Giving-Up Densities and Habitat Preferences of European Starlings and American Robins

Oyugi, Joseph O.; Brown, Joel S.

doi:10.1650/0010-5422(2003)105[130:gudahp]2.0.co;2

Cited by 16 publications

(8 citation statements)

References 16 publications

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“…Such assumption is ensured by using pairwise traits (e.g., Mandelik et al 2003;Wasserberg et al 2005; Abu Baker and Brown 2010, among many others). The few studies that do not rely on pairwise data show risk as a categorical variable (Brown et al 1992a;Oyugi and Brown 2003;Shapira et al 2008;Tsurim et al 2010; but see Brown et al 1992b andDruce et al 2006 for exceptions). In addition, even the theoretical models on patch allocation assume a linear effect of predation risk (Brown 1988(Brown , 1992.…”

Section: Predictions and Discussionmentioning

confidence: 99%

Uniform predation risk in nature: common, inconspicuous, and a source of error to predation risk experiments

Menezes

Kotler

Mourão³

2014

Behav Ecol Sociobiol

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Previous studies indicate that when predation risk is uniform across habitats, foragers concentrate their exploitation in fewer patches. Although uniform predation risk may seem rare in nature, some scenarios might cause it. Testing all scenarios in a single experiment is unfeasible; therefore, we developed a model that points whether concentration of exploitation in specific habitats due to uniform risk requires parameter values similar to what is found in literature. This model was based on Brown's (Behav Ecol Sociobiol 22:37-47, 1988) fitness function but rescaled to multiple habitats and predators, including uniform risk predators. Deriving function's maximum allowed comparisons with giving-up density studies. Results showed that uniform predation risk had a ushaped effect in habitat exploitation, causing a concentration of habitat exploitation at probabilities of survival from 0.2 to 0.8. However, the length of this interval and degree of concentration depended on the value of safety to forager fitness. Heterogeneous, nonuniform, predation risk decreases habitat exploitation where it was higher, therefore suppressing the effect of uniform risk on prey behavior. Time spent in the focal habitat and metabolic costs reduced the detectability of habitat concentration, while total time did not. We also found that uniform risk reduced accuracy of heterogeneous risk measurements. Future studies should aim to control all possible predators, as even the mild ones can induce complex behavior.

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Section: Predictions and Discussionmentioning

confidence: 99%

Uniform predation risk in nature: common, inconspicuous, and a source of error to predation risk experiments

Menezes

Kotler

Mourão³

2014

Behav Ecol Sociobiol

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“…The time robins spent foraging on the ground decreased steadily as the distance from cover increased (Oyugi and Brown 2003).…”

Section: Habitatmentioning

confidence: 96%

Northern goshawk and its prey in the Black Hills: Habitat assessment

Graham¹,

Volo²,

Reynolds³

2015

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The northern goshawk is classified as a Sensitive Species in all USDA Forest Service regions, including on the Black Hills National Forest in western South Dakota and northeastern Wyoming. An assessment was conducted of the quality of northern goshawk nesting and foraging habitat, along with the habitat quality of 22 of the goshawk's prey species. A Delphi (expert panel) evaluation of goshawk and prey habitat in 3,414 watersheds averaging 449 acres (182 ha) in size was completed by wildlife biologists from the Black Hills National Forest. The quality of goshawk nesting and foraging habitat and of prey group habitats was reported individually, then combined for each watershed. The optimum goshawk and prey habitat, totaling 67 watersheds or 34,427 acres (13,932 ha), was distributed throughout the nearly 1.5 million-acre (about 607,000-ha) Black Hills National Forest. Panel members found that the Bear Lodge Mountains, located in northeastern Wyoming, proportionally had the most optimum, high-, and medium-rated habitat. Wildfire, bark beetles, urban encroachment, and timber harvest can negatively affect northern goshawks and their prey's habitat. However, increasing the amount and presence of quaking aspen forests within the Black Hills will most likely improve the habitat of the goshawk by improving the habitat for many of its prey. Using previously articulated conditions as a template in the Forest Vegetation Simulator, we designed an example 100-year silvicultural system to create and maintain forest conditions for the northern goshawk and its prey on the Black Hills Experimental Forest.Keywords: northern goshawk, Accipiter gentilis atricapillus, silviculture, forest structure, bark beetles, ponderosa pine, forest management. AuthorsRussell T. Graham is a research forester (silviculturist) with the U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, in Moscow, Idaho. His research activities include the role that coarse woody debris plays in forests, large-scale ecosystem assessment and planning, describing northern goshawk habitat, and developing forest management strategies (silvicultural systems) for a wide array of management objectives. Shelley Bayard deVolo is an environmental coordination specialist for the Larimer County Engineering Department in Fort Collins, Colorado. She studied wildlife for several decades in California, Arizona, Colorado, and South Dakota. During her 15-year tenure with the Rocky Mountain Research Station in Fort Collins, Colorado, she assisted in studying demographic and habitat relationships for northern goshawks on the Kaibab Plateau, Arizona. She also determined genetic diversity for Kaibab goshawks and investigated genetic relationships for goshawk populations across North America.Richard T. Reynolds is a research wildlife biologist with the Rocky Mountain Research Station in Fort Collins, Colorado. He has investigated the relationship between the composition and structure of habitats as well as the demographic performance of apex avian predat...

