Bird Ecology and Conservation A Handbook of Techniques

164 |Migration

Equator

12

11

10

9

8

7

6

55 57 59 61 63 65 67 69

Latitude

(^15) δ
N
Fig. 7.1Map showing recoveries of willow warblers ringed in Sweden. Recoveries
from birds ringed in southern Sweden are shown as filled circles and those from
northern Sweden by squares. The breeding distribution shows the approximate
location of the hybrid zone where there is a migration divide. The diagram shows the
^13 N signature from southern Sweden, through the hybrid zone and northern Sweden.
These data represent the location of the winter molt taking place in Africa and hence
show the differing wintering areas for the two populations (based on Chamberlain
et al. 2000).