Population, Diet and Reproductive Success of Double-Crested Cormorants Breeding on Lake Winnipegosis, Manitoba, in 1987

Hobson, Keith A.; Knapton, Richard W.; Lysack, Walter

doi:10.2307/1521340

Cited by 37 publications

(33 citation statements)

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“…Most previous monitoring of colonial waterbirds in Manitoba has focused on breeding populations on lakes Winnipeg, Winnipegosis, and Manitoba (Vermeer 1970(Vermeer , 1973Koonz and Rakowski 1985;Hobson et al 1989;Koonz 2000). The results reported here indicate that medium-sized lakes in adjacent regions to the north also support notable populations of some species.…”

Section: Discussionmentioning

confidence: 99%

“…From the 1960s through the 1980s, several studies reported on the abundance and distribution of colonial waterbirds on lakes Winnipeg, Winnipegosis, and Manitoba, south of the 54th parallel (Vermeer 1969(Vermeer , 1970Koonz and Rakowski 1985;Hobson et al 1989). No region-wide monitoring has taken place in central and southern Manitoba in over two decades despite observed declines in the populations of some colonial species further east on the Great Lakes (Morris et al 2010(Morris et al , 2011) and a number of regional threats to waterbirds, including persecution, flooding of colonies due to water level manipulation, and eutrophication of the lakes, which may subsequently impact breeding waterbirds (Hobson et al 1989;Lindenschmidt et al 2012;Schindler et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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Abundance, distribution, and species assemblages of colonial waterbirds in the boreal region of west-central Manitoba and east-central Saskatchewan

Wilson

2013

Can Field Nat

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Central and southern Manitoba contain some of the largest breeding populations of several colonial waterbird species in North America. Despite the value of this region for waterbirds, very little monitoring has been conducted on Lake Winnipeg, Lake Winnipegosis, or Lake Manitoba in the past three decades and little is known about the smaller boreal lakes in adjacent areas to the north. In June 2011, boat surveys were conducted on 11 boreal lakes in west-central Manitoba and east-central Saskatchewan to examine current abundance and distribution of colonial waterbirds in that region. Data from this survey were compared with abundance of colonial waterbirds on Lake Winnipegosis and Lake Manitoba from an aerial survey of these lakes in 2012. Waterbird colonies were located on 7 of the 11 lakes in 2011 and included Double-crested Cormorants (Phalacrocorax auritus) (2373 adults, 1134 pairs in 7 colonies), Common Terns (Sterna hirundo) (1367 adults, 772 pairs in 29 colonies), Forster’s Terns (Sterna forsteri) (20 adults, 11 pairs in 1 colony), Herring Gulls (Larus argentatus) (876 adults, 568 pairs in 23 colonies), and Ring-billed Gulls (Larus delawarensis) (3752 adults, 16 colonies). Common Terns and Herring Gulls appeared to be predominantly breeders and pair abundance for both species increased in a sigmoidal fashion; lakes <100 km2 in area had few breeding pairs. Numbers of Double-crested Cormorants and especially, Ring-billed Gulls, may have included a sizeable non-breeding component. Densities (pairs/lake area) of Common Terns and Herring Gulls were about 2 and 4 times higher, respectively, on these lakes than on Lake Winnipegosis and Lake Manitoba, while Double-crested Cormorant and Ring-billed Gull densities were higher on lakes Winnipegosis and Manitoba. Additional studies of productivity in relation to lake characteristics and connectivity among colonies throughout the region would further our understanding of the importance and sustainability of waterbird populations in this region of the boreal forest.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Abundance, distribution, and species assemblages of colonial waterbirds in the boreal region of west-central Manitoba and east-central Saskatchewan

Wilson

2013

Can Field Nat

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“…Monitoring of colonial waterbirds in southern Manitoba has included surveys of nests conducted on the ground (e.g., Vermeer 1970aVermeer , 1970bHobson et al 1989;Koonz 2000), mixed aerial visual counts and ground nest counts (Koonz and Rakowski 1985) and aerial surveys with digital photography. Ground counts typically have low error (4-22% ;Hutchinson 1979;Erwin 1980) and are usually based on nests, thus providing a more direct link to the number of breeding pairs at a colony.…”

