A partnership between Oregon State University, Real Time Research, and the USGS - Oregon Cooperative Fish and Wildlife Research Unit

Columbia River Estuary

Weekly Update 6/19 – 6/25/2017

6/19/17 ›

Two boat-based surveys to count California brown pelicans roosting on East Sand Island were conducted; the first survey was conducted around noon, and a total of 1,100 individual brown pelicans were counted, all located on the southeast beach near the tern colony; the second survey was conducted at dusk, and a total of 570 individual brown pelicans were counted, all again located on the southeast beach; these data suggest that the former behavior pattern of more brown pelicans using East Sand Island as a night-time roost than as a day-time roost has changed, and many of the pelicans that use the island during the day are leaving in the evening to roost elsewhere; there have been no observations of nest building or breeding behavior by brown pelicans on East Sand Island so far this season; intentional disturbances of roosting brown pelicans by jet-skis were again observed on 6/23 and 6/24; these two incidents were similar to disturbances witnessed by the field crew on 5/26 and 6/13, when the operator of a wave-runner type watercraft sped towards the southeast beach and intentionally flushed pelicans that were roosting on the beach; these incidents have been reported to the Oregon State Police and the USFWS 

6/19 – 6/25/17 ›

High count for the week of about 990 individual Caspian terns on the East Sand Island tern colony, much less than the estimated high count the previous week (ca. 4,400 individuals); after total collapse of the tern colony the previous week, the colony site has been virtually abandoned starting 6/23; since then there have been no terns present on the colony for more than a few minutes at a time, and no terns have spent the night on the colony; small numbers of tern eggs were laid on the colony early in the week, but those eggs were quickly abandoned and/or taken by gulls, and during the latter part of the week there was no evidence that any tern eggs were being laid on the colony site; it appears unlikely that the terns will regroup and make a late season nesting attempt this year; the combination of disturbance to the tern colony by bald eagles and peregrine falcons, coupled with intense predation pressure on tern nest contents by western/glaucous-winged gulls was the proximate cause of colony collapse, but the declining food supply for terns was clearly a contributing factor, as was the availability of alternative prey for bald eagles and gulls

6/19 – 6/25/17 ›

Monitoring continued at Caspian tern nest dissuasion areas outside the 1-acre colony area on the east end of East Sand Island; there were no observations of breeding behavior by Caspian terns on the beaches at the east end of East Sand Island this week, with no new nest scrapes or tern eggs discovered; no terns were seen this week on potential nesting habitat above the high tide line on the east end of East Sand Island; the numbers of terns on the beaches below the tide line fluctuated between 1,000 and 2,000 individuals this week

6/19 – 6/25/17 ›

Signs of multiple predators observed on East Sand Island; frequency of bald eagle and peregrine falcon overflights of the prepared 1-acre tern colony continued to be high, leading to flushing of nesting terns and consequent depredation of tern eggs by western/glaucous-winged gulls early in the week; as was the case the previous week, gulls were observed depredating tern eggs that were being attended by adult terns; one ring-billed gull carcass and one glaucous-winged/western gull carcass were found on the beach, apparently the result of avian predation; mink tracks and mink prey remains were observed near the tern colony; river otter tracks continue to be commonly observed on the north beach; so far this breeding season, there has been no direct evidence that mammalian predators have caused nest failure on the tern colony, but nocturnal predation events by mammals would be difficult to detect

Weekly Update 6/12 – 6/18/2017

6/12 – 6/18/17 ›

High count for the week of about 4,400 individual Caspian terns on the East Sand Island tern colony, less than the estimated high count the previous week (ca. 6,800 individuals); the tern colony experienced complete failure on 6/14, with no tern eggs or chicks remaining on the colony that evening; some terns attempted to re-nest and laid eggs following the colony collapse, but those eggs were depredated by gulls soon after being laid; the combination of disturbance to the tern colony by bald eagles and peregrine falcons, coupled with intense predation pressure on tern nest contents by western/glaucous-winged gulls was the proximate cause of colony collapse; the food supply for terns was a contributing factor, as was the availability of alternative prey for bald eagles and gulls

6/12 – 6/18/17 ›

Monitoring continued at Caspian tern nest dissuasion areas outside the 1-acre colony area on the east end of East Sand Island; the field crew conducted regular hazing of terns prospecting on the upper beaches at the east end of the island; maximum of 12 adult terns and no tern eggs were observed on the upper beaches this week; the numbers of adult terns observed loafing on the beaches at the east end of the island is declining, with less than 400 individual terns typically counted each day this week, a sharp drop from the numbers observed on the beach in May (about 1,000-2,000 terns)

