Open Access. Powered by Scholars. Published by Universities.®

Digital Commons Network™

Open Access. Powered by Scholars. Published by Universities.®

2001

Discipline
Institution
Keyword
Publication
Publication Type
File Type

Articles 50911 - 50940 of 55078

Full-Text Articles in Entire DC Network

Effects Of Management Practices On Grassland Birds: Sprague’S Pipit, Jill A. Dechant, Marriah L. Sondreal, Douglas H. Johnson, Lawrence D. Igl, Christopher M. Goldade, Melvin P. Nenneman, Betty R. Euliss Jan 2001

Effects Of Management Practices On Grassland Birds: Sprague’S Pipit, Jill A. Dechant, Marriah L. Sondreal, Douglas H. Johnson, Lawrence D. Igl, Christopher M. Goldade, Melvin P. Nenneman, Betty R. Euliss

United States Geological Survey, Northern Prairie Wildlife Research Center: Publications

Sprague’s Pipit (Anthus spragueii):
Breeding range
Suitable habitat
Area requirements
Brown-headed Cowbird brood parasitism
Breeding-season phenology and site fidelity
Species’ response to management
Management Recommendations
Habitat Characteristics


Effects Of Management Practices On Grassland Birds: Marbled Godwit, Jill A. Dechant, Marriah L. Sondreal, Douglas H. Johnson, Lawrence D. Igl, Christopher M. Goldade, Melvin P. Nenneman, Betty R. Euliss Jan 2001

Effects Of Management Practices On Grassland Birds: Marbled Godwit, Jill A. Dechant, Marriah L. Sondreal, Douglas H. Johnson, Lawrence D. Igl, Christopher M. Goldade, Melvin P. Nenneman, Betty R. Euliss

United States Geological Survey, Northern Prairie Wildlife Research Center: Publications

Marbled Godwit (Limosa fedoa):
Breeding range
Suitable habitat
Area requirements
Brown-headed Cowbird brood parasitism
Breeding-season phenology and site fidelity
Species’ response to management
Management Recommendations
Habitat Characteristics


Differential Effects Of Incentive Motivators On Work Performance, Alexander D. Stajkovic, Fred Luthans Jan 2001

Differential Effects Of Incentive Motivators On Work Performance, Alexander D. Stajkovic, Fred Luthans

Department of Management: Faculty Publications

In this field experiment, we first compared the performance effects of money systematically administered through the organizational behavior modification (O.B. Mod.) model and routine pay for performance and then compared the effects of O.B. Mod.- administered money, social recognition, and performance feedback. The money intervention based on the O.B. Mod. outperformed routine pay for performance (performance increase = 37% vs. 11%) and also had stronger effects on performance than social recognition (24%) and performance feedback (20%).


A Critical Look At Self-Dual Codes, Judy L. Walker Jan 2001

A Critical Look At Self-Dual Codes, Judy L. Walker

Department of Mathematics: Faculty Publications

We investigate self-dual codes from a structural point of view. In particular, we study properties of critical indecomposable codes which appear in the spectrum of a self-dual code. As an application of the results we obtain, we revisit the study of self-dual codes of dimension at most 10.

In the late 1950’s, Slepian [4] became the first to take an abstract approach to the study of error-correcting codes. He introduced a structure theory for binary linear codes, developing in particular the idea of an indecomposable code; that is, a code which is not isomorphic to a nontrivial direct sum of …


Efficient Traitor Tracing Algorithms Using List Decoding, Alice Silverberg, Jessica Staddon, Judy L. Walker Jan 2001

Efficient Traitor Tracing Algorithms Using List Decoding, Alice Silverberg, Jessica Staddon, Judy L. Walker

Department of Mathematics: Faculty Publications

We use powerful new techniques for list decoding error-correcting codes to efficiently trace traitors. Although much work has focused on constructing traceability schemes, the complexity of the tracing algorithm has received little attention. Because the TA tracing algorithm has a runtime of O(N) in general, where N is the number of users, it is inefficient for large populations.We produce schemes for which the TA algorithm is very fast. The IPP tracing algorithm, though less efficient, can list all coalitions capable of constructing a given pirate. We give evidence that when using an algebraic structure, the ability to …


