Direct and Indirect Effects of Avian Predation on Grasshopper Communities in Northern Mixed-grass Prairie

Branson, David H.

doi:10.1093/ee/34.5.1114

Cited by 17 publications

(16 citation statements)

References 25 publications

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“…In the simulation series of the Senegal 2004 situation, the grasshopper density was at least one order of magnitude higher, but the simulated result was removal of approximately the same percentage of grasshoppers. These outputs contrast with the conclusion of Branson (2005) that avian predation effects become less important at high grasshopper densities. The main reason for the relatively important role of birds in the Senegal simulations, where the grasshopper densities were relatively high, was the higher density of birds in Senegal.…”

Section: Discussioncontrasting

confidence: 59%

“…Joern 1986Joern , 1992Fowler et al 1991;Bock et al 1992). At higher grasshopper densities, however, predation effects become less important, and overall the role of avian predation in the dynamics of grasshopper populations is variable (Branson 2005). Based on measurements and estimates of field metabolic rates of small passerines, Kirk et al (1996) estimated that a pair of Savannah Sparrow Passerculus sandwichensis and their young would consume 3.7 kg of fresh grasshopper biomass per season.…”

Section: Introductionmentioning

confidence: 99%

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Simulation studies of Senegalese Grasshopper ecosystem interactions II: the role of egg pod predators and birds

Axelsen¹,

Petersen²,

Maïga

et al. 2009

International Journal of Pest Management

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We present a simulation study of the role of birds and egg pod predators in the population dynamics of the Senegalese grasshopper. The model was an energetics-driven ecosystem model that included a natural Sahelian grass, millet, grasshoppers, the egg pod predators bombyliidae and Tenebrionidae, and 24 species of birds that prey on grasshopper nymphs and adults. The model simulated the rain-dependent dynamics and migration along a five-location south-north transect in Niger and Senegal, and the main outputs were the grasshopper pressure on the transect, measured as accumulated transect grasshopper days, and the density of eggs ready to emerge the following rainy season. The model was calibrated using observations from transects in Niger (2003Niger ( , 2004 and Senegal (2004).When input data from Niger 2003 and 2004 were applied, simulated reductions in grasshopper pressure during the rainy season from egg pod predators and birds, respectively, were within a range of 18-25%, but taken together the overall reduction in grasshopper pressure ranged between 35 and 37%. Using input from Senegal (2004) the birds accounted for reductions of around 25%.When the impact of the natural enemies was measured in terms of reduction in the density of eggs hatching the following year, the simulated impact of the egg pod predators ranged between 45 and 83% and that of the birds between 33 and 39%, and the two groups combined caused reductions between 60 and 75%.Analyses of the sensitivity to the bird species, added one by one, showed 'predator saturation' along the Niger transects (with low grasshopper density) but not along the Senegal transect.

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Section: Discussioncontrasting

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Simulation studies of Senegalese Grasshopper ecosystem interactions II: the role of egg pod predators and birds

Axelsen¹,

Petersen²,

Maïga

et al. 2009

International Journal of Pest Management

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“…Experiments were conducted in 2003 and 2004 at a northern mixed-grass prairie site in eastern Montana (47.47Ј N,104.08Ј W). More than 90% of vegetative biomass is graminoids, with both cool (C 3 ) and warm (C 4 ) season grasses (Branson 2005). Graminoids included western wheatgrass (Pascopyrum smithii), blue grama (Bouteloua gracilis), needle and thread (Stipa comata), prairie junegrass (Koeleria pyramidata), and threadleaf sedge (Carex filifolia).…”

Section: Methodsmentioning

confidence: 99%

Density-Dependent Effects of an Early Season Insect Herbivore on a Later Developing Insect Herbivore

Branson

2010

Environ Entomol

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Although most North American grasshopper species overwinter as eggs, some species hatch in late summer, overwinter as nymphs, and become adults in late spring. These species periodically reach outbreak densities, but it is unknown if they impact the population dynamics of later developing egg-overwintering grasshopper species. Two experiments were conducted in a northern mixed-grass prairie to examine the effects of herbivory by nymph-overwintering grasshoppers on survival of an egg-overwintering grasshopper, Ageneotettix deorum. When very high densities of nymph-overwintering grasshoppers reduced grass biomass by 80%, survival of A. deorum nymphs was significantly reduced. There was no effect of early season herbivory at a lower density of 16/m(2) on survival of A. deorum nymphs. The effects of early season herbivory appear consistent with exploitative competition. Although a strong reduction in peak grass biomass caused by early season herbivory negatively affected late season grass-feeding grasshopper densities, additional research is needed to examine the potential importance of early summer herbivory on population dynamics of later developing grasshoppers.

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“…The monthly average maximum daily temperature at a nearby weather station during June was close to the long-term average, while temperatures in July and August were 3.2 and 2.3 ∘ C higher than the long-term average. Peak mid-summer grasshopper densities in the close vicinity of the site ranged from ∼ 13 to 130 m -2 between 1998 and 2001 (Branson, 2005(Branson, , 2008a, with no significant effect of avian predation found on grasshopper density or species composition at the same location from 1999 to 2001 (Branson, 2005).…”

Section: Introductionmentioning

confidence: 90%

Insect herbivory and vertebrate grazing impact food limitation and grasshopper populations during a severe outbreak

Branson

Haferkamp

2014

Ecological Entomology

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1. Competition between herbivores often plays an important role in population ecology and appears strongest when densities are high or plant production is low. Phytophagous insects are often highly abundant, but relatively few experiments have examined competition between vertebrates and phytophagous insects.2. In grassland systems worldwide, grasshoppers are often the dominant phytophagous insect, and livestock grazing is a dominant land use. For this study, a novel experiment was conducted examining competition between vertebrates and invertebrates, where both grasshopper densities and sheep grazing were manipulated inside 10-m 2 caged mesocosms during a grasshopper outbreak. We examined how grasshopper densities and the timing of vertebrate herbivory affected grasshopper densities, if the effects of vertebrates on survival and reproduction changed with grasshopper density, and how a naturally occurring grasshopper outbreak affected grasshopper populations in the following year.3. Densities of grasshoppers at the site peaked at 130 m -2 . Food-limited competition was stronger in treatments with higher grasshopper densities and repeated or late livestock herbivory, leading to reduced survival, femur length, and functional ovarioles, a measure of future reproduction. Strong food-limited density-dependent reproduction and survival led to reduced hatching densities in 2001.4. As competition was typically stronger with high grasshopper densities than with livestock grazing, competition from vertebrates could be relatively less important for phytophagous insect population dynamics during outbreaks. The experiment provides insights into how competition between insect and vertebrate herbivores influences insect population dynamics, and indicates that severe outbreaks can rapidly subside with strong competition from vertebrate and insect herbivores.

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Direct and Indirect Effects of Avian Predation on Grasshopper Communities in Northern Mixed-grass Prairie

Cited by 17 publications

References 25 publications

Simulation studies of Senegalese Grasshopper ecosystem interactions II: the role of egg pod predators and birds

Simulation studies of Senegalese Grasshopper ecosystem interactions II: the role of egg pod predators and birds

Density-Dependent Effects of an Early Season Insect Herbivore on a Later Developing Insect Herbivore

Insect herbivory and vertebrate grazing impact food limitation and grasshopper populations during a severe outbreak

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