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Geology topics

C.S. Robbins

Publications and source records attributed to C.S. Robbins.

At least 253 records · Page 14Linked to original sources
USGS1977

Bird atlasing in the United States

Since the Breeding Bird Survey provides an annual quantitative sample of about 75% of the 1? blocks of latitude and longitude in every state except Alaska and Hawaii, and 47% of the 1/2? blocks (equivalent on the average to a 48 km square), no national Atlas based on merely presence or absence has been contemplated. Conventional atlases are in progress in the states of Maryland (2.5 km), Massaohusetts (5 km) and Vermont (5 km) and in parts of 3 other states. Quantitative studies including mapping have been published for North Dakota (10 km) and are in progress in Wyoming (1?). A Montana project (1?) is continuing.

Polish Ecological Studies↗
USGS1977

Bird population trends detected by the North American breeding bird survey

Continental populations of most bird species have remained quite stable since 1966, but there have been many regional changes associated with migration disasters, breeding failures and range expansions, and a few dramatic increases in populations of introduced species. These changes often are better represented by curvilinear than by linear regressions.

Polish Ecological Studies↗
USGS1977

Application of census techniques to habitat preservation strategy

Island biogeography concepts applied to breeding bird populations of woodlots clearly explain why certain passerine species typical of tracts of 1 km2 or more are absent from tracts one-half or one-quarter that size. Many 'natural areas' now being preserved are too small to support the complete complement of nesting species; this is partly because little knowledge of the minimum areas required is available to the agencies and individuals making the decisions

Polish Ecological Studies↗
USGS1977

A comparison of 2 techniques for estimating deer density

We applied mark-resight and area-conversion methods to estimate deer abundance at a 2,862-ha area in and surrounding the Gettysburg National Military Park and Eisenhower National Historic Site during 1987-1991. One observer in each of 11 compartments counted marked and unmarked deer during 65-75 minutes at dusk during 3 counts in each of April and November. Use of radio-collars and vinyl collars provided a complete inventory of marked deer in the population prior to the counts. We sighted 54% of the marked deer during April 1987 and 1988, and 43% of the marked deer during November 1987 and 1988. Mean number of deer counted increased from 427 in April 1987 to 582 in April 1991, and increased from 467 in November 1987 to 662 in November 1990. Herd size during April, based on the mark-resight method, increased from approximately 700-1,400 from 1987-1991, whereas the estimates for November indicated an increase from 983 for 1987 to 1,592 for 1990. Given the large proportion of open area and the extensive road system throughout the study area, we concluded that the sighting probability for marked and unmarked deer was fairly similar. We believe that the mark-resight method was better suited to our study than the area-conversion method because deer were not evenly distributed between areas suitable and unsuitable for sighting within open and forested areas. The assumption of equal distribution is required by the area-conversion method. Deer marked for the mark-resight method also helped reduce double counting during the dusk surveys.

American Birds↗