Starvation in young Tawny Owls

Hirons, G. J. M.; Hardy, Anthony; Stanley, P.I.

doi:10.1080/00063657909476618

Cited by 21 publications

(9 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Their food cries make them easily registrable by researchers (Muir 1954;Southern, Vaughan & Muir 1954). In August-September (exceptionally till November), they disperse and suffer considerable mortality, mainly from starvation, during the period of early independence (Olsson 1958;Hirons, Hardy & Stanley 1979). In August-September (exceptionally till November), they disperse and suffer considerable mortality, mainly from starvation, during the period of early independence (Olsson 1958;Hirons, Hardy & Stanley 1979).…”

Section: Suggested That Stable Numbers and Persistent Life-time Terrimentioning

confidence: 99%

Tawny Owl (Strix aluco) Predation in a Pristine Deciduous Forest (Bialowieza National Park, Poland)

Jędrzejewski¹,

Jędrzejewska²,

Szymura³

et al. 1996

The Journal of Animal Ecology

View full text Add to dashboard Cite

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. Tawny owl Strix aluco predation on its main prey (bank voles Clethrionomys glareolus and yellow-necked mice Apodemusflavicollis) and alternative prey (shrews, birds, and amphibians) was studied in the pristine deciduous forests of eastern Poland during a 7-year period (1985/86-1991/92) that included 5 years of moderate densities of rodents and 2 years of outbreak and crash triggered by a heavy seed crop of oak, hornbeam, and maple. 2. Number of resident owls was rather stable; 45-53 owls per 10km2 in years of moderate and high rodent numbers, and 33 owls per 10km2 in a rodent crash year. Numerical response of owls to rodent densities was log shaped. 3. In the cold season, the dietary (functional) response of owls to autumn density of rodents was of type II (logarithmic). No functional response of owls was observed to shrew numbers. Owl hunting rate on amphibians in winter was shaped by the mean temperature of the cold season and, to a lesser extent, by availability of rodents. Owl hunting rate on birds was inversely related to rodent abundance. 4. During the seven cold seasons (1 October-15 April), tawny owls removed 3-19 mice, 2-18 voles, 2-7 shrews, 0-2 birds, and 1-9 frogs from an average hectare of the forest. Total predation on rodents (N prey removed ha-1) was lowest during the crash of rodents and highest during the outbreak; it grew logarithmically with increasing density of rodents. On average, in the cold season, tawny owls removed 54% of autumn numbers of mice and 40% of those of bank voles. Percentage predation peaked at 22 rodents ha-l in autumn. At both higher and lower prey densities, percentage predation declined. 5. The percentage predation curve of tawny owl was compared to the frequency distribution of autumn densities of rodents in Bialowieza (from 23-year trapping). The heaviest predation fell to prey densities that occurred most frequently. 6. In summer seasons (July-September 1988-92), tawny owls (both adults and juveniles) consumed 0-5-19 mice and 0-4-10 voles from an average hectare. Percentage predation varied from 6% to 74% of rodent numbers recorded in July, but rodents bred rapidly and recruitment usually more than compensated for losses due to predation. 7. Total predation by tawny owls on rodents was quite stable as a consequence of high stability of owl numbers. Percentage predation, although heavy in all years except for rodent outbreak, was not density-dependent and therefore tawny owls did not regulate rodent numbers. In the deciduous forests of Bialowieza National Park, the pattern of predation by tawny owl, a ...

show abstract

Section: Suggested That Stable Numbers and Persistent Life-time Terrimentioning

confidence: 99%

Tawny Owl (Strix aluco) Predation in a Pristine Deciduous Forest (Bialowieza National Park, Poland)

Jędrzejewski¹,

Jędrzejewska²,

Szymura³

et al. 1996

The Journal of Animal Ecology

View full text Add to dashboard Cite

show abstract

“…The average weight of female Tawny owls at the start of incubation is probably around 580 g (Fig. 2), but when they cease to brood young they may weigh as little as 440 g which is only 60 g more than the weight at which female owls begin to starve (Hirons, Hardy & Stanley, 1979). For an owl weighing 510 g (the mid point between the weight at the start of incubation and that when brooding ceases), the daily energy requirement (0.82 x MEm) would be 57.1 kcals.…”

Section: The Ration Of Prey Brought To the Nest By Males During Incubmentioning

confidence: 99%

The importance of body reserves for successful reproduction in the Tawny owl (Strix aluco)

Hirons

1985

Journal of Zoology

View full text Add to dashboard Cite

With 3 figures in the text)One-quarter of Tawny owl nests fail to hatch young, mainly because the eggs are chilled and/or deserted. In 1973-74 automatic photography was employed at four nests near Oxford to relate the incubation behaviour of females to the ration of prey supplied to them by their mates. The eggs did not hatch in two nests and young fledged from only one of the others. Females were less attentive at the nests which failed during incubation and on average received less prey, but even at successful nests there were some nights when the female was supplied with less than her estimated daily food requirement. Female Tawny owls accumulate large reserves of fat and protein before laying. These buffer against any temporary inability of the male to provide sufficient food during incubation, and enable the female to stay on the nest rather than hunt for herself and risk the eggs becoming chilled. When prey are scarce, many females do not lay at all, and the ultimate factor determining whether breeding takes place may be the female's ability to acquire body reserves sufficient to provide a chance of breeding successfully.

show abstract

“…In studying the condition of a bird, such as its total fat content, total protein content and the weight of the pectoral muscles have been used (King et al 1965, George and Berger 1966, Blem 1976, Visser 1978, Hirons et al 1979. However, in avial ecological studies it is often necessary to be able to estimate the condition of the birds without killing them.…”

Section: Introductionmentioning

confidence: 99%

Criteria for Estimating the Condition of Birds: Relationship between Fat Content and Body Size Dimensions in the Hooded Crow Corvus corone cornix

Slagsvold¹

1982

Ornis Scandinavica

View full text Add to dashboard Cite

show abstract

Starvation in young Tawny Owls

Cited by 21 publications

References 13 publications

Tawny Owl (Strix aluco) Predation in a Pristine Deciduous Forest (Bialowieza National Park, Poland)

Tawny Owl (Strix aluco) Predation in a Pristine Deciduous Forest (Bialowieza National Park, Poland)

The importance of body reserves for successful reproduction in the Tawny owl (Strix aluco)

Criteria for Estimating the Condition of Birds: Relationship between Fat Content and Body Size Dimensions in the Hooded Crow Corvus corone cornix

Contact Info

Product

Resources

About