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J. L. Morrison

Publications and source records attributed to J. L. Morrison.

6 recordsLinked to original sources
USGS2009

Environmental correlates of breeding in the Crested Caracara ( Caracara cheriway )

We evaluated the influence of weather on reproduction of the Crested Caracara ( Caracara cheriway ) in an agricultural landscape in south-central Florida. We used a mixed logistic-regression modeling approach within an information-theoretic framework to examine the influence of total rainfall, rainfall frequency, and temperature on the number of breeding pairs, timing of breeding, nest success, and productivity of Crested Caracaras during 1994–2000. The best models indicated an influence of rainfall frequency and laying period on reproduction. More individuals nested and more pairs nested earlier during years with more frequent rainfall in late summer and early fall. Pairs that nested later in each breeding season had smaller clutches, lower nest success and productivity, and higher probability of nest failure. More frequent rainfall during early spring months that are usually characterized by water deficit (March–May), more frequent rainfall during the fall drawdown period (September–November), and a shorter winter dry period showed some association with higher probability of brood reduction and lower nest success. The proportion of nests that failed was higher in “wet” years, when total rainfall during the breeding season (September–April) was >10% above the 20-year average. Rainfall may influence reproduction in Crested Caracaras indirectly through food resources. As total rainfall increased during February–April, when most pairs are feeding nestlings or dependent fledglings, the proportion of drawdown-dependent species (those that become available as rainfall decreases and wetlands become isolated and shallow) in the diet of Crested Caracaras declined, which may indicate reduced availability of foraging habitat for this primarily terrestrial raptor.

The Auk↗
USGS2009

Broadening our approaches to studying dispersal in raptors

Dispersal is a behavioral process having consequences for individual fitness and population dynamics. Recent advances in technology have spawned new theoretical examinations and empirical studies of the dispersal process in birds, providing opportunities for examining how this information may be applied to studies of the dispersal process in raptors. Many raptors are the focus of conservation efforts; thus, reliable data on all aspects of a species' population dynamics, including dispersal distances, movement rates, and mortality rates of dispersers, are required for population viability analyses that are increasingly used to inform management. Here, we address emerging issues and novel approaches used in the study of avian dispersal, and provide suggestions to consider when developing and implementing studies of dispersal in raptors. Clarifying study objectives is essential for selection of an appropriate methodology and sample size needed to obtain accurate estimates of movement distances and rates. Identifying an appropriate study-area size will allow investigators to avoid underestimating population connectivity and important population parameters. Because nomadic individuals of some species use temporary settling areas or home ranges before breeding, identification of these areas is critical for conservation efforts focusing on habitats other than breeding sites. Study designs for investigating raptor dispersal also should include analysis of environmental and social factors influencing dispersal, to improve our understanding of condition-dependent dispersal strategies. Finally, we propose a terminology for use in describing the variety of movements associated with dispersal behavior in raptors, and we suggest this terminology could be used consistently to facilitate comparisons among studies. ?? 2009 The Raptor Research Foundation, Inc.

Journal of Raptor Research↗
USGS1992

Modernization and multiscale databases at the U.S. Geological Survey

The U.S. Geological Survey (USGS) has begun a digital cartographic modernization program. Keys to that program are the creation of a multiscale database, a feature-based file structure that is derived from a spatial data model, and a series of “templates” or rules that specify the relationships between instances of entities in reality and features in the database. The database will initially hold data collected from the USGS standard map products at scales of 1:24,000, 1:100,000, and 1:2,000,000. The spatial data model is called the digital line graph-enhanced model, and the comprehensive rule set consists of collection rules, product generation rules, and conflict resolution rules. This modernization program will affect the USGS mapmaking process because both digital and graphic products will be created from the database. In addition, non-USGS map users will have more flexibility in uses of the databases. These remarks are those of the session discussant made in response to the six papers and the keynote address given in the session.

Computers, Environment and Urban Systems↗
USGS1984

Applied cartographic communication: map symbolization for atlases.

A detailed investigation of the symbolization used on general-purpose atlas reference maps. It indicates how theories of cartographic communication can be put into practice. Two major points emerge. First, that a logical scheme can be constructed from existing cartographic research and applied to an analysis of the choice of symbolization on a map. Second, the same structure appears to allow the cartographer to specify symbolization as a part of map design. An introductory review of cartographic communication is followed by an analysis of selected maps' usage of point, area and line symbols, boundaries, text and colour usage.-after Author

Cartographica: The International Journal for Geogr↗