The Spacing of Black Eagles in the Matopos, Rhodesia

Gargett, Valerie

doi:10.1080/00306525.1975.9639380

Cited by 28 publications

(22 citation statements)

References 36 publications

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“…A d d solden ea@ in neSt tree @hot0 ig Hans Peeters) preferred foraging habitat (Gargett 1975). In Sweden, the distance to the nearest neighbor was greater in forested areas than in mountainous regions where prey densities and prey availability were greater (Tjernberg 1985).…”

Section: Golden Eagle Population Project 29mentioning

confidence: 99%

“…Gargett's (1975) study of black eagles in Rhodesia showed that territorial aggression was greatest towards floaters (non-breeding adults); encounters with established, neighboring pairs were few. Tjernberg (1985) reported that nearest neighbor distances between pairs in Sweden averaged 10, 16, and 17 km, depending on the richness of habitat; he also cited reports of average distances in other areas: 7-8 km (Scotland), 7-25 krn (France), and 10 km in Switzerland.…”

Section: Golden Eagle Population Project 29mentioning

confidence: 99%

“…Floaters are adults which, in order to breed, must either wait for a vacancy or forcefully evict it territory owner (Gargett 1975). Floating segments are well known in golden eagle populations (Haller 1982, Tjernberg 1985 and in those of other raptors (Hunt 1988, McCrary et al 1992.…”

Section: Population Segmentsmentioning

confidence: 99%

“…Brown and Watson (1964) believed that territory size was adequate to provide food in all seasons and in different years and that breeding density was little changed over many years, and not related to prey numbers. Gargett (1975) described the dynamics of 18 black eagle territories which, over a three year period, remained constant in number. A vacated territory was incorporated by neighbors, a new territory was established partially in a vacant area and partially by appropriating portions of two adjacent territories.…”

Section: Spacing Of Pairsmentioning

confidence: 99%

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A pilot golden eagle population study in the Altamont Pass Wind Resource Area, California

Hunt

1995

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NREL/TP-44 1 -7821 UC Category: 1 2 1 0 DE95009220This pilblici~Iioll wus reproduced from the best iivaili\ble camera-ready copy submilled by the subcontractor and received no editorial review at NREL. NOTICEThis report was prepared as an account of work sponsored by an agency of the United States government.Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof GOLDEN EAGLE POPULATION PROJECT i EXECUTIVE SUMMARYDuring 1994, the Predatory Bird Research Group, University of California, Santa Cruz, conducted a preliminary field investigation of the ecology of golden eagles (Aquila chrymem) in the vicinity of the Altamont Pass Wind Resource Area (WRA). The facility contains about 6,500 wind turbines on 189 km2 just east of San Francisco Bay in California. Grassland and oak savanna habitats surrounding the WRA support a substantial population of golden eagles. Each year, the U.S. Fish and Wildlife Service receives reports from the wind industry of about 30 golden eagle casualties occurring at the WRA, with over 90 percent attributed to collisions with wind turbines. The purpose of this pilot study was to clarify and set in motion a research program that will identify (1) the effect of turbine-related mortality on the golden eagle population, (2) factors attracting eagles to the WRA, and (3) conditions that increase the risk of turbine strikes.To show the distribution of the population potentially impacted and to obtain survival data, we radio-tagged 31 adult and subadult eagles in the WRA vicinity during January and February 1994 and an additional 25 juveniles from nests surrounding the WRA in spring. Each transmitter contained a mortality sensor and was expected to last five years. Throughout 1994, we determined the location and status of each eagle in twice-weekly airplane roll-call surveys.Of the 31 winter-tagged eagles, 5 were members of pairs breeding near the WRA. Of the remaining 26 birds, 19 were subadults and seven were non-breeding adults (floaters). Over the course of the year, four (15 %) of the 26 non-breeders either departed the region or their radios failed. The remainder traveled within the northern Diablo Range which extends from the Qakland Hills southeast to San Luis Reservoir, an area of about 3,500 km2, for which we developed a digitized (GIS) vegetation map from satellite photographs. Our findings suggest that at least three-quarters of the golden eagles frequenting the WRA vicinity in winter are yearround residents of the Diablo Range.T...

