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At least 37 records · Page 2Linked to original sources
USGS2015

Colonial waterbird predation on Lost River and shortnose suckers based on recoveries of passive integrated transponder tags

We evaluated predation on Lost River suckers ( Deltistes luxatus ) and shortnose suckers ( Chasmistes brevirostris ), both listed under the Endangered Species Act (ESA), from American white pelicans ( Pelecanus erythrorhynchos ) and double-crested cormorants ( Phalacrocorax auritus ) nesting at mixed species colonies on Clear Lake Reservoir, CA and Upper Klamath Lake, OR during 2009-2014. Predation was evaluated by recovering passive integrated transponder (PIT) tags that were implanted in suckers, subsequently consumed by pelicans or cormorants, and deposited on the birds&rsquo; nesting colonies. Data from PIT tag recoveries were used to estimate predation rates (proportion of available tagged suckers consumed) by birds to evaluate the relative susceptibility of suckers to avian predation in Upper Klamath Basin. Data on the size of pelican and cormorant colonies (number of breeding adults) at Clear Lake and Upper Klamath Lake were also collected and reported in the context of predation on suckers. Results indicate that predation rates varied by sucker species (Lost River, shortnose), sucker age-class (adult, juvenile), bird colony location (Upper Klamath Lake, Clear Lake), and year (2009-2014), demonstrating that predator-prey interactions in the system were dynamic during the study period. Tagged suckers ranging from 72 mm to 730 mm were susceptible to cormorant or pelican predation; all but the largest of the tagged Lost River suckers were susceptible to avian predation. Estimates of minimum, annual predation rates ranged from <0.1% to 4.6% of the available Lost River suckers and from <0.1% to 4.2% of the available shortnose suckers during the study period. Of the two colony locations evaluated, predation rates on suckers in Clear Lake were generally higher by birds nesting at mixed-species colonies on Clear Lake. Birds nesting on Clear Lake also commuted over 75 kilometers to forage on suckers in Upper Klamath Lake. Conversely, there was no evidence that birds nesting in Upper Klamath Lake foraged on tagged suckers in Clear Lake. Although sample sizes of tagged juvenile suckers were small and limited to fish tagged in Upper Klamath Lake, there was evidence that bird predation on juvenile suckers was higher than on adult suckers, with annual predate rate estimates on juvenile suckers ranging from 5.7% to 8.4% of available fish. The minimum annual predation rates presented here suggests that avian predation may be a factor limiting recovery of populations of Lost River and shortnose suckers, particularly juvenile suckers in Upper Klamath Lake and adult suckers in Clear Lake. Additional research is needed, however, to better assess the impacts of avian predation on sucker populations by (1) recovering PIT tags in a manner so that the species of avian predator is known (i.e., pelican vs. cormorant), (2) measuring predator-specific PIT tag deposition probabilities at each colony, (3) increasing the sample of juvenile suckers in the population that are PIT-tagged, and (4) recovering sufficient sample sizes of PIT tags on bird colonies to describe how various biotic and abiotic factors (e.g., fish size and condition, water levels and quality, and other factors) contribute to sucker susceptibility to avian predation in the Upper Klamath Basin.

California, Oregon↗
USGS2025

Predation of Lost River and Shortnose Suckers by piscivorous colonial waterbirds in the Upper Klamath Basin: An analysis of predation effects in 2024

