Last Updated June 25

Note: The following data are preliminary and may change upon further review.

Caspian Tern Colony Counts

Rice Island and Other Upper Estuary Islands

During the past week, no terns were observed attempting to nest on Rice Island (i.e., former colony site, East Ridge, North Shore) or on any other island in the upper estuary (i.e., Miller Sands Spit, Pillar Rock Sands). At this late date it is very unlikely that any additional nesting attempts will be initiated at these sites in 2001.

East Sand Island

The high and low on-colony counts for the week on East Sand Island were on June 18th (15,155 terns) and June 24th (10,170 terns), respectively. This represents a 12% decrease in the median count of terns on the East Sand Island colony from last week to this week. A satellite tern colony continues to be active on the beach southeast of the main colony, above the high-high tide line. Approximately 250 terns were counted in this area, of which about half were sitting in nest scrapes. At least 5 tern chicks have been sighted in this area. The first fledged tern chick was observed flying around the East Sand Island tern colony on June 24th. We suspect that production of young terns at the East Sand Island tern colony this year could be considerably higher compared to last year.

Commencement Bay and Surrounding Area, WA

For the past three weeks we have been searching the Puget Sound area for the terns that have left Commencement Bay following the removal of the experimental tern barge. On Thursday (6/21) this past week, we conducted an aerial survey (thanks to Jennifer Whitney of WDFW) for terns from Bellingham to Tacoma. The only large concentration of terns we observed was on or near Pier 90 at the Port of Seattle, a site that terns used previous to the barge removal (see weekly report for May 28 - June 3 for further information on the removal of the experimental tern barge). The terns that were nesting on the roof of the Northcoast Yachts building at the Port of Tacoma apparently failed, since there were no terns visible on the roof during the flight. There is evidence to suggest that at least some of the terns from Commencement Bay have relocated to the Columbia River estuary (e.g., 3 out of 54 banded terns from Commencement Bay have been resighted on the East Sand Island tern colony). Additional sites we would like to survey for terns are; Jetty Island near Everett and Padilla Bay. Any information on tern use of these or any other areas in Puget Sound or along the coast can be reported to clientservices@realtimeresearch.org.)

Mid-Columbia River Sites (Crescent Is., Miller Rock Is.)

The high and low on-colony counts for the week on Crescent Island were on June 19th (698 terns) and June 22nd (644 terns), respectively. This represents a 16% decrease in the median count of terns on the Crescent Island colony from last week to this week. The first fledged tern chick was observed flying around the Crescent Island tern colony on June 22nd.

The Miller Rock gull and tern colony was not visited this past week.

Inland Washington Sites (Potholes Reservoir)

Solstice Island, located in Potholes Reservoir, was not visited this past week.

Diet Composition

For the week of 18 June - 24 June, 16% of the identifiable fish delivered to the East Sand Island tern colony (N = 361) were salmonids, a 42% decrease from the previous week (see Seasonal Trends for the weekly salmonid proportion of the diet for terns on East Sand Island). The proportion of the tern diet that was salmonids has decreased dramatically over the past two weeks. Concurrently, there has been a sharp increase in the number of herring, anchovies, and smelt (all marine species) in the diet. We have also noted a sharp decrease in foraging trip duration during this same time period, presumably due to an increase in the local availability of marine fish. Year to date, 43% of the identifiable fish delivered to the East Sand Island tern colony (N = 4,230) were salmonids. This compares to 58% juvenile salmonids in the diet of terns on East Sand Island by the same date in 2000.

For the week, 82% of the identifiable fish delivered to Crescent Island (N = 151) were salmonids, a 5% increase from the previous week. Year to date, 74% of the identifiable fish delivered to terns on Crescent Island (N = 1,514) were salmonids.

Off-Colony Distribution

Radio-Tracking

Two radio-tracking flights (6/18 and 6/19) were conducted in the Columbia River estuary this past week. Fifty-one of the 66 relocations of radio-tagged terns (77%) were on the East Sand Island colony; 15 of the 30 terns radio-tagged on Rice Island in 2001 (50%) and 18 of the 24 terns radio-tagged on East Sand Island in 2001 (75%) are known to have active nests on East Sand Island. Of all the off-colony detections of radio-tagged terns that are known to be nesting on East Sand Island (N = 5), one (20%) was in Willapa Bay, two (40%) were above Rice Island, and 2 (40%) were below Rice Island.

We continue to observe relatively few terns roosting at sites in the upper estuary and along the Washington Coast (i.e., Willapa Bay and Grays Harbor) this year, as compared to last year.

Predator Activity

Gull kleptoparasitism and predation rates at the East Sand Island tern colony remained low this past week. As mentioned above, the relatively low gull predation rates on tern eggs and chicks at the East Sand Island tern colony will likely lead to higher nesting success of terns this year, as compared to last year.

Media & Other Visitors

This past week, Nancy Butterfield from the Chinook Observer visited our field house in Chinook, WA to see the tern chicks that we are rearing in captivity (see weekly report for May 28 - June 3 for further information on the chick rearing experiment).