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

Caspian Tern Colony Preparations

In late September 2004, the tern colony area on East Sand Island was treated with herbicide (i.e., Round-up) which helped to suppress encroaching beach and dune grass on the colony site over the winter. On March 24-25, habitat improvements on the Caspian tern colony site were accomplished by the U.S. Army Corps of Engineers. Similar to the last three years, approximately 6.5 acres of suitable bare sand nesting habitat was prepared at the eastern end of East Sand Island by mechanical removal of encroaching grass and other invasive plants. Tern decoys (30) and an audio playback system were deployed on the colony site. On March 31, a camp was set up on East Sand Island and will be continuously occupied by two colony monitors throughout the tern breeding season.

The former tern colony site on Rice Island (roughly 7 acres) is completely vegetated and is unsuitable for tern nesting.

Caspian Tern Colony Counts

East Sand Island

The high and low on-colony counts for the week on East Sand Island were 3,677 terns (April 10) and 639 terns (April 5), respectively. Early breeding behaviors (i.e., nest scrape digging, courtship feeding, copulation) increased in frequency at the colony site throughout the week.

Rice Island and Other Upper Estuary Islands

During this past week, no terns were observed roosting or attempting to nest in upland areas of Rice Island, Miller Sands Spit, or Pillar Rock Sands, three dredged material disposal sites in the upper part of the Columbia River estuary.

Given that the entire former colony site on Rice Island is now vegetated, we do not expect that terns will attempt to nest there in 2005. We will continue to monitor Rice Island and the other upper estuary dredged material disposal islands for early signs of nesting (e.g., nest scrape digging) and will promptly inform resource managers of any such activity.

Up-river Sites (Crescent Island)

The high and low on-colony counts for the week on Crescent Island were 250 terns (April 9) and 122 terns (April 6), respectively. Nesting terns have not been observed at other sites along the Mid-Columbia River.

Diet Composition

For the week of April 4 – 10, 25% of the identifiable fish delivered to the East Sand Island colony (N = 87) were salmonids. The majority of the non-salmonid prey items being delivered to the East Sand Island colony were smelt (26%), clupeids (e.g., herring; 22%), and sand lance (22%)

For the week, 97% of the identifiable fish delivered to the Crescent Island tern colony (N = 35) were salmonids.

Predator Activity

At East Sand Island, bald eagles have been observed at the colony throughout the week, frequently causing terns to take flight. A total of 4 colony disturbances were observed (all causes) at a rate of 0.4 disturbances/hr of observation. Generally, these disturbances are short, causing terns to flush for only 10-30 seconds before returning to the colony.

There were no disturbances observed at the Crescent Island tern colony tern colony this past week.

This past week, gull kleptoparasitism rates at East Sand Island were 7% of all known fates of fish delivered by terns. At Crescent Island, gull kleptoparasitism rates were 9% of all known fates of fish delivered by terns this past week. At the East Sand Island tern colony, kleptoparasitism is by glaucous-winged/western gulls, while at Crescent Island kleptoparasitism is by the smaller California gull.

To date, there have been no signs of mammalian predators on any of the tern colonies monitored as part of this study.

Media & Other Visitors

During March 24 - 25, USACE personnel (lead by Geoff Dorsey) were on East Sand Island to prepare suitable tern nesting habitat.

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