Conservation of marine birds of northern North America: / papers from the international symposium held at the Seattle Hyatt House

by Unknown

There are about 86 actual or potential seabird colony sites in this area; 25 (30%) are now considered important. Eleven islands are under Federal protection as National Wildlife Refuges. Part of Protection Island is owned by the Washington State Game Department to protect the largest rhinoceros auklet colony in the State. Most colony sites are on small islands with poorly developed soil which prevents burrowing species from using them. Consequently, the dominant species are surface nesters (such as gulls and cormorants) and rock-crevice nesters (like the pigeon guillemot). In all, about 31,000 seabirds of 7 species breed in the San Juan Island area. Breeding seabird population estimates for 49 of the 86 nesting sites are given in Table 6. Even though this does not represent all the colonies, it covers the most important islands and those islands where there appears to be potential for seabird breeding.

Fig. 7. Photograph of Smith Island in the Strait of Juan de Fuca, Washington. The glacial deposits are evident from the composition of the cliff faces.

Table 5. Estimated breeding seabird populations of the outer coast of Washington.[9] (Unpublished data from U.S. Fish and Wildlife Service and University of Washington)

Breed­ing site	Species
	Storm-pet­rels		Cor­mo­rants				Black oys­ter-catch­er	Gulls		Com­mon mur­re	Pi­geon guil­le­mot	Auk­lets		Tuft­ed puf­fin	To­tal
	Fork-tail­ed	Le­ach's	Un­i­den­ti­fied	Dou­ble-crest­ed	Bran­dt's	Pe­lag­ic		West­ern	Glau­cous-wing­ed west­ern			Cass­in's	Rhi­noc­er­os
Copalis Rock	—	—	15	—	—	—	—	30	—	—	—	—	—	—	45
Point Grenville	—	—	—	60	30	80	—	165	40	1,100	—	—	—	—	1,475
Grenville Arch	—	—	—	30	20	—	1	60	—	3,000	4	—	—	3	3,118
Flat Rock	—	—	30	—	—	—	—	—	60	300	—	—	—	—	390
Split Rock	—	—	—	100	—	—	1	150	—	2,100	4	—	—	—	2,355
Willoughby Rock	—	—	—	80	40	15	—	150	—	3,000	—	—	—	25	3,310
South Rock	—	—	—	—	—	40	—	—	50	—	—	—	—	—	90
Abbey Islet	—	—	—	—	—	30	3	—	50	—	—	—	—	10	93
Destruction Island	—	—	—	—	—	—	12	350	—	—	25	—	10,940	350	11,677
Middle Rock	—	—	—	—	—	25	—	—	25	—	50	—	—	—	100
North Rock	—	—	—	—	—	—	—	—	25	—	—	—	—	—	25
Alexander Island	—	—	—	—	—	50	5	—	225	—	—	—	—	1,550	1,830
Rounded Island	—	—	—	—	—	25	—	25	—	—	1	—	—	—	51
Giant's Graveyard	—	—	—	—	—	10	—	—	—	150	—	50	150	—	360
Quillayute Needles	—	—	—	50	50	50	—	—	150	900	—	—	—	350	1,550
James Island	—	30	—	—	—	40	—	—	150	750	40	—	—	20	1,030
Cake Rock	—	500	—	—	—	150	—	—	600	300	12	—	50	1,000	2,612
Sealion Rock	—	—	—	70	—	30	—	—	250	—	—	—	—	5	355
Carroll Island	—	3,100	—	—	—	100	3	—	550	—	—	25	250	2,400	6,428
Ball Rock	—	—	—	—	—	50	7	—	150	—	—	—	—	750	957
White Rock	—	—	—	—	—	100	—	—	75	250	—	—	—	100	525
Ozette Island	—	—	—	—	—	—	1	—	15	—	—	—	—	—	16
Bodelteh Island	1,900	—	—	—	—	100	2	—	300	—	5	—	—	750	3,057
Tatoosh Island	—	25	—	—	—	100	—	—	1,500+	100	20	25?	25?	30	1,825
Total	1,900	3,655	45	390	140	995	35	930	4,215	11,950	161	100	11,415	7,343	43,274