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Section: Golden Eagle Population Project 29mentioning

confidence: 99%

Section: Golden Eagle Population Project 29mentioning

confidence: 99%

Section: Population Segmentsmentioning

confidence: 99%

Section: Spacing Of Pairsmentioning

confidence: 99%

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A pilot golden eagle population study in the Altamont Pass Wind Resource Area, California

Hunt

1995

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“…Often the adults hit the young, with their talons interlocked, making them lose their balance and lose height. This behaviour has been observed in other raptor species (Rowe 1947, Cade 1960, Gargett 1972,1975, Steyn 1973, Sherrod 1983, Robertson 1984 and is usually interpreted as aggression from adults to young. T h e first signs of aggression were highly correlated in time with the highest intensity of autumn aerial display in the different pairs studied (r7 = 0.98, P < 0.01), as well as with the termination of parental feedings (r7 = 0.90, P < 0.01 ; Table 3).…”

Section: Parental Aggression Towards Youngmentioning

confidence: 99%

Parental care and the transition to independence of Spanish Imperial Eagles Aquila heliaca in Doñana National Park, southwest Spain

Alonso

González

Heredia

et al. 1987

Ibis

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T h e behaviour of five broods of radio-tagged Spanish Imperial Eagles Aquila helium udalberti was studicd in Dofiana National Park, Spain during the post-fledging period. T h e distance between perching sites and nest, the mean flight duration and distance, the percentage o f time spent flying and the home range all increased exponentially with age. As the young got older, the parents spent less time in their vicinity. Young were not seen hunting, but depended on their parents for food. They begged and chased their parents throughout the post-fledging period, with hrgher intensity at the end. Nevertheless, the adults became progressively more reluctant to feed them, as reflected in the dccrease in feeding frequency and in the number of approaching flights towards the young. At the end of the post-fledging period, adults often performed aerial displays and frequently chased their offspring. T h e age of independence of the different young studied varied between 123 and 145 days. T h e correlations between individual independence and the dates when the young were last fed by their parents, and when the highest intensity of parental aggressive behaviour occurred, were higher than correlations with the variables related to the maturation of flying. Therefore, it is suggested that parental 'meanness' and aggressive behaviour may be the factors determining the date of juvenile independence and dispersal from the home territory.

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Social organization and foraging in emballonurid bats

Bradbury,

Vehrencamp

1977

Behav Ecol Sociobiol

246

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1. A general model of mating system evolution in mammals is developed, which takes into account the different male strategies of resource defense, female group defense, and male mating aggregations. The critical environmental variables determining differential defensibility of females and resources are identified by generalizing the resource defense model of Orians (1969). The model is then applied to available data on African antelopes (Jarman, 1974) to establish a set of hypothetical relations between certain patterns of habitat use and mating structures. The resulting relations are only likely to apply to species in which food determines female dispersion and in which any resource defense exhibited by males is directed towards food supplies.2. The relations developed for antelopes are then compared to recently published data on mating systems in five neotropical emballonurid bats (Bradbury and Vehrencamp, 1976 a).3. Antelopes and the bats are found to share the following features. Species living in wet and stable forests tend to be fine-grained socially and to have groups consisting of monogamous pairs or nested male-female territories. Species in more seasonal habitats show an inverse relation between the size stability of groups and the duration of use of a given foraging site. As the model predicts, in both groups resource defense occurs where groups are least stable and female defense where groups are most stable. Also as the model predicts, the numbers of females accessible to each male and the number of reproductive males per group can be anticipated in each of the two taxa wherever sufficient data for the critical variables are available.4. Antelopes and bats differ in the following ways. Whereas body size is a good predictor of antelope habitat use and social dispersions, it is a poor predictor for emballonurid patterns. Similarly, although the numbers of females per male generally increase with group size in antelopes, this correlation does not hold for the bats in this study. These differences lead to the conclusion that application of the general model cannot be simplified

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The Spacing of Black Eagles in the Matopos, Rhodesia

Cited by 28 publications

References 36 publications

A pilot golden eagle population study in the Altamont Pass Wind Resource Area, California

A pilot golden eagle population study in the Altamont Pass Wind Resource Area, California

Parental care and the transition to independence of Spanish Imperial Eagles Aquila heliaca in Doñana National Park, southwest Spain

Social organization and foraging in emballonurid bats

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