We trapped more than 23,000 migrating raptors at Cedar Grove, Wisconsin during the autumns of 195... more We trapped more than 23,000 migrating raptors at Cedar Grove, Wisconsin during the autumns of 1953-1996, permitting accurate identification of age and sex. Adults migrated significantly later than juveniles in 8 of 10 species, and males migrated later than females in 7 species. We suggest that it is adaptive for adults and males to remain on breeding territories as long as possible. Adult Peregrine Falcons (Falco peregrinus) migrated before juveniles. There was no age difference in migration of Rough-legged Hawks (Buteo lagopus). Both species breed in the Arctic where the brief breeding season requires that adults leave as soon as possible so adults might then migrate more rapidly than juveniles. We compare our results with those of 16 other studies. Juveniles migrated significantly later than adults in 8 of 13 species at Falsterbo in southern Sweden (Kjellen 1992). Falsterbo is more than 12 latitude (1300 km) north of Cedar Grove and the breeding range of most of the species occurring there extends north of the Arctic Circle, where birds suffer from the same abbreviated breeding seasons as do the Peregrine Falcon and Rough-legged Hawk in North America. Adult females migrated after adult males in the two large species of Accipiter; this may be because the females, not the males, establish and maintain territory in these species. Received 16 April 1999, accepted 13 Feb. 2000.
Abstract: Over the last several decades, remote sensing has emerged as an effective tool to monit... more Abstract: Over the last several decades, remote sensing has emerged as an effective tool to monitor irrigated lands over a variety of climatic conditions and locations. The objective of this review, which summarizes the methods and the results of existing remote sensing studies, is to synthesize principle findings and assess the state of the art. We take a taxonomic approach to group studies based on location, scale, inputs, and methods, in an effort to categorize different approaches within a logical framework. We seek to evaluate the ability of remote sensing to provide synoptic and timely coverage of irrigated lands in several spectral regions. We also investigate the value of archived data that enable comparison of images through time. This overview of the studies to date indicates that remote sensing-based monitoring of irrigation is at an intermediate stage of development at local scales. For instance, there is overwhelming consensus on the efficacy of vegetation indices in id...
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, a... more 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.
Wing area, wing loading and other aerodynamic characteristics are particularly important for the ... more Wing area, wing loading and other aerodynamic characteristics are particularly important for the diurnal raptors, birds that spend considerable time on the wing or rely on agility in flight for the capture of prey. Brown and Amadon (1968) summarize data available on wing loading for various Falconiformes and list measurements for only 56 species. Of these 56, exactly half of the wing loadings are based on a sample of only one, both sexes were measured for only seven species and age was not noted for any. In this paper we examine age and sex differences in wing area, wing loading and other aerodynamic characteristics of Sharp-shinned Hawks (Accipiter striatus) based on a sample of 255 wings and 108 tails. The hawks were captured in a variety of traps (see Bub 1974) at the Cedar Grove Ornithological Station, on the western shore of Lake Michigan near Cedar Grove, Sheboygan Co., Wisconsin. A description of the Cedar Grove region can be found in Mueller and Berger (1966) and an account ...
researchers are too busy to be instructors. Serious students of hawk migration usually concentrat... more researchers are too busy to be instructors. Serious students of hawk migration usually concentrate their efforts at one locality and rarely visit other stations; we thus rarely have the opportunity to evaluate the abilities of other workers. Trappers and banders have the advantage of verifying some of their identifications with the bird in the hand. In our combined, more than 70 man-years of watching and trapping hawks, we have banded more than 6000 Accipiters and observed many thousands more. During migration we trap more than 20 per cent of the Accipiters we observe. Our expertise was not acquired quickly and easily. The first Cooper's Hawk (Accipiter cooperil) we caught, about 30 years ago, became a Broad-winged Hawk (Buteo platypterus) after an embarrassingly long examination in the hand.
... By HELMUT C. MUELLER, DANIEL D. BERGER, AND GEORGE ALLEZ The Goshawk (Accipiter gentilis), th... more ... By HELMUT C. MUELLER, DANIEL D. BERGER, AND GEORGE ALLEZ The Goshawk (Accipiter gentilis), the largest and least sexually dimor-phic member of the genus in North America (Storer, 1966), shows an increase in wing length and weight and a decrease in tail length ...
Page 1. AGE AND SEX VARIATION IN THE SIZE OF GOSHAWKS BY HELMUT C. MUELLER, DANIEL D. BERGER, AND... more Page 1. AGE AND SEX VARIATION IN THE SIZE OF GOSHAWKS BY HELMUT C. MUELLER, DANIEL D. BERGER, AND GEORGE ALLEZ We have shown that it is possible to determine the sex of live Goshawks (Accipiter gentilis ...