Fungal Symbiosis From Mutualism To Parasitism: Who Controls The Outcome, Host Or Invader?, Regina S. Redman, David Dunigan, Rusty J. Rodriguez Jan 2001

Fungal Symbiosis From Mutualism To Parasitism: Who Controls The Outcome, Host Or Invader?, Regina S. Redman, David Dunigan, Rusty J. Rodriguez

Department of Plant Pathology: Faculty Publications

• Plant symbiotic fungi are generally thought to express a single lifestyle that might increase (mutualism), decrease (parasitism), or have no influence (commensalism) on host fitness. However, data are presented here demonstrating that plant pathogenic Colletotrichum species are able to asymptomatically colonize plants and express nonpathogenic lifestyles.

• Experiments were conducted in growth chambers and plant colonization was assessed by emergence of fungi from surface sterilized plant tissues. Expression of symbiotic lifestyles was assessed by monitoring the ability of fungi to confer disease resistance, drought tolerance and growth enhancement.

• Several pathogenic Colletotrichum species expressed either mutualistic or commensal lifestyles …


The Aspergillus Nidulans Snt Genes Are Required For The Regulation Of Septum Formation And Cell Cycle Checkpoints, Peter R. Kraus, Steven D. Harris Jan 2001

The Aspergillus Nidulans Snt Genes Are Required For The Regulation Of Septum Formation And Cell Cycle Checkpoints, Peter R. Kraus, Steven D. Harris

Department of Plant Pathology: Faculty Publications

In Aspergillus nidulans, germinating conidia undergo multiple rounds of nuclear division before forming a septum. Previous genetic results suggest that the ability to separate nuclear division and septum formation depends upon a threshold level of activity of the cyclin-dependent kinase NIMXcdk1. Mutations in nimX and nimT, the gene encoding the NIMXcdk1-activating phosphatase, have revealed that Tyr-15 phosphorylation is important for determining the timing of the formation of the first septum. Here, we describe a screen for suppressors of nimT23 (snt), designed to identify additional components of the pathway regulating septum formation. We show that a subset …


Age-Related Resistance In Bell Pepper To Cucumber Mosaic Virus , Hernan Garcia-Ruiz, John F. Murphy Jan 2001

Age-Related Resistance In Bell Pepper To Cucumber Mosaic Virus , Hernan Garcia-Ruiz, John F. Murphy

Department of Plant Pathology: Faculty Publications

We demonstrated the occurrence of mature plant resistance in Capsicum annuum 'Early Calwonder' to Cucumber mosaic virus (CMV) under greenhouse conditions. When Early Cal wonder plants were sown at 10 day intervals and transplanted to 10-cm square pots, three distinct plant sizes were identified that were designated small, medium and large. Trials conducted during each season showed that CMV accumulated in inoculated leaves of all plants of each size category. All small plants (with the exception of the winter trial) developed a systemic infection that included accumulation of CMV in uninoculated leaves and severe systemic symptoms. Medium plants had a …


Interferon Regulatory Factor 7 Mediates Activation Of Tap-2 By Epstein-Barr Virus Latent Membrane Protein 1, Luwen Zhang, Joseph S. Pagano Jan 2001

Interferon Regulatory Factor 7 Mediates Activation Of Tap-2 By Epstein-Barr Virus Latent Membrane Protein 1, Luwen Zhang, Joseph S. Pagano

Nebraska Center for Virology: Faculty Publications

Transporter associated with antigen processing 2 (Tap-2) is responsible for ATP-dependent transport of peptides from the cytosol to the endoplasmic reticulum, where peptides bind to newly synthesized human leukocyte antigen (HLA) class I molecules, which are essential for cellular immune responses. Epstein-Barr virus (EBV) latent membrane protein 1 (LMP-1) has been shown to induce the expression of Tap-2. In this study, the induction of endogenous Tap-2 by LMP-1 is shown to be associated with and requires the expression of interferon regulatory factor 7 (IRF-7). In DG75 Burkitt’s lymphoma (BL) cells, in which LMP-1 induces the expression of IRF-7, LMP-1 induced …


