Daniel Twedt, Ph.D. (Former Employee)
Science and Products
Filter Total Items: 93
Distribution and composition of bottomland hardwood forests within the Mississippi Alluvial Valley Distribution and composition of bottomland hardwood forests within the Mississippi Alluvial Valley
No abstract available.
Authors
D.J. Twedt, W. Limp, M. Swan, C.R. Loesch
Point counts of birds in bottomland hardwood forests of the Mississippi Alluvial Valley: Duration, minimal sample size, and points versus visits Point counts of birds in bottomland hardwood forests of the Mississippi Alluvial Valley: Duration, minimal sample size, and points versus visits
The purpose of the research was to evaluate the efficacy of point count surveys in bottomland hardwood forests. The specific objectives were to determine: (1) whether the recommended distance measures for point count circular plots are useful in bottomland hardwood forests, (2) the optimum duration for each point count, (3) the optimum number of points to sample at each locality, (4) the...
Authors
W.P. Smith, D.J. Twedt, D.A. Wiedenfeld, P.B. Hamel, R.P. Ford, R.J. Cooper
Point counts of landbirds in bottomland hardwood forests of the Mississippi Alluvial Valley: How long and how many? Point counts of landbirds in bottomland hardwood forests of the Mississippi Alluvial Valley: How long and how many?
To quantify efficacy of point count sampling in bottomland hardwood forests, we examined the influence of point count duration on corresponding estimates of number of individuals and species recorded. To accomplish this we conducted a totalof 82 point counts 7 May-16 May 1992distributed among three habitats (Wet, Mesic, Dry) in each of three regions within the lower Mississippi Alluvial...
Authors
W.P. Smith, D.A. Wiedenfeld, P.B. Hanel, D.J. Twedt, R.P. Ford, R.J. Cooper
Sampling bird communities in bottomland hardwood forests of the Mississippi Alluvial Valley: Number of points visited versus number of visits to a point Sampling bird communities in bottomland hardwood forests of the Mississippi Alluvial Valley: Number of points visited versus number of visits to a point
Within each of 4 forest stands on Delta Experimental Forest (DEF), 25 points were visited 5 to 7 times from 8 May to 21 May 1991, and 6 times from 30 May to 12 June 1992. During each visit to a point, all birds detected, visuallyor aurally, at any distance were recorded during a 4-minute interval. Using these data, our objectives were to recommend the number of point counts and the...
Authors
D.J. Twedt, W.P. Smith, R.J. Cooper, R.P. Ford, P.B. Hamel, D.A. Wiedenfeld
Species richness and relative abundance of breeding birds in forests of the Mississippi Alluvial Valley Species richness and relative abundance of breeding birds in forests of the Mississippi Alluvial Valley
In 1992, the Vicksburg Field Research Station of the National Wetlands Research Center initiated research on the ecology of migratory birds within forests of the Mississippi Alluvial Valley (MAV). The MAV was historically a nearly contiguous bottomland hardwood forest, however, only remnants remain. These remnants are fragmented and often influenced by drainage projects, silviculture...
Authors
C.O. Nelms, D.J. Twedt
Selective dipnetting of largemouth bass during electrofishing Selective dipnetting of largemouth bass during electrofishing
We electrofished 10 north‐central Texas reservoirs from 1987 through 1990 by either dipnetting all electroshocked fish (intensive dipnetting) or selectively dipnetting only fish visually identified as largemouth bass Micropterus salmoides. We compared selected indices of population structure (proportional stock density, relative stock density, and young–adult ratio) and abundance (catch...
Authors
Daniel Twedt, W. Guest, Bobby Farquhar
Comparison of algorithms for replacing missing data in discriminant analysis Comparison of algorithms for replacing missing data in discriminant analysis
We examined the impact of different methods for replacing missing data in discriminant analyses conducted on randomly generated samples from multivariate normal and non-normal distributions. The probabilities of correct classification were obtained for these discriminant analyses before and after randomly deleting data as well as after deleted data were replaced using: (1) variable means...
Authors
Daniel Twedt, D.S. Gill
Genetic variation in male Yellow-headed Blackbirds from the northern Great Plains Genetic variation in male Yellow-headed Blackbirds from the northern Great Plains
Electrophoretic differences at 15 presumptive loci were used to assess allelic frequencies, heterozygosities, and polymorphism for male Yellow-headed Blackbirds (Xanthocephalus xanthocephalus) collected in east-central Alberta, north-central North Dakota, and east-central South Dakota. Five loci were polymorphic and mean heterozygosities ranged from 0.119 to 0.133. Significant...
Authors
Daniel Twedt, William Bleier, George Linz
Geographic and temporal variation in the diet of Yellow-headed Blackbirds Geographic and temporal variation in the diet of Yellow-headed Blackbirds
Yellow-headed Blackbirds (Xanthocephalus xanthocephalus) are presumed predators of sunflower (Helianthus annuus) in the northern Great Plains. Their esophageal contents varied temporally and among three provinces and three states in relation to regional agricultural bases but males contained more sunflower and small grains than females whereas females contained more weed seeds and...
