I asked earlier on TWEETERS: Why did the Barred Owl's range expand? Anthropogenic or natural causes?
Anthropgenic causes seem to get the nod in the literature (as Rob has pointed out) for their expansion across the Plains. But there is no evidence for or against logging as being involved in the Barred Owl range expansion.
Two of Kent Livesey's papers deal with this in a detailed way looking at the chronological progression of the Barred Owl's range in "Range Expansion of Barred Owls, Part I: Chronology and Distribution" (Livezey 2009a.pdf) and "Range Expansion of Barred Owls, Part II: Facilitating Ecological Changes" (Livezey 2009b.pdf). They're PDF files zipped up into an archive (without a password) on rapidshare.
http://rapidshare.com/files/447227260/Kent_Livezey_-_Spotted_Owl_papers.zip Two quote:
Elizabeth G. Kelly 2001 thesis for an MS in Wildlife Science at OSU ("Range Expansion of the Northern Barred Owl: an Evaluation of the Impact on Spotted Owls") has a nice intro and literature survey on the problem. It's a good intro to the issue.
The intro discusses the literature on hypotheses on why the Barred Owl's range expanded.
Quote:
> Historically, the range of the barred owl was limited to the eastern United States and eastern Canada (Bent 1938). In the early 1900s the range of the barred owl gradually expanded westward across Canada to British Columbia, then north into southeast Alaska and south into western Montana, Idaho, and Washington (Grant 1966, Campbell 1973, Reichard 1974, Shea 1974, Boxall and Stepney 1982, American Ornithologists' Union 1983, Sharp 1989, Dunbar et al. 1991, Wright and Hayward 1998). Barred owls first appeared in Oregon in 1974 (Taylor and Forsman 1976) and California in 1981 (Dark et al. 1998).>> Avifaunal range expansions in North America are common and have been attributed to anthropogenic or natural causes, or both (DeSante and George 1994, Johnson 1994, Root and Weckstein 1994). Woodlands that developed on the Great Plains during glacial periods became grasslands during warmer interglacial periods, thereby creating a barrier to the east-west movement of forest-dwelling species (Knopf 1986). More recently, changes in climate and natural forest cover, as well as tree planting and fire suppression, have created forest cover in grasslands and prairies that may have facilitated range expansions of forest birds (Ehrlich et al. 1988, Johnson 1994).>> Hypotheses that have been proposed to explain the range expansion of the barred owl across Canada include changes in climate (Johnson 1994), tree planting and development of riparian forest (Dark et al. 1998) or increased adaptation to coniferous forests (Boxall and Stepney 1982). Range expansions of other North American owls during the same period include the apparent expansion of the boreal owl (Aegoliusfunereus) from Canada southward to Colorado and northern New Mexico (Johnson 1994) and movements of barn owls (Tyto alba) into parts of British Columbia and California (DeSante and George 1994). In Europe, the tawny owl (Strix aluco) was first documented in Finland in 1875 and has since expanded its range northward, becoming common in southern Finland (Mikkola 1983).>> Although some have suggested that the range expansion of the barred owl into the Pacific Northwest was facilitated by forest management practices (Hamer 1988, Root and Weckstein 1994, Dark et al. 1998, Konig et al. 1999), there is no data to support or refute this hypothesis. In fact, the range expansion may have occurred regardless of forest management activities (Johnson 1994). Barred owls appear to be habitat generalists that can occupy a broad range of forest conditions, from highly fragmented forests in managed landscapes to pristine forests in Wilderness Areas (Shea 1974, Hamer 1988, Dunbar et al. 1991, Wright and Hayward 1998). In a study of habitat use by barred owls in the North Cascades of Washington, Hamer et al. (1989) found that although some individual barred owls selected young forests, the majority used old-growth, mature and young forests in proportion to availability. This suggested that in general, barred owls did not select any particular forest age class among those that were available to them. Thus, it is by no means clear that the range expansion of the barred owl has been facilitated by forest management activities. In any event, to state unequivocally that "Logging actually favours the expansion of this species... " (Konig et al. 1999:328) without mention of other equally probable hypotheses is misleading and possibly erroneous.
You can find the whole of her thesis here (including the references) in a PDF
http://ir.library.oregonstate.edu/dspace/bitstream/1957/9653/1/Kelly_Elizabet... Or read it in the Google PDF viewer online
http://docs.google.com/viewer?url=http%3A%2F%2Fir.library.oregonstate.edu%2Fd... BNA has some notes on historical range change (written in 2000). See the link for details and references.
http://bna.birds.cornell.edu/bna/species/508/articles/distribution http://bna.birds.cornell.edu.ezproxy.spl.org:2048/bna/species/508/articles/di... > Historical Changes
>> During twentieth century, range extended across boreal forest of Canada to montane forests of w. Canada and the w. U.S. (Grant 1966, Taylor and Forsman 1976, Sharp 1989). First record for s. Manitoba riparian forests in 1886 (Seton 1886). First recorded in Saskatchewan boreal forest 1948, and first nest 1961 (Houston 1959, 1961). Earliest record for Alberta, 1932 from the boreal forest (Preble 1941); first nest 1966 (Jones 1966). First record for British Columbia 1943 at Liard Crossing; first nest 1946; has spread south and west to coast (Grant 1966). By 1965, observed in ne. Washington; breeding by 1974 (Rogers 1966, Smith et al. 1997). Spread west across Cascade Mtns. by 1973 (Sharp 1989). First record for Idaho 1968 (Stephens and Sturts 1997) and Oregon 1974 (Gilligan et al. 1994). Expanded to nw. California 1981 (Evens and LeValley 1982), first breeding 1991 (Dark et al. 1998). Early record from Colorado, nest observed 1897 (Aiken 1900), and Wyoming, Crook Co. 1905 (Cooke 1909). Mechanism that possibly facilitated westward expansion not clear; explanations are anthropogenic in nature: fire suppression in boreal forest, increasing age of forest and size of trees (for nests), and establishment of riparian forests and planting of shelterbelts in n. Great Plains.
>> Populations and range reduced locally in e. Canada and U.S. due to forest clearing for agriculture over last 200 yr (Cadman et al. 1987, Erskine 1992, Jackson 1996, Nicholson 1997).
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