Growth, Structure, Electronic, And Magnetic Properties Of Mgo/Fe(001) Bilayers And Fe/Mgo/Fe(001) Trilayers, M. Klaua, D. Ullmann, J. Barthel, W. Wulfhekel, J. Kirschner, R. Urban, Theodore L. Monchesky, Axel Enders, John F. Cochran, Brett Heinrich Jan 2001

Growth, Structure, Electronic, And Magnetic Properties Of Mgo/Fe(001) Bilayers And Fe/Mgo/Fe(001) Trilayers, M. Klaua, D. Ullmann, J. Barthel, W. Wulfhekel, J. Kirschner, R. Urban, Theodore L. Monchesky, Axel Enders, John F. Cochran, Brett Heinrich

Axel Enders Publications

Single-crystal epitaxial MgO thin films were grown directly onto high-quality Fe single crystal and Fe whisker substrates and covered with Fe/Au layers. Reflection high-energy electron diffraction and low-energy electron diffraction patterns and scanning tunneling microscopy images showed that the growth of MgO proceeded pseudomorphically in a nearly layer-by-layer mode up to six monolayers. A misfit dislocation network is formed for MgO layers thicker than six monolayers. The thin MgO films were characterized electrically by scanning tunneling spectroscopy. The tunneling barrier in MgO was found to depend on the MgO layer thickness, starting from 2.5 eV at two monolayer thickness to …


Perspectives Of Giant Magnetoresistance, Evgeny Y. Tsymbal, David G. Pettifor Jan 2001

Perspectives Of Giant Magnetoresistance, Evgeny Y. Tsymbal, David G. Pettifor

Evgeny Tsymbal Publications

Giant magnetoresistance (GMR) is one of the most fascinating discoveries in thin-film magnetism, which combines both tremendous technological potential and deep fundamental physics. Within a decade of GMR being discovered in 1988 commercial devices based on this phenomenon, such as hard-disk read-heads, magnetic field sensors and magnetic memory chips, had become available in the market. These achievements would not have been possible without a detailed understanding of the physics of GMR, which requires a quantum-mechanical insight into the electronic spin-dependent transport in magnetic structures.


Occurrence Of Cyanazine Compounds In Groundwater: Degradates More Prevalent Than The Parent Compound, Dana Kolpin, E. Michael Thurman, S. Michael Linhart Jan 2001

Occurrence Of Cyanazine Compounds In Groundwater: Degradates More Prevalent Than The Parent Compound, Dana Kolpin, E. Michael Thurman, S. Michael Linhart

United States Geological Survey: Staff Publications

A recently developed analytical method using liquid chromatography/mass spectrometry was used to investigate the occurrence of cyanazine and its degradates cyanazine acid (CAC), cyanazine amide (CAM), deethylcyanazine (DEC), and deethylcyanazine acid (DCAC) in groundwater. This research represents some of the earliest data on the occurrence of cyanazine degradates in groundwater. Although cyanazine was infrequently detected in the 64 wells across Iowa sampled in 1999, cyanazine degradates were commonly found during this study. The most frequently detected cyanazine compound was DCAC (32.8%) followed by CAC (29.7%), CAM (17.2%), DEC (3.1%), and cyanazine (3.1%). The frequency of detection for cyanazine or one …


Experimental Infection Of Nontarget Species Of Rodents And Birds With Brucella Abortus Strain Rb51 Vaccine, Matt C. Januszewski, Steven C. Olsen, Robert G. Mclean, Larry Clark, Jack C. Rhyan Jan 2001

