Interactions Between Double-crested Cormorants and Other Ground-Nesting Species

Somers, Christopher M.; Doucette, Jennifer L.; Weseloh, D. V.; Kjoss, Victoria A.; Brigham, R. Mark

doi:10.1675/063.034.0205

Cited by 11 publications

(15 citation statements)

References 36 publications

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“…For centuries we have been in conflict with the double-crested cormorant (Phalacrocorax auritus, hereafter cormorant), a piscivorous, colonial-nesting waterbird with numerous breeding colonies throughout North America (Wires and Cuthbert, 2006). Cormorants can be factors in the decline of sport and commercial fisheries (Burnett et al, 2002;Lantry et al, 2002;Rudstam et al, 2004), alter soil characteristics and vegetation (Boutin et al, 2011;Rush et al, 2011), and potentially displace other bird species near their nesting colonies (Cuthbert et al, 2002;Somers et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Invasive species sustain double-crested cormorants in southern Lake Michigan

Madura

Jones

2016

Journal of Great Lakes Research

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Double-crested cormorants (Phalacrocorax auritus) have long and often been implicated in having detrimental effects on fisheries. Resulting persecution, as well as DDT water contamination, led to a major decline of the species throughout its range. Research shows that the main components of cormorant diets vary significantly among forage, invasive, or economically important fish species. A recent, rapid increase in cormorant abundance in the Great Lakes has led, in some instances, to calls for the management of cormorant populations.Thus the objective of this study was to determine the prey composition of the double-crested cormorant colony in East Chicago, Indiana. This study builds on previous work in the north basin of Lake Michigan by focusing on cormorant diet composition at their only significant nesting colony in the southern basin where cormorant diet has been unstudied. Regurgitated pellets were collected from the colony and diagnostic bones were used to elucidate diet composition. Alewife (Alosa pseudoharengus), round goby (Neogobius melanostomus), Lepomis spp., white perch (Morone americana) and yellow perch (Perca flavescens) were the most frequently found prey items depending on cormorant breeding stage. Invasive species (i.e., alewife, round goby, white perch) contributed over ninety percent of the individuals and eighty percent of the biomass to cormorant diet over the study period. No salmonine species were detected suggesting that negative effects on this important fishery would likely occur only via direct competition for prey (e.g., alewife). Predation on yellow perch, which occurred mainly prior to and during the perch spawning season (i.e., of age-1 and older individuals), may warrant further study to quantify the effects on the local recreational yellow perch fishery. However, because yellow perch abundance is thought to be currently limited by poor recruitment at age-0, these results do not support active management of the cormorants at this colony to protect local fisheries. NORTHERN

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Section: Introductionmentioning

confidence: 99%

Invasive species sustain double-crested cormorants in southern Lake Michigan

Madura

Jones

2016

Journal of Great Lakes Research

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“…Herring gulls and ring‐billed gulls showed a strongly positive response to cormorant abundance, contrary to an earlier finding by Somers et al () of reduced reproductive success in herring gulls nesting with cormorants. The herring gull work conducted by Somers et al (, ) may have been confounded by human disturbance, but according to our fitted models, herring gulls in particular have an almost exclusively positive response to presence of cormorant management, a situation in which human disturbance is almost unavoidable. Indeed, there are indications that cormorant management is associated with increased herring gull nest success (B. S. Dorr, U.S. Department of Agriculture [USDA] Wildlife Services, personal communication).…”

Section: Discussionmentioning

confidence: 70%

“…Herring gulls and ring-billed gulls showed a strongly positive response to cormorant abundance, contrary to an earlier finding by Somers et al (2007) of reduced reproductive success in herring gulls nesting with cormorants. The herring gull work conducted by Somers et al (2007Somers et al ( , 2011 (taken in 1989-1991, 1997-1999, and 2007-2010) from all sites occupied by the conesting species at least once within the 4 survey periods. Several researchers have reported that gulls can take advantage of human disturbance of cormorant colonies to depredate cormorant nests (Kury and Gochfeld 1975, Ellison and Cleary 1978, DesGranges and Reed 1981, and this food resource may explain the boost in colony growth index.…”

