Last Updated July 26th
Note: This will be the last weekly update for the 2005 field season. We plan to provide additional updates on a less frequent basis, including a season summary that will be posted in the coming months. The following data are preliminary and may change upon further review. Caspian Tern Colony Counts East Sand Island A second aerial photo census of the East Sand Island tern colony was conducted on 7 July in order to estimate production of young terns. Once these aerial photos are counted (Fall 2005), we will be able to accurately estimate the number of young terns fledged from the East Sand Island colony this year. On 12-13 July, 250 young terns that were raised on East Sand Island were banded, 209 with a unique color combination of plastic leg bands. Most young terns raised at the East Sand Island colony this year have fledged and left the island. Nesting success at the East Sand Island tern colony appears somewhat lower than in recent years. This agrees with reports from throughout the coastal Pacific Northwest of poor ocean conditions and very poor nesting success by fish-eating seabirds at most breeding colonies.
No active Caspian tern nests (nest scrapes containing eggs) were detected at any of the upper estuary dredge disposal sites (i.e., Rice Island, Miller Sands Spit, or Pillar Rock Sands) this year, and we do not anticipate the formation of any new colonies this late in the breeding season.
No evidence of nesting Caspian terns along the southwest coast of Washington (i.e., Willapa Bay, Grays Harbor) was detected this year, and we do not anticipate the formation of any new colonies this late in the breeding season. Former Caspian tern colony sites at the Port of Tacoma, Port of Seattle, Port of Bellingham, Padilla Bay, and the Fraser River Delta ( British Columbia) were checked, but no active Caspian tern colonies were found. A roof-top Caspian tern colony reported by USDA-Wildlife Services in the Bremerton Naval Shipyard was confirmed. The Caspian tern colony consists of about 130 breeding pairs spread over the roofs of three adjacent warehouses on the waterfront in the shipyard. Glaucous-winged/western gulls are also nesting on these and other roof-tops in the shipyard. The Caspian tern colony at Bremerton Naval Shipyard is the only known active Caspian tern breeding colony along the coast of Washington other than the larger colony at Dungeness National Wildlife Refuge, which we are monitoring under a separate contract with the U.S. Fish and Wildlife Service.
Nesting Caspian terns have not been observed at former colony sites along the Mid-Columbia River at Three Mile Canyon Island (John Day Pool), Miller Rocks (The Dalles Pool), and Cabin Island (Priest Rapids Pool). A small Caspian tern breeding colony was discovered this season on Rock Island in the Blalock Islands, John Day pool (between the towns of Boardman and Irrigon, Oregon). On 5 July, there were 3 adults and one black-capped fledgling observed on the island. This one fledgling appears to be the only young tern raised at this colony this year; as many as six breeding pairs were observed during previous visits to the island. Nesting Caspian terns shared the island with nesting California gulls and Forster’s terns (ca. 60 pairs), but no Forster’s terns apparently raised young on the island. Inland Washington Sites off the Columbia River ( Sprague Lake and Banks Lake) Caspian terns nested on Harper Island in Sprague Lake (approximately 50 miles east of Moses Lake on I-90), but apparently failed to produce any young in 2005. In early July, 19 adult terns were counted on Dry Falls Island and 7 adult terns were counted on Goose Island, both located in Banks Lake (just above Dry Falls Dam near Coulee City). Caspian tern chicks were observed on both of these islands, indicating that terns nesting in Banks Lake were successful in hatching young.
For the week, 24% of the identifiable fish delivered to the Crescent Island tern colony (N = 70) were salmonids, a significant drop in the salmonid percentage from previous weeks. This likely reflects a decline in availability of out-migrating smolts near the Crescent Island colony. Year to date, 66% of the identifiable fish delivered to the Crescent Island tern colony (N = 2,925) were salmonids (this cumulative percent is an average of the previous weeks’ percentages). This compares to 70% salmonids in the diet at this time last year.
At East Sand Island, one colony disturbance was observed at a rate of 0.1 disturbances/hr of observation. Generally, disturbances of the East Sand Island tern colony by bald eagles have been more frequent and more intense than last year, including observations of eagles roosting on the colony and preying on adult Caspian terns on or near the colony. During these eagle disturbances, a large proportion of the adult terns on the colony may flush, leaving tern eggs and chicks vulnerable to predation by gulls nesting near the tern colony. Gull predation on Caspian tern eggs and chicks at the East Sand Island colony has been more frequent this year than in any other year since the colony was established in 1999, and has contributed to the lower nesting success of terns compared to previous years. At Crescent Island, no colony disturbances were observed this past week. This past week, gull kleptoparasitism rates at East Sand Island were 0.3% of all known fates of fish delivered by terns. At Crescent Island, gull kleptoparasitism rates were 2% of all known fates of fish delivered by terns this past week. At the East Sand Island tern colony, kleptoparasitism is by glaucous-winged/western gulls, while at Crescent Island kleptoparasitism is by the smaller California gull. To date, there have been no signs of mammalian predators on any of the tern colonies monitored as part of this study.
There were no visitors in the field this past week.
The Principal Investigators for this project, Dan Roby and Ken Collis, would like to take this opportunity to thank the crew members whose hard work and dedication were essential to the success of our research and monitoring efforts along the Columbia River in 2005. We are very grateful to Jessica Adkins, Lindsay Adrean, Andrea Barnetche, Joseph Brandt, Mike Callaizakis, Chris Couch, Brendan Courtot, Allen Evans, Karen Fischer, Ramona Flatz, Mike Hawbecker, Jon Laslett, Nolan Lewis, Rachel Lord, Don Lyons, Anne Mary Myers, Lauren Reinalda, Risha Sparhawk, Monica Stevens, Yasuko Suzuki, and Ali Theuer.
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The high and low on-colony counts for the week on East Sand Island were 5,510 terns (18 July) and 2,240 terns (22 July), respectively. The annual photo census of the Caspian tern colony on East Sand Island was conducted on 17 May. Once these aerial photos are counted (Fall 2005), we will be able to accurately estimate colony size and determine whether there has been a significant change in colony size since 2004. Visual estimates of colony size from the ground suggest that the East Sand Island colony was somewhat smaller this year than in 2004. 
For the week of 18 July – 24 July, 6% of the identifiable fish delivered to the East Sand Island colony (N = 313) were salmonids. The majority of the prey items being delivered to the East Sand Island colony were anchovies (69%) and surfperch (14%). Year to date, 23% of the identifiable fish delivered to the East Sand Island tern colony (N = 5,323) were salmonids (this cumulative percent is an average of the previous weeks’ percentages). This compares to 17% salmonids in the diet at this time last year. In the last half of the breeding season the percent salmonids in the diet of East Sand Island Caspian terns has declined to the levels seen last year at this time, suggesting that there has been an influx of anchovies and other marine forage fishes into the estuary concurrent with the decline in out-migrating salmonid smolts.. 