Use of Feather Minerals as Biological Tracers 
to Determine the Breeding and Molting Grounds 
of Wild Geese 
, 
HAROLD C. HANSON and ROBERT L. JONES! 
Most PoPULATIONS AND SUBPOPULATIONS of wild geese 
are distributed on their breeding grounds in discrete units 
that occupy distinct physiographic and geologic areas. 
The possibility that feathers of these various populations 
contain an assortment of minerals bearing some relation- 
ship to the occurrence of elements in the nutrient chain— 
parent rocks, soils, waters, and food plants—of the breed- 
ing grounds was suggested by studies made of the min- 
eral content of the body and feathers of ruffed grouse 
(Bonasa umbellus) in New Hampshire.? It was found 
that a grouse could be associated with one of the four 
geological areas in the state by the content of minerals 
occurring in its tail feathers. 
After we had confirmed, from studies beginning in 
1965, that a similar relationship existed between the min- 
erals in the primary feathers of all the races of Canada 
geese examined* and the minerals in the ecosystems of 
their breeding grounds (Illinois Natural History Survey 
1966) , the study was extended to all species and races of 
wild geese breeding in or migrating into North America. 
In this report the analytical techniques used are described 
and the types of results obtained are illustrated by data 
for two populations of blue and lesser snow geese (Anser 
caerulescens caerulescens) * which nest adjacent to Hud- 
son Bay. 
Waterfowl nesting in temperate and more northerly 
portions of the northern hemisphere undergo a precipi- 
tous molt of primary and secondary wing feathers. The 
molt occurs in breeding geese about 7-10 days after the 
young have hatched and about an equivalent time earlier 
in the nonbreeding birds. The time required for growth 
of new flight feathers is directly related to the size of the 
bird. In Canada geese (Branta canadensis) , which range 
in weight from 3 to 18 pounds, the flightless period 
varies from about 24 to 42 days (Hanson 1965 and un- 
1Dr. Harold C. Hanson is a Wildlife Specialist at the Survey. 
Dr. Robert L. Jones is a Soil Mineralogist at the University of 
Illinois College of Agriculture. 
*Studies by Robert A. McCullough and C, L. Grant in 1952- 
1953 in connection with Pittman-Robertson—Dingell-Johnson 
gre reeling laboratory analyses of fish and game and 
eir foods. 
* Studies in progress by the senior author indicate the exist- 
ence of 20, rather than the currently recognized 12, races of 
Canada geese. 
*Most authorities now recognize the blue goose and lesser 
snow goose as color phases of the same subspecies. 
published) . 
25 days. 
The primary wing feathers were selected for analysis 
because their growth must be complete before the birds 
leave their natal area or, in the case of nonbreeding birds 
that have made a molt migration, their molting area. 
In contrast, the replacement of tail and body feathers 
may continue well into autumn and winter. 
The likelihood of a distinctive regional profile of 
minerals being incorporated into the protein matrix of 
the feather is increased by the dramatic degradation and 
synthesis of muscle and bone that take place during the 
period of principal growth of the wing feathers. A recent 
study of Canada geese (Hanson 1962) has shown that by 
the midperiod of the molt the sternal muscles lose 25-41 
percent of their weight and the leg muscles increase in 
weight 41—57 percent, depending on age and sex. By the 
time flight 1s resumed, the weights of these muscle groups 
are almost back to normal. The degradation of the 
sternal muscles appears to be a survival-related evolu- 
tionary development whereby amino acids, particularly 
the sulfur amino acids, are made available for rapid 
feather growth. The hypertrophy of the leg muscles, 
however, reflects their temporarily increased use. 
In addition to these dramatic changes in mass of the 
muscles, dynamic changes in the mineral metabolism of 
the muscle tissues also take place (Hanson and Johnson, 
unpublished). The deposition and high turnover of 
medullary bone during egg laying in birds is well docu- 
mented (Sturkie 1965: 491-501) ; less well understood is 
the osteoporosis of the long bones of the leg, particularly 
the tarsi, that takes place during molt (Meister 1951; 
Hanson unpublished) . 
As a result of these various degradational processes, 
a high turnover of some minerals and selective conserva- 
tion of others is implicit during molting and breeding 
cycles. 
For lesser snow geese this period is about 
ACKNOWLEDGMENTS 
The senior author is deeply grateful to the John Sim- 
on Guggenheim Foundation for a research grant that 
made continentwide travel possible on behalf of this and 
related studies on Canada geese. He is also indebted to 
Allen G. Studholme of the U.S. Bureau of Sport Fish- 
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