Numbers of Terns Breeding Inland in California: Trends or Tribulations?

Shuford, W. David

doi:10.21199/wb47.3.1

Cited by 14 publications

(32 citation statements)

References 16 publications

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“…The Salton Sea in inland southern California has been an intermittent breeding site for double‐crested cormorants since the lake was formed by flooding of the Colorado River in 1905–1907 (Molina and Sturm , Shuford ). Nesting at this site has been especially sporadic over the last 2 decades.…”

Section: Resultsmentioning

confidence: 99%

“…C. Robinson‐Nilsen, San Francisco Bay Bird Observatory, personal communication; Shuford et al (); Shuford (); Shuford and Henderson (); D. Woolington, USFWS, personal communication.…”

Section: Methodsmentioning

confidence: 99%

“…The first comprehensive survey of this region in 1997 estimated 1,415 breeding pairs, 69% of which nested at Sheepy Lake in Lower Klamath NWR (Shuford ). Total number of breeding pairs in 1998 and 1999 were greatly affected by low numbers at Sheepy Lake due to high water levels inundating the nesting site.…”

Section: Methodsmentioning

confidence: 99%

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Recent population size, trends, and limiting factors for the double-crested cormorant in western North America

et al. 2014

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The status of the double-crested cormorant (Phalacrocorax auritus) in western North America was last evaluated during [1987][1988][1989][1990][1991][1992][1993][1994][1995][1996][1997][1998][1999][2000][2001][2002][2003]. In the interim, concern has grown over the potential impact of predation by double-crested cormorants on juvenile salmonids (Oncorhynchus spp.), particularly in the Columbia Basin and along the Pacific coast where some salmonids are listed for protection under the United States Endangered Species Act. Recent re-evaluations of double-crested cormorant management at the local, flyway, and federal level warrant further examination of the current population size and trends in western North America. We collected colony size data for the western population (British Columbia, Washington, Oregon, Idaho, California, Nevada, Utah, Arizona, and the portions of Montana, Wyoming, Colorado and New Mexico west of the Continental Divide) by conducting aircraft-, boat-, or ground-based surveys and by cooperating with government agencies, universities, and non-profit organizations. In 2009, we estimated approximately 31,200 breeding pairs in the western population. We estimated that cormorant numbers in the Pacific Region (British Columbia, Washington, Oregon, and California) increased 72% from 1987-1992 to circa 2009. Based on the best available data for this period, the average annual growth rate (l) of the number of breeding birds in the Pacific Region was 1.03, versus 1.07 for the population east of the Continental Divide during recent decades. Most of the increase in the Pacific Region can be attributed to an increase in the size of the nesting colony on East Sand Island in the Columbia River estuary, which accounts for about 39% of all breeding pairs in the western population and is the largest known breeding colony for the species (12,087 breeding pairs estimated in 2009). In contrast, numbers of breeding pairs estimated in coastal British Columbia and Washington have declined by approximately 66% during this same period. Disturbance at breeding colonies by bald eagles (Haliaeetus leucocephalus) and humans are likely limiting factors on the growth of the western population at present. Because of differences in biology and management, the western population of double-crested cormorants warrants consideration as a separate management unit from the population east of the Continental Divide. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

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Section: Resultsmentioning

confidence: 99%

“…C. Robinson‐Nilsen, San Francisco Bay Bird Observatory, personal communication; Shuford et al (); Shuford (); Shuford and Henderson (); D. Woolington, USFWS, personal communication.…”

Section: Methodsmentioning

confidence: 99%

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Recent population size, trends, and limiting factors for the double-crested cormorant in western North America

et al. 2014

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“…The populations of many of these species can vary greatly with short-term changes in climate, and recent estimates are likely toward the low end of the expected range in abundance from dry to wet climatic cycles. For example, nesting numbers for three species of terns in 2010-2012 were well below those recorded in the Central Valley on earlier surveys during a wetter period in 1998-1999 (Shuford et al 2016c). By contrast, numbers of pairs of the Double-crested Cormorant (Phalacrocorax auritus) nesting in the Central Valley increased from 1998-1999 to 2011-2012 consistent with upward trends in the interior of California overall (Shuford 2014b) and throughout western North America as a whole (Adkins et al 2014).…”

Section: Discussionmentioning

confidence: 51%

“…Changes between these periods are difficult to interpret, however, because those in the late 1990s were during a wet period, whereas those in 2010-2012 were during a drought. were well below those recorded in the Central Valley in 1998 (Shuford et al 2016c), and no Caspian Terns were found nesting, likely reflecting environmental fluctuation between the two periods rather than any consistent trend over time. Regardless, we are unaware of comparable survey data from other sources that provide robust estimates of population sizes and trends for any other colonial nesting, solitary nesting, or non-breeding waterbird species in the Central Valley.…”