Section: Discussionmentioning

confidence: 99%

“…The only estimates of abundance for all three lakes within a short period of 1-3 years occurred around 1970 (Vermeer 1969, 1970a, 1970b, 1972), in 1979(Koonz and Rakowski 1985 and for our survey in 2012. A survey of Lake Winnipegosis for all species was conducted in 1999 (Koonz 2000), while monitoring specifically for Double-crested Cormorants occurred in 1945, 1950, 1951(McLeod and Bondar 1953 and 1987 (Hobson et al 1989). Thus, for Double-crested Cormorants, we have a 68-year time series on one of the most important breeding lakes for this species in North America.…”

Section: Discussionmentioning

confidence: 99%

“…Lakes Winnipeg, Winnipegosis and Manitoba have historically contained substantial breeding populations of several colonial waterbird species including Double-crested Cormorant (Phalacrocorax auritus), American White Pelican (Peleca-nus erythrorhynchos), Ring-billed Gull (Larus delawarensis), Herring Gull (L. argentatus), Caspian Tern (Hydroprogne caspia) and Common Tern (Sterna hirundo). Despite the importance of this region, the last complete survey of all three lakes took place in 1979 (Koonz and Rakowski 1985), and only local surveys have been conducted since, mainly on Lake Winnipegosis (Hobson et al 1989;Koonz 2000).…”

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confidence: 99%

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Distribution and abundance of nesting common and Caspian terns on the North American Great Lakes, 1976 to 1999

Morris¹,

Weseloh

Cuthbert

et al. 2010

Journal of Great Lakes Research

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Migratory Flyways May Affect Population Structure in Double‐Crested Cormorants

et al. 2020

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Double‐crested cormorants (Phalacrocorax auritus) recovered from a demographic bottleneck so well that they are now considered a nuisance species at breeding and wintering grounds across the United States and Canada. Management of this species could be improved by refining genetic population boundaries and assigning individuals to their natal population. Further, recent radio‐telemetry data suggest the existence of Interior and Atlantic migratory flyways, which could reduce gene flow and result in substantial genetic isolation. In this study, we used 1,784 individuals collected across the eastern United States, a large panel of microsatellite markers developed for this species, and individuals banded as chicks and recaptured as adults to explore the effects of migratory flyways on population structure, quantify the genetic effects of demographic bottlenecks, and determine whether individuals could be assigned to their natal population based on genotype. We found evidence for genetic population division only along migratory flyways, no evidence of genetic bottlenecks, and mixed effectiveness of assignment tests. Our population structure findings suggest that gene flow is high across large scales; for example, individuals from New York, Minnesota, and Alabama are all in panmixia. We also found that traditional subspecies ranges may not be valid because >1 subspecies was present in single genetic populations. The lack of evidence for genetic bottlenecks also likely underscores the vagility of this species, suggesting that even during demographic bottlenecks, populations were not isolated from allelic exchange. Finally, the failure of assignment tests to consistently perform is likely due in part to imperfect a priori sampling of Atlantic and Interior chicks and the high vagility of adults. We conclude that the demographic bottleneck is not likely to have reduced genetic diversity, and that assignment tests remain unreliable for this species. We recommend double‐crested cormorants be managed by flyway. Further development of genomic resources in this species could improve population subdivision resolution, improve assignment tests, and reveal further information on demographic histories. © 2020 The Wildlife Society.

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Population, Diet and Reproductive Success of Double-Crested Cormorants Breeding on Lake Winnipegosis, Manitoba, in 1987

Cited by 37 publications

References 15 publications

Abundance, distribution, and species assemblages of colonial waterbirds in the boreal region of west-central Manitoba and east-central Saskatchewan

Abundance, distribution, and species assemblages of colonial waterbirds in the boreal region of west-central Manitoba and east-central Saskatchewan

Distribution and abundance of nesting common and Caspian terns on the North American Great Lakes, 1976 to 1999

Migratory Flyways May Affect Population Structure in Double‐Crested Cormorants

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