The recovery of endangered fish requires an understanding of the sources of mortality that regulate population dynamics. We estimated avian predation rates on passive integrated transponder tagged (PIT) adult and juvenile Lost River Suckers ( Deltistes luxatus ), Shortnose Suckers ( Chasmistes brevirostris ), Klamath Largescale Suckers ( C. snyderi ), and juvenile Chinook Salmon ( Oncorhynchus tshawytscha ) by breeding colonies of American White Pelicans ( Pelecanus erythrorhynchos ), Doublecrested Cormorants ( Nannopterum auritum ), Caspian Terns ( Hydroprogne caspia ), California Gulls ( Larus californicus ), Ring-billed Gulls ( L. delawarensis ), Great Blue Herons ( Ardea herodias ), Great Egrets ( A. alba ), and Black-crowned Night Herons ( Nycticorax nycticorax ) in the Upper Klamath Basin (UKB) in 2024. Results from 2024 contribute to a long-term (2009–2023) avian predation dataset in the UKB. The largest numbers of pelicans (1,422 breeding adults), terns (610 adults), and gulls (3,872) were nesting on islands in Clear Lake Reservoir. The largest number of cormorants (787 adults) were on an island in Sheepy Lake, and the largest numbers of herons (450 adults) were at arboreal sites adjacent to Upper Klamath Lake. Predation rate estimates in 2024 were highly variable depending on the fish species, ageclass (juvenile, adult), waterbody (Upper Klamath Lake, Clear Lake Reservoir, Sheepy Lake, Tule Lake), and release or reencounter date for juveniles (spring/summer or fall/winter). Results indicated that avian predation rates were the highest on wild and hatchery juvenile suckers. An estimated 19.4% (95% credible interval = 15.7–24.0) of Sucker Assisted Rearing Program (SARP) hatchery fish, released or reencountered during the spring and summer, were consumed by the colonies included in the study. Predation was also appreciable on wild juvenile suckers in Clear Lake Reservoir (13.4% [9.9–17.7]) and SARP juvenile suckers released or reencountered in Upper Klamath Lake in the fall/winter (11.2% [9.6 13.2]). Predation rate estimates on adult suckers were significantly lower than those of juvenile suckers, with predation ranging from 0.3% (0.2–0.7) to 2.6% (1.9–3.5) in adult Lost River Suckers in Upper Klamath Lake and adult Shortnose Suckers-Klamath Largescale Suckers in Clear Lake Reservoir, respectively. Predation rate estimates on juvenile Chinook Salmon, which were released in fall/winter, were 2.9% (2.2–3.6). Pelican (312 adults) and cormorant (301 adults) colonies in Upper Klamath Lake, however, were not scanned for fish PIT tags following breeding season, resulting in minimum estimates of predation on UKB fishes (both suckers and Chinook Salmon) in 2024. Future research could examine what biotic and abiotic factors best explain variation in predation and to what degree predation limits sucker survival using the long-term dataset that has been complied to date.

California, Oregon↗
USGS2001

Persistent organochlorine pollutants in eggs of colonial waterbirds from Galveston Bay and East Texas, USA

Eggs of neotropic cormorants ( Phalacrocorax brasilianus ), black-crowned night herons ( Nycticorax nycticorax ), and great egrets ( Ardea alba ) nesting on several locations in Galveston Bay (TX, USA) and at two control sites outside the bay were collected during April–May 1996 and analyzed for chlorinated pesticides, PCBs, polychlorinated dibenzo- p -dioxins, and polychlor-inated dibenzofurans. Additionally, concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQs) were determined by use of relative potency factors (TEQs) or the H4IIE-luc bioassay TCDD-EQs. Concentrations of 1,1,-dichloro-2,2-bis( p -chlo-rophenyl)ethylene (DDE) were greater in eggs of neotropic cormorants from Alexander Island (mean = 1,040 ng/g wet wt) in the Houston Ship Channel (Houston, TX, USA) and in those from Telfair Island (mean = 1,460 ng/g wet wt), a reference location outside the bay, than in most locations inside the bay (mean range = 119–453 ng/g wet wt). Mean PCB concentrations were greater in eggs of neotropic cormorants from Alexander Island (mean = 5,720 ng/g wet wt) than in eggs of cormorants from areas farther away from the ship channel, including two reference sites outside the bay (mean range = 404–3,140 ng/g wet wt). The TCDD was the main dioxin congener detected in eggs from all locations within Galveston Bay. Instrumental TEQs in eggs ranged from 67 pg/g wet weight at control sites to 452 pg/g wet weight at Alexander Island. Concentrations of TCDD-EQs determined in the H4IIE assay were correlated with instrumental TEQs and were greater in eggs of cormorants from islands within the bay, although these were farther away from the ship channel. Overall, concentrations of DDE, PCBs, TCDD, and TCDD-EQs were less than the threshold levels known to affect reproduction. However, some eggs contained concentrations of total PCBs or DDE greater than what would elicit adverse effects on birds. No identifiable deformities or abnormalities were detected in embryos collected from all sites.