Table 6. Breeding seabird population estimates for the San Juan Islands and Strait of Juan de Fuca, Washington, 1973-75.[10]

Breeding site	Species
	Cor­mo­rants		Black oys­ter-catch­er	Glau­cous-wing­ed gull	Pi­geon guil­le­mot	Tuft­ed puf­fin	Rhi­noc­er­os Auk­let	To­tal
	Dou­ble-crest­ed	Pe­lag­ic
Bare Island	—	50	1	120	+	—	2	173
Barren Island	—	—	—	—	—	—	—	0
Battleship Island	—	—	—	—	—	—	—	0
Bird Rocks	30	—	+	320	—	—	—	350
Cactus Island	—	—	1	—	—	—	—	1
Castle Island	—	—	—	—	30	—	—	30
Colville Island	—	40	1	1,000	—	—	—	1,041
Danger Island	—	—	—	125	7	—	—	132
Decatur Island	—	—	—	—	—	—	—	0
Eliza Island	—	—	—	3	1	—	—	4
Eliza Rock	—	—	—	1	—	—	—	1
Flat Top Island	—	—	—	—	+	—	—	+
Flower Island	—	17	—	90	—	—	—	107
Goose Island	—	—	—	60	—	—	—	60
Gull Rock	—	—	+	125	7	—	—	132
Gull Reef	—	—	—	—	—	—	—	0
Hall Island	—	—	1	275	—	—	—	276
Harbor Rock	—	—	—	—	—	—	—	0
Iceberg Island	—	—	—	—	—	—	—	0
Johns Island	—	—	1	—	—	—	—	1
Long Island	—	—	8	80	—	—	—	88
Low Island	—	—	1	75	17	—	—	93
Lummi Rocks	—	—	—	4	—	—	—	4
Matia Island	—	—	—	—	+	—	—	+
Mummy Rocks	—	—	—	55	—	—	—	55
Minor Island	—	—	—	100	—	—	—	100
O'Neal Island	—	—	—	—	—	—	—	0
Patos Island	—	—	—	20	+	—	—	20
North Peapod Island	—	—	1	220	2	—	—	223
South Peapod Island	—	—	1	75	2	—	—	78
Pearl Island	—	—	—	—	—	—	—	0
Pointer Island	—	—	—	58	2	—	—	60
Protection Island	3	110	3	1,500	30	9,200	35	10,881
Puffin Island	—	—	1	350	15	—	—	366
Ripple Island	—	—	—	—	—	—	—	0
Sentinel Island	—	—	—	—	10	—	—	10
Sentinel Rock	—	—	1	—	—	—	—	1
Skip Jack Island	—	—	—	75	20	—	—	95
Smith Island	—	20	6	10	30	600	—	666
Speiden Island	—	—	—	—	—	—	—	0
South Sister Island	2	11	1	131	—	—	—	145
Middle Sister Island	—	—	1	22	—	—	—	23
North Sister Island	—	—	2	412	3	—	—	417
Viti Rocks	29	80	1	387	1	—	—	498
Waldron Island	—	—	—	—	2	—	—	2
Williamson Rocks	—	67	1	346	2	—	—	416
Whale Island	—	—	1	70	—	—	—	71
White Rock	—	—	+	125	13	—	—	138
Yellow Island	—	—	—	—	—	—	—	0
Total per species	64	395	34	6,234	194	9,800	37	16,758
Percent of total population	0.4	2.3	0.2	37.2	1.2	58.5	0.2	100.0

The major colony sites with more than 250 breeding pairs are located at Protection and Smith islands, Bird Rocks, Colville Island, Hall Island, North and South Peapod rocks, Puffin Island, North Sisters, Viti Rocks, and Williamson Rocks (Fig. 6). Glaucous-winged gulls are the predominant species on all these islands except Protection and Smith islands, where there are large colonies of rhinoceros auklets. Rhinoceros auklets (65%) and glaucous-winged gulls (32%) make up 97% of the total San Juan Islands seabird population.

Nest-site Preferences

Food supply and availability of nest sites are two critically important factors influencing the distribution and abundance of seabirds. Whereas information on general diet composition is known for most seabird species, we know little about the availability of favored seabird prey. The dynamics of seabird food chains is reviewed elsewhere in these proceedings.