Experimental Infection Of Nontarget Species Of Rodents And Birds With Brucella Abortus Strain Rb51 Vaccine, Matt C. Januszewski, Steven C. Olsen, Robert G. Mclean, Larry Clark, Jack C. Rhyan

United States Department of Agriculture Wildlife Services: Staff Publications

The Brucella abortus vaccine strain RB51 (SRB51) is being considered for use in the management of brucellosis in wild bison (Bison bison) and elk (Cervus elaphus) populations in the Greater Yellowstone Area (USA). Evaluation of the vaccine’s safety in non-target species was considered necessary prior to field use. Between June 1998 and December 1999, ground squirrels (Spermophilus richardsonii, n=21), deer mice (Peromyscus maniculatus, n=14), prairie voles (Microtus ochrogaster, n=21), and ravens (Corvus corax, n=13) were orally inoculated with SRB51 or physiologic saline. Oral and …


Serological Responses Of Coyotes To Two Commercial Rabies Vaccines, Frederick F. Knowlton, Marianna Roetto, Deborah Briggs Jan 2001

Serological Responses Of Coyotes To Two Commercial Rabies Vaccines, Frederick F. Knowlton, Marianna Roetto, Deborah Briggs

United States Department of Agriculture Wildlife Services: Staff Publications

Between August 1993 and September 1994 we documented serological responses of coyotes (Canis latrans) vaccinated with two commercial rabies vaccines licensed for use in domestic dogs. Serologic responses were documented by testing for rabies virus neutralizing antibodies with the rapid fluorescent focus inhibition test (RFFIT) at 30, 90, 180, 270, and 365 days post-vaccination. All coyotes vaccinated with Imrab 3® (Rhone-Merieux, Inc.), and 75% of those vaccinated with Dura-Rab 3® (Immunovet, Inc.) seroconverted, as evidenced by the presence of antirabies antibody titers ≥1:5 in one or more of the five post-vaccination samples. The percent of coyotes …


Crop Potassium Nutrition – Implications For Fertilizer Recommendations, Achim R. Dobermann Jan 2001

Crop Potassium Nutrition – Implications For Fertilizer Recommendations, Achim R. Dobermann

Department of Agronomy and Horticulture: Faculty Publications

During the past 35 years, average corn yields in the North Central Region (NCR) have increased at a rate of 1.7 bu/acre per year, mainly due to the adoption of improved crop management technologies and genetic improvement of corn hybrids. Fertilizer K rates used on corn are typically within a range of 0 to 110 lb K2O/acre, but average usage varies widely among states. Commercial fertilizer use rose sharply in the 1960s and 1970s, but corn yield increases since 1980 were achieved with stagnating fertilizer-N use and declining rates of P and K. Signs of emerging K deficiencies …


Light-Saturated Co2 Assimilation Rates Of Corn And Velvetleaf In Response To Leaf Nitrogen And Development Stage, John L. Lindquist Jan 2001

Light-Saturated Co2 Assimilation Rates Of Corn And Velvetleaf In Response To Leaf Nitrogen And Development Stage, John L. Lindquist

Department of Agronomy and Horticulture: Faculty Publications

Single-leaf CO2 assimilation rate under saturating light (CA) varies as a function of leaf nitrogen content per unit leaf area (NL). Measured CA for many crop species also declines with developmental stage. Because these relationships may have strong implications for crop–weed competition, a field experiment was conducted to quantify corn and velvetleaf CA as influenced by leaf NL and stage of development. Crop and weed CA were measured on the most recent fully expanded leaves of plants grown in four nitrogen (N) application treatments. Both corn and velvetleaf CA increased …


Performance Of Intercom For Predicting Corn– Velvetleaf Interference Across North-Central United States, John L. Lindquist Jan 2001

Performance Of Intercom For Predicting Corn– Velvetleaf Interference Across North-Central United States, John L. Lindquist

