piles along the south side of the island (between colonies 10 and 11, Fig. 1).

Crested Auklet. Aethia cristatella: Several hundreds were seen off the south side near boulder piles in locations indicated in Fig. 1.

Cassin’s Auklet. Ptychoramphus aleuticus: A freshly killed bird was found.

Horned Puffin. Fratercula corniculata : At least 100 were seen nearshore.

Tufted Puffin. Fratercula cirrhata: At least a several hundreds noticed in nearshore waters.

Common Raven. Corvus corax: At least 4 were seen on coastal cliffs.

Winter Wren. Troglodytes troglodytes: Wrens were heard frequently from the skiff. They appeared to be on second broods, some still had eggs (shore based party found a nest with eggs) and there were lots of fledglings around.

Gray-crowned Rosy Finch. Leucosticte tephrocotis: At least 2 were seen.