Last Updated July 17
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 July 10th
(662 terns) and July 11th (338 terns), respectively. This represents a 20% decrease
in the average number of terns counted on the Rice Island tern colony this week,
as compared to last week. Only 48 tern chicks remained on the Rice Island tern
colony as of Saturday, July 15th.
The Rice Island camp was removed on Friday, July 14th. Ian Rose and Jason Wolf, the two Rice Island monitors, have been relieved after 3 months living on the island. Everyone on the research team would like to thank them for their hard work and dedication. We will continue to monitor colony size and diet composition at Rice Island, but on a less frequent basis, through the end of July.
For the past couple of weeks we have seen small numbers of terns roosting on islands in the upper estuary (Puget Island and Miller Sands).
Click here to see an aerial photo of the Rice Island tern colony taken on May 31st.
East Sand Island
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The
high and low on-colony counts for the week on East Sand Island were on July
10th (6,530 terns) and July 16th (3,590 terns), respectively. This represents
a 27% decrease in the average number of terns counted on the East Sand Island
tern colony this week, as compared tolast week. Young
terns continue to fledge from the East Sand Island colony and are roosting at
various off-colony locations (both on and off East Sand Island). Yesterday,
roughly 1,000 tern fledglings were counted on the beaches (north and south)
adjacent the East Sand Island tern colony.
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
Two complete aerial surveys of sites along the coast of Washington were conducted this week (see below). The number and size of tern aggregations along the Washington coast seems to be declining in comparison to the previous two weeks. In Willapa Bay, we did not observe any sizable aggregations of terns (>10). In Grays Harbor, we observed small aggregations (30 - 50 terns) on Cate Island and a small sand bar NE of Sand Island.
Mid-Columbia River Sites (Three Mile Canyon Island and Crescent Island)
The high and low on-colony counts for the week on Crescent Island were on July 12th (71 terns) and July 15th (68 terns), respectively. This represents a 71% 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 attributable to chicks continuing to fledge from the Crescent Island colony. Three Mile Canyon Island was not visited this week. No young were produced from the Three Mile Canyon Island tern colony this season due to mink predation on young chicks and eggs.
Click here to see a map of the up-river tern colony locations.
Inland Washington Sites (Potholes Reservoir, Banks Lake, and Sprague Lake)
O ur up-river crew (Michelle Antolos and Naomi Bargmann) investigated the northern end of Banks Lake this week looking for active Caspian tern nesting sites. No new sites were discovered. Our surveys of inland Washington suggest that Solstice Island in Potholes Reservoir, Goose Island in Banks Lake, and Harper Island in Sprague Lake are the only active Caspian tern colonies in Eastern Washington off the Columbia River. We will continue to investigate other potential Caspian tern nesting sites at inland locations in Washington and Oregon over the next several weeks.
Click here to see a map of the inland Washington tern colonies.
Diet Composition
For the week (10 July - 16 July), 14% of the identifiable fish delivered to East Sand Island were salmonids (n = 362), compared to 83% at Rice Island (n = 374). Compared to the previous week, there was a slight increase in the proportion of salmonids in the diet of East Sand Island terns (12%) and a 9% reduction in the proportion of salmonids in the diet of Rice Island terns from last week to this week. Year to date, 48% of the identifiable fish delivered to the East Sand Island tern colony were salmonids (n = 4,835), compared to 92% at the Rice Island tern colony (n = 4,595). 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 (48%), whereas the year-to-date total for Rice Island terns is higher this year as compared to last year (78%).
So far this year, terns nesting on East Sand Island have consumed 48% fewer juvenile salmonids than terns nesting on Rice Island.
At Crescent Island, 48% of the identifiable fish delivered to the colony this week (n = 100) were salmonids, more than double the proportion of salmonids in the diet from last week.