6/19 – 6/25/17 ›

Frequency of bald eagle overflights of the east end of East Sand Island continued to be high this week; evidence of avian predation on gulls observed

Weekly Update 6/5 – 6/11/2017

6/5 – 6/11/17 ›

High count for the week of about 6,800 individual Caspian terns on the East Sand Island tern colony, slightly less than the estimated high count the previous week (ca. 7,200 individuals); numbers of active tern nests on colony are declining, associated with an increase in gull predation on tern eggs and chicks following more frequent bald eagle flushes of the colony; the western quarter and edges of the core colony area were especially hard hit, and very few tern eggs or chicks were left in these parts of the colony by the end of the week; a predator disturbance sometime between Saturday evening, 6/10, and Sunday morning, 6/11, caused significant declines in the numbers of active tern nests even in the core colony area

6/5 – 6/11/17 ›

Monitoring continued at Caspian tern nest dissuasion areas outside the 1-acre colony area on the east end of East Sand Island; the field crew conducted regular hazing of terns prospecting on the upper beaches at the east end of the island; maximum of 17 new tern nest scrapes were dug between dissuasion walk-throughs and no tern eggs were discovered on the upper beach this week;  up to 500 terns are regularly loafing on the beaches at the east end of the island throughout the day, a sharp drop from the numbers observed on the beach in May (about 1,000-2,000 terns)

6/5 – 6/11/17 ›

Signs of multiple predators observed on East Sand Island; bald eagle overflights of the prepared 1-acre tern colony and surrounding area increased in frequency this week compared to the previous week, leading to increased flushing of nesting terns and consequent depredation of tern eggs and chicks by western/glaucous-winged gulls; gulls were also observed depredating terns and chicks this week that were being attended by adult terns; as was the case the previous week, high frequency of peregrine falcon disturbances to the ring-billed gull colony was also reported by field personnel this week; two western/glaucous-winged gull carcasses and two Caspian tern carcasses, apparently the result of avian predation, were discovered on the beaches this week; a bald eagle was observed depredating a tern chick on the main colony on 6/5, causing a major disturbance to the colony; no observations of mink or mink sign this week, but river otter tracks continue to be commonly observed on the north beach

Weekly Update 5/29 – 6/4/2017

6/4/17 ›

Two boat-based surveys to count California brown pelicans roosting on East Sand Island were conducted; the first survey was conducted around noon, and a total of 750 individual brown pelicans were counted, all located on the south beach near the tern colony; the second survey was conducted at dusk, and a total of 510 individual brown pelicans were counted, all again located on the south beach

6/4/17 ›

First Caspian tern chicks (2) observed on the 1-acre tern colony area on East Sand Island; both chicks were hatched near the center of the colony, approximately 16 m from the colony edge

5/29 – 6/4/17 ›

High count for the week of about 7,200 individual Caspian terns on the East Sand Island tern colony, the same as the estimated high count the previous week (ca. 7,200); large increase in the frequency of bald eagle flushes of the tern colony and a consequent increase in the rate of gull depredation on tern eggs resulted in a large reduction in the number of tern nests containing eggs around the edges of the colony this week; western quarter of the colony area, where tern egg-laying was delayed compared to the rest of the colony, was hit especially hard; few tern eggs were present in the western quarter by the end of the week and most tern eggs laid this week in that portion of the colony were lost shortly after laying

5/29 – 6/4/17 ›

Monitoring continued at Caspian tern nest dissuasion areas outside the 1-acre colony area on the east end of East Sand Island; the field crew conducted regular hazing (nearly continuous) of terns prospecting on the upper beaches at the east end of the island; nest scraping and egg-laying by Caspian terns outside of the prepared 1-acre colony area were reduced this week compared to previous weeks; a total of five tern eggs were discovered on the upper beach this week, none of which persisted for 24 hours; maximum of 25 new tern nest scrapes were dug between dissuasion walk-throughs this week; field personnel installed 18 (10’x10’) cells of supplemental nest dissuasion materials on the south beach on 6/1 and four cells of passive nest dissuasion on the south-east beach on 6/2; about 100-500 terns are regularly loafing on the beaches at the east end of the island throughout the day, a sharp drop from the number observed in previous weeks (about 1,000-2,000 terns)

