zngmqk19
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 Posted: Sat 18:39, 19 Mar 2011 Post subject: owl reproductive output is variable ed hardy bags |
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Spotted owl reproductive output is variable. In Douglas-fir/hardwoods, mixed-conifer, and Oregon white oak (Quercus garryana) forests of northwestern California, average annual northern spotted owl reproductive output ranged from 0.150 to 0.810 fledged young/pair [8].[link widoczny dla zalogowanych] The percentage of years (n=5) in which pairs in coniferous forests and Douglas-fir/hardwood woodlands produced at least 1 fledging ranged from 0 to 80% [33]. In a study of both northern and California spotted owls in California, fledging rate varied from 0 to 100% over 8 years and 2 study sites [34]. In oak woodland and coniferous forests of the southern Sierra Nevada, the average annual reproductive output of California spotted owl varied from 0.07 to 1.67 young/pair over a 9-year period [20].
Several factors contribute to spotted owl's variable reproductive success. For instance, spotted owl pairs do not breed every year [30]. Over a 5-year period in western Oregon,[link widoczny dla zalogowanych], the percentage of nesting northern spotted owls averaged 62% and ranged from 16% to 89% [30].
Another source of the variation in reproductive output is spotted owl age. Spotted owls are typically reproductive by 3 years of age. They may, albeit rarely, breed as young as 1 year old [30][35]. In Washington and Oregon,[link widoczny dla zalogowanych] the majority of radio-marked northern spotted owls were paired by 2 years of age, and recruitment of banded owls into the territorial population occurred at an average age of 2.4 years [35]. The average number of fledglings produced by 1-year-old northern spotted owls in 11 study areas across their range was 0.074 fledglings/territorial female. Two-year-olds fledged an average of 0.208 young/territorial female, and individuals 3 years and older fledged an average of 0.372 young/territorial female [36]. Increased reproductive output of northern spotted owls 3 years or older compared to juveniles and subadults (1 and 2 year olds) has been observed in several study areas [8][37]. In Arizona and New Mexico, Mexican spotted owls 2 years and older had greater fecundity than 1-year-olds
Northern spotted owls in nonglaciated montane slopes of the eastern Cascade Range of Washington averaged 0.57 fledglings/year, significantly (P<0.01) more than those in glacially scoured regions, which averaged 0.38 fledgling/year? [7]. [link widoczny dla zalogowanych] In the Sacramento Mountains of New Mexico, Mexican spotted owls in mixed-conifer forests had higher average annual reproductive output (0.38 female fledged/territory) than those in ponderosa pine and Colorado pinyon-alligator juniper (Pinus edulis-Juniperus deppeana) woodlands (0.13 female fledged/territory)? [40].
Weather and food have a strong influence on spotted owl reproductive success. Good weather, such as lower precipitation and higher minimum temperatures during the nesting season, is associated with higher reproduction
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