Last week we reported collecting 55 PIT tags from the Solstice Island tern colony in Potholes Reservoir (see map ). Of the 55 PIT tags recovered, 51 were intact and readable. Of those 51 tags, 50 were from juvenile salmonids tagged and released in the mid or upper Columbia River between April 21st to May 28th, 2000. One tag was from a wild summer steelhead released in the Grand Ronde River (a Snake River tributary) on February 29, 2000. None of the tags recovered from the Solstice Island colony were from previous migration years suggesting that this is the first year that terns bred at that particular site. Thirty-nine PIT tags were from steelhead (76%), 7 PIT tags were from chinook (14%), and 5 PIT tags were from coho (10%). The majority of the PIT tags recovered (75%) were from steelhead used in a survival study at Wells Dam. According to Dean Park (Biomark), roughly 64,000 PIT tagged fish were released as part of that study in 2000. These tag recoveries are significant because they suggest that Caspian terns will travel a considerable distance from their nesting colony (a minimum of 30 miles from the Solstice Island colony) to forage on the Columbia River.
We will attempt to collect additional PIT tags at Solstice Island and other newly discovered inland tern colonies in the coming weeks. We will present those results and any new findings in a subsequent report. We would like to thank Carter Stein and Dave Marvin at Pacific States Marine Fisheries Commission for providing information on the PIT tags recovered on Solstice Island.
Radio Telemetry
Nesting Distribution
Two complete radio-tracking flights were conducted in the Columbia River estuary this past week. Of the 49 terns that were radio-tagged on Rice Island prior to egg laying, 1 tern is currently nesting on Rice Island (2%), 20 terns are currently nesting on East Sand Island (41%), 19 terns are either not nesting or their nesting status is unknown (39%), and 9 terns were not detected in the survey area (18%). Of those terns radio-tagged on Rice Island whose nesting status is known (n = 21), the majority (95%) is nesting on East Sand Island.
Of the 23 terns radio-tagged on East Sand Island that had the eggs removed from their nests, 3 terns have re-nested on Rice Island (13%), 7 terns have re-nested on East Sand Island (30%), 11 terns have not re-nested or their nesting status is unknown (48%), and 2 terns were not detected in the survey area (9%). Of those terns radio-tagged on East Sand Island that had their nest contents removed and whose nesting status is known (n = 10), the majority (70%) re-nested on East Sand Island.
Off-Colony Distribution
Of the 3 off-colony detections of radio-tagged terns currently nesting on Rice Island (n = 4), 2 detections were above the Astoria Bridge and 1 detection was outside the estuary along the Washington Coast. Of the 22 off-colony detections of radio-tagged terns currently nesting on East Sand Island (n = 27), 3 detections were above the Astoria Bridge (14%), 7 detections were below the Astoria Bridge (32%), and 12 detections were outside the estuary along the Washington Coast (54%).
Chick Banding
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On
July 12 -13, 240 chicks were banded at the East Sand Island tern colony. Each
chick was banded with a numbered U.S. Fish and Wildlife Service metal leg band.
Of the 240 chicks that were banded, 231 were also banded with unique color band
combinations placed on both legs. No mortality or injuries occurred to tern
chicks during this banding operation. These marked fledglings will provide important
data on survivorship and dispersal patterns of young terns to breeding colonies
in future years.
Gull and Predator Control
There have been no signs of mammalian predators on either Rice or East Sand islands so far this season. 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.
Media and Other Visitors
On Wednesday (7/12), Zoe Banks (Pacific States Marine Fisheries Commission; PSMFC), Pete Bison (Independent Scientific Advisory Board; ISAB), Dan Bottoms (National Marine Fisheries Service; NMFS), Tom Campbell (NMFS), Chuck Coutant (ISAB), Dennis Enright (NMFS), Bob Gramling (ISAB), Susan Hinton (NMFS), Dick Ledgerwood (NMFS), Jim Lichatowich (ISAB), Eric Loudenslager (ISAB), Chip McConnaha (Northwest Power Planning Council; NPPC), Lyman McDonald (ISAB), Erik Merrill (NPPC), William Muir (NMFS), Brian Riddell (ISAB), Brad Ryan (NMFS), and Mike Scheiwe (NMFS) visited East Sand Island. On Friday (7/14), Mike Crouse, Ben Meyer, and Mike Tehan of the Habitat Division at National Marine Fisheries Service in Portland visited the East Sand Island tern colony.
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