Reversed Size Dimorphism in Birds of Prey, Especially in Tengmalm's Owl Aegolius funereus: A Test of the "Starvation Hypothesis"

Korpimäki, Erkki

doi:10.2307/3676820

Cited by 41 publications

(35 citation statements)

References 23 publications

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“…Decreasing male hunting time per day (e.g. by rain or wind, VILLAGE, 1983;RIJNSDORP et al, 1981) (NEWTON & MARQuISS, 1984), ospreys (POOLE, 1985), Ural owls Strix uralensis (PIETIÄINEN et al, 1986) and Tengmalm's owls Aegolius funereus (KORPIMÄKI, 1986a). The advance in laying date of kestrel pairs given extra food is in agreement with the majority of surplus feeding experiments in the field in 18 species (Table 1).…”

Section: Laying Datesupporting

confidence: 64%

Family Planning in the Kestrel (Falco Tinnunculus): the Proximate Control of Covariation of Laying Date and Clutch Size

Daan

Dijkstra

Tinbergen

1990

Behav

269

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The time in spring when a male kestrel rapidly increases his daily hunting time and his hunting yield, and thereby the amount of food delivered to the female, determines the date when she lays the first egg. Food experiments in free-living and captive kestrels gave a significant advance in laying date. Clutch size, which decreases with progressive laying date, did not change independent of date in response to food manipulation. These effects are in agreement with most other feeding experiments. Photoperiod experiments in kestrels advanced the reproductive cycle in constant long days, and a similar seasonal decline in clutch size was found. It seems that there is an internally preprogrammed decrease in clutch size within an annual "reproductive window". A proximate control model for the seasonal decline of clutch size is proposed, modified from an earlier model by HAFTORN (1985). This incorporates an increasing tendency to incubate the first eggs with progression of the season, an egg contact-incubation positive feedback loop, and the resorption of further follicles in the ovary when the laying female incubates 50% of the time. This follicle resorption fixes the clutch size ca. four days before the last egg is laid. the 50% incubation level is reached earlier in late females and consequently resorption starts earlier and the resulting clutch is smaller than in early females. Experiments in kestrels with removal and addition of eggs, in combination with measurements of incubation behaviour are discussed in relation to the model. Plasma prolactin data of female kestrels show that this hormone is a serious candidate for a physiological component relaying time of year in our model for clutch size regulation.

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Section: Laying Datesupporting

confidence: 64%

Family Planning in the Kestrel (Falco Tinnunculus): the Proximate Control of Covariation of Laying Date and Clutch Size

Daan

Dijkstra

Tinbergen

1990

Behav

269

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“…In general, the species is characterized as nomadic, at times exhibiting year-round residence within a stable home range but dispersing in years of poor prey populations (Mysterud 1970, Wallin and Andersson 1981, Sonerud et al 1988, Schelper 1989. Korpimaki (1986b) recognized a trend of increased population fluctuations in more northern populations associated with a greater degree of nomadism. He related the pattern to winter snow depth and range of prey available to the owls in winter.…”

Section: Annual Movements and Site Tenacity Of Adultsmentioning

confidence: 99%

“…In southern Fennoscandia males are resident and females and juveniles nomadic. In northern Sweden, both adults and juveniles exhibit nomadism (Korpimaki 1986b).…”

Section: Annual Movements and Site Tenacity Of Adultsmentioning

confidence: 99%

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Flammulated, boreal, and great gray owls in the United States: A technical conservation assessment

