Does the Presence of Barred Owls Suppress the Calling Behavior of Spotted Owls?

Crozier, Michelle L.; Seamans, Mark E.; Gutiérrez, R. J.; Loschl, Peter J.; Horn, Robert B.; Sovern, Stan G.; Forsman, Eric D.

doi:10.1650/0010-5422(2006)108[760:dtpobo]2.0.co;2

Cited by 36 publications

(18 citation statements)

References 13 publications

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“…For example, competition for a similar set of resources (i.e., nest cavities and food) over time could lead to delayed nesting in spotted owls to reduce overlap in breeding phenologies with barred owls, as has been demonstrated in studies of competitive interactions between Tengmalm's owls ( Aegolius funereus ) and Ural owls ( Strix uralensis ; Hakkarainen and Korpimäki ) and cavity‐nesting birds and invasive European starlings ( Sturnus vulgaris ; Ingold , Wiebe ). Spotted owls may also be less vocal in the presence of barred owls (Crozier et al ), which could lead to delays in pair formation during courtship. In addition, males engaged in territorial encounters with neighboring barred owls may not be able to invest much time in courtship feeding, which could delay the start of egg‐laying because females rely almost entirely on food provided by males during egg production.…”

Section: Discussionmentioning

confidence: 99%

Competitive interactions and resource partitioning between northern spotted owls and barred owls in western Oregon

Wiens

Anthony

Forsman

2014

Wildlife Monographs

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122

239

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The federally threatened northern spotted owl (Strix occidentalis caurina) is the focus of intensive conservation efforts that have led to much forested land being reserved as habitat for the owl and associated wildlife species throughout the Pacific Northwest of the United States. Recently, however, a relatively new threat to spotted owls has emerged in the form of an invasive competitor: the congeneric barred owl (S. varia). As barred owls have rapidly expanded their populations into the entire range of the northern spotted owl, mounting evidence indicates that they are displacing, hybridizing with, and even killing spotted owls. The range expansion by barred owls into western North America has made an already complex conservation issue even more contentious, and a lack of information on the ecological relationships between the 2 species has hampered recovery efforts for northern spotted owls. We investigated spatial relationships, habitat use, diets, survival, and reproduction of sympatric spotted owls and barred owls in western Oregon, USA, during 2007USA, during -2009. Our overall objective was to determine the potential for and possible consequences of competition for space, habitat, and food between these previously allopatric owl species. Our study included 29 spotted owls and 28 barred owls that were radio-marked in 36 neighboring territories and monitored over a 24-month period. Based on repeated surveys of both species, the number of territories occupied by pairs of barred owls in the 745-km 2 study area (82) greatly outnumbered those occupied by pairs of spotted owls (15). Estimates of mean size of home ranges and core-use areas of spotted owls (1,843 ha and 305 ha, respectively) were 2-4 times larger than those of barred owls (581 ha and 188 ha, respectively). Individual spotted and barred owls in adjacent territories often had overlapping home ranges, but interspecific space sharing was largely restricted to broader foraging areas in the home range with minimal spatial overlap among coreuse areas. We used an information-theoretic approach to rank discrete-choice models representing alternative hypotheses about the influence of forest conditions, topography, and interspecific interactions on species-specific patterns of nighttime resource selection. Spotted owls spent a disproportionate amount of time foraging on steep slopes in ravines dominated by old (>120 yr) conifer trees. Barred owls used available forest types more evenly than spotted owls, and were most strongly associated with patches of large hardwood and conifer trees that occupied relatively flat areas along streams. Spotted and barred owls differed in the relative use of old conifer forest (greater for spotted owls) and slope conditions (steeper slopes for spotted owls), but we found no evidence that the 2 species differed in their use of young, mature, and riparian-hardwood forest types. Mean overlap in proportional use of different forest types between individual spotted owls and barred owls in adjacent territories was 81% (range ¼ 30...

