Last Updated July 3

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

Colony Counts

Rice Island and Other Upper Estuary Islands

The high and low on-colony counts for the week on Rice Island were on June 26th (969 terns) and June 30th (446 terns), respectively. This represents a 16% increase in the average number of terns counted on the Rice Island tern colony this week, as compared to last week. This increase may represent post-breeding dispersal of terns from other colonies, including East Sand Island.

Gull harassing Caspian terns. Photo courtesy of Mike Wilhelm.Gull activity on the Rice Island tern colony is still down from the levels observed earlier in the season; however, gulls continue to steal chick meals from adult terns (i.e., kleptoparasitism) and prey on tern eggs. These late nesting attempts are presumably by terns that failed in earlier nesting attempts. We expect that terns re-nesting this late in the season will not be successful in rearing young. The chicks that remain on the colony (n = 90) are large enough now that they are relatively safe from predation by gulls.

In earlier weekly updates we reported on the high rates of gull predation on tern eggs and chicks at the Rice Island colony. The two colony monitors on Rice Island (Ian Rose and Jason Wolf) recently tallied up their observations of predation events for the season. They observed 710 eggs and 59 chicks taken by gulls. If these minimum estimates are extrapolated to the total daylight hours for the observation period, it comes to 1,575 eggs and 105 chicks. These are minimum estimates because not all parts of the colony can be watched at one time, so predation events are missed. Nevertheless, this provides some indication of the magnitude of gull predation on tern eggs and chicks at the Rice Island tern colony this year.

Click here to see an aerial photo of the Rice Island tern colony taken on May 31st. These photos are in the process of being analyzed by the Photogrammetry Department at the Bonneville Power Administration (BPA). These results will not be available for several weeks.

East Sand Island

Adult tern feeding chick. Photo courtesy of Mike Wilhelm.The high and low on-colony counts for the week on East Sand Island were on June 27th (9,060 terns) and July 1st (4,900 terns), respectively. This represents an 8% decline in the average number of terns counted on the East Sand Island tern colony this week, as compared to last week. This decline in colony attendance is at least partially attributable to chicks beginning to fledge from the East Sand Island colony. Up to 100 chicks are now flying around the colony and roosting at various off-colony locations (both on and off East Sand Island). Estimates of the number of tern chicks on the East Sand Island colony are 7 - 9,000. This represents about 1.1 chicks per active tern nest.

The latest on-colony counts indicate that roughly 91% of the total number of terns counted on both the Rice Island and East Sand Island colonies are on East Sand Island.

Click here to see an aerial photo of the East Sand Island tern colony taken on May 31st (see above).

Coastal Sites

One complete aerial survey of sites along the coast of Washington was conducted this week (see below). Beginning this week, we observed large aggregations of terns in Willapa Bay and Grays Harbor. These terns are likely roosting in these areas after having completed, either successfully or unsuccessfully, previous nesting attempts at either East Sand or Rice islands. In Willapa Bay, roughly 1,000 and 200 terns were observed on Snag Island and Gunpowder Sands, respectively. In Grays Harbor, roughly 300 and 200 terns were observed on No-name Island and Cate Island, respectively. Prior to beginning their southern migration to over-wintering grounds, many terns that nested in the estuary will first disperse to coastal sites north and south of the estuary, presumably to feed.

Upriver Sites (Three Mile Canyon and Crescent Islands)

The high and low on-colony counts for the week on Crescent Island were on June 27th (410 terns) and July 2nd (278 terns), respectively. This represents a 33% decrease in the average number of terns counted on the Crescent Island tern colony this week, as compared to last week. This decline in colony attendance is at least partially attributable to chicks beginning to fledge from the Crescent Island colony. Three Mile Canyon Island was not visited this week.

One tern banded at Rice Island at the beginning of the nesting season was sighted at the Crescent Island tern colony on July 2nd. This is presumably part of the post-breeding season dispersal of terns from the Columbia River Estuary.

