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Author

Dean Amadon

Bio: Dean Amadon is an academic researcher. The author has contributed to research in topics: Subspecies & Chimney. The author has an hindex of 8, co-authored 30 publications receiving 938 citations.

Papers
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Book
01 Jan 1968

686 citations

Book
01 Jan 1973

97 citations

Journal ArticleDOI
01 Apr 1943-The Auk

29 citations

Journal ArticleDOI
01 Oct 1953-The Auk
TL;DR: The writer investigated migratory birds of relict distribution and revealed how a species, even one possessing great powers of flight and of migratory habits, may become restricted, in a comparatively short time, to very limited nesting and wintering areas.
Abstract: To determine why one species, genus, or family has been replaced by another during the course of evolution is a problem at once important and difficult. The study of this question led the writer to investigate migratory birds of relict distribution. The results, though tentative, seemed so interesting that they are summarized here. The following species will serve as a basis for the later discussion. 1. Ross's Goose (Chen rossii).-This diminutive goose, whose total present population is thought to be less than 5,000 individuals, breeds only in a relatively small area in the Perry River district of the Canadian Arctic. In late or cold summers, as found by Peter Scott and H. C. Hanson, only a fraction of the total population may succeed in nesting, or even attempt to nest. The winter range is equally circumscribed, and comprises only the interior valleys of California. 2. Labrador Duck (Camptorhynchus labradorius).-This extinct species is believed to have nested on the coast of Labrador. It wintered coastally in the area from the Maritime Provinces to Chesapeake Bay. The Labrador Duck is apparently the only bird whose range was restricted to the American coast of the North Atlantic. The other coastal species of this area nest also in northwestern Europe, in Iceland, or in other areas. (The Ipswich Sparrow [Passerculus princeps] is an exception to this statement, but it is merely an insular race or representative of the widespread Savannah Sparrow [P. sandwichensis]). 3. Whooping Crane (Grus americana).-The Whooping Crane has revealed how a species, even one possessing great powers of flight and of migratory habits, may become restricted, in a comparatively short time, to very limited nesting and wintering areas. The nesting range of this crane once covered a vast area in the center of the NorthAmerican continentfrom the far north, south to Iowa or even Louisiana. The breeding range of the few remaining pairs was for some years a mystery, despite the conspicuousness of this huge white bird, but is now believed, on the basis of one or two individuals observed in the summer of 1952, to be in the marshes adjoining Great Slave Lake. Its winter range is at present almost confined to the Aransas Wildlife Refuge on the Gulf coast of Texas. A few may winter elsewhere, as there is recent sight record of a pair in Tamaulipas, Mexico (Evenden, 1952).

16 citations


Cited by
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Journal ArticleDOI
TL;DR: Throughout, emphasis will be placed on strategic aspects of feeding rather than on what Holling (75) has called "tactics," and possible answers to the first problem may be given to the second problem.
Abstract: Natural history is replete with observations on feeding, yet only recently have investigators begun to treat feeding as a device whose performance­ as measured in net energy yield/feeding time or some other units assumed commensurate with fitness-may be maximized by natural selection (44, 1 13, 135, 156, 181) . The primary task of a theory of feeding strategies is to specify for a given animal that complex of behavior and morphology best suited to gather food energy in a particular environment. The task is one, therefore, of optimization, and like all optimization problems, it may be tri­ sected: 1. Choosing a currency: What is to be maximized or minimized? 2. Choosing the appropriate cost-benefit functions: What is the mathematical form of the set of expressions with the currency as the dependent variable? 3. Solving for the optimum: What computational technique best finds ex­ trema of the cost-benefit function? In this review, most of the following section is devoted to possible answers to the first problem. Then four key aspects of feeding strategies will be considered: (a) the optimal diet, (b) the optimal foraging space, (c) the optimal foraging period, and (d) the optimal foraging-group size. For each, possible cost-benefit formulations will be discussed and compared, and predictions derived from these will be matched with data from the literature on feeding. Because the third problem is an aspect of applied mathematics, it will be mostly ignored. Throughout, emphasis will be placed on strategic aspects of feeding rather than on what Holling (75) has called "tactics."

3,356 citations

Book
17 Mar 1996

1,701 citations

Journal ArticleDOI
TL;DR: It is concluded that vervet alarm calls function to designate different classes of external danger, and context was not a systematic determinant of response.

876 citations

Journal ArticleDOI
TL;DR: Present knowledge about the species of mammals in which females are larger than males is quite rudimentary and much more information is needed before the authors will be able to speak of the selective pressures accounting for the phenomenon with any reasonable degree of certainty.
Abstract: Females are larger than males in more species of mammals than is generally supposed. A provisional list of the mammalian cases is provided. The phenomenon is not correlated with an unusually large degree of male parental investment, polyandry, greater aggressiveness in females than in males, greater development of weapons in females, female dominance, or matriarchy. The phenomenon may have evolved in a variety of ways, but it is rarely, if ever, the result of sexual selection acting upon the female sex. The most common selective pressures favoring large size in female mammals are probably those associated with the fact that a big mother is often a better mother and those resulting from more intense competintion among females for some resource than among males. It appears that, in general, more than one such pressure must affect the females of a species, and that their combined effects must not be countered by even stronger selective pressures favoring large size in males, before the result is that of larger size in the female sex. Sexual selection may often be operating upon the male sux in mammals even when it is smaller. Present knowledge about the species of mammals in which females are lager than males is quite rudimentary. Much more information is needed before we will be able to speak of the selective pressures accounting for the phenomenon with any reasomable degree of certainty. Perhaps the most fruitful approach would be a series of field studies of groups of related species in which females are larger in some species and males are larger in others.

645 citations