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locations: mid-Atlantic in the north, Chesapeake in the centre of the range, and
the Carolinas in the south. Using a multi-strata capture recapture model, con-
trolling for survival and sighting probabilities, the probabilities of moving from
one sub-population to another were estimated as:
Year
t
1
Year
t
Mid-Atlantic
Chesapeake
Carolinas
Mid-Atlantic
0.71
0.287
0.003
Chesapeake
0.096
0.889
0.015
Carolinas
0.067
0.371
0.562
The low degree of fidelity to the Carolinas sub-population provides some support
for redistribution of the population away from the south as an explanation for
decline in the Carolinas, perhaps driven by improving conditions in the north
allowing geese to shorten their migration (a phenomenon observed in several
other migratory goose species). However, the high rates of fidelity and immigra-
tion to the Chesapeake region do not match the decline observed there during the
study period. Differences in survival rates were a more likely explanation for
changes in the more northerly sub-populations.
8
Mid-Atlantic
7
6
Chesapeake
Chesapeake
5
4
Carolinas
3
Mid-Atlantic
2
Carolinas
1
0
© 2007 Europa Technologies
Image © 2007 NASA
Image © 2007 TerraMetrics
48
53
58
63
68
73
78
83
88
93
Year
Fig. 2.16
Atlantic Canada geese have increasingly been adjusting their
migration behaviour to spend the winter further north (a process known as
short-stopping). This is in response to trends in food availability, driven by a
combination of changing farming practices and climate warming.
Source:
Hestbeck
et al
. (1991).