Department of Agronomy and Horticulture: Faculty Publications

Cost-effective weed management requires accurate estimates of yield and the potential yield loss resulting from weed infestations. However, crop yield and the effects of weeds are highly variable across years and locations. Ecophysiological models may be useful for predicting the effects of environment and management on crop and weed growth and competitive ability. Ability of the model INTERCOM to predict corn (Zea mays) growth and yield, velvetleaf (Abutilon theophrasti) interference on corn yield loss, and single-year economic threshold velvetleaf density (Te) was evaluated using 13 data sets collected in four states. Predicted and observed …


Testing The Effects Of Moisture On Seedcoat Color Of Pinto Dry Beans, Muharrem Ergun, Ellen T. Paparozzi, Dermot P. Coyne, Durward Smith, Stephen D. Kachman, David S. Nuland Jan 2001

Testing The Effects Of Moisture On Seedcoat Color Of Pinto Dry Beans, Muharrem Ergun, Ellen T. Paparozzi, Dermot P. Coyne, Durward Smith, Stephen D. Kachman, David S. Nuland

Department of Agronomy and Horticulture: Faculty Publications

Seedcoat color is an important trait, as it affects marketing and consumer acceptance of pinto beans (Phaseolus vulgaris L.). Pinto breeding line NE 94-4 showed seedcoat yellowing in on-farm field trials in Nebraska in 1996 and 1997. Hail, sprinkler irrigation, and fall rainfall appeared to be involved in increasing seedcoat yellowing, based on analysis of field and weather data of on-farm trial sites. The objective of this study was to determine the effect of moisture on seedcoat yellowing of pinto line NE 94-4 (susceptible) and pinto ‘UI-114’ (highly resistant). Two greenhouse experiments were conducted involving misting of bean plants …


Storage And Handling Characteristics Of Trinexapac-Ethyl Treated Kentucky Bluegrass Sod, Neil L. Heckman, Garald L. Horse, Roch E. Gaussoin, Kevin Frank Jan 2001

Storage And Handling Characteristics Of Trinexapac-Ethyl Treated Kentucky Bluegrass Sod, Neil L. Heckman, Garald L. Horse, Roch E. Gaussoin, Kevin Frank

Department of Agronomy and Horticulture: Faculty Publications

Internal heating during sod storage can lead to plant deterioration and is a limiting factor in sod transportation. Storage practices such as the use of refrigeration and vacuum packaging have increased storage time; however, these are usually not practical or economical. Experiments were conducted to develop a feasible growth regulator management technique, using trinexapac-ethyl, to increase the storage life of Kentucky bluegrass (Poa pratensis L.) sod. Experimental setup for all experiments was a completely randomized design with a 2 (trinexapac-ethyl vs. control) × 3 (storage times) factorial treatment arrangement with 3 replications. Trinexapac-ethyl was applied at 0.23 kg·ha–1 …


Comments On April 16, 2001 Exposure Draft By The Aicpa Professional Ethics Executive Committee’S Proposal To Modernize Its Auditor Independence Rules And Interpretations, Arthur Siegel, Independence Standards Board Jan 2001

Comments On April 16, 2001 Exposure Draft By The Aicpa Professional Ethics Executive Committee’S Proposal To Modernize Its Auditor Independence Rules And Interpretations, Arthur Siegel, Independence Standards Board

Association Sections, Divisions, Boards, Teams

No abstract provided.


Tillage And Fallow Effects On Selected Soil Quality Characteristics Of Former Conservation Reserve Program Sites, John E. Gilley, John W. Doran, Bahman Eghball Jan 2001

Tillage And Fallow Effects On Selected Soil Quality Characteristics Of Former Conservation Reserve Program Sites, John E. Gilley, John W. Doran, Bahman Eghball

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Tillage and fallow have been suggested as management options for converting Conservation Reserve Program (CRP) areas to cropland. This study was conducted to measure selected soil quality characteristics of former CRP sites in Mississippi, Nebraska, and South Dakota that were tilled and then left fallow for 21 or 22 months. Soil samples from depth intervals of 0-7.6 cm and 0-30.5 cm were collected for laboratory assessment of the following soil quality indicators: bulk density, EC, pH, total C, organic C, total N, NO3-N, NH4-N, PO4-P, biomass C, biomass N, anaerobic NH4-N, lab …