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Section: Discussionmentioning

confidence: 99%

Competitive interactions and resource partitioning between northern spotted owls and barred owls in western Oregon

Wiens

Anthony

Forsman

2014

Wildlife Monographs

Self Cite

122

239

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show abstract

“…We excluded areas above 1524 m elevation from analyses because no Spotted or Barred owls have been detected above that elevation in our study area. Spotted Owls may respond less frequently to survey calling in areas where Barred Owls are present (Olson et al 2005, Crozier et al 2006, resulting in non-detection of resident Spotted Owls. Additionally, Spotted Owl sites may be vacant for a number of years but then recolonized (T. Fleming pers.…”

Section: Methodsmentioning

confidence: 99%

Spotted Owls, Barred Owls, and Late-Successional Reserves

Pearson¹,

Livezey

2007

Journal of Raptor Research

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“…However, similar response frequencies between treatments and an increased capacity for northern spotted owl strikes to cause head injury did not meet predictions of the Acquiescence Hypothesis. The Acquiescence Hypothesis has also been partially supported by previous studies where northern spotted owls responded less often to broadcast calls from conspecifics after barred owl calls were broadcast in an area (Crozier et al, 2006) and northern spotted owls had lower detection probabilities in the presence of barred owls (Bailey et al, 2009;Olson et al, 2005). Crozier et al (2006) also found that northern spotted owls responded less often in areas with higher barred owl density, suggesting that northern spotted owls may exhibit shifts in vocal behavior in the presence of barred owls.…”

Section: Acquiescence Versus Exclusion Hypothesesmentioning

confidence: 60%

“…Also, northern spotted owls may learn to exhibit short-term behavioral avoidance to reduce the frequency of agonistic interactions with barred owls. Some evidence suggests that this might already be occurring in some areas of co-existence, with northern spotted owls calling less frequently in the presence of barred owls and subsequently decreasing the rate at which barred owls detect these individuals (Crozier et al, 2006).…”

Section: Competitive Exclusion Of Northern Spotted Owls?mentioning

confidence: 99%

Who hits and hoots at whom? Potential for interference competition between barred and northern spotted owls

Lanen

Franklin

Huyvaert

et al. 2011

Biological Conservation

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The northern spotted owl (Strix occidentalis caurina) is a controversial species in the Pacific Northwest that is listed as threatened under the Endangered Species Act. The barred owl (Strix varia), a species historically restricted to eastern North America, has recently expanded its range to completely overlap that of the northern spotted owl. Recent evidence suggests that barred owls may compete with northern spotted owls and may be one cause for recent declines in some northern spotted owl populations. Our focus was to examine whether barred owls have the potential to competitively exclude northern spotted owls from their territories through interference competition. We used a playback experiment to quantify aggressive vocal and physical behavior of barred and northern spotted owls during territorial defense. Experimental trials consisted of displaying northern spotted or barred owl taxidermy mounts, and broadcasting recorded vocalizations of the corresponding species, in both barred and northern spotted owl territories. The frequency of interspecific interactions was lower compared to intraspecific interactions between northern spotted owls alone. However, barred owls responded with higher levels of vocal and physical aggression than did northern spotted owls when agonistic interspecific interactions occurred. Our results suggest that barred owls are likely to assume the dominant role during interspecific interactions with northern spotted owls. Thus, interference competition is a plausible mechanism by which barred owls could contribute to observed population declines of northern spotted owls in areas where the species co-occur.

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Does the Presence of Barred Owls Suppress the Calling Behavior of Spotted Owls?

Cited by 36 publications

References 13 publications

Competitive interactions and resource partitioning between northern spotted owls and barred owls in western Oregon

Competitive interactions and resource partitioning between northern spotted owls and barred owls in western Oregon

Spotted Owls, Barred Owls, and Late-Successional Reserves

Who hits and hoots at whom? Potential for interference competition between barred and northern spotted owls

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