5/29 – 6/4/17 ›

Signs of multiple predators observed on East Sand Island; bald eagle overflights of the prepared 1-acre tern colony and surrounding area increased in frequency this week compared to the previous week, leading to increased flushing of nesting terns and consequent egg depredation by gulls; high frequency of peregrine falcon disturbances to the ring-billed gull colony was also reported by field personnel this week; two western/glaucous-winged gull carcasses and a double-crested cormorant wing, apparently the result of avian predation, were discovered on the beaches this week; no observations of mink or mink sign this week, but river otter tracks continue to be commonly observed on the north beach

Weekly Update 5/22 – 5/28/2017

5/22 – 5/28/17 ›

High count for the week of ca. 7,200 individual Caspian terns on the East Sand Island tern colony, similar to the estimated high count the previous week (ca. 7,300); by week’s end, there were ca. 2,400 Caspian tern nests with eggs on the 1-acre colony area (up from ca. 1,000 nests with eggs the previous week), with 30-40% of nests containing 2 or more eggs; the tern colony appears to be much more settled this week, with the rates of kleptoparasitism and tern egg depredation by gulls greatly reduced compared to previous weeks

5/22 – 5/28/17 ›

Monitoring continued at Caspian tern nest dissuasion areas outside the 1-acre colony area on the east end of East Sand Island; the field crew conducted regular hazing (nearly continuous) of terns prospecting on the upper beaches at the east end of the island; high count of 25 new tern nest scrapes discovered on the east beaches this week (lower than the high count of 38 nest scrapes the previous week); 3 tern eggs were laid in the tern nest dissuasion areas this week, and all were either depredated by gulls or washed away during high tide events; minor repairs to the existing passive nest dissuasion materials were completed following a high tide event this week; a total of 1,000-2,000 terns were observed loafing on the beaches at the eastern end of the island each day this week

5/22 – 5/28/17 ›

Signs of multiple predators observed on East Sand Island; bald eagles continued to cause frequent disturbances to the tern colony that lead to gull depredation of tern eggs in unattended nests, although the intensity and frequency of these events has gradually declined over the last two weeks; carcasses of three Caspian terns, one ring-billed gull, and one double-crested cormorant were found on the eastern beaches this week, all believed to be the result of avian predation; river otter and mink tracks were observed on the north beach and mink scat was observed near the field camp; so far this season, there has been no evidence of mammalian predation on colonial waterbirds on East Sand Island

Weekly Update 5/15 – 5/21/2017

5/17/17 ›

Aerial survey of the Columbia River estuary, Willapa Bay, and Grays Harbor; other than at East Sand Island, significant numbers of Caspian terns were only observed at No-Name Island in Grays Harbor, where 85 adult terns were counted and a few appeared to be initiating nesting; appreciable numbers of terns (nesting or roosting) were not observed elsewhere during this survey

5/20/17 ›

Second boat-based survey of roosting California brown pelicans conducted at East Sand Island this season; a total of 148 brown pelicans counted on the island, all of which were on the southeast tip of the island; no nesting behavior by brown pelicans has been observed on East Sand Island so far this season

5/15 – 5/21/17 ›

High count for the week of ca. 7,300 individual Caspian terns on the East Sand Island tern colony, higher than the estimated count the previous week (ca. 6,700); rate of egg-laying by terns on the colony continues to be high; tern egg losses due to gull depredation of tern eggs in unattended nests following frequent flushes of the tern colony by bald eagles was high initially and declined as the week progressed; although most terns attending active nests with eggs (minimum of 1,000 nests, up from ca. 500 active nests the previous week) are located near the center of the 1-acre colony area, numbers of nests that retained eggs over several consecutive days on the eastern and southern portions of the 1-acre area increased substantially from last week

5/15 – 5/21/17 ›

Monitoring continued at Caspian tern nest dissuasion areas outside the 1-acre colony area on the east end of East Sand Island; field crew conducted regular hazing (nearly continuous) of terns using the upper beaches on the east end of the island; high count of 38 tern new nest scrapes (similar to the high count of 32 the previous week) discovered on the south beach this week; 15 tern eggs were laid in the tern nest dissuasion areas this week, and all were either depredated by gulls or washed away during high tide events; passive nest dissuasion materials were added in multiple areas this week; a total of 1,000-2,000 terns were observed loafing on the beaches at the eastern end of the island each day this week

5/15 – 5/21/17 ›

Signs of multiple predators observed on East Sand Island; bald eagles continued to cause frequent disturbances to the tern colony that lead to gull depredation of tern eggs in unattended nests, although terns are beginning to guard their nests more aggressively from gulls; a family of 5 river otters were observed on the north beach this week, but the field crew has seen no evidence that otters are having an impact on nesting terns; an adult peregrine falcon was observed on the north beach