Phosphorus Risk Assessment Index Evaluation Using Runoff Measurements, Bahman Eghball, John E. Gilley Jan 2001

Phosphorus Risk Assessment Index Evaluation Using Runoff Measurements, Bahman Eghball, John E. Gilley

Department of Agricultural and Biological Systems Engineering: Faculty Publications

An index to evaluate the phosphorus (P) pollution potential of agricultural fields was proposed by Lemunyon and Gilbert in 1993. Data from three rainfall simulation studies were used to evaluate the relative importance of the variables in the P index. These studies included plots containing sorghum (Sorghum bicolor L.), winter wheat (Triticum aestivum L.), and corn (Zea mays L.) residues on which chemical fertilizer and composted or noncomposted beef cattle feedlot manure were applied under no-till and disked conditions. The factors of erosion, runoff, soil P level P application source, and method, and rate of P addition …


Reducing Long-Term Atrazine Runoff From South Central Nebraska, Walter Scott Gorneau, Thomas G. Franti, Brian L. Benham, Steve D. Comfort Jan 2001

Reducing Long-Term Atrazine Runoff From South Central Nebraska, Walter Scott Gorneau, Thomas G. Franti, Brian L. Benham, Steve D. Comfort

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Heavy reliance on chemical weed control in field crops of South Central Nebraska has resulted in the appearance of atrazine at concentrations greater than established drinking water standards. Our objective was to evaluate the best management practices for atrazine runoff for the tillage and herbicide management practices common to the region under study. Field experiments were performed to measure edge–of–field atrazine and water loss from disk–till, ridge–till, and slot plant (no–till) management systems. Results indicated less water runoff from no–till (34% less) and ridge–till (36% less) than from disk–till. Similarly, atrazine loss was also less: 24% less for no–till and …


Application Of Fuzzy Logic In Automated Cow Status Monitoring, R. M. De Mol, Wayne Woldt Jan 2001

Application Of Fuzzy Logic In Automated Cow Status Monitoring, R. M. De Mol, Wayne Woldt

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Sensors that measure yield, temperature, electrical conductivity of milk, and animal activity can be used for automated cow status monitoring. The occurrence of false-positive alerts, generated by a detection model, creates problems in practice. We used fuzzy logic to classify mastitis and estrus alerts; our objective was to reduce the number of false-positive alerts and not to change the level of detected cases of mastitis and estrus. Inputs for the fuzzy logic model were alerts from the detection model and additional information, such as the reproductive status. The output was a classification, true or false, of each alert. Only alerts …


Estimation Of Reference Crop Evapotranspiration Using Fuzzy State Models, Lameck O. Odhiambo, R. E. Yoder, D. C. Yoder Jan 2001

Estimation Of Reference Crop Evapotranspiration Using Fuzzy State Models, Lameck O. Odhiambo, R. E. Yoder, D. C. Yoder

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Daily evapotranspiration (ET) rates are needed for irrigation scheduling. Owing to the difficulty of obtaining accurate field measurements, ET rates are commonly estimated from weather parameters. A few empirical or semi–empirical methods have been developed for assessing daily reference crop ET, which is converted to actual crop ET using crop coefficients. The FAO Penman–Monteith method, which is now accepted as the standard method for the computation of daily reference ET, is sophisticated. It requires several input parameters, some of which have no actual measurements but are estimated from measured weather parameters. In this study, we examined the suitability of fuzzy …


Optimization Of Fuzzy Evapotranspiration Model Through Neural Training With Input–Output Examples, Lameck O. Odhiambo, R. E. Yoder, D. C. Yoder, J. W. Hines Jan 2001

Optimization Of Fuzzy Evapotranspiration Model Through Neural Training With Input–Output Examples, Lameck O. Odhiambo, R. E. Yoder, D. C. Yoder, J. W. Hines