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“…During high temperatures, they are exposed both to heating and the risk of predation by aerial predators such as raptors. Foraging animals may therefore perceive exposed areas as highly risky (Watts 1990(Watts , 1991Lima and Valone 1991;Olsson et al 2002;Oyugi and Brown 2003;Brown and Kotler 2004;Molokwu et al 2008) as well as thermally stressful (Bozinovic and Vasquez 1999;Bozinovic et al 2000;Tieleman and Williams 2002;Kenagy et al 2004). Foragers may therefore choose to forage close to shade to reduce exposure to predation or to avoid heat stress when temperature is relatively high.…”

Section: Predation Risk Versus Thermal Stressmentioning

confidence: 99%

“…The intermediate patches were probably perceived as riskier than the patches within a bush increasing the likelihood of being detected by aerial predators, despite being close to cover. Birds that are cover-dependent for escape from predators may perceive even small distances from cover as risky (Lima 1990;Watts 1990;Lima and Valone 1991;Oyugi and Brown 2003). The most regular visitors to the experimental patches were village weaver, speckle-fronted weaver and rock firefinch.…”

Section: Effect Of Watermentioning

confidence: 99%

Effects of season, water and predation risk on patch use by birds on the African savannah

Molokwu

Nilsson

Ottosson³

et al. 2010

Oecologia

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Birds from semi-arid regions may suffer dehydration during hot, dry seasons with low food availability. During this period, both energetic costs and water requirements for thermoregulation increase, limiting the scope of activity. For granivorous birds feeding on dry seeds, this is a major challenge and availability of water may affect the value of food. Water availability could (1) increase the value of a food patch when the surrounding environment is poor, due to an increase in the marginal value of energy, and (2) increase the value of the entire environment to the forager when environmental quality increases, due to an increase in the marginal value of time. We aimed to test this by measuring giving-up densities (GUDs, remaining food densities after foraging) of granivorous birds in the presence or absence of filled water pots, at different seasons differing in background food and water availability. We predicted that GUDs will increase with water provision during the dry season with moderate food, but in the early wet season with low food and water availability, GUDs will decrease with water provision. Later in the wet season, our experimental addition of water should have no effect. During seasons with low water availability but differing in food availability, results confirmed our predictions. However, when water became more abundant as the wet season progressed, birds still foraged more intensely during days with added water. In all seasons, birds fed more intensely in cover than in exposed areas, suggesting that predation risk rather than heat influenced microhabitat selection.

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Giving-Up Densities and Habitat Preferences of European Starlings and American Robins

Cited by 16 publications

References 16 publications

Uniform predation risk in nature: common, inconspicuous, and a source of error to predation risk experiments

Uniform predation risk in nature: common, inconspicuous, and a source of error to predation risk experiments

Northern goshawk and its prey in the Black Hills: Habitat assessment

Effects of season, water and predation risk on patch use by birds on the African savannah

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