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Geology topics

A.J. Duvall

Publications and source records attributed to A.J. Duvall.

6 recordsLinked to original sources

Distribution and migration of races of the mourning dove

The Mourning Dove is a widespread species breeding in the non-boreal regions of North and Middle America and from the West Indies south to Panama. It is hunted extensively in many sections of the United States and in some sections of Canada, the West Indies, and Mexico....The trends in geographic variation of Mourning Doves are from dark coloration in the east to pale coloration in the west and from shorter wing length in tropical areas to longer in the temperate region. More rusty underparts are associated with birds of the West Indies, and extremely saturated coloration and relatively large bills and feet have been developed by the population on Clarion Island off the western coast of Mexico. The combinations of geographic variation result in the recognition of five geographic races, two of which breed on the mainland of North America. The race carolinensis of eastern United States can be distinguished from the western race, marginella, by the color of the wings alone, which makes possible the recognition of these racial components from the wings of doves taken from hunters? bags.....Taking Ridgway?s account in ?Birds of North and Middle America? as a basis, discrepancies in the descriptions of sex and racial characters are pointed out. Two races recognized by Ridgway and one suggested as possibly distinct were not substantiated. The occurrence of dark and pale types among the West Indian populations are considered of possible racial significance, but sufficient breeding material is lacking to study the problem satisfactorily.....The allocation of type specimens and names to the various recognizable races which appears in the most recent literature is considered satisfactory. The ecological boundaries between tropical and temperate life zones and between the western grasslands and eastern deciduous forest zones, generally speaking, separate distinct races from each other.....There is an extensive postbreeding wandering of birds in all directions, particularly northward, and there is an extensive mingling of racial types during migration. Concentrations of fall migrants occur in certain areas in the southwestern states and both east and west of the Gulf of Mexico.

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Investigations of methods of determining abundance of breeding mourning doves in certain eastern states

A call count over a 20 mile route (beginning 1/2 hour before local official sunrise and with 20 stops of 3 minutes duration 1 mile apart) gives a more practical index to the abundance of mourning doves in the breeding season than roadside counts and area population studies tried in 1950. Calling activities showed relatively high peaks and low depressions during April and May of 1951, with a plateau in June; a decline in calling was noted after July 3, and continued until September 11, when activity apparently ceased. Although there seems to be a direct correlation between the total number of doves heard and the total number of calls recorded, available evidence indicates that the breeding index should still be based on the number of doves heard. In general, more doves were heard calling than were seen up to about mid-July, 1951, after which time doves became conspicuous and relatively few were heard; and there was an increase in doves seen from July through September with a noticeable decline in October in cental Maryland. Very little difference was noted between morning and evening roadside counts from the end of July through October, although one route indicated that morning was more favorable. Our data probably are too meager to determine if any significant difference exists. A statistical analysis of calling counts covering the period from May 15-June 26, 1951 indicates that with 3 routes, 12 trips per route must be made in order to reflect a 15 percent change. Calling counts should begin in this area (central Maryland and northeastern Virginia) no later than May 15, and the counts must be completed by the end of the third week in June to conform to the present schedule of formulating hunting regulations.

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