Last Updated July 23

Note: 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 5,120 terns (July 16th) and 2,523 terns (July 17th), respectively. This represents a 46% 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 40 young tern chicks have been sighted in this area. During this past week, we banded chicks near fledging age at the East Sand Island tern colony (see below for more details).

Mid-Columbia River Sites (Crescent Island)

The high and low on-colony counts for the week on Crescent Island were 88 terns (July 21st) and 44 terns (July 22nd), respectively. This represents a 47% 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 16 July - 22 July, 6% of the identifiable fish delivered to the East Sand Island tern colony (N = 307) were salmonids, a 33% decrease 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, 35% of the identifiable fish delivered to the East Sand Island tern colony (N = 5,593) were salmonids. This compares to 46% juvenile salmonids in the diet of terns on East Sand Island by the same date in 2000.

For the week, 50% of the identifiable fish delivered to Crescent Island (N = 100) were salmonids, a 2% decrease from the previous week. Year to date, 70% of the identifiable fish delivered to terns on Crescent Island (N = 2,064) were salmonids.

Off-Colony Distribution

Radio-Tracking

One radio-tracking flight was conducted in the Columbia River estuary this past week. Only five radio-tagged terns were detected this past week, suggesting that many of the radio-tagged terns have already emigrated from the Columbia River estuary. Three of the five relocations of radio-tagged terns (60%) 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 = 2), both were in the lower Columbia River estuary below Rice Island.

Chick Banding

On July 16 - 17, a total of 290 chicks that were near fledging 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 and unique color band combinations placed on both legs. No mortality or injuries occurred to tern chicks during this banding operation. These banded fledglings will provide important data on survivorship and dispersal patterns of young terns to breeding colonies in future years.

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

There were no visitors in the field this past week.