Authors
Daniel Twedt, William Bleier, George Linz
Science and Products
Filter Total Items: 93
Distribution and composition of bottomland hardwood forests within the Mississippi Alluvial Valley Distribution and composition of bottomland hardwood forests within the Mississippi Alluvial Valley
No abstract available.
Authors
D.J. Twedt, W. Limp, M. Swan, C.R. Loesch
Point counts of birds in bottomland hardwood forests of the Mississippi Alluvial Valley: Duration, minimal sample size, and points versus visits Point counts of birds in bottomland hardwood forests of the Mississippi Alluvial Valley: Duration, minimal sample size, and points versus visits
The purpose of the research was to evaluate the efficacy of point count surveys in bottomland hardwood forests. The specific objectives were to determine: (1) whether the recommended distance measures for point count circular plots are useful in bottomland hardwood forests, (2) the optimum duration for each point count, (3) the optimum number of points to sample at each locality, (4) the...
Authors
W.P. Smith, D.J. Twedt, D.A. Wiedenfeld, P.B. Hamel, R.P. Ford, R.J. Cooper
Point counts of landbirds in bottomland hardwood forests of the Mississippi Alluvial Valley: How long and how many? Point counts of landbirds in bottomland hardwood forests of the Mississippi Alluvial Valley: How long and how many?
To quantify efficacy of point count sampling in bottomland hardwood forests, we examined the influence of point count duration on corresponding estimates of number of individuals and species recorded. To accomplish this we conducted a totalof 82 point counts 7 May-16 May 1992distributed among three habitats (Wet, Mesic, Dry) in each of three regions within the lower Mississippi Alluvial...
Authors
W.P. Smith, D.A. Wiedenfeld, P.B. Hanel, D.J. Twedt, R.P. Ford, R.J. Cooper
Sampling bird communities in bottomland hardwood forests of the Mississippi Alluvial Valley: Number of points visited versus number of visits to a point Sampling bird communities in bottomland hardwood forests of the Mississippi Alluvial Valley: Number of points visited versus number of visits to a point
Within each of 4 forest stands on Delta Experimental Forest (DEF), 25 points were visited 5 to 7 times from 8 May to 21 May 1991, and 6 times from 30 May to 12 June 1992. During each visit to a point, all birds detected, visuallyor aurally, at any distance were recorded during a 4-minute interval. Using these data, our objectives were to recommend the number of point counts and the...
Authors
D.J. Twedt, W.P. Smith, R.J. Cooper, R.P. Ford, P.B. Hamel, D.A. Wiedenfeld
Species richness and relative abundance of breeding birds in forests of the Mississippi Alluvial Valley Species richness and relative abundance of breeding birds in forests of the Mississippi Alluvial Valley
In 1992, the Vicksburg Field Research Station of the National Wetlands Research Center initiated research on the ecology of migratory birds within forests of the Mississippi Alluvial Valley (MAV). The MAV was historically a nearly contiguous bottomland hardwood forest, however, only remnants remain. These remnants are fragmented and often influenced by drainage projects, silviculture...
Authors
C.O. Nelms, D.J. Twedt
Selective dipnetting of largemouth bass during electrofishing Selective dipnetting of largemouth bass during electrofishing
We electrofished 10 north‐central Texas reservoirs from 1987 through 1990 by either dipnetting all electroshocked fish (intensive dipnetting) or selectively dipnetting only fish visually identified as largemouth bass Micropterus salmoides. We compared selected indices of population structure (proportional stock density, relative stock density, and young–adult ratio) and abundance (catch...
Authors
Daniel Twedt, W. Guest, Bobby Farquhar
Comparison of algorithms for replacing missing data in discriminant analysis Comparison of algorithms for replacing missing data in discriminant analysis
We examined the impact of different methods for replacing missing data in discriminant analyses conducted on randomly generated samples from multivariate normal and non-normal distributions. The probabilities of correct classification were obtained for these discriminant analyses before and after randomly deleting data as well as after deleted data were replaced using: (1) variable means...
Authors
Daniel Twedt, D.S. Gill
Genetic variation in male Yellow-headed Blackbirds from the northern Great Plains Genetic variation in male Yellow-headed Blackbirds from the northern Great Plains
Electrophoretic differences at 15 presumptive loci were used to assess allelic frequencies, heterozygosities, and polymorphism for male Yellow-headed Blackbirds (Xanthocephalus xanthocephalus) collected in east-central Alberta, north-central North Dakota, and east-central South Dakota. Five loci were polymorphic and mean heterozygosities ranged from 0.119 to 0.133. Significant...
Authors
Daniel Twedt, William Bleier, George Linz
Geographic and temporal variation in the diet of Yellow-headed Blackbirds Geographic and temporal variation in the diet of Yellow-headed Blackbirds
Yellow-headed Blackbirds (Xanthocephalus xanthocephalus) are presumed predators of sunflower (Helianthus annuus) in the northern Great Plains. Their esophageal contents varied temporally and among three provinces and three states in relation to regional agricultural bases but males contained more sunflower and small grains than females whereas females contained more weed seeds and...
Authors
Daniel Twedt, William Bleier, George Linz