Environmental Toxicology and Chemistry↗
USGS2021

Factors affecting nest success of colonial nesting waterbirds in southwest Louisiana

Subsidence and accelerated sea level rise impact nesting area availability and flood probabilities of breeding islands for colonial nesting waterbirds. In 2017 and 2018, we monitored 855 nests of four species of colonial nesting waterbirds on Rabbit Island, LA, to determine factors affecting nest and chick success. Based on logistic exposure models of nests, tricolored herons had the greatest likelihood of survival to hatch (mean (95% confidence interval)) (77% (65.9–83.1%)), followed by brown pelicans (70% (59.9–98.5%)), roseate spoonbills (70% (38.9–83.8%)), and Forster’s terns (12% (10.7–12.2%)). Likelihood of survival to fledge was highest for tricolored herons (32% (12.8–40.7%)), followed by brown pelicans (28% (19.5–28.6%)), roseate spoonbills (47% (43.7–53.3%)), and Forster’s terns (0% (0.005–0.01%)). Nesting strategy and nest timing impacted survival rate; however, the effect depended on timing of inundation events as the timing of inundation events varied across years. Flooding was the primary cause of nest failure for most species. In 2003–2012, rapid expansion in brown pelican colony numbers and significant chick production occurred at Rabbit Island, but hydrologic records indicate no island inundation occurred during the breeding season from the beginning of the hydrologic record (2006) through 2011. Thus, our results contrast with those of previous studies conducted under different hydrologic conditions and demonstrate the challenges of short-term studies informing coastal restoration in a system that is influenced by multi-year to multi-decadal climatic cycles.

Louisiana↗
USGS2016

Avian predation on juvenile Salmonids: Spatial and temporal analysis based on acoustic and passive integrated transponder tags

We evaluated the impact of predation on juvenile steelhead Oncorhynchus mykiss and yearling and subyearling Chinook Salmon O. tshawytscha by piscivorous waterbirds from 11 different breeding colonies in the Columbia River basin during 2012 and 2014. Fish were tagged with both acoustic tags and PIT tags and were tracked via a network of hydrophone arrays to estimate total smolt mortality (1 – survival) at various spatial and temporal scales during out‐migration. Recoveries of PIT tags on bird colonies, coupled with the last known detections of live fish passing hydrophone arrays, were used to estimate the impact of avian predation relative to total smolt mortality. Results indicated that avian predation was a substantial source of steelhead mortality, with predation probability (proportion of available fish consumed by birds) ranging from 0.06 to 0.28 for fish traveling through the lower Snake River and the lower and middle Columbia River. Predation probability estimates ranged from 0.03 to 0.09 for available tagged yearling Chinook Salmon and from 0.01 to 0.05 for subyearlings. Smolt predation by gulls Larus spp. was concentrated near hydroelectric dams, while predation by Caspian terns Hydroprogne caspia was concentrated within reservoirs. No concentrated areas of predation were identified for double‐crested cormorants Phalacrocorax auritus or American white pelicans Pelecanus erythrorhynchos . Comparisons of total smolt mortality relative to mortality from colonial waterbirds indicated that avian predation was one of the greatest sources of mortality for steelhead and yearling Chinook Salmon during out‐migration. In contrast, avian predation on subyearling Chinook Salmon was generally low and constituted a minor component of total mortality. Our results demonstrate that acoustic and PIT tag technologies can be combined to quantify where and when smolt mortality occurs and the fraction of mortality that is due to colonial waterbird predation relative to non‐avian mortality sources.

Transactions of the American Fisheries Society↗
USGS2003

Created versus natural coastal islands: Atlantic waterbird populations, habitat choices, and management implications

Nesting colonial waterbirds along the Atlantic Coast of the United States face a number of landscape-level threats including human disturbance, mammalian predator expansion, and habitat alteration. There have been changes from 1977 to the mid-1990s in use of nesting habitats and populations of a number of seabird species of concern in the region, including black skimmers Rynchops niger Linnaeaus, common terns Sterna hirundo Linnaeaus, gull-billed terns Sterna nilotica Linnaeaus, least terns Sterna antillarum Lesson, royal terns Sterna maxima Boddaert, and sandwich terns Sterna sandvicensis Cabot. These species form colonies primarily on the following habitat types: large, sandy barrier or shoal islands, natural estuarine or bay islands (mostly marsh), man-made islands of dredged deposition materials (from navigation channels), and the mainland. Significant changes in the use of the dredged material islands have occurred for these species in New Jersey and North Carolina, but not in Virginia. Population declines and changes in bird habitat use appear to be at least partially associated with the conditions and management of the existing dredged material islands, coastal policy changes associated with creating new dredged material islands, and competing demands for sand for beach augmentation by coastal communities. As these and other coastal habitats become less suitable for colonial waterbirds, other manmade sites, such as bridges and buildings have become increasingly more important. In regions with intense recreational demands, coastal wildlife managers need to take a more aggressive role in managing natural and man-made habitats areas and as stakeholders in the decision-making process involving dredged materials and beach sand allocation.

