Distribution, Density, and Age Structure of Spotted Owls on Two Southern California Habitat Islands

Gutiérrez, R. J.; Pritchard, James A.

doi:10.2307/1368246

Cited by 18 publications

(9 citation statements)

References 7 publications

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“…The Sierra Nevada are farther north, higher in elevation, hold massive snowpack that irrigates lower elevations throughout the dry summer (Kattelmann ), and support a larger, more contiguous population of spotted owls relative to southern California's meta‐populations (LaHaye et al ). Furthermore, spotted owl surveys in the Sierra Nevada study were primarily associated with timber‐harvest projects in mixed‐conifer habitats, whereas the southern California study areas incorporated sites in all forested habitats within the SBM and SJM (Gutiérrez and Pritchard , LaHaye et al ), including vegetation types not typically monitored for spotted owls in the Sierra Nevada, such as pure hardwoods and conifer‐hardwood forests associated with chaparral (Smith ). Moreover, southern California owl sites associated with vegetation such as bigcone Douglas‐fir–canyon live oak forests have no corollary in the Sierra Nevada.…”

Section: Discussionmentioning

confidence: 99%

Influence of fire and salvage logging on site occupancy of spotted owls in the San Bernardino and San Jacinto Mountains of Southern California

Lee

Bond

Borchert³

et al. 2013

J Wildl Manag

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Fire over the past decade has affected forests in the San Bernardino Mountains of southern California, providing an excellent opportunity to examine how this disturbance, and subsequent post-fire salvage logging, influenced California spotted owl (Strix occidentalis occidentalis) breeding-season site occupancy dynamics there and in the nearby San Jacinto Mountains. Using occupancy survey data from 2003 to 2011 for all-detections and pairs-only data, we estimated annual extinction and colonization probabilities at 71 burned and 97 unburned breeding-season sites before and after fire, while controlling for confounding effects of non-fire-related temporal variation and among-site differences in habitat characteristics. We found no statistically significant effects of fire or salvage logging on occupancy dynamics of spotted owls of southern California. However, we found some evidence that fire and logging effects could be biologically meaningful. For pairs data, the model-averaged mean of fire-related effects on colonization and extinction probabilities resulted in a 0.062 lesser site-occupancy probability in burned sites 1-year post-fire relative to unburned sites. Post-fire salvage logging reduced occupancy an additional 0.046 relative to sites that only burned. We documented a threshold-type relationship between extinction and colonization probabilities and the amount of forested habitat (conifer or hardwood tree cover types) that burned at high severity within a 203-ha core area around spotted owl nests and roost centroids. Sites where approximately 0-50 ha of forested habitat within the core area burned at high severity had extinction probabilities similar to unburned sites, but where more than approximately 50 ha of forested habitat burned severely, extinction probability increased approximately 0.003 for every additional hectare severely burned. The majority (75%) of sites burned below this threshold. Sites where high-severity fire affected >50 ha of forested habitat could still support spotted owls, so all burned sites should be monitored for occupancy before management actions such as salvage logging are undertaken that could be detrimental to the subspecies. We also recommend that managers strive to reduce human-caused ignitions along the wildland-urban interface, particularly at lower elevations where owl sites are at higher risk of extinction from fire. Ó 2013 The Wildlife Society.

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Section: Discussionmentioning

confidence: 99%

Influence of fire and salvage logging on site occupancy of spotted owls in the San Bernardino and San Jacinto Mountains of Southern California

Lee

Bond

Borchert³

et al. 2013

J Wildl Manag

View full text Add to dashboard Cite

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“…In southern California, Spotted Owls inhabit isolated upper-elevation (915-1,525 m) forests surrounded by lower-elevation desert and semidesert vegetation (Gutiérrez and Pritchard 1990, Gutiérrez et al 1992, LaHaye et al 1994, 1997. Forest fires in these southern Californian forests occur largely as a result of human-caused ignition (Halsey 2005) and typically burn in a mosaic of severities (Weatherspoon et al 1992, Stephenson andCalcarone 1999), with the largest high-severity fires burning under extreme Santa Ana weather conditions typical of the region (Keeley et al 2009).…”

Section: Study Areamentioning

confidence: 99%

Previous year's reproductive state affects Spotted Owl site occupancy and reproduction responses to natural and anthropogenic disturbances

Lee

Bond

2015

The Condor

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“…First, nucleotide diversity tracks population size; thus, there might be many fewer California spotted owls than northern or Mexican spotted owls. However, this seems unlikely because recent surveys (e.g., Gutierrez and Pritchard 1990;Gutierrez 1994;Gutierrez et al 1995;U.S. Department of the Interior 1995) suggest that the population of birds in the Sierra Nevada, San Bernardino Mountains, and on Mount San Jacinto is approximately one-half to one-third of the number of northern spotted owls, not one-tenth or less (the number of Mexican spotted owls is poorly known, especially in Mexico).…”

Section: Genetic Variation Within Populationsmentioning

confidence: 99%

PHYLOGEOGRAPHY OF SPOTTED OWL (STRIX OCCIDENTALIS) POPULATIONS BASED ON MITOCHONDRIAL DNA SEQUENCES: GENE FLOW, GENETIC STRUCTURE, AND A NOVEL BIOGEOGRAPHIC PATTERN

1999

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Mitochondrial DNA control region sequences of spotted owls (Strix occidentalis) allowed us to investigate gene flow, genetic structure, and biogeographic relationships among these forest-dwelling birds of western North America Estimates of gene flow based on genetic partitioning and the phylogeography of haplotypes indicate substantial dispersal within three long-recognized subspecies. However, patterns of individual phyletic relationships indicate a historical absence of gene flow among the subspecies, which are essentially monophyletic. The pattern of haplotype coalescence enabled us to identify the approximate timing and direction of a recent episode of gene flow from the Sierra Nevada to the northern coastal ranges. The three subspecies comprise phylogenetic species, and the northern spotted owl (S. o. caurina) is sister to a clade of California (S. o. occidentalis) plus Mexican spotted owls (S o lucida); this represents a novel biogeographic pattern within birds. The California spotted owl had substantially lower nucleotide diversity than the other two subspecies; this result is inconsistent with present patterns of population density A causal explanation requires postulating a severe bottleneck or a selective sweep, either of which was confined to only one geographic region.

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Distribution, Density, and Age Structure of Spotted Owls on Two Southern California Habitat Islands

Cited by 18 publications

References 7 publications

Influence of fire and salvage logging on site occupancy of spotted owls in the San Bernardino and San Jacinto Mountains of Southern California

Influence of fire and salvage logging on site occupancy of spotted owls in the San Bernardino and San Jacinto Mountains of Southern California

Previous year's reproductive state affects Spotted Owl site occupancy and reproduction responses to natural and anthropogenic disturbances

PHYLOGEOGRAPHY OF SPOTTED OWL (STRIX OCCIDENTALIS) POPULATIONS BASED ON MITOCHONDRIAL DNA SEQUENCES: GENE FLOW, GENETIC STRUCTURE, AND A NOVEL BIOGEOGRAPHIC PATTERN

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