Last Updated April 23

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

Caspian Tern Colony Preparations (during prior weeks)

Rice Island

On March 20, work crews from ODFW and CRITFC fenced and flagged all but roughly 0.5 acres of the core colony area on Rice Island. Silt fences were repaired in the area surrounding the core colony and colored bailing twine and orange flagging were used everywhere else. In total, between 7-8 acres of the former tern nesting habitat was either fenced or flagged to discourage terns from nesting on Rice Island.

On April 4, dummy rocket nets were set up in the middle of the core colony area that was left open. One hundred decoys and two sound systems were set up to lure terns into the area near the rocket nets so that some terns could be captured for radio-tagging and color-banding (see below).

On April 14, a camp was set up on Rice Island and was continuously occupied by two colony monitors throughout the rocket-netting. Colony monitors collected information on the number of terns on the island and other information that proved helpful in trapping terns on the island.

East Sand Island

On March 26-30, work crews from USACE, ODFW, and the research team prepared roughly 4 acres of high quality bare sand habitat on East Sand Island. In addition, a narrow buffer (20-30 meters wide) was prepared on the west and northeast end of the core colony area. This buffer zone was cleared of vegetation, but no work was done to remove rhizomes or roots of scarified plants. This buffer was to provide nesting terns with protection from glaucous-winged/western gulls that previously used these areas for nesting. Two hundred fifty decoys and two sound systems were deployed on East Sand Island on March 31st.

On April 3, a camp was set up on the island and will be continuously occupied by two colony monitors throughout the breeding season.

Experimental Barge in Commencement Bay, WA

With funding from the USFWS, USACE, and NMFS, a barge (90ft x 40ft) was prepared as a temporary tern nesting site on April 13th. The deck of the barge was covered with 10 inches of sand as a nesting substrate. One hundred forty Caspian tern decoys and two solar-powered audio playback systems were placed on the barge to provide social attraction and encourage prospecting terns to settle and nest on the barge. The barge was anchored roughly 200 ft offshore near Browns Point in Commencement Bay, roughly 4 miles from the Asarco Industrial Site. An observation blind was constructed onshore to allow colony monitors to record (1) the number of breeding terns using the barge, (2) nesting chronology and nesting success of terns breeding on the barge, (3) composition of forage fishes consumed by terns nesting on the barge, and (4) factors limiting the numbers of breeding pairs of terns and their nesting success on the barge colony. This information will be used to determine the suitability of the Commencement Bay area for a more permanent tern colony. Food habits studies of the terns nesting on the barge are especially crucial because these data will be used to assess the potential impact of a larger tern colony on the survival of local forage fish species of special concern, especially salmonids.

Asarco Industrial Site, WA

On April 14, 55 decoys and a sound system were deployed at the Asarco Industrial Site. Prior to initiation of egg laying, we will attempt to cannon net adult Caspian terns on the former Asarco colony site. We will place USGS numbered metal leg bands and a unique color combination of plastic leg bands on captured adults. The purpose of banding a sample of adult terns is to determine what proportion of terns that formerly nested on the Asarco site shift to the barge to nest, as opposed to the Columbia River estuary or other colony sites. Subsequent observations of marked terns by various biologists throughout Washington and elsewhere over the course of the summer will allow us to determine where the terns hazed from Asarco colony site ultimately attempt to nest.

Caspian Tern Colony Counts

Rice Island

The high and low on-colony counts for the week on Rice Island were on April 17th (150 terns) and April 18th (41 terns), respectively. The low numbers of terns at the Rice Island tern colony may be attributable to (1) the flagging and fencing erected at the colony site to dissuade tern nesting (see above), (2) rocket-netting activities conducted on the open portion of the colony (see below), and (3) the attraction of East Sand Island, where larger numbers of terns are gathered.

No tern eggs have been observed at the Rice Island colony, nor have we observed much nesting behavior (e.g., nest scrape digging, courtship feeding, copulation). Given that the entire colony area is now either fenced or flagged (see below), we do not expect that terns will attempt to nest at the former colony site on Rice Island in 2001.

No terns have been observed nesting at other off-colony areas on Rice Island (i.e., East Ridge) or on other upper estuary islands (i.e., Miller Sands Spit and Pillar Rock Sands).

East Sand Island

The high and low on-colony counts for the week on East Sand Island were on April 22nd (11,425 terns) and April 17th (1,387 terns), respectively. The number of terns observed on the East Sand Island colony nearly doubled from April 21st to April 22nd, perhaps due to the onset of egg-laying at the colony (see below).

The first tern egg was spotted on the East Sand Island colony on April 19th, nearly a week earlier than the date eggs were first discovered at the East Sand Island tern colony in 2000. On April 19th and 20th, only one-egg nests were observed (1 nest and 6 nests, respectively). Multiple eggs were observed in nest scrapes at the East Sand Island tern colony on April 22nd.

Experimental Barge in Commencement Bay, WA

To date, no terns have been observed perching or nesting on the experimental barge located in Commencement Bay near Browns Point. On several occasions, terns (some with fish) have been observed circling the barge, but none have landed on the barge. On one occasion, it appeared that a tern was going to land on the barge (hovering 5 ft above the barge), until a boat passing nearby disturbed the bird and it flew off. Terns at the Asarco Industrial Site (located roughly 4 miles from the barge site) were probably serving as a greater attraction to terns prospecting for nest sites in the area.