Diet Composition

For the week (26 June - 2 July), 19% of the identifiable fish delivered to East Sand Island were salmonids (n = 368), compared to 91% at Rice Island (n = 358). Compared to the previous week, there was no change in the proportion of salmonids in the diet of East Sand Island terns (19%) and a slight increase in the proportion of salmonids in the diet of Rice Island terns (86%). Year to date, 54% of the identifiable fish delivered to the East Sand Island tern colony were salmonids (n = 4,103), compared to 93% at Rice Island tern colony (n = 3,863). The year-to-date total for percent salmonids in the diet of terns nesting on East Sand Island is the same as the corresponding value from last year (54%), whereas the year-to-date total for Rice Island terns is higher this year as compared to last year (83%).

So far this year, terns nesting on East Sand Island have consumed 42% fewer juvenile salmonids than tern nesting on Rice Island.

At Crescent Island, 55% (n = 200) of the identifiable fish delivered to the colony this week were salmonids, representing a 10% decline in the proportion of salmonids in the diet from last week to this week.

Radio Telemetry

Nesting Distribution

One complete radio-tracking flight was conducted in the Columbia River estuary this past week. Of the 49 terns that were radio-tagged on Rice Island prior to egg laying, 3 terns are currently nesting on Rice Island (6%), 26 terns are currently nesting on East Sand Island (53%), 14 terns are either not nesting or their nesting status is unknown (29%), and 6 terns were not detected in the survey area (12%). Of those terns radio-tagged on Rice Island whose nesting status is known (n = 29), the majority (90%) is nesting on East Sand Island.

Of the 23 terns radio-tagged on East Sand Island that had their nest contents removed (i.e., eggs), 2 terns have re-nested on Rice Island (9%), 7 terns have re-nested on East Sand Island (30%), 13 terns have not re-nested or their nesting status is unknown (57%), and 1 tern was not detected in the survey area (4%). Of those terns radio-tagged on East Sand Island that had their nest contents removed and whose nesting status is known (n = 9), the majority (78%) re-nested on East Sand Island.

Off-Colony Distribution

The one off-colony detection of a radio-tagged tern currently nesting on Rice Island (n = 5) was above the Astoria Bridge. Of the 14 off-colony detections of radio-tagged terns currently nesting on East Sand Island (n = 33), 1 detection was above the Astoria Bridge (7%), 9 detections were below the Astoria Bridge (64%), and 4 detections were outside the estuary along the Washington Coast (29%).

Gull and Predator Control

There have been no signs of mammalian predators on either Rice or East Sand islands so far this season. Limited gull control is still being carried out at the East Sand Island tern colony to enhance prospects for tern colony restoration at that site. No gulls were shot this past week at East Sand Island, for a total of 40 gulls shot on the East Sand Island tern colony to date this season. The low level of gull control activities over the last few weeks is a reflection of the low level of gull activity on the East Sand Island tern colony, not a reduction in gull control efforts.

Media and Other Visitors

On Friday (6/30), members of the Pacific Northwest Institute for Journalism and Natural Resources visited the East Sand Island tern colony. The group included: Chris Bryant (University of Oregon, School of Journalism), Tara Burghart (The Associated Press), John Butterworth (Corvallis - Gazette Times), Christian Cascone (CNN), Cheryl Colopy (KQED Public Radio, San Francisco), Sam Eaton (KUOW Public Radio, Seattle), Avi Hesterman (Duke University, School of Journalism), Helen Jung (The Wall Street Journal), Jennifer Langston (Post Register, Idaho Falls), Mike Lee (Tri-City Herald, Kennewick), Alice Perry Linker (The Observer, La Grande), Karen Mockler (The Daily Astorian), Theo Stein (The Denver Post), Craig Welch (The Seattle Times), Patty Wentz (Willamette Week), Frank Isaac (Pacific Northwest Institute for Journalism and Natural Resources, Founder), and Peter Anon (Pacific Northwest Institute for Journalism and Natural Resources, Field Coordinator). Visitors to the East Sand Island tern colony on Friday also included Carol Schuler and Joan Jewett from the U.S. Fish and Wildlife Service.

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