| Note:
The following data are
preliminary and may change upon further review.
Caspian Tern Colony
Preparations
 At East Sand Island, habitat improvements on the Caspian tern colony site were accomplished by the U.S. Army Corps of Engineers during April 1 – 5. Similar to the last two 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 European beach grass and other invasive plants. Tern decoys (58) and an audio playback system were deployed near the newly-situated north blind to attract nesting terns to that part of the colony site. On April 6, 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 6,465 terns (April 10) and 1,690 terns (April 6), respectively. During the period when habitat work was conducted on East Sand Island (April 1 – 5), terns were continuously roosting on portions of the colony site. 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 2004. 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,
Three Mile Canyon Island, Miller Rocks)
 The high and low on-colony counts for the week on Crescent Island were 48 terns (April 6) and 47 terns (April 8), respectively. Nesting terns have not been observed at other sites along the Mid-Columbia River.
.Diet Composition
For the week of April 5 – 11, 8% of the identifiable fish delivered to the East Sand Island colony (N = 40) were salmonids. The majority of the prey items being delivered to the East Sand Island colony were clupeids (e.g., herring; 48%) and smelt (43%).
No fish were identified at the Crescent island tern colony this past week.
Predator Activity
At East Sand Island, bald eagles have been observed at the colony throughout the week, frequently causing terns to take flight. 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.
At East Sand Island and Crescent Island, no kleptoparasitism was observed this past week.
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 April 1 – 5, USACE personnel (lead by Geoff Dorsey) were on East Sand Island to prepare suitable tern nesting habitat.
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