Last Updated April 15th

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

Caspian Tern Colony Preparations

On April 2, a settlement agreement between the plaintiffs (National Audubon Society, Defenders of Wildlife, Seattle Audubon Society, and American Bird Conservancy) and defendants (U.S. Army Corps of Engineers and U.S. Fish and Wildlife Service) was signed by Federal District Judge Barbara Rothstein. The signed agreement allowed habitat work to begin on Rice Island (to discourage tern nesting) and on East Sand Island (to encourage tern nesting). At East Sand Island, habitat improvements were conducted by the USACE from April 6-8. Roughly 6.5 acres of suitable bare sand habitat was prepared on East Sand Island. Tern decoys (252) and sound systems (2) were deployed in the center of the colony area to attract nesting terns to the site. On April 8, a camp was set up on East Sand Island and will be continuously occupied by two colony monitors throughout the breeding season.

At Rice Island, work crews from NMFS, ODFW, and USACE flagged roughly 0.5 acres of bare sand habitat at the former Rice Island tern colony site on April 8. In addition, eagle decoys and eagle perches were deployed at the periphery of the former colony site. The remaining colony area 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 5,551 terns (April 13) and 809 terns (April 9th), respectively. During the period when habitat work was being done on East Sand Island (April 6-8), terns were continuously using portions of the colony site. Early breeding behaviors (i.e., scrape digging, courtship feeding, copulation) have increased in frequency at the colony site throughout the week.

On April 13, a severe rainstorm caused flooding on the colony (30-35% of the occupied colony area had standing water). This temporarily displaced roughly 500 terns to other areas on the colony. The areas with standing water dried out by the following day, at which time the terns returned to those areas.

Rice Island and Other Upper Estuary Islands

Terns have not been observed at the former Rice Island colony site or on the East Ridge so far this year. Some terns have been observed on the beaches adjacent to the former colony site (<100), but far fewer than have been observed in previous years. On April 12, only 10 terns were observed on Rice Island (on north beach below the high tide line). On that same day, 41 terns were observed loafing below the high tide line on the west end of Miller Sands Spit and 4 terns were observed at an upland site at the east end on the island. On April 14, the upland site where terns were observed on Miller Sands was visited again and no terns were seen at the site. Thus far, no nest scrapes have been observed at any upland site on either Miller Sands Spit or Rice Island.

Given that the entire former colony area on Rice Island is now either flagged or vegetated, we do not expect that terns will attempt to nest at the former colony site on Rice Island in 2002. We will continue to monitor Rice Island and other upper estuary dredge disposal islands looking for early signs of nesting (e.g., 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 105 terns (April 11) and 45 terns (April 9), respectively. Terns have not been observed on Three Mile Canyon Island so far this season, where mink predation caused complete colony failures in the previous two years. Thus far in 2002, terns have not been observed at Miller Rocks either, the site of a new tern colony (roughly 10-15 pairs) in 2001.

Diet Composition

For the week of April 8 - 14, 30% of the identifiable fish delivered to the East Sand Island colony (N = 187) were salmonids. The majority of the prey items being delivered to the East Sand Island colony were anchovies.

For the week, 25% of the identifiable fish delivered to Crescent Island (N = 28) were salmonids. Most of the non-salmonids observed at Crescent Island were yellow perch, cyprinids (e.g., northern pikeminnow, peamouth), and bass.

Off-Colony Distribution

In 2002, researchers will be investigating the distribution and predation activity of piscivorous waterbirds (primarily gulls, terns, cormorants, and pelicans) at McNary Dam. Periodic surveys during the week revealed very few piscivorous waterbirds in the immediate vicinity of McNary Dam. Other studies of fish-eating birds at Columbia River dams have shown that the greatest level of activity is in late April and May, presumably associated with peak numbers of juvenile salmonids passing the dams at that time.

Predator Activity

Bald eagles have been observed in the estuary at both Rice and East Sand islands. On April 12, three eagles were observed perched on the East Ridge at Rice Island. At East Sand Island, bald eagles and peregrine falcons have been observed at the colony throughout the week, frequently causing terns to take flight (0.34 disturbances/hr of observation). Generally, these disturbances are short, causing terns to leave the colony for only 10-15 seconds before returning to the colony.

Bald eagles have also caused disturbances at the Crescent Island tern colony. Early in the week (April 8-10), these disturbances caused terns to leave the colony for long periods of time (1-3 hours). On April 11, the terns seemed to be more settled on the Crescent Island colony, returning quickly (10-15 seconds) following disturbances. As the nesting season progresses and more nesting terns and gulls arrive at the Crescent Island colony site, we expect terns will be less likely to leave the colony for extended periods of time. Furthermore, we expect the number of eagle disturbances to terns on Crescent Island to decrease once migratory waterfowl in the vicinity of Crescent Island leave the area.

To date, there have been no signs of mammalian predators on any of the tern colonies monitored as part of this study. Gull kleptoparasitism rates on terns nesting at East Sand Island have been low.

Media & Other Visitors

On April 8, several Portland television news crews (KGW, KOIN, KPDX) and a reporter and photographer from the Vancouver Columbian visited East Sand Island.

On April 9, Herb Curl and Alex Morgan (Seattle Audubon Society) visited the East Sand Island tern colony site.