Estuaries↗
USGS2011

Recovery of coded wire tags at a caspian tern colony in San Francisco Bay: A technique to evaluate impacts of avian predation on juvenile salmonids

We recovered coded wire tags (CWTs) from a colony of Caspian terns Hydroprogne caspia on Brooks Island in San Francisco Bay, California, to evaluate predation on juvenile salmonids originating from the Sacramento and San Joaquin rivers. Subsamples of colony substrate representing 11.7% of the nesting habitat used by the terns yielded 2,079 salmonid CWTs from fish released and subsequently consumed by terns in 2008. The estimated number of CWTs deposited on the entire tern colony was 40,143 (ranging from 26,763 to 80,288), once adjustments were made to account for tag loss and the total amount of nesting habitat used by terns. Tags ingested by terns and then egested on the colony were undamaged, and the tags' complete numeric codes were still identifiable. The CWTs found on the tern colony indicated that hatchery Chinook salmon Oncorhynchus tshawytscha trucked to and released in San Pablo Bay were significantly more likely to be consumed by Caspian terns than Chinook salmon that migrated in-river to the bay; 99.7% of all tags recovered were from bay-released Chinook salmon. Of the CWTs recovered on the tern colony, 98.0% were from fall-run Chinook salmon, indicating a higher susceptibility to tern predation than for the spring run type. None of the approximately 518,000 wild Chinook salmon that were coded-wire-tagged and released in the basin were recovered on the tern colony, suggesting that the impacts on wild, U.S. Endangered Species Act-listed Chinook salmon populations were minimal in 2008. Overall, we estimate that 0.3% of the approximately 12.3 million coded-wire-tagged Chinook salmon released in the basin in 2008 were subsequently consumed by Caspian terns from the Brooks Island colony. These results indicate that CWTs implanted in juvenile salmon can be recovered from a piscivorous waterbird colony and used to evaluate smolt losses for runs that are tagged. Abstract We recovered coded wire tags (CWTs) from a colony of Caspian terns Hydroprogne caspia on Brooks Island in San Francisco Bay, California, to evaluate predation on juvenile salmonids originating from the Sacramento and San Joaquin rivers. Subsamples of colony substrate representing 11.7% of the nesting habitat used by the terns yielded 2,079 salmonid CWTs from fish released and subsequently consumed by terns in 2008. The estimated number of CWTs deposited on the entire tern colony was 40,143 (ranging from 26,763 to 80,288), once adjustments were made to account for tag loss and the total amount of nesting habitat used by terns. Tags ingested by terns and then egested on the colony were undamaged, and the tags' complete numeric codes were still identifiable. The CWTs found on the tern colony indicated that hatchery Chinook salmon Oncorhynchus tshawytscha trucked to and released in San Pablo Bay were significantly more likely to be consumed by Caspian terns than Chinook salmon that migrated in-river to the bay; 99.7% of all tags recovered were from bay-released Chinook salmon. Of the CWTs recovered on the tern colony, 98.0% were from fall-run Chinook salmon, indicating a higher susceptibility to tern predation than for the spring run type. None of the approximately 518,000 wild Chinook salmon that were coded-wire-tagged and released in the basin were recovered on the tern colony, suggesting that the impacts on wild, U.S. Endangered Species Act-listed Chinook salmon populations were minimal in 2008. Overall, we estimate that 0.3% of the approximately 12.3 million coded-wire-tagged Chinook salmon released in the basin in 2008 were subsequently consumed by Caspian terns from the Brooks Island colony. These results indicate that CWTs implanted in juvenile salmon can be recovered from a piscivorous waterbird colony and used to evaluate smolt losses for runs that are tagged ?? American Fisheries Society 2011.

North American Journal of Fisheries Management↗