Foraging Behavior and Switching by the Grasshopper Sparrow Ammodramus savannarum Searching for Multiple Prey in a Heterogeneous Environment

Joern, Anthony

doi:10.2307/2425805

Cited by 27 publications

(19 citation statements)

References 25 publications

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“…Grasshoppers may be attracted to the NO BIRDS plots because the mesh roof provides a favorable microclimate. However, Joern (1986) found little difference in wind speed or solar radiation inside exclosures that were very similar to ours. In addition, we did not detect any difference in vegetation height or composition between our BIRDS and NO BIRDS plots in 1989.…”

Section: Discussionsupporting

confidence: 85%

“…Our results suggest avian predators may have significant negative impacts on grasshopper population size. Similar experiments performed by Joern (1986) in western Nebraska and C. E. Bock in southern Arizona (personal communication) also found densities of grasshoppers were 30-50% higher in treatments from which birds were excluded.…”

Section: Discussionsupporting

confidence: 66%

“…We used a second method (Joern 1986, G. E. Belovsky, personal communication) to sample grasshopper densities at the end of the study each year. Heavy plastic or fiberglass screen ( 1 m high) was stretched around the outside of each plot to minimize grasshopper movement in and out of the plot; the sides on the NO BIRDS plots and the SIDES plots were left standing.…”

Section: Methodsmentioning

confidence: 99%

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Effects of Avian Predation on Grasshopper Populations in North Dakota Grasslands

Fowler¹,

Knight²,

George³

et al. 1991

Ecology

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We experimentally studied the effects of avian predation on grasshopper abundance in western North Dakota during the summers of 1988 and 1989. Grasshopper densities in 15 ° 15 m plots from which birds were excluded (NO BIRDS) were compared with similar—sized plots where birds were allowed to forage (BIRDS). Plots were established in early June at 16 sites (8 per year), and grasshopper densities were estimated from hoop counts in NO BIRDS and BIRDS plots at 2—wk intervals until the end of July. There were significantly more grasshoppers in NO BIRDS plots than in BIRDS plots in 1989 (P < .0001), but not in 1988 (P = .137). The difference between treatments in 1989 was first detected 6 wk after the exclosures were erected. Between years there were no differences in initial grasshopper abundance in all treatments (P > .388). After the final hoop count each year, sweep—net sampling was also used to estimate grasshopper densities. By this method, average grasshopper density in late July was 26% and 37% lower in BIRDS plots than in NO BIRDS plots in 1988 and 1989, respectively. Average length, total biomass of grasshoppers, species richness, and species diversity, however, did not differ between the treatments.In 1988, 2 of 15 grasshopper species were significantly more abundant in the NO BIRDS plots. There was no difference between the treatments among 16 species identified in the 1989 samples, but the power of our tests to detect differences for individual species was low. Our results support the hypothesis that avian predation reduces insect populations at low and moderate densities.

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Section: Discussionsupporting

confidence: 85%

Section: Discussionsupporting

confidence: 66%

Section: Methodsmentioning

confidence: 99%

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Effects of Avian Predation on Grasshopper Populations in North Dakota Grasslands

Fowler¹,

Knight²,

George³

et al. 1991

Ecology

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“…Numerous predators of grasshoppers reside in this system, including spiders, robberflies, various tachinid and sarcophagid parasitoids, mites, solitary wasps, and birds (primarily grasshopper sparrows and western meadowlarks) (Joern and Rudd 1982;Joern 1988Joern , 1992Joern 1998, 2000). Birds tend to feed on larger adult grasshoppers (Joern and Gaines 1990;Joern 1992), while immature grasshoppers are susceptible to spider and insect predation, especially from lycosid wolf spider species (Schizocosa spp.…”

Section: Study Sitementioning

confidence: 99%

Resource-mediated impact of spider predation risk on performance in the grasshopper Ageneotettix deorum (Orthoptera: Acrididae)

Danner

Joern

2003

Oecologia

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In response to increased exposure to predators when searching for food, many prey increase the frequency of antipredator behaviors, potentially reducing foraging rate and food intake. Such direct, nonlethal interactions between predators and prey resulting in reduced food intake can indirectly influence lifecycle development through effects on growth, developmental rate, and survival. We investigated the general hypothesis that individual performance of a herbivorous insect can be negatively affected when exposed to nonlethal predation risk, and that the response can be mediated by food quality. This hypothesis was tested using the common rangeland grasshopper Ageneotettix deorum with and without exposure to common wolf spider predators (Lycosidae, Schizocosa spp.) on both untreated natural and fertilized vegetation. All spiders were rendered temporarily incapable of direct feeding by restricting function of the chelicerae with beeswax. Detectable responses by grasshoppers to spiders indicate indirect consequences for lifecycle development. Grasshopper performance was measured as hind femur growth, duration of nymphal lifecycle stages, and survivorship in a caged field experiment conducted over 2 years. Grasshoppers developed faster and grew 3-5% larger when allowed to forage on fertilized vegetation in the absence of risk from a spider predator. Failure-time analysis illustrated enhanced survival probability in response to elevated food quality and the negative effects of grasshopper susceptibility to nonlethal predation risk. Performance on food of relatively low, ambient quality with no predation risk equaled that of grasshoppers caged with high quality vegetation in the presence of a modified spider. Increased resource quality can clearly moderate the negative life history responses caused by the behavioral modification of grasshoppers when exposed to spider predation risk, a compensatory response.

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“…Predator will switch to the alternative food when the density of the preferred prey is low [34]. Joern [26] observed switching among four alternative grasshopper species by the grasshopper sparrow (Ammodramus savannarun). Fryxell and Lundberg [15,16] have reported, using numerical simulation studies of predator-prey models where predator preys on two preys, that predator will switch to low-quality prey only if they have reduced the more profitable prey to low levels.…”

Section: Introductionmentioning

confidence: 99%

Alternative food and external source of infection stabilize predator–prey oscillations — A conclusion drawn from an eco-epidemiological model

Das¹

2015

Int. J. Biomath.

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Das et al.[Effect of disease-selective predation on prey infected by contact and external sources, Biosystems 95(3) (2009) 188-199] proposed an eco-epidemiological model where the prey species is infected through the external source of infection and contact of the species. In this present study we have modified their model by assuming that the predator consumes both the susceptible as well as the infected prey following the modified Holling type-II functional response. Our main focusing points of this study are the role of infection rate (both internal and external), alternative food, and half-saturation constant in the predator-prey dynamics with disease in the prey population. We have shown the local stability of the boundary as well as the interior equilibrium point under certain conditions. We have also worked out the permanence of the system. Our simulation results show that the system enters into limit cycle oscillations from stable position for higher values of the contact rate. But it is also shown that the external infection rate, enrichment of the alternative food of the predator population and the half-saturation constant can prevent limit cycle oscillations and stabilize the system. Thus external disease propagation, enrichment of the alternative food resource, and the half-saturation constant are the key factors for preventing the oscillatory behavior of the species.

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Foraging Behavior and Switching by the Grasshopper Sparrow Ammodramus savannarum Searching for Multiple Prey in a Heterogeneous Environment

Cited by 27 publications

References 25 publications

Effects of Avian Predation on Grasshopper Populations in North Dakota Grasslands

Effects of Avian Predation on Grasshopper Populations in North Dakota Grasslands

Resource-mediated impact of spider predation risk on performance in the grasshopper Ageneotettix deorum (Orthoptera: Acrididae)

Alternative food and external source of infection stabilize predator–prey oscillations — A conclusion drawn from an eco-epidemiological model

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