Asarco Industrial Site, WA

The high and low counts for the week at the Asarco Industrial Site were on April 18th (190 terns) and April 22nd (15 terns), respectively. Over the week, there has been a trend towards decreasing numbers of terns counted at the Asarco Industrial Site. The low numbers of terns at the Asarco Industrial Site may be attributable to (1) tarps used to cover the nesting substrate at the former colony site, (2) cannon-netting activities conducted to capture adult terns for color banding, and (3) attraction to other roost sites in the area, where larger numbers of terns are gathered (e.g., at the mouth of McCallister Creek in the Nisqually National Wildlife Refuge).

Up-river Sites (Three Mile Canyon and Crescent Islands)

The high and low on-colony counts for the week on Crescent Island were on April 19th (403 terns) and April 16th (188 terns), respectively. The high and low on-colony counts for the week on Three Mile Canyon Island were on April 22nd (70 terns) and April 16th (30 terns), respectively. The number of terns counted at the Three Mile Canyon Island tern colony is down from the number counted on-colony last year at this time, presumably due to visits to the colony by a mink. The mink has killed several adult gulls on the adjacent California gull colony. The first tern eggs were observed at the Crescent Island and Three Mile Canyon Island tern colonies on April 16th and April 22nd, respectively. Each of the tern nests observed had only one egg, indicating that these dates may represent the date eggs were first laid at each colony. A California gull subsequently depredated the egg laid at the Three Mile Canyon Island tern colony.

Diet Composition

For the week of April 16 - 22, 31% of the identifiable fish delivered to East Sand Island (N = 437) were salmonids. Fish watch data have not been collected at the Rice Island tern colony site due to the low and inconsistent numbers of terns observed at the site in 2001. Year to date, 38% of the identifiable fish delivered to East Sand Island (N = 994) were salmonids. This compares to 55% juvenile salmonids in diet of terns on East Sand Island by the same date in 2000.

For the week, 46% of the identifiable fish delivered to Crescent Island (N = 152) were salmonids. Fish watch data have not been collected at the Three Mile Canyon Island tern colony site due to the low and inconsistent numbers of terns observed at the site to date.

Off-Colony Distribution

Banding and Radio-Tagging

The research team, with help from Dan Felber (ODFW) and many volunteers, successfully rocket-netted 49 adult terns on the Rice Island colony site. All the captured terns were color-banded with a unique color combination of plastic leg bands, as well as a federal numbered metal leg band. The color-banded terns will be identifiable when perched on a nesting or roosting site. Thirty of the terns were also radio-tagged with small transmitters that were attached to the base of the central tail feathers, and part of the plumage was dyed pink for visual identification at a distance and while in flight. The on-colony attendance and off-colony movements of the 30 radio-tagged terns will be monitored using both fixed-wing aircraft and stationary tracking stations. During the entire rocket-netting operation none of the captured terns were injured. Once rocket-netting was completed (April 20th), the sound system and decoys that were used to lure the terns within rocket-netting range were removed from the colony site, and the area was filled in with flagging to discourage tern nesting at the site. On April 20th, the entire former tern colony area on Rice Island was covered with fencing or flagging.

Chris Thompson of WDFW, with help from the research team and Gary Shugart (University of Puget Sound), successfully cannon-netted 29 adult terns at the Asarco Industrial Site near Tacoma, Washington. All of these birds (with the exception of one tern that was already banded) were color-banded and released unharmed. These marked terns will help determine the dispersal pattern of terns to other nesting areas. The WDFW will prevent all tern nesting at the Asarco Industrial Site in 2001.

Radio-Tracking & Resightings of Banded Birds

A stationary tracking station was set up at East Sand Island to monitor attendance of radio-tagged terns at the colony site. Off-colony distributions of radio-tagged terns will be monitored using fixed-wing aircraft beginning next week.

Gull Control & Predator Activity

Gull control has not commenced at the East Sand Island tern colony because the necessary permits have not been issued. Despite the lack of gull control at the East Sand Island colony to date, no gull predation on tern eggs has been observed and gull kleptoparasitism rates have been low. Furthermore, there have been no signs of mammalian predators on either Rice or East Sand islands in 2001.

Bald eagle activity seems to be particularly high at East Sand Island this year. A least 8 eagles were present on the island at one time on April 20th. Several eagle-induced disturbance events were observed at both the Caspian tern and the double-crested cormorant colonies on that same date. Although bald eagles are known predators of adult terns, no evidence of eagle predation on terns has been observed so far this year.

Media & Other Visitors

ODFW personnel assisted the research group with rocket-netting at Rice Island from April 16 -20. We would like to thank Dan Felber, Holly Michael, Mark Nebeker, Jerry Ronne, and Gary Salem for their assistance with these activities.

We would like to thank Ken Larson with Larson Marine Services for all his help in setting up the experimental barge in Commencement Bay. Chris Thompson of WDFW also played a crucial role in getting the barge project off the ground.

We would like to thank Gary Shugart (University of Puget Sound) and Michelle Tirhi (WDFW) for their help with cannon-netting at Asarco this week.

On Friday (April 20th), Rowan Gould (Deputy Regional Director, USFWS), David Wesley (Assistant Regional Director for Migratory Birds and State Programs, USFWS), Tara Zimmerman (Nongame Migratory Bird Coordinator, USFWS), Cat Brown (Oregon State Office, USFWS), and Laura Todd (Oregon State Office, USFWS) visited Rice and East Sand islands.