Conservation grasslands can provide valuable habitat resource for breeding songbirds, but their value for wintering raptors has received little attention. We hypothesized that increased availability of grassland habitat through the Conservation Reserve Enhancement Program (CREP) has resulted in an increase or redistribution in numbers of four species of raptors in Pennsylvania since 2001. We tested this by analyzing winter raptor counts from volunteer surveys, conducted from 2001 to 2008, for Red‐tailed Hawks (Buteo jamaicensis), Rough‐legged Hawks (Buteo lagopus), Northern Harriers (Circus cyaneus), and American Kestrels (Falco sparverius). During that period, numbers of wintering Northern Harriers increased by more than 20% per year. Log‐linear Poisson regression models show that all four species increased in the region of Pennsylvania that had the most and longest‐established conservation grasslands. At the county scale (N= 67), Bayesian spatial models showed that spatial and temporal population trends of all four species were positively correlated with the amount of conservation grassland. This relationship was particularly strong for Northern Harriers, with numbers predicted to increase by 35.7% per year for each additional 1% of farmland enrolled in CREP. Our results suggest that conservation grasslands are likely the primary cause of the increase in numbers of wintering Northern Harriers in Pennsylvania since 2001.
The characteristics of the pressure ionization chamber at t he National Bureau of Standards have been studied for the gamma radiation from a cesium-137 sou rce (0.6614 Mev) and from a cobalt-60 source (1.1715 and 1.3316 Mev). The dosage rates produced in air by these sources were measured with this chamber with an accuracy of about 2 percent. Dosage rates obtained with an extrapolation chamber and a Victoree n thimble chamber agreed with the values measured by the pressure chamber within t he limits of the experimental errors.
An 8.5-day biological half-life for tritium was determined from seven occurrences in six males. A method for estimating the average total body water is presented. An average body-water to effective-body weight ratio of 0.60 was calculated.
The Ifound Laboratory Progiess Report, issued monthly, is intended to be a means of lepoitinK items of current technical Interest in research and development programs. To issue this report as soon as possible after the end of the month, editorial work is limited; and since this is an informal progress report, the results and data presented are preliminary and subject to change.These reports are not intended to constitute publication in any sense of the word. Final results either will be submitted for publication in regular professional Journals or will be published in the form of MLM topical reports.
The Reactor Fuels and Materials Development Reports, issued quar terly, are intended to be a means of reporting items of current tech nical interest in plutonium research and development programs. To issue these reports as soon as possible after the end of the quarter, editorial work is limited; and since these are progress reports, the results and data are preliminary and subject to change.These reports are not intended to constitute publication in any, Sense of the word, Final results either will be submitted for publication in regular professional journals or will be published in the form of MLM topical reports.The previous reports published in this series are:
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