Section: Gull Response To Cormorant Abundance and Managementmentioning

confidence: 99%

“…Declines in wading bird abundance have been observed at some shared breeding sites, but authors of these studies were unable to or did not conclusively link declines directly or indirectly to activities of cormorants (Skagen et al , Cuthbert et al ). On the other hand, cormorant presence has been observed to change the frequency with which co‐nesters engage in agonistic interactions, particularly in ground‐nesting colonies (Somers et al , Somers et al , Wyman and Cuthbert ). In one case, cormorants were associated with reduced herring gull ( Larus argentatus ) breeding success, although human disturbance was a confounding factor in the study (Somers et al ).…”

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Great lakes double‐crested cormorant management affects co‐nester colony growth

2017

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The population of double-crested cormorants (Phalacorocorax auritus; cormorants) in the North American Great Lakes has increased substantially since the 1970s, sparking economic, social, and biological concerns that have led to widespread management of the species within United States waters. Previous studies have quantified behavioral impacts of cormorants on other waterbird species that share breeding colony sites with cormorants. However, no study has yet examined how these impacts might scale to entire colonies, nor have potential effects of cormorant management on co-nesters been examined. Our objective was to estimate effects of cormorant abundance and management on colony growth indices of 4 species that commonly co-nest with cormorants in the North American Great Lakes; 3 of these species are conservation or stewardship priorities for the region. We estimated colony growth using the Great Lakes Colonial Waterbird Survey and comparable Canadian surveys, conducted between 1976 and 2010. We then applied linear mixed models to determine association of co-nester colony growth indices with cormorant abundance and management presence and intensity while controlling for other factors that likely influenced growth rates. According to the fitted models, black-crowned night-heron (Nycticorax nycticorax) colony growth was negatively related to cormorant abundance and management, whereas great blue herons (Ardea herodias) had little response to cormorant abundance, and herring gulls (Larus argentatus) and ring-billed gulls (Larus delawarensis) responded positively to cormorant abundance and management. These results suggest that cormorant management may not be as neutral to co-nesters as is often assumed. Responsible management plans for cormorants should take into account the likely effects on co-nesters present so that conservation and management goals for co-nesters can also be met. Ó 2017 The Wildlife Society.

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“…On Lake Erie, breeding cormorant populations increased from 174 individuals in 1979 to 32,564 birds in 2011 (Canadian Wildlife Service [CWS], unpublished data). Expanding cormorant populations have gained attention on the Laurentian Great Lakes because of perceived impacts on fish (Wires et al , Burnett et al , Lantry et al , Stapanian and Bur , Hebert and Morrison , Ridgway et al ), other birds (Cuthbert et al , Weseloh et al , Somers et al ), and their breeding habitats (Hebert et al , Duffe , Boutin et al , Rush et al , McGrath and Murphy ).…”

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confidence: 99%

Nesting cormorants and temporal changes in Island habitat

Hebert

Pasher

Weseloh³

et al. 2014

J Wildl Manag

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Double‐crested cormorant (Phalacrocorax auritus) populations have increased greatly across North America. The interior North America subpopulation is the largest with many birds nesting on the Laurentian Great Lakes. Lake Erie supports a large number of breeding pairs that nests primarily on islands in the western basin of the lake. These islands also harbor many rare plant species constituting some of the last vestiges of Carolinian plant communities in Canada. Nesting cormorants can adversely affect the plant communities on the islands on which they nest. Annual ground censuses were conducted from 1979 to 2011 to assess temporal changes in the density of nesting cormorants on 3 islands in western Lake Erie. We used aerial photographs taken over a maximum 16‐year span to assess changes in forest cover on these island ecosystems. We observed declines in forest cover on all 3 islands ranging from 47% to 85%. Trends among islands differed reflecting differences in cormorant colonization histories and the degree to which cormorants were managed, thereby influencing nest densities. Islands without cormorant management had cormorant nest densities ranging from approximately 300–500 nests/ha and forests declined continuously through time. On the island where cormorants were culled, nest densities were lower (approx. 200 nests/ha) and forest decline stabilized. © 2014 The Wildlife Society.

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Interactions Between Double-crested Cormorants and Other Ground-Nesting Species

Cited by 11 publications

References 36 publications

Invasive species sustain double-crested cormorants in southern Lake Michigan

Invasive species sustain double-crested cormorants in southern Lake Michigan

Great lakes double‐crested cormorant management affects co‐nester colony growth

Nesting cormorants and temporal changes in Island habitat

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