Section: Population Sizes and Trendsmentioning

confidence: 61%

Conservation Objectives for Wintering and Breeding Waterbirds in California's Central Valley

Shuford¹,

Dybala²

2017

SFEWS

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Birds associated with wetlands have declined historically across North America from extensive habitat loss and degradation. Among the regions most affected is California's Central Valley, where over 90% of the wetland base has been lost. Still, this region remains of continental importance to waterbirds. On-the-ground conservation efforts for all bird groups are the focus of the Central Valley Joint Venture, guided by a periodically updated implementation plan. To track progress toward goal attainment, that plan sets time-bound, quantitative conservation goals. Lacking robust data on the size and trends of populations of most species of waterbirds in the Central Valley, we set conservation goals for this group by selecting 10 focal species. These species are of heightened conservation concern or are otherwise representative of the habitat needs of Central Valley waterbirds. Given the great loss of historical habitat, we assumed focal species populations have declined by ≥ 50%. Hence, we defined population objectives for most focal species as increasing their current populations by 10% over 10 years and doubling them in 100 years. The corresponding habitat objectives are to increase wetlands or enhance suitable crops for waterbirds in proportion to the population objectives. These include an increase over 10 years of 7,948 ha (19,641 acres) of winter seasonal wetlands, 921 ha (2,276 acres) each of semi-permanent and summer seasonal wetlands, and 573 ha (1,416 acres) of strategically placed riparian forest. Agricultural needs include additional winter flooding of 15,160 ha (37,461 acres) of rice and 2,137 ha (5,281 acres) of corn. We distributed the habitat objectives across five planning regions, in some cases favoring proportionally larger increases in those regions with the greatest need. To maximize success, however, conservationists must take into account the specific needs of individual waterbird species, as a one-size-fits-all approach will not support the highest diversity of waterbirds.

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Avian Predation on Juvenile and Adult Lost River and Shortnose Suckers: An Updated Multi‐Predator Species Evaluation

Evans

Payton

Banet

et al. 2022

N American J Fish Manag

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Previous research suggests that predation by piscivorous colonial waterbirds may negatively influence the survival of Lost River Suckers (LRS) Deltistes luxatus and Shortnose Suckers (SNS) Chasmistes brevirostris in the Upper Klamath Basin (UKB), USA. However, estimates of predation from past studies, which were based on suckers with PIT tags, represent minimum estimates of sucker mortality because analyses did not account for the proportion of tags that were consumed by birds and deposited beyond their breeding colony. To address this uncertainty, we fed PIT‐tagged suckers to American white pelicans Pelecanus erythrorhynchos to estimate deposition probabilities. A hierarchical Bayesian model was then used to estimate predation rates (percentage of available tagged fish that were consumed) on juvenile suckers that were released as part of the Sucker Assisted Rearing Program (SARP) and on wild juvenile and adult LRS and SNS during 2009–2020. Pelican deposition probabilities were estimated to be 0.47 (95% credible interval = 0.36–0.60), indicating that for every 100 tags consumed, 47 tags on average were deposited on breeding colonies by birds. Deposition‐corrected estimates of predation rates were approximately two times greater than those previously reported and ranged annually from 4.3% (95% credible interval = 2.9–6.7%) to 8.5% (6.3–12.7%) on SARP juvenile suckers, from 4.3% (0.9–13.2%) to 10.5% (3.8–24.5%) on wild juvenile suckers, and from 0.1% (<0.1–0.3%) to 7.2% (2.8–16.4%) on adult suckers, depending on species and location. Results suggest that predation by colonial waterbirds, although not the original cause of sucker declines, was a substantial source of sucker mortality in some years. Future studies should consider models that jointly estimate both predation and survival and models that include environmental factors that potentially influence sucker susceptibility to avian predators in the UKB.

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Numbers of Terns Breeding Inland in California: Trends or Tribulations?

Cited by 14 publications

References 16 publications

Recent population size, trends, and limiting factors for the double-crested cormorant in western North America

Recent population size, trends, and limiting factors for the double-crested cormorant in western North America

Conservation Objectives for Wintering and Breeding Waterbirds in California's Central Valley

Avian Predation on Juvenile and Adult Lost River and Shortnose Suckers: An Updated Multi‐Predator Species Evaluation

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