The Relationship between Herring Gulls and the Vegetation of their Breeding Colonies

Sobey, D. G.; Kenworthy, J. B.

doi:10.2307/2259108

Cited by 88 publications

(92 citation statements)

References 17 publications

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“…Because of high rainfall at Palmyra (4,500 mm per year), these direct soil measurements of nutrients almost certainly underestimate larger changes to nutrient throughflow and nutrient availability to plants. This trend for increasing soil nutrients near areas of high bird density is well established for temperate and polar zones (17,18). However, there is considerably less understanding of the effects of these subsidies in ecosystems where rainfall is relatively high, coastal marine waters are relatively oligotrophic, and bird densities are relatively low; despite the fact that these conditions typify most of the coastal zones in the tropics (19,20).…”

Section: Discussionmentioning

confidence: 95%

Plants cause ecosystem nutrient depletion via the interruption of bird-derived spatial subsidies

Young¹,

McCauley²,

Dunbar

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

109

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Plant introductions and subsequent community shifts are known to affect nutrient cycling, but most such studies have focused on nutrient enrichment effects. The nature of plant-driven nutrient depletions and the mechanisms by which these might occur are relatively poorly understood. In this study we demonstrate that the proliferation of the commonly introduced coconut palm, Cocos nucifera, interrupts the flow of allochthonous marine subsidies to terrestrial ecosystems via an indirect effect: impact on birds. Birds avoid nesting or roosting in C. nucifera, thus reducing the critical nutrient inputs they bring from the marine environment. These decreases in marine subsidies then lead to reductions in available soil nutrients, decreases in leaf nutrient quality, diminished leaf palatability, and reduced herbivory. This nutrient depletion pathway contrasts the more typical patterns of nutrient enrichment that follow plant species introductions. Research on the effects of spatial subsidy disruptions on ecosystems has not yet examined interruptions driven by changes within the recipient community, such as plant community shifts. The ubiquity of coconut palm introductions across the tropics and subtropics makes these observations particularly noteworthy. Equally important, the case of C. nucifera provides a strong demonstration of how plant community changes can dramatically impact the supply of allochthonous nutrients and thereby reshape energy flow in ecosystems.Cocos nucifera | community shifts | indirect effects | seabird | tropical islands

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Section: Discussionmentioning

confidence: 95%

Plants cause ecosystem nutrient depletion via the interruption of bird-derived spatial subsidies

Young¹,

McCauley²,

Dunbar

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

109

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“…228 Direct impacts of seabirds on vegetation include the input and distribution of guano, which can be toxic or 229 inhibit photosynthesis in some plants (Ishida, 1997), and physical disturbance due to trampling, nest 230 construction and territorial defence (Sobey & Kenworthy, 1979;Ellis, 2005). We found that islands with 231 gull colonies exhibited higher concentrations of soil C and N in meadows than those without them, as also 248 (Arcese, 1989;Mcatee, 2009; Bennett et al, 2011).…”

supporting

confidence: 53%

“…Observational results 56 further suggest that humans can affect island plant communities via their impacts on island-nesting 57 seabirds, including via predator introduction, changes in harvest rate, the provision of anthropogenic 58 foods or depletion of native prey species (Croll et al, 2005;Mulder et al, 2011; Baumberger et al, 2012). 59 These activities can in turn affect rates of physical disturbance and chemical input to vegetation linked to 60 changes in nest density or guano deposition, as has been described for gulls (Laridae) and cormorants 61 (Phalacrocoracidae;Sobey and Kenworthy 1979, Ishida 1996, 1997, Ellis 2005. On islands with 62 historically low seabird abundances, increases of guano deposition in particular can cause long-lasting 63 changes in soil chemistry and nutrients (García et al, 2002; Wait, Aubrey & Anderson, 2005; Caut et al, 64 2012) that facilitate increases to the cover and richness of species adapted to nutrient-rich soils 65 (Baumberger et al, 2012) or reduce the cover and richness of species adapted to poor, shallow soils 66 (García et al, 2002;Ellis, 2005).…”

mentioning

confidence: 97%

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Supplemental Information 3: Dataset of Vegetation Surveys on All Islands (2007 - 2012) and on Mandarte Island (1986 &Amp; 2006)

