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Trait-mediated trophic cascade creates enemy-free space for nesting hummingbirds.

Greeney HF, Meneses MR, Hamilton CE, Lichter-Marck E, Mannan RW, Snyder N, Snyder H, Wethington SM, Dyer LA - Sci Adv (2015)

Bottom Line: The indirect effects of predators on nonadjacent trophic levels, mediated through traits of intervening species, are collectively known as trait-mediated trophic cascades.We demonstrate that hummingbirds in Arizona realize increased breeding success when nesting in association with hawks.An enemy-free nesting space is created when jays, an important source of mortality for hummingbird nests, alter their foraging behavior in the presence of their hawk predators.

View Article: PubMed Central - PubMed

Affiliation: Yanayacu Biological Station & Center for Creative Studies, Cosanga, Napo, Ecuador. ; Department of Biology, University of Nevada, Reno, NV 89557, USA. ; Department of Natural Resources, University of Arizona, Tucson, AZ 85721, USA.

ABSTRACT
The indirect effects of predators on nonadjacent trophic levels, mediated through traits of intervening species, are collectively known as trait-mediated trophic cascades. Although birds are important predators in terrestrial ecosystems, clear examples of trait-mediated indirect effects involving bird predators have almost never been documented. Such indirect effects are important for structuring ecological communities and are likely to be negatively impacted by habitat fragmentation, climate change, and other factors that reduce abundance of top predators. We demonstrate that hummingbirds in Arizona realize increased breeding success when nesting in association with hawks. An enemy-free nesting space is created when jays, an important source of mortality for hummingbird nests, alter their foraging behavior in the presence of their hawk predators.

No MeSH data available.


Related in: MedlinePlus

Interannual comparisons of jay foraging patterns in study plots, illustrating the effect of raptor presence on the spatial distributions of foraging jays.Each point represents the mean height above the ground of individual jays within a single flock. Plots with active hawk nests are shaded gray. Upper panels show pooled data from two plots that were occupied in both years, middle panels represent four plots that were not reoccupied in 2009, and bottom panels show one plot occupied for the first time in 2009. ANCOVA with all plots and years combined revealed a significant interaction (F1, 341 = 36.4; P < 0.0001) between distance to a raptor nest and activity of the raptor (presence/absence). Plots that were unoccupied for the duration of the study are not illustrated.
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Figure 3: Interannual comparisons of jay foraging patterns in study plots, illustrating the effect of raptor presence on the spatial distributions of foraging jays.Each point represents the mean height above the ground of individual jays within a single flock. Plots with active hawk nests are shaded gray. Upper panels show pooled data from two plots that were occupied in both years, middle panels represent four plots that were not reoccupied in 2009, and bottom panels show one plot occupied for the first time in 2009. ANCOVA with all plots and years combined revealed a significant interaction (F1, 341 = 36.4; P < 0.0001) between distance to a raptor nest and activity of the raptor (presence/absence). Plots that were unoccupied for the duration of the study are not illustrated.

Mentions: The foraging height of jays was not associated with the location of hawk nests in plots with inactive nests, but jays foraged higher above the ground when closer to active hawk nests [analysis of covariance (ANCOVA), distance by raptor activity interaction, F1, 341 = 36.4; P < 0.0001; Fig. 3]. This behavioral shift in the presence of hawks creates a roughly cone-shaped space around active hawk nests, within which jays are infrequently detected (Fig. 2). The shape of this enemy-free space is due to the fact that jays are much safer from the hawks when they are at least as high above ground as the hawks, which hunt from perches within the canopy in horizontal or descending chases. An interannual comparison of jay foraging heights in seven plots (two reoccupied, four not reoccupied, and one occupied for the first time in 2009) demonstrated the effect of hawk presence on the spatial foraging habits of jays (Fig. 3).


Trait-mediated trophic cascade creates enemy-free space for nesting hummingbirds.

Greeney HF, Meneses MR, Hamilton CE, Lichter-Marck E, Mannan RW, Snyder N, Snyder H, Wethington SM, Dyer LA - Sci Adv (2015)

Interannual comparisons of jay foraging patterns in study plots, illustrating the effect of raptor presence on the spatial distributions of foraging jays.Each point represents the mean height above the ground of individual jays within a single flock. Plots with active hawk nests are shaded gray. Upper panels show pooled data from two plots that were occupied in both years, middle panels represent four plots that were not reoccupied in 2009, and bottom panels show one plot occupied for the first time in 2009. ANCOVA with all plots and years combined revealed a significant interaction (F1, 341 = 36.4; P < 0.0001) between distance to a raptor nest and activity of the raptor (presence/absence). Plots that were unoccupied for the duration of the study are not illustrated.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643763&req=5

Figure 3: Interannual comparisons of jay foraging patterns in study plots, illustrating the effect of raptor presence on the spatial distributions of foraging jays.Each point represents the mean height above the ground of individual jays within a single flock. Plots with active hawk nests are shaded gray. Upper panels show pooled data from two plots that were occupied in both years, middle panels represent four plots that were not reoccupied in 2009, and bottom panels show one plot occupied for the first time in 2009. ANCOVA with all plots and years combined revealed a significant interaction (F1, 341 = 36.4; P < 0.0001) between distance to a raptor nest and activity of the raptor (presence/absence). Plots that were unoccupied for the duration of the study are not illustrated.
Mentions: The foraging height of jays was not associated with the location of hawk nests in plots with inactive nests, but jays foraged higher above the ground when closer to active hawk nests [analysis of covariance (ANCOVA), distance by raptor activity interaction, F1, 341 = 36.4; P < 0.0001; Fig. 3]. This behavioral shift in the presence of hawks creates a roughly cone-shaped space around active hawk nests, within which jays are infrequently detected (Fig. 2). The shape of this enemy-free space is due to the fact that jays are much safer from the hawks when they are at least as high above ground as the hawks, which hunt from perches within the canopy in horizontal or descending chases. An interannual comparison of jay foraging heights in seven plots (two reoccupied, four not reoccupied, and one occupied for the first time in 2009) demonstrated the effect of hawk presence on the spatial foraging habits of jays (Fig. 3).

Bottom Line: The indirect effects of predators on nonadjacent trophic levels, mediated through traits of intervening species, are collectively known as trait-mediated trophic cascades.We demonstrate that hummingbirds in Arizona realize increased breeding success when nesting in association with hawks.An enemy-free nesting space is created when jays, an important source of mortality for hummingbird nests, alter their foraging behavior in the presence of their hawk predators.

View Article: PubMed Central - PubMed

Affiliation: Yanayacu Biological Station & Center for Creative Studies, Cosanga, Napo, Ecuador. ; Department of Biology, University of Nevada, Reno, NV 89557, USA. ; Department of Natural Resources, University of Arizona, Tucson, AZ 85721, USA.

ABSTRACT
The indirect effects of predators on nonadjacent trophic levels, mediated through traits of intervening species, are collectively known as trait-mediated trophic cascades. Although birds are important predators in terrestrial ecosystems, clear examples of trait-mediated indirect effects involving bird predators have almost never been documented. Such indirect effects are important for structuring ecological communities and are likely to be negatively impacted by habitat fragmentation, climate change, and other factors that reduce abundance of top predators. We demonstrate that hummingbirds in Arizona realize increased breeding success when nesting in association with hawks. An enemy-free nesting space is created when jays, an important source of mortality for hummingbird nests, alter their foraging behavior in the presence of their hawk predators.

No MeSH data available.


Related in: MedlinePlus