We trapped more than 23,000 migrating raptors at Cedar Grove, Wisconsin during the autumns of 195... more We trapped more than 23,000 migrating raptors at Cedar Grove, Wisconsin during the autumns of 1953-1996, permitting accurate identification of age and sex. Adults migrated significantly later than juveniles in 8 of 10 species, and males migrated later than females in 7 species. We suggest that it is adaptive for adults and males to remain on breeding territories as long as possible. Adult Peregrine Falcons (Falco peregrinus) migrated before juveniles. There was no age difference in migration of Rough-legged Hawks (Buteo lagopus). Both species breed in the Arctic where the brief breeding season requires that adults leave as soon as possible so adults might then migrate more rapidly than juveniles. We compare our results with those of 16 other studies. Juveniles migrated significantly later than adults in 8 of 13 species at Falsterbo in southern Sweden (Kjellen 1992). Falsterbo is more than 12 latitude (1300 km) north of Cedar Grove and the breeding range of most of the species occurring there extends north of the Arctic Circle, where birds suffer from the same abbreviated breeding seasons as do the Peregrine Falcon and Rough-legged Hawk in North America. Adult females migrated after adult males in the two large species of Accipiter; this may be because the females, not the males, establish and maintain territory in these species. Received 16 April 1999, accepted 13 Feb. 2000.
Abstract: Over the last several decades, remote sensing has emerged as an effective tool to monit... more Abstract: Over the last several decades, remote sensing has emerged as an effective tool to monitor irrigated lands over a variety of climatic conditions and locations. The objective of this review, which summarizes the methods and the results of existing remote sensing studies, is to synthesize principle findings and assess the state of the art. We take a taxonomic approach to group studies based on location, scale, inputs, and methods, in an effort to categorize different approaches within a logical framework. We seek to evaluate the ability of remote sensing to provide synoptic and timely coverage of irrigated lands in several spectral regions. We also investigate the value of archived data that enable comparison of images through time. This overview of the studies to date indicates that remote sensing-based monitoring of irrigation is at an intermediate stage of development at local scales. For instance, there is overwhelming consensus on the efficacy of vegetation indices in id...
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, a... more 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.
Wing area, wing loading and other aerodynamic characteristics are particularly important for the ... more Wing area, wing loading and other aerodynamic characteristics are particularly important for the diurnal raptors, birds that spend considerable time on the wing or rely on agility in flight for the capture of prey. Brown and Amadon (1968) summarize data available on wing loading for various Falconiformes and list measurements for only 56 species. Of these 56, exactly half of the wing loadings are based on a sample of only one, both sexes were measured for only seven species and age was not noted for any. In this paper we examine age and sex differences in wing area, wing loading and other aerodynamic characteristics of Sharp-shinned Hawks (Accipiter striatus) based on a sample of 255 wings and 108 tails. The hawks were captured in a variety of traps (see Bub 1974) at the Cedar Grove Ornithological Station, on the western shore of Lake Michigan near Cedar Grove, Sheboygan Co., Wisconsin. A description of the Cedar Grove region can be found in Mueller and Berger (1966) and an account ...
researchers are too busy to be instructors. Serious students of hawk migration usually concentrat... more researchers are too busy to be instructors. Serious students of hawk migration usually concentrate their efforts at one locality and rarely visit other stations; we thus rarely have the opportunity to evaluate the abilities of other workers. Trappers and banders have the advantage of verifying some of their identifications with the bird in the hand. In our combined, more than 70 man-years of watching and trapping hawks, we have banded more than 6000 Accipiters and observed many thousands more. During migration we trap more than 20 per cent of the Accipiters we observe. Our expertise was not acquired quickly and easily. The first Cooper's Hawk (Accipiter cooperil) we caught, about 30 years ago, became a Broad-winged Hawk (Buteo platypterus) after an embarrassingly long examination in the hand.
... By HELMUT C. MUELLER, DANIEL D. BERGER, AND GEORGE ALLEZ The Goshawk (Accipiter gentilis), th... more ... By HELMUT C. MUELLER, DANIEL D. BERGER, AND GEORGE ALLEZ The Goshawk (Accipiter gentilis), the largest and least sexually dimor-phic member of the genus in North America (Storer, 1966), shows an increase in wing length and weight and a decrease in tail length ...
Page 1. AGE AND SEX VARIATION IN THE SIZE OF GOSHAWKS BY HELMUT C. MUELLER, DANIEL D. BERGER, AND... more Page 1. AGE AND SEX VARIATION IN THE SIZE OF GOSHAWKS BY HELMUT C. MUELLER, DANIEL D. BERGER, AND GEORGE ALLEZ We have shown that it is possible to determine the sex of live Goshawks (Accipiter gentilis ...
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