Last Updated June 11

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 have been observed attempting to nest in upland areas on Rice Island (i.e., former colony site, East Ridge, North Shore) or elsewhere in the upper estuary (i.e., Miller Sands Spit, Pillar Rock Sands).

East Sand Island

The high and low on-colony counts for the week on East Sand Island were on June 7th (17,210 terns) and June 9th (11,795 terns), respectively. This represents an 8% decrease in the median count of terns on the East Sand Island colony from last week to this week. This past week, a satellite tern colony was started above the high-high tide line on the beach southeast of the East Sand Island tern colony. Up to 250 terns were counted in this area, of which 100 terns were apparently incubating eggs. Among this group of nesting terns was a tern that was banded at the Asarco Industrial Site in Commencement Bay earlier this year (4/20). That same bird was seen on the experimental tern barge on May 23rd and was not resighted again until it was seen on East Sand Island on June 7th. These data suggest that at least some of the terns that left Commencement Bay have relocated to the Columbia River Estuary.

Experimental Barge in Commencement Bay, WA

Washington Department of Fish and Wildlife (WDFW) in consultation with its research partners cut short the experimental tern barge project. The barge was dismantled and removed from Commencement Bay on May 31st. This was done at the request of the Puyallup Tribe because of concerns for a release of out-migrating salmon smolts and for endangered salmon stocks in the area. (Note: This was the explanation given by WDFW for the barge removal at that time. Subsequently, the WDFW revised that explanation (see 2001 Draft Season Summary)). Any questions regarding the removal of the experimental tern barge should be directed to WDFW, Wildlife Program at wildthing@dfw.wa.gov.

See seasonal trends and previous weekly reports for research results from the experimental tern barge prior to its removal from Commencement Bay, WA

Click here to see additional photos of the experimental tern barge.

Other Sites in Commencement Bay, WA

Following the removal of the experimental tern barge (5/31), most of terns using the experimental tern barge and the nearby barges on the Foss barge boom, apparently left Commencement Bay. Roughly 150 - 200 terns remain in the Commencement Bay area (all near the Port of Tacoma), compared to bay-wide counts ranging between 675 - 900 terns prior to the removal of the experimental tern barge. We will continue to conduct surveys in Commencement Bay and the surrounding area for roosting and nesting terns.

Mid-Columbia River Sites (Three Mile Canyon Is., Crescent Is., and Miller Rocks)

The high and low on-colony counts for the week on Crescent Island were on June 7th (886 terns) and June 9th (831 terns), respectively. These high and low counts on Crescent Island are lower than those same counts last week (982 terns and 904 terns, respectively). Due to the presence of a mink on Three Mile Canyon Island, the terns have abandoned that colony site.

On Thursday (6/7), Dave Craig (Willamette University) and Brad Ryan (NMFS) discovered Caspian terns nesting on Miller Rocks, an island located on the lower Columbia River just upstream of the mouth of the Deschutes River. Thirty-two terns were counted on the island, of which 17 terns were incubating eggs. The terns were nesting amidst a larger California gull colony. We suspect that this tern colony was recently established, perhaps by failed breeders from Three Mile Canyon Island (see above) and elsewhere. This is the first documentation of tern nesting on Miller Rocks, or any other upriver location on the lower Columbia River other than Three Mile Canyon and Crescent islands.

Inland Washington Sites (Potholes Reservoir)

Solstice Island, located in Potholes Reservoir, was not visited this past week. We will continue to monitor this site and other potential Caspian tern nesting sites at inland locations in the coming months.

Diet Composition

For the week of 4 June - 10 June, 45% of the identifiable fish delivered to the East Sand Island tern colony (N = 359) were salmonids, nearly the same percentage as the previous week (46%; see Seasonal Trends for the weekly salmonid proportion of the diet for terns on East Sand Island). This past week, there was a dramatic increase in the proportion of the diet that was anchovies for terns nesting on East Sand Island. Large feeding flocks (terns, cormorants, and pelicans) were observed near East Sand Island apparently in response to an increase in the availability of anchovies in the lower estuary. Year to date, 47% of the identifiable fish delivered to the East Sand Island tern colony (N = 3,537) were salmonids. This compares to 65% juvenile salmonids in the diet of terns on East Sand Island by the same date in 2000.

For the month of May, 77% of the identifiable fish delivered to terns in Commencement Bay (N = 1,061) were salmonids.

For the week, 73% of the identifiable fish delivered to Crescent Island (N = 150) were salmonids, a 22% decrease from the previous week. Year to date, 73% of the identifiable fish delivered to terns on Crescent Island (N = 1,213) were salmonids.

Off-Colony Distribution

Banding and Radio-Tagging

Banding and radio-tagging of adult terns has been completed in the Columbia River Estuary and the Asarco Industrial Site in 2001.

Radio-Tracking

One radio-tracking flight (6/6) was conducted in the Columbia River estuary this past week. Twenty-eight of the 35 relocations of radio-tagged terns (80%) were on the East Sand Island colony: 15 of the 30 terns radio-tagged on Rice Island in 2001 (50%) and 20 of the 24 terns radio-tagged on East Sand Island in 2001 (83%) 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), all were in the Columbia River estuary, of which 4 (80%) 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. Glaucous-winged/western gulls also nest on East Sand Island and are behind the terns in their nesting chronology (i.e., gulls are currently incubating eggs, while terns are well into the chick rearing phase).

Media & Other Visitors

Eric Apalategui (Longview Daily News), Bill Wagner (Longview Daily News), and Phil Carroll (USFWS) visited East Sand Island on June 8th.