Last Updated July 30

Note: This will be the last weekly update for the 2001 field season. We plan to provide additional updates on a less frequent basis, including a season summary that will be posted in September 2001. The following data are preliminary and may change upon further review.

Caspian Tern Colony Counts

East Sand Island

The high and low on-colony counts for the week on East Sand Island were 3,746 terns (July 24th) and 2,154 terns (July 23rd), respectively. This represents a 23% decrease in the median count of terns on the East Sand Island colony from last week to this week. This past week, approximately 250 adult terns were counted on a satellite colony adjacent the main colony, of which half were sitting in nest scrapes. At least 50 young tern chicks have been sighted in this area.

Mid-Columbia River Sites (Crescent Island)

The high and low on-colony counts for the week on Crescent Island were 76 terns (July 24th) and 16 terns (July 23rd), respectively. This represents a 30% decrease in the median count of terns on the Crescent Island tern colony from last week to this week.

Diet Composition

For the week of 23 July - 29 July, 9% of the identifiable fish delivered to the East Sand Island tern colony (N = 411) were salmonids, a 50% increase from the previous week (see Seasonal Trends for the weekly salmonid proportion of the diet for terns on East Sand Island). Anchovies made up the majority of the tern diet (60-70%) this past week. Year to date, 34% of the identifiable fish delivered to the East Sand Island tern colony (N = 6,004) were salmonids. This compares to 44% juvenile salmonids in the diet of terns on East Sand Island by the same date in 2000.

For the week, 38% of the identifiable fish delivered to Crescent Island (N = 100) were salmonids, a 24% decrease from the previous week. Year to date, 68% of the identifiable fish delivered to terns on Crescent Island (N = 2,164) were salmonids.

Post-Breeding Dispersal

Recently, there has been an increase in the number of terns (adults and juveniles) counted at locations along the Washington Coast and in the Puget Sound, including Commencement Bay. As we reported last year, many terns that nested in the Columbia River estuary appear to disperse northward along the coast before heading south to over-winter along the Pacific coast of Mexico and Central America. Roughly 1,000 post-breeding terns were counted in Commencement Bay this past week, mostly at locations within the Port of Tacoma (on or near the Northcoast Yachts building and the Olympic Capitol warehouse). In June and early July, there were fewer than 200 adult terns counted in Commencement Bay.

Predator Activity

Gull kleptoparasitism and predation rates at the East Sand Island tern colony has increase somewhat now that the number of terns on colony has declined.

Media & Other Visitors

On Thursday (July 26th), 12 people attending the Wildlife Diversity Conference in Long Beach, Washington visited East Sand Island. The group included state non-game biologists from around the country.

Thanks to the Field Crew

As mentioned earlier in this report, this will be our last weekly update for the 2001 field season. We would like to take this opportunity to thank all of the field biologists we had working with us this season. Their passion, dedication, and hard work contributed greatly to the success of our research and monitoring efforts.