Last Updated July 02

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 or on any other island in the upper estuary. 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 12,410 terns (June 26th) and 7,740 terns (June 29th), respectively. This represents a 20% 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. This week, approximately 250 terns were counted in this area, of which about half were sitting in nest scrapes. At least 8 young tern chicks have been sighted in this area.

Today (July 2nd) a second aerial photo census is being conducted for the East Sand Island tern colony. The purpose of this census is to determine the number of young terns that have been raised to fledging age this year. We suspect that production of young terns at the East Sand Island tern colony this year could be considerably higher compared to last year.

Click here to see movie of the East Sand Island tern colony in 2001.

Mid-Columbia River Sites (Crescent Is.)

The high and low on-colony counts for the week on Crescent Island were 595 terns (June 25th) and 347 terns (June 29th), respectively. This represents a 30% decrease in the median count of terns on the Crescent Island colony from last week to this week. Currently, there are about 769 young terns on the Crescent Island tern colony; this represents somewhat higher productivity as compared to last year.

Inland Washington Sites (Potholes Reservoir and Banks Lake)

Solstice Island, located in Potholes Reservoir, was visited on June 28th. A total of 245 adult terns and 219 chicks were counted on the colony. Some tern chicks at the Solstice Island colony are capable of flight.

Goose Island, located in Banks Lake near Coulee City, was visited on June 27th when 29 adult terns and 15 nearly full-grown chicks were observed on the colony. Our best estimate of the number of nesting pairs on the Goose Island colony is 25. Last year at this time there were only 10 pairs nesting at this colony, all of which ultimately failed.

Diet Composition

For the week of 25 June - 1 July, 20% of the identifiable fish delivered to the East Sand Island tern colony (N = 358) were salmonids, a 20% increase from the previous week (see Seasonal Trends for the weekly salmonid proportion of the diet for terns on East Sand Island). Currently, anchovies are the most prevalent fish in tern diets on East Sand Island. Year to date, 41% of the identifiable fish delivered to the East Sand Island tern colony (N = 4,588) were salmonids. This compares to 54% juvenile salmonids in the diet of terns on East Sand Island by the same date in 2000.

For the week, 77% of the identifiable fish delivered to Crescent Island (N = 150) were salmonids, a 6% decrease from the previous week. Year to date, 74% of the identifiable fish delivered to terns on Crescent Island (N = 1,664) were salmonids.

On June 28th, 50 fish were identified on Solstice Island as they were fed to chicks on the colony. Of these fish, 22% were salmonids, while Centrarchids (e.g., sunfish, bass) were the most prevalent fish in the sample.

Off-Colony Distribution

Radio-Tracking

Two radio-tracking flights (6/25 and 6/26) were conducted in the Columbia River estuary this past week. Thirty-eight of the 52 relocations of radio-tagged terns (73%) were on the East Sand Island colony. Of all the off-colony detections of radio-tagged terns that are known to be nesting on East Sand Island (N = 6), five (83%) were in Willapa Bay and 1 (17%) was in the lower Columbia River estuary below the Astoria Bridge.

Predator Activity

Gull kleptoparasitism and predation rates at the East Sand Island tern colony remained low this past week.

Media & Other Visitors

There were no visitors in the field this past week.