Weekly Update 5/8 – 5/14/2017

5/8 – 5/14/17 ›

High count for the week of an estimated 6,700 individual Caspian terns on the East Sand Island tern colony, similar to the estimated high count for the previous week (ca. 6,900); rate of egg-laying by terns has increased from the previous week, but tern egg losses have remained high due to gull depredation of tern eggs in unattended nests following frequent flushes of the tern colony by bald eagles and after heavy rains that caused colony flooding late in the week; most terns that remain on active nests with eggs (ca. 500 nests, some with two-egg clutches) are located near the center of the 1-acre colony area

5/8 – 5/14/17 ›

Monitoring continued at Caspian tern nest dissuasion areas on the east end of East Sand Island; field crew conducted regular hazing (6 times daily) of terns using the upper beaches on the east end of the island; high count of 32 tern nest scrapes (down from 43 the previous week) discovered on the south beach this week; one tern egg discovered in the tern nest dissuasion areas this week, and was presumably depredated by a gull or washed away during a high tide event; passive nest dissuasion materials were added in multiple areas this week; a total of 1,000-2,000 terns observed loafing on the beaches at the eastern end of the island (below the wrack line) each day this week

5/8 – 5/14/17 ›

Signs of multiple predators observed on East Sand Island; bald eagles continued to cause frequent disturbances to the tern colony that leads to gull depredation of tern eggs in unattended nests; river otter tracks were regularly observed on the north beach this week, but the field crew has seen no evidence that the otters are having an impact on nesting terns; five tern carcasses were found on beaches at the eastern end of the island this week and were attributed to avian predation

Weekly Update 5/1 – 5/7/2017

5/6/17 ›

First boat-based survey of roosting California brown pelicans conducted at East Sand Island this season; a total of 11 brown pelicans counted throughout the island, all of which were on the southeast tip of the island; no nesting behavior by brown pelicans has been observed on East Sand Island so far this season

5/1 – 5/7/17 ›

High count for the week of an estimated 6,900 individual Caspian terns on the East Sand Island tern colony, up from the estimated high count for the previous week (ca. 5,030); about 95% of the 1-acre core colony area is occupied by nesting and pre-nesting terns, with only the extreme western end of the colony area remaining unoccupied; rate of egg-laying by terns has increased from the previous week, but tern egg losses to gull predation during frequent bald eagle flushes of the tern colony have remained high, and very few tern eggs have persisted on-colony for more than 24 hours

5/1 – 5/7/17 ›

Monitoring continued at Caspian tern nest dissuasion areas on the east end of East Sand Island; field crew conducted regular hazing (6 times daily) of terns using the upper beaches on the east end of the island; high count of 43 tern nest scrapes discovered on the southeast beach this week; one tern egg discovered in the tern nest dissuasion areas this week, and was presumably depredated by a gull or washed away during a high tide event; passive nest dissuasion materials were added in the area where the tern egg was found; 1,000-2,000 terns observed loafing on the east beaches (below the wrack line) each day this week

5/1 – 5/7/17 ›

Signs of multiple predators observed on East Sand Island; bald eagles continued to cause frequent disturbances to the tern colony, with up to 5 colony flushes observed per hour; river otter tracks were regularly observed on the north beach this week, near an apparent otter den, but the field crew has seen no evidence that the otters are having an impact on nesting terns; a brown pelican was observed on the Caspian tern colony on Friday, 5/5, consuming tern eggs that it took from nests (three tern eggs were observed being consumed), as well as kleptoparasitizing bill-load fish from terns on-colony

Weekly Update 4/24 – 4/30/2017

4/27/17 ›

First Caspian tern egg (broken) observed on the 1-acre tern colony on East Sand Island; the egg had apparently been depredated by a gull

4/24 – 4/30/17 ›

High count for the week of an estimated 5,030 individual Caspian terns on the East Sand Island tern colony, up from the estimated high count for the previous week (ca. 4,230); about 90% of the 1-acre core colony area is occupied by nesting and pre-nesting terns, with only the extreme western end of the colony area remaining unoccupied; the east end of the 1-acre core colony area continues to be subject to flooding during heavy rain events

4/24 – 4/30/17 ›

Monitoring continued at Caspian tern nest dissuasion areas on the east end of East Sand Island; field crew conducted regular hazing (5-6 times daily) of terns using the upper beaches on the east end of the island; high count of 28 tern nest scrapes discovered on the southeast beach this week; no tern eggs discovered in the tern nest dissuasion areas this week

