Is the decline of Burrowing OwlsSpeotyto cuniculariain prairie Canada linked to changes in Great Plains ecosystems?

Abstract

SummaryWe examined population and ecosystem patterns hoping to inform conservation strategies for Burrowing OwlsSpeotyto cuniculariain Canada. The owls chose moderately to heavily grazed grasslands for nesting and roosting, and avoided cultivated fields. Where grassland patches were isolated in 90% cultivation, owls dispersed later, for shorter distances and less often. Mortality rate during the 5-month study was high (adult ratio 0.45, juveniles 0.55), which may contribute to local declines. Additional mortality may occur on migration and during winter. We extrapolate from local effects (loss of grassland habitat with burrows for roosting, and ~2% “incidental” predation) to suggest that such changes detrimental to the owls occur throughout the central Great Plains ecosystem which the owls occupy year-round. The changes include ecosystem processes such as plant succession, owl dispersal and predation. These changes are likely to be irreversible on a scale that would be required to help this owl. The species may face extinction in Canada, at the northern limit of its range.

Pre-Migratory Movements by Juvenile Burrowing Owls in a Patchy Landscape

“…Thus, limits to dispersal may play a role in limiting habitat occupancy and, ultimately, population size. Pre-migratory movements of juvenile Burrowing Owls in large tracts of grassland Avian Conservation and Ecology -Écologie et conservation des oiseaux 2(2): 4 http://www.ace-eco.org/vol2/iss2/art4/ occur in a slow but incremental fashion away from their original nest site, with juveniles using several satellite burrows before migration (Clayton andSchmutz 1999, King andBelthoff 2001). These movements presumably result in juvenile owls gaining knowledge of the natal landscape before migration, and may aid in decision making about locations they might return to in subsequent breeding seasons.…”

Effects of management practices on grassland birds: Burrowing Owl

“…More frequently, Burrowing Owls reuse traditional nesting areas without necessarily using the same burrow (Wedgwood 1976, Gleason 1978, Otnes 1980, Rich 1984, Plumpton 1992, Haug et al 1993, Pezzolesi 1994, De Smet 1997, Plumpton and Lutz 1998, Clayton and Schmutz 1999, Lutz and Plumpton 1999. Burrow fidelity and nest area re-use may be enhanced if birds are reproductively successful during the previous year (Pezzolesi 1994, De Smet 1997, Feeney 1997, Plumpton and Lutz 1998.…”

“…Create a patchwork of reserves with sustainable land uses in surrounding buffer areas (Clayton and Schmutz 1999). Because owls forage over tall grass and nest and roost in short grass, a mosaic of habitats may be important in conserving habitat.…”

“…They use well-drained, level to gently sloping areas characterized by sparse vegetation and bare ground such as moderately or heavily grazed pasture (Salt and Wilk 1958;Bent 1961;Grant 1963Grant , 1965James and Seabloom 1968;Stewart 1975;Wedgwood 1976;Haug 1985;MacCracken et al 1985a;Haug and Oliphant 1987;Stockrahm 1995). Burrowing Owls breed in native prairie (Bent 1961, Butts 1973, Wedgwood 1976, Konrad and Gilmer 1984, Faanes and Lingle 1995, Clayton and Schmutz 1999, as well as in tame pasture, hayland, fallow fields, road and railway rights-of-way, and in a number of urban habitats (Scott 1940, Bue 1955, Hall 1961, Richards 1972, Butts 1973, Zarn 1974, Konrad and Gilmer 1984, Haug 1985, Haug and Oliphant 1987, James et al 1990, Haug et al 1993. Although Burrowing Owls occasionally nest in cropland (Grant 1965, Butts 1973, Schmutz and Moody 1989, John and Romanow 1993, most of these nests probably fail when the land is cultivated (T. I. Wellicome, University of Alberta, Edmonton, Alberta, pers.…”

“…In Alberta, fewer (41% of 34) nest sites than non-nest sites (59%) occurred within 0.5 km of cropland (Schmutz 1997). Clayton and Schmutz (1999) examined habitat selection of breeding owls in southeastern Alberta and on the Regina Plains, Saskatchewan. Land use was categorized into native pasture, re-seeded pasture, cultivation, and a miscellaneous category.…”