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We used 116-years of floral and faunal records from Mandarte Island, British Columbia, Canada, to estimate the indirect effects of humans on plant communities via their effects on the population size of a surface-nesting, colonial seabird, the Glaucous-winged gull (Larus glaucescens). Comparing current to historical records revealed 18 extirpations of native plant species (32% of species historically present), 31 exotic species introductions, and one case of exotic introduction followed by extirpation. Contemporary surveys indicated that native species cover declined dramatically from 1986 to 2006, coincident with the extirpation of 'old-growth' conifers. Because vegetation change co-occurred with an increasing gull population locally and regionally, we also tested predictions from the hypothesis that the presence and activities of seabirds help to explain those changes.Specifically, we predicted we would observe high nutrient loading and exotic plant species richness and cover on nearby islands with versus without gull colonies as a consequence of competitive dominance in species adapted to high soil nitrogen and trampling. As predicted, we found that native plant species cover and richness were lower, and exotic species cover and richness higher, on islands with versus without gull colonies. In addition, we found that soil carbon and nitrogen on islands with nesting gulls were positively related to soil depth and exotic species richness and cover across plots and islands. Our results suggest that gulls have the potential to drive rapid change in insular plant communities by increasing nutrients and disturbing vegetation. 29 exotic species introductions, and one case of exotic introduction followed by extirpation. Contemporary 30 surveys indicated that native species cover declined dramatically from 1986 to 2006, coincident with the 31 extirpation of 'old-growth' conifers. Because vegetation change co-occurred with an increasing gull 32 population locally and regionally, we also tested predictions from the hypothesis that the presence and 33 activities of seabirds help to explain those changes. Specifically, we predicted we would observe high 34 nutrient loading and exotic plant species richness and cover on nearby islands with versus without gull 35 colonies as a consequence of competitive dominance in species adapted to high soil nitrogen and 36 trampling. As predicted, we found that native plant species cover and richness were lower, and exotic 37 species cover and richness higher, on islands with versus without gull colonies. In addition, we found that 38 soil carbon and nitrogen on islands with nesting gulls were positively related to soil depth and exotic 39 species richness and cover across plots and islands. Our results suggest that gulls have the potential to 40 drive rapid change in insular plant communities by increasing nutrients and disturbing vegetation. Collins & Armesto, 1987;Strayer et al., 2006) but rarely studied over multiple decades (Bakker et al., 49 1996). Comparing contemporary and h...

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“…Observational results 56 further suggest that humans can affect island plant communities via their impacts on island-nesting 57 seabirds, including via predator introduction, changes in harvest rate, the provision of anthropogenic 58 foods or depletion of native prey species (Croll et al, 2005;Mulder et al, 2011; Baumberger et al, 2012). 59 These activities can in turn affect rates of physical disturbance and chemical input to vegetation linked to 60 changes in nest density or guano deposition, as has been described for gulls (Laridae) and cormorants 61 (Phalacrocoracidae;Sobey and Kenworthy 1979, Ishida 1996, 1997, Ellis 2005. On islands with 62 historically low seabird abundances, increases of guano deposition in particular can cause long-lasting 63 changes in soil chemistry and nutrients (García et al, 2002;Wait, Aubrey & Anderson, 2005; Caut et al, 64 2012) that facilitate increases to the cover and richness of species adapted to nutrient-rich soils 65 (Baumberger et al, 2012) or reduce the cover and richness of species adapted to poor, shallow soils 66 (García et al, 2002;Ellis, 2005).…”

mentioning

confidence: 97%

A century of ecosystem change: human and seabird impacts on plant species extirpation and invasion on islands

Lameris

Bennett

Blight

et al. 2016

Preprint

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We used 116-years of floral and faunal records from Mandarte Island, British Columbia, Canada, to estimate the indirect effects of humans on plant communities via their effects on the population size of a surface-nesting, colonial seabird, the Glaucous-winged gull (Larus glaucescens). Comparing current to historical records revealed 18 extirpations of native plant species (32% of species historically present), 31 exotic species introductions, and one case of exotic introduction followed by extirpation. Contemporary surveys indicated that native species cover declined dramatically from 1986 to 2006, coincident with the extirpation of 'old-growth' conifers. Because vegetation change co-occurred with an increasing gull population locally and regionally, we also tested predictions from the hypothesis that the presence and activities of seabirds help to explain those changes.Specifically, we predicted we would observe high nutrient loading and exotic plant species richness and cover on nearby islands with versus without gull colonies as a consequence of competitive dominance in species adapted to high soil nitrogen and trampling. As predicted, we found that native plant species cover and richness were lower, and exotic species cover and richness higher, on islands with versus without gull colonies. In addition, we found that soil carbon and nitrogen on islands with nesting gulls were positively related to soil depth and exotic species richness and cover across plots and islands. Our results suggest that gulls have the potential to drive rapid change in insular plant communities by increasing nutrients and disturbing vegetation. Because human activities have contributed to long-term change in gull populations, our results further suggest compelling, indirect links between human management decisions and plant community composition on islands of the Georgia Basin. Collins & Armesto, 1987;Strayer et al., 2006) but rarely studied over multiple decades (Bakker et al., 49 1996). Comparing contemporary and historical surveys can help rectify this deficit and enhance 50 understanding of long-term ecological change (Macdougall & Turkington, 2005; Arcese et al., 2014; 51 McKechnie et al., 2014). In particular, human disturbance and habitat conversion via exotic species 52 invasion are both identified as drivers of plant community change (Davis, Grime & Thompson, 2000; 53 Macdougall & Turkington, 2005;Seabloom et al., 2006), with recent evidence indicating that human 54 impacts can arise indirectly via predator removal or herbivore introductions that facilitate trophic 55 cascades, particularly in island systems (Estes et al., 2011; Arcese et al., 2014). Observational results 56 further suggest that humans can affect island plant communities via their impacts on island-nesting 57 seabirds, including via predator introduction, changes in harvest rate, the provision of anthropogenic 58 foods or depletion of native prey species (Croll et al., 2005;Mulder et al., 2011; Baumberger et al., 2012). 59 These activities can in...

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The Relationship between Herring Gulls and the Vegetation of their Breeding Colonies

Cited by 88 publications

References 17 publications

Plants cause ecosystem nutrient depletion via the interruption of bird-derived spatial subsidies

Plants cause ecosystem nutrient depletion via the interruption of bird-derived spatial subsidies

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A century of ecosystem change: human and seabird impacts on plant species extirpation and invasion on islands

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