Analysis of Bald Eagle Spatial Use of Linear Habitat. Harmata, A., R. & Montopoli, G., J. Journal of Raptor Research, 35(3):207-213, 2001.
abstract   bibtex   
T.--Several techniques are available fi)r areal analysis of animal locations but few are applicable to those that use linear (i.e., riparian) habitats. Bald Eagles (Haliaeetus leucocephalus) often are associated with rivers and concentrate perch sites near shorelines. Distribution of cumulative proportion of perches by distance t•om most recently active nest sites determined by radio tracking were used to compare spatial use among five adult Bald Eagles breeding along the Snake River, Wyoming. Spatial Use Indicators (SUIs) were developed from logistic regression parameters in attempts to: (1) understand and model underlying processes from which the data may have emerged, (2) compare with simple descriptive statistical techniques to evaluate utility for presenting a clear, accurate representation of spatial use differences among eagles, and, (3) relate measures of eagle spatial use with long-term productivity of breeding areas. Distance Indicator (DI) was the distance from the nest including 50% of all detected perches used by a radio-tagged eagle and was representative of the size of the range. Slope Indicator (SI) was the slope of the fitted logistic regression curve at the DI (inflection point). SI was an indicator of linear dispersion of perch sites within the breeding area. Bald Eagles associated with more productive (>0.77 young per occupied nest over 11 years) breeding areas perched closer to nest sites (similar Dis) than eagles of their respective gender in a breeding areas of low productivity (<0.77 young per occupied nest). Male Bald Eagles in highly productive breeding areas dispersed perch sites more evenly throughout the breeding area (flat SI) than a male in a low production breeding area, while the opposite was true for females. Spatial use profiles derived from analysis of mean and confidence intervals and median and Interquartile Ranges were not as descriptive or illustrative of individual or group similarities or differences as SUIs. Logistic analysis suggested Zone II (primary tbraging zone) limits recommended in regional Bald Eagle management plans may need to be extended to maintain performance of highlyproductive pairs nesting along rivers. SUIs derived from logistic regression models of distance of locations from important habitat components may be indirect indicators of habitat quality and useful tools for describing and comparing spatial use of linear habitats of other species
@article{
 title = {Analysis of Bald Eagle Spatial Use of Linear Habitat},
 type = {article},
 year = {2001},
 keywords = {Greater Yellowstone Ecosystem,Haliaeetus leucocephalus,linear habitat,logistic retiression,radio-trackin,spatial use indicators},
 pages = {207-213},
 volume = {35},
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 abstract = {T.--Several techniques are available fi)r areal analysis of animal locations but few are applicable to those that use linear (i.e., riparian) habitats. Bald Eagles (Haliaeetus leucocephalus) often are associated with rivers and concentrate perch sites near shorelines. Distribution of cumulative proportion of perches by distance t•om most recently active nest sites determined by radio tracking were used to compare spatial use among five adult Bald Eagles breeding along the Snake River, Wyoming. Spatial Use Indicators (SUIs) were developed from logistic regression parameters in attempts to: (1) understand and model underlying processes from which the data may have emerged, (2) compare with simple descriptive statistical techniques to evaluate utility for presenting a clear, accurate representation of spatial use differences among eagles, and, (3) relate measures of eagle spatial use with long-term productivity of breeding areas. Distance Indicator (DI) was the distance from the nest including 50% of all detected perches used by a radio-tagged eagle and was representative of the size of the range. Slope Indicator (SI) was the slope of the fitted logistic regression curve at the DI (inflection point). SI was an indicator of linear dispersion of perch sites within the breeding area. Bald Eagles associated with more productive (>0.77 young per occupied nest over 11 years) breeding areas perched closer to nest sites (similar Dis) than eagles of their respective gender in a breeding areas of low productivity (<0.77 young per occupied nest). Male Bald Eagles in highly productive breeding areas dispersed perch sites more evenly throughout the breeding area (flat SI) than a male in a low production breeding area, while the opposite was true for females. Spatial use profiles derived from analysis of mean and confidence intervals and median and Interquartile Ranges were not as descriptive or illustrative of individual or group similarities or differences as SUIs. Logistic analysis suggested Zone II (primary tbraging zone) limits recommended in regional Bald Eagle management plans may need to be extended to maintain performance of highlyproductive pairs nesting along rivers. SUIs derived from logistic regression models of distance of locations from important habitat components may be indirect indicators of habitat quality and useful tools for describing and comparing spatial use of linear habitats of other species},
 bibtype = {article},
 author = {Harmata, Alan R. and Montopoli, George J.},
 journal = {Journal of Raptor Research},
 number = {3}
}
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