4/24 – 4/30/17 ›

Signs of multiple predators observed on East Sand Island; although no great horned owls or other nocturnal predators were observed this week, the tern colony was frequently disturbed at night, causing complete colony abandonment on two nights this week; it appears that colony abandonment is occurring on clear nights and not on cloudy nights; bald eagles continued to cause frequent disturbances to the tern colony, stealing fish from terns during flushing events; evidence of predation on adult terns by bald eagles and peregrine falcons on seen on east beach

Weekly Update 4/17 – 4/23/2017

4/18/17 ›

First California brown pelican sighted in Columbia River estuary by project staff in 2017; no pelicans were seen on East Sand Island

4/19/17 ›

First California brown pelican (1) observed on East Sand Island, a juvenile loafing on the east beach

4/21/17 ›

First evidence of Caspian terns attempting to nest outside the core 1-acre colony area on East Sand Island; one nest scrape discovered just outside of the passive nest dissuasion materials on the beach south of the colony; field crew filled in the scrape and increased their monitoring and hazing efforts in this area

4/17 – 4/23/17 ›

High count for the week of an estimated 4,230 individual Caspian terns on East Sand Island tern colony, up from the estimated high count for the previous week (ca. 1,330); roughly 80% of the 1-acre core colony area is occupied by pre-nesting terns, with observations of nesting behaviors (i.e. digging nest scrapes, copulation, courtship feeding) increasing throughout the week; east end of 1-acre core colony area subject to flooding during heavy rain events

4/17 – 4/23/17 ›

Monitoring continued at Caspian tern nest dissuasion areas on the east end of East Sand Island; field crew conducted regular hazing (3-4 times daily) of terns using the upper beaches on the east end of the island

4/17 – 4/23/17 ›

Signs of multiple predators observed on East Sand Island; although the great horned owl was not observed this week, there were signs of owl predation on terns discovered during the week, likely causing overnight colony abandonment on 4/19 and 4/20; bald eagles and peregrine falcons observed daily, causing terns to flush from the colony regularly; fresh river otter tracks seen on the north beach; evidence of avian predation on adult terns and gulls seen on east beach

Update 3/10 – 4/16/2017

3/10/17 ›

Seasonal field crew began work on East Sand Island

3/27/17 ›

Completed deployment of passive nest dissuasion materials (stakes, rope, and flagging) on potential Caspian tern nesting habitat on the west end of East Sand Island

3/30/17 ›

First Caspian terns sighted in Columbia River estuary by project staff in 2017; two terns seen flying over East Sand Island

4/1/17 ›

First Caspian terns (12) observed on East Sand Island (loafing on the east beach)

4/11/17 ›

First Caspian terns (157) observed on East Sand Island tern colony

4/13/17 ›

Completed colony preparations on the East Sand Island tern colony; 1.0 acre of nesting habitat was prepared for Caspian terns; within that 1.0-acre colony area, only the vegetated areas were tilled and harrowed; a 105-meter long fence row was erected along the southern border of the prepared colony area and another 80-meter fence row was erected inside and parallel to the southern boundary fence to reduce the total amount of available tern nesting habitat to 1.0 acre; observation blinds and above-ground tunnels were repaired, rope grids were laid out on the tern colony as aids in monitoring the colony, and PIT tags were spread on the colony for detection efficiency studies

4/13/17 ›

Completed deployment of passive nest dissuasion materials (stakes, rope, and flagging) on potential Caspian tern nesting habitat on the east end of East Sand Island adjacent to the 1-acre core colony area

4/16/17 ›

Commenced daily active hazing of Caspian terns attempting to nest on East Sand Island outside the 1.0-acre core colony area; no terns were observed in upland areas outside the core colony area on East Sand Island

4/10 – 4/16/17 ›

High count for the week of an estimated 1,325 Caspian terns on East Sand Island tern colony; most of the terns observed on colony were loafing, while a small number of the birds were engaged in pre-nesting behaviors (i.e. digging nest scrapes, copulation); in addition, 400-500 Caspian terns were regularly seen loafing on beaches near the main colony area on East Sand Island

4/10 – 4/16/17 ›

Signs of multiple predators observed on East Sand Island; bald eagles, red-tailed hawks, and peregrine falcons were observed occasionally flying over island; fresh river otter tracks seen daily on the north and west beaches; evidence of avian predation on adult terns and gulls seen on the east beach

The weekly update of events at various piscivorous waterbird colonies in the Columbia River estuary

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