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

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.

Spatial patterns of burrowing owl (Speotyto cunicularia) nests within black-tailed prairie dog (Cynomys ludovicianus) towns

The spatial patterns of burrowing owl (Speotyto cunicularia) nests in black-tailed prairie dog (Cynomys ludovicianus) towns were examined in the Nebraska panhandle during the spring and summer of 1989–1991. Because of higher nest densities (≥ 0.20 nests/ha) and internest distance requirements, it was not possible for owls to demonstrate patterns other than random in the smaller (< 35 ha) prairie dog towns. In large prairie dog towns (> 35 ha), burrowing owls were less dense (≤ 0.20 nests/ha), and choice of nest sites by pairs resulted in a clumped nest distribution. In prairie dog towns < 35 ha, nearest neighbor distance was positively related to prairie dog town size, whereas no relationship was found between prairie dog town size and nearest neighbor distance for towns ≥ 35 ha. Burrow availability was not responsible for clumping. Ample burrows were available throughout the towns in 1990 and 1991. In 1991, two towns with clumped distributions of owls showed no differences in numbers of burrows around active owl nests and random burrows throughout the towns. Other possible explanations for clumping, including food availability and reduced predation risk, are discussed.