Hayward¹,

Verner²

1994

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Flammulated (Otus flammeolus), boreal (Aegolius funereus), and great gray (Strix nebulosa) owls occur over a broad portion of North America and each is designated as a "sensitive species" in four or more USDA Forest Service regons. The insectivorous flammulated owl is a neotropical migrant requiring suitable wintering habitat in the extreme southwestern United States, Mexico, and Central America as well as breeding habitat in the mountains of the western United States. Flammulated owls breed predominantly in yellow-pine (Pinus ponderosa and Pinus jefieyi) forests and are cavity nesters. The mature and older ponderosa pine forests used as breeding habitat by flammulated owls have changed during the past century due to fire management and timber harvest. In contrast, the boreal owl is a nomadic, small mammal specialist that occurs as an "island" species occupying subalpine and boreal forests. Movements among populations are probably important to boreal owl persistence, and coordinated management of disjunct populations in different Forest Service regions may be important. While the boreal owl's high altitude spruce-fir forests have remained relatively undisturbed in the past, they are coming under increasing harvest pressure as the stock of lower elevation older stands are depleted or reserved. Great gray owls in the western United States occur in mid to high elevation conifer forests. These owls usually nest in mature and older forest stands using existing raptor nests or tops of broken trees and snags for a nest platform. The species' requirement of a secure nesting platform leads to one potential ecological limitation on population size. Prey availability is the other factor thought to limit populations. Flammulated and boreal owls may face significant conservation problems in the absence of conservation planning. Both owls are associated with older forest habitats. Limited research on these species indicates that their demography and life history coupled with their fairly narrow habitat associations make them vulnerable to habitat change. Current forest management practices in many areas (i.e., stand replacement systems) remove quality habitat for these species. Therefore, on at least a local basis, persistence of these species could be in jeopardy, even in the short term. Long-term concerns are greater because the habitats that seem most important to these species require one to two centuries to regenerate. Furthermore, the population biology of both species necessitates across-region planning to facilitate effective conservation planning. Based on limited information, the persistence of great gray owl populations in the United States over both the short and long-term is more certain. Great gray owl foraging habitat use is more compatible with current forest management practices. Our understanding of the ecology and biology of these three species is not sufficient to produce a conclusive assessment of their conservation status. The enclosed assessments, however, give a sufficiently clear picture of ea...

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“…Great Gray Owls exhibit the most extreme RSD observed among Holarctic owls (Earhart and Johnson 1970;Mueller 1986). Nearly two dozen hypotheses have been proposed for the evolution of RSD in raptorial birds (Earhart and Johnson 1970;Amadon 1975;Andersson and Norberg 1981;Jehl and Murray 1986;Korpimäki 1986;Lundberg 1986;Mueller 1986Mueller , 1990Hakkarainen and Korpimäki 1991;Bildstein 1992;Krüger 2005). These can be roughly classified as (i) ecological hypotheses pertaining to niche partitioning and prey size, (ii) reproductive and physiological hypotheses, and (iii) behavioral hypotheses related to sexual dominance and pair formation.…”

Section: Introductionmentioning

confidence: 99%

Nutritional stress and body condition in the Great Gray Owl (Strix nebulosa) during winter irruptive migrations

et al. 2012

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The largest irruptive migration of the Great Gray Owl ( Strix nebulosa Forster, 1772) recorded since 1831 occurred in Minnesota, USA, during the winter of 2004–2005. We tested the hypothesis that morphometric indicators of nutritional stress covary with stable isotope signatures in a sample of 265 owls killed by vehicle collisions. The ratio of carbon to nitrogen in muscle (C/Nmuscle) was shown to be a reliable proxy of nutritional stress. δ13C values for liver and muscle were significantly higher in owls in poor condition, reflecting the depletion of lipid reserves in fasting individuals. On the other hand, δ15N values for liver and muscle were marginally lower or unchanged in owls in poor condition. Stomachs of emaciated owls were less likely to contain prey, implying that many nutritionally stressed individuals were too weak to hunt and were near the tipping point of irreversible fasts. In a broader context, sexual differences in the correlative relationships between stable isotope signatures, C/N, and body condition suggest that the consequences of reversed sexual size dimorphism extend to physiological processes during the nonbreeding season.

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Reversed Size Dimorphism in Birds of Prey, Especially in Tengmalm's Owl Aegolius funereus: A Test of the "Starvation Hypothesis"

Cited by 41 publications

References 23 publications

Family Planning in the Kestrel (Falco Tinnunculus): the Proximate Control of Covariation of Laying Date and Clutch Size

Family Planning in the Kestrel (Falco Tinnunculus): the Proximate Control of Covariation of Laying Date and Clutch Size

Flammulated, boreal, and great gray owls in the United States: A technical conservation assessment

Nutritional stress and body condition in the Great Gray Owl (Strix nebulosa) during winter irruptive migrations

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