Department of Agricultural and Biological Systems Engineering: Faculty Publications

In a previous study, we demonstrated that fuzzy evapotranspiration (ET) models can achieve accurate estimation of daily ET comparable to the FAO Penman–Monteith equation, and showed the advantages of the fuzzy approach over other methods. The estimation accuracy of the fuzzy models, however, depended on the shape of the membership functions and the control rules built by trial–and–error methods. This paper shows how the trial and error drawback is eliminated with the application of a fuzzy–neural system, which combines the advantages of fuzzy logic (FL) and artificial neural networks (ANN). The strategy consisted of fusing the FL and ANN on …


A Direct Correlation Function For Mesomorphic Polymers And Its Application To The ‘Smectic’ Phase Of Isotactic Polypropylene, Y Cohen, Ravi F. Saraf Jan 2001

A Direct Correlation Function For Mesomorphic Polymers And Its Application To The ‘Smectic’ Phase Of Isotactic Polypropylene, Y Cohen, Ravi F. Saraf

Papers in Materials Science

A general model to calculate the structure of a smectic to nematic-like order in polymer systems is proposed. The model is limited to well-aligned molecules with respect to each other. It is especially suited for systems where the packing between neighboring chains is described by liquid-like disorder with axial registration in the chain-axis direction. In such a case the diffraction pattern from the oriented structure exhibits broad liquid-like reflections on the equatorial but sharper reflections on the layer lines. An Ornstein-Zernike approach is adopted to calculate the inter-chain packing and inter-chain registration, where the direct correlation function of packing and …


Way-Finding And Landmarks: The Multiple Bearings Hypothesis, Alan C. Kamil, Ken Cheng Jan 2001

Way-Finding And Landmarks: The Multiple Bearings Hypothesis, Alan C. Kamil, Ken Cheng

Papers in Behavior in Biological Sciences

Clark’s nutcrackers (Nucifraga columbiana) are capable of very precise searching using the metric relationships between a goal and multiple landmarks to relocate the goal location. They can judge the direction more accurately than the distance to a landmark when the landmark is distant from the goal. On the basis of these findings, we propose that nutcrackers use a set of bearings, each a measure of the direction from the goal to a different landmark, when searching for that goal. The results of a simulation demonstrate that increasing the number of landmarks used results in increasingly precise searching. This …


Search For A Hidden Goal By Clark's Nutcrackers (Nucifraga Columbiana) Is More Accurate Inside Than Outside A Landmark Array, Brett M. Gibson, Alan C. Kamil Jan 2001

Search For A Hidden Goal By Clark's Nutcrackers (Nucifraga Columbiana) Is More Accurate Inside Than Outside A Landmark Array, Brett M. Gibson, Alan C. Kamil

Papers in Behavior in Biological Sciences

In three experiments in which an open-room delayed response task was used, we explored how Clark's nutcrackers use landmarks to search for a hidden goal when multiple potential goal locations were present. In Experiment 1, nutcrackers presented with three spatial samples were able to use relative local cues from an array that changed positions throughout a session to return to a hidden goal during a test. In Experiment 2, the number of samples varied from one to three prior to the test. The nutcrackers performed as well with one sample as with two or three samples. In Experiment 3, we …


The Use Of Relative And Absolute Bearings By Clark's Nutcrackers, Nucifraga Columbiana, Juli E. Jones, Alan C. Kamil Jan 2001

The Use Of Relative And Absolute Bearings By Clark's Nutcrackers, Nucifraga Columbiana, Juli E. Jones, Alan C. Kamil

Papers in Behavior in Biological Sciences

Two groups of Clark's nutcrackers were trained to find buried seeds whose location was defined by a constant angle from two landmarks whose interlandmark distance and position in the room varied across trials. The first group had a landmark array that was always placed in the same orientation with respect to the walls, allowing the animals to use both relative and absolute bearings. The second group had a landmark array that rotated across trials so that only relative bearings could be used to locate the seeds. The birds in each group learned the task and transferred to new interlandmark distances …