Foraging Patch Selection by Shrubsteppe Sparrows

Rotenberry, John T.; Wiens, John A.

doi:10.1890/0012-9658(1998)079[1160:fpsbss]2.0.co;2

Cited by 50 publications

(35 citation statements)

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“…Sage Sparrows forage mainly by gleaning from shrubs or from the relatively bare, open spaces between shrubs. They frequently move among shrubs by walking or hopping across the bare interstices between them (Wiens et al 1987 b , Rotenberry and Wiens 1998), and they appear to avoid areas with dense non‐native vegetation and deep litter. Of course, we cannot rule out a positive attraction for native forbs and black sage, but we currently have no information on why that would be so.…”

Section: Discussionmentioning

confidence: 99%

Choices and Consequences of Habitat Occupancy and Nest Site Selection in Sage Sparrows

Misenhelter

Rotenberry

2000

Ecology

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160

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If habitat selection is adaptive, habitat choice by individuals should be directly associated with reproductive success. With that expectation in mind, we examined consequences of habitat choice in Sage Sparrows (Amphispiza belli) in southern California. Habitat selection in Sage Sparrows was pronounced, with vegetation measurements within territories differing significantly from those of interspersed unoccupied areas. Likewise, sites where sparrows placed their nests were significantly different from random sites within territories. Both successful territories (those containing a nest that fledged at least one young) and successful nest sites differed significantly in habitat from those that were unsuccessful. However, there was an inverse relationship between choice and its consequences; the mean score of unsuccessful territories on a discriminant function describing the habitat gradient from unoccupied to occupied areas (i.e., choice) was significantly higher than the mean for successful ones. In other words, birds preferred to settle in areas in which they did worse. Thus, attractiveness of habitat has become inversely related to its suitability, and the study site now serves as an “ecological trap.” Because predation accounted for 80–90% of nest loss, we speculate that decoupling of habitat attractiveness from suitability has been produced by redistribution of predators (mainly snakes) due to anthropogenic landscape‐level changes in the region.

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Section: Discussionmentioning

confidence: 99%

Choices and Consequences of Habitat Occupancy and Nest Site Selection in Sage Sparrows

Misenhelter

Rotenberry

2000

Ecology

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160

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“…Nest predation, the main cause of reproductive failure in the sparrow, varies with habitat structure (A. Chalfoun & T. Martin, unpublished). Food resources also vary spatially and temporally in shrub steppe (Rotenberry & Wiens 1998). Therefore the shrub steppe included potentially large ambient variation in habitat structure and two environmental factors (nest predation risk and food abundance) that are thought to exert strong influences on fitness and possibly operate at differing spatial scales.…”

Section: Methodsmentioning

confidence: 99%

Assessments of habitat preferences and quality depend on spatial scale and metrics of fitness

Chalfoun

Martin

2007

Journal of Applied Ecology

212

208

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Summary 1.Identifying the habitat features that influence habitat selection and enhance fitness is critical for effective management. Ecological theory predicts that habitat choices should be adaptive, such that fitness is enhanced in preferred habitats. However, studies often report mismatches between habitat preferences and fitness consequences across a wide variety of taxa based on a single spatial scale and/or a single fitness component. 2. We examined whether habitat preferences of a declining shrub steppe songbird, the Brewer's sparrow Spizella breweri , were adaptive when multiple reproductive fitness components and spatial scales (landscape, territory and nest patch) were considered. 3. We found that birds settled earlier and in higher densities, together suggesting preference, in landscapes with greater shrub cover and height. Yet nest success was not higher in these landscapes; nest success was primarily determined by nest predation rates. Thus landscape preferences did not match nest predation risk. Instead, nestling mass and the number of nesting attempts per pair increased in preferred landscapes, raising the possibility that landscapes were chosen on the basis of food availability rather than safe nest sites. 4. At smaller spatial scales (territory and nest patch), birds preferred different habitat features (i.e. density of potential nest shrubs) that reduced nest predation risk and allowed greater season-long reproductive success. Synthesis and applications.Habitat preferences reflect the integration of multiple environmental factors across multiple spatial scales, and individuals may have more than one option for optimizing fitness via habitat selection strategies. Assessments of habitat quality for management prescriptions should ideally include analysis of diverse fitness consequences across multiple ecologically relevant spatial scales.

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“…Much of the current research in patch and gap dynamics focuses on the consequences of patchiness: response of foragers to habitat patches (e.g., Rotenberry and Wiens 1998), ecological responses to habitat frag- Ecology,Vol. 82,No.…”

Section: Approaches To the Study Of Patch Dynamicsmentioning

confidence: 99%

Patch Dynamics of Mussels on Rocky Shores: Integrating Process to Understand Pattern

Hunt

Scheibling

2001

Ecology

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Within any particular landscape, patch structure and dynamics likely will differ among habitat types because of environmental differences influencing the intensity and outcome of biological interactions. We compared the dynamics of natural and experimentally constructed mussel patches (Mytilus trossulus and M. edulis) in two intertidal habitats, tidepools and emergent rock, over a time series (5, 10, 15 mo) and among seasons (three successive 5-mo intervals). In tidepools, mussels naturally occurred in small patches (median Ͻ25 cm 2 ). In contrast, mussels on emergent rock formed extensive beds with decimeter-scale gaps, but these beds start as small patches following disturbance such as ice scour. For our experimental patches (15 cm 2 ) in both habitats, we assessed the relative importance of physical (wave disturbance) and biological (predation, growth, recruitment, and immigration) processes in determining patch size and structure. Although individual experimental and natural patches varied greatly in size over time, mean patch area remained relatively constant. In general, mean size of individuals in experimental patches decreased due to the loss of larger mussels while numbers increased due to recruitment. Wave disturbance, which removes and redistributes mussels, appeared to be more important than predation (by the whelk Nucella lapillus) in determining patch structure and dynamics on this shore, although losses due to either process did not differ consistently between habitats over time. Individual growth rates were low (shell length Յ0.4 mm/mo) but greater in tidepools than on emergent rock, whereas recruitment and immigration rates generally did not differ between habitats. Although each process contributed to changes in patch size and structure, collectively they did not result in a marked divergence in mean patch area or biomass between tidepools and emergent rock over the 15-mo experiment. We suggest that the broad patterns of distribution and abundance of mussels develop slowly on this shore largely because of low individual growth rates. Over time scales of years, however, positive relationships between individual growth and recruitment rates and patch size may accelerate the expansion of aggregations on emergent rock. Mussel assemblages at our site differ from those examined in many other studies in terms of the relative importance of wave dislodgment and predation as causes of loss and in the role of growth in offsetting these losses. This study shows how integrative approaches, with monitoring of patches and individuals within patches, can provide detailed mechanistic understanding of patch structure and dynamics.

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Foraging Patch Selection by Shrubsteppe Sparrows

Cited by 50 publications

References 50 publications

Choices and Consequences of Habitat Occupancy and Nest Site Selection in Sage Sparrows

Choices and Consequences of Habitat Occupancy and Nest Site Selection in Sage Sparrows

Assessments of habitat preferences and quality depend on spatial scale and metrics of fitness

Patch Dynamics of Mussels on Rocky Shores: Integrating Process to Understand Pattern

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