Central place food caching: a field experiment with red-backed shrikes (Lanius collurio L.)

Summary Red-backed shrikes (Lanius collurio L.) stored experimentally presented mice (Mus musculus L) by reimpaling them on thorns of sloe bushes (Prunus spinosa L.) in the vicinity of the nest. Large mice (20 g) were stored further away from the nest than small mice (4 g), while the smallest mice (1 g) were transported directly to the nest and cut up there. Large prey required more round trips to deliver than smaller prey (4 g). Time to immobilize, load and deliver the prey and the proportion of undigestable tissue increased with prey size. Birds used stored prey as an alternative to hunting in other patches as expected from patch use models. The birds maintained a high rate of food delivery to the young by using stored mice during periods when their foraging success of natural prey was low. Several aspects of the shrike's food storing behaviour are in qualitative accord with suggestions derived from models assuming maximization of energy delivery rate.     

Interactions of tillage and rainfall on atrazine leaching under field and laboratory conditions

Laboratory studies were conducted to evaluate effects of tillage reversal and rainfall on ¹⁴C-atrazine (2-chloro4-ethylamino-6-isopropylamino- -triazine) leaching patterns. Twelve intact soil cores (16 cm dia x 20 cm deep) were collected from 8-yr no-till (NT) fields. Half the cores were tilled (5 cm deep) prior to ¹⁴C-atrazine treatment (2.7 mg core⁻¹) to all cores. All cores received two rains (27 mm rain in 1.5 h, one day after application followed, two days later, by a 17 mm rain in 2.5 h) and leachate was collected and analyzed for atrazine. These rains simulated the timing, amount and duration of natural rainfall events from a tillage reversal field study. During the first high inte ity rainfall event, a pulse (2.1 μg L-1) of atrazine leached through tilled cores while leaching rate was linear and decreased (1.25 to 0.9 μg L-1) through un-tilled cores. Leaching rate was linear for both the tilled and un-tilled cores during the second rain. Less atrazine was left in the surface 5 cm of tilled soil than un-tilled after the two rains. Results confirmed field observations and suggested that when tillage is reversed on well structured soils, pesticide leaching may increase relative to un-tilled soil but these effects are probably confined to the first rain events after application only.     

Design training and aesthetic evaluation: An intergroup comparison

A number of studies have observed differences in the evaluation of visual, aesthetic stimuli between those with and without professional training in art and design. If exposure to design training underlies such differences it follows that evidence of training effects should be observable when comparing subjects at different stages of design training, and not observable when comparing subjects at different stages of non-design training. In addition, this evidence should be consistent with directional predictions. The study reported in this paper investigated this question using a sample of 192 trained and untrained subjects in an evaluative task. Subjects were from two departments (Design and Computer Studies) of the same educational establishment and comprised balanced groups of lecturers, 1st, 2nd and 3rd year undergraduate students. The results obtained demonstrated evaluative differences and patterns of association both within and between the subject groups consistent with a training hypothesis.     

Careers as repositories of knowledge: A new perspective on boundaryless careers

This paper argues for a reconceptualization of careers as repositories of knowledge. Careers are visualized as accumulation of information and knowledge rather than simply progressions of work experiences. This definition is considered in light of theories which characterize organizations as knowledge creators. The paper then applies this perspective to the emerging phenomenon of boundaryless careers and concludes that a knowledge perspective provides significant insight into the implications of such careers for individuals and organizations.     

Distribution of some trace metals and their fluxes in the Genesee River,NY

Total and particulate metal concentrations, measured during intensive synoptic studies of the Genesee River, NY, correlated with suspended-sediment concentration and river discharge. Dissolved metal concentrations, on the other hand, showed little systematic variation over the length of the river. Metal and sediment fluxes for two elevated-discharged periods peaked at a midbasin sampling site. For most metals at most sampling sties particulate materials comprised over one-half of the total material. Comparison of particulate material metal concentrations, normalized to the measured suspended-sediment concentrations had with basinwide average values shows that sites having low suspended-sediment concentrations had high particulate material metal contents relative to the basin averages, while sites with high suspended-sediment concentration had low metal contents. These results are consistent with a metal transport mechanism in the Genesee River involving (1) a nearly constant dissolved component, (2) a fine acid-soluble component, and (3) a coarse component that is effectively a neutral diluent in the sediment. Chemical factors, such as sediment organic content, also appear to affect metal transport in the Genesee River.     

Effect on fatality risk of changing from secondary to primary seat belt enforcement

BACKGROUND: Most seat belt use laws originally passed in the United States contained language restricting enforcement to drivers already stopped for some other reason. States that have since removed this secondary enforcement restriction have reported increased seat belt use. The purpose of the present study was to estimate the effect of these law changes on driver fatality rates. METHOD: Trends in passenger vehicle driver death rates per billion miles traveled were compared for 10 states that changed from secondary to primary seat belt enforcement and 14 states that remained with secondary enforcement. RESULTS: After accounting for possible economic effects and other general time trends, the change from secondary to primary enforcement was found to reduce annual passenger vehicle driver death rates by an estimated 7% (95% confidence limits 3.0-10.9). CONCLUSION: The majority of U.S. states still have secondary enforcement laws. If these remaining secondary laws were amended, an estimated 696 deaths per year could be prevented.