jL. Dispersai from the centre of the breeding range of the Baltic. Greylag Goose Anser anser was studied using observa tions of individuals with neck collars.
D ispersal of Greylag Geese 21
Natal and breeding dispersal in the Baltic Greylag Goose Anser anser L. Nilsson & H. Persson
D e p a rtm e n t of A n im a l Ecology, U niv e rs ity of Lund, Ecology B u ild in g , S -223 62 Lund, Sweden. E m ail: le if.n ils s o n 0 z o o e k o l.lu .s e .
D isp e rsa i fro m the ce n tre o f the b reeding range o f the B a ltic
jL
Greylag Goose A n s e r a n s e r was s tu d ie d using o b se rva tio ns o f in d iv id u a ls w ith neck c o lla rs . The m edian n a ta l d is p e rs a l d istance was 0 km in fe m a le s and 25 k m in mates, respectively. A ll o f the fe m a le s re c ru ite d to w ith in 7 km o f w here th e y had been reared, 87% to the n a ta l la ke and 11% to n e ig h b o u rin g w a te r bodies. Of the m ates, o nly 11% re c ru ite d to the n a ta l lake, w h ile one in d iv id u a l was fo u n d m ore than 1,000 km fro m its place o f b irth . Even though the m a le s d isp e rse d to a g re a te r d istance w ith in the p o p u la tio n 's b re e d in g range, th e ir d is trib u tio n was s till h ig h ly s ke w e d tow ards th e ir p o in t o f o rig in . Two th ird s o f a ll m ates re c ru ite d w ith in 30 km o f the site w here they had been reared. Once re c ru ite d , both sexes e xh ib ite d an e x tre m e ly s tro n g p h ilo p a try to th e ir b re e d in g area. Only 1.5% o f the m ales and 0.5% o f the fe m a le s changed b re e d in g site betw een successive years. A lt bre e d in g d is p e rs a l o c c u rre d w ith in the lo c a l p o p u la tio n , and in no case exceeded 6 km. K e y W o r d s : B re e d ing d is p e rs a l, n a ta l d is p e rs a l, Greylag Goose, Sweden
“ The q u e stio n of th e r e tu rn of birds to t h e i r
homes
is one
m odern
b e h a v io u r a l
t e r m i n o lo g y .
of p e re n n ia l
M o v e m e n t fr o m th e site of b irth to th a t
interest. How fa ith fu lly do a d u lt birds,
of firs t re p ro d u c tio n o r p o te n tia l re p r o
m a le s and fe m a le s , re tu rn to t h e i r t e r
d u c tio n is te r m e d n a ta l d is p e rs a l, w h ile
rito rie s ? H ow fa r fr o m t h e i r b irth place
s u b s e q u e n t m o v e m e n t betw een site s is
do young b irds se ttle ? Over ho w m u c h
te r m e d breeding d is p e rs a l (Greenwood
g ro u n d does one fa m ily s c a tte r? " (Nice
1980).
1937). These q u e s tio n s r e m a in highly
D is p e rs a l p a tte rn is of f u n d a m e n ta l
relevant today, th o u g h n o w p hrased in
im p o rta n c e to s e v e ra l a s p e c ts of pop u -
© W ild fo w l & W e tla n d s T r u s t
W ild fo w l [2001 ) 52: 2 1 -3 0
22 D ispersal of Greylag Geese
lation biology, being an e s se n tia l c o m ponent
of
g e n e tic
d y n a m ic s ,
stru ctu re
and
in fe rio r
q u a lity ,
re s u ltin g
in
an
and
e xcep tio na lly high ra te of c o lla r loss
flo w ,
a m o n g m a les. For th a t reason, a ll in d i
e v o lu tio n a r y
v id u a ls m a r k e d w ith su ch c o lla rs w e re
m e ta -p o p u la tio n
s o u rc e -s in k
an
ge n e
change. However, la rg e -s c a le s tud ie s
excluded fr o m th e analysis.
a d d re s sin g th e se issues are rare (for a
D urin g th e years 1985-1999, re g u la r
1997).
c h e c k s fo r th e o c c u rre n c e of neck c o l
Detailed field s tu d ie s are a p p ro p ria te
lared geese w e re u n d e rta k e n fr o m the
fo r in vestigatin g s m a l l- s c a le d ispersal,
tim e of t h e i r a rr iv a l in s p rin g u n til th e ir
sum m ary,
see
C la r k e
e t at.
but they are u s u a lly unab le to fo llo w
d e p a rtu re
in divid u als th a t leave th e stu dy area.
stu d y area w a s visited s e v eral ti m e s a
S m a l l- s c a l e
w e e k in o rd e r to e s ta b lis h th e re tu rn of
s tu d ie s
are v a lu a b le
in
in a u tu m n .
In s p rin g , th e
e va luatin g th e p ro x im a te ca uses of d is
m a r k e d birds and t h e i r breeding p e r
persal, but d is p e rs a l o u tsid e such local
fo r m a n c e . F ro m th e end of May u n til
areas can only be s tu die d w ith a m a r k
th e last young fledged, th e breeding
ing
area w a s visited a lm o s t daily to e s ta b
schem e
o p e ra tin g
over a m u c h
la r g e r scale. Neck
lish
c o l la r i n g
of
both
th e
fate
of each
neck
c o lla re d
b re e d in g
gosling . G o slin g s w e re neck c o lla re d
a d u lt and g o s lin g Greylag Geese A n s e r
fr o m th e age of a b o u t six w e e k s u n til
anser, has been u n d e rta k e n a n n u a lly in
th e y w e re
flyin g
and
i m p r a c t ic a l to
s o u th w e s te r n Scania, in s o u th e r n m o s t
catch. In s u m m e r and a u tu m n , fi e l d
Sweden since 1985 (N ils so n & P ersson
w o rk
1994,
B e s id e s
n e ig h b o u rin g s ta g in g areas, espe cially
d etailed s tu d ie s in th e b reeding area,
th e Foteviken area on th e coast w h e re a
N ils s o n
e t at.
1997).
was
e x te n d e d
to
co v e r
been fo llo w e d
large p ro p o r tio n of th e Greylag Geese
o u tsid e th e stu d y area by a n e tw o rk of
fr o m th e s tu d y area g a th e r at th is tim e
v o lu n te e rs . Thus, w e are now able to
of ye a r (ef. N ils s o n & Persson 1992).
th e s e
birds have a lso
analyse n a tal and b reeding d is p e rs a l th roughout
th e
B a lt ic
p o p u la t io n s
bre e d in g range.
K n o w le d g e
of
b ird s
r e c r u it e d
o th e r p a rts of th e species'
to
breeding
range is based m a in ly on re p o rts fr o m a n e tw o rk of m o re th a n 1,000 vo lu nte e rs. Observers are located across m u c h of
Methods
the p o te n tia l d is trib u tio n A to t a l of 1,014 g os lin gs , 552 m a le s and 462 fe m a le s w e re ne ck c o lla re d in Lakes
K lo s t e r v ik e n ,
F jä llfo ta s jö n th e y e a rs
and
B ö r r i n g e s jö n ,
Y ddin gesjön
1985-1994
(P ersson
d u rin g 1994,
2000; F igure D.The fir s t g e n e ra tio n of neck c o lla rs used in th e pro ject w a s of
m arked
geese,
a l th o u g h
area of the th e r e
is a
m a rk e d bias to w a rd s th e N e th e rla n d s . F ie ld w o rk outsid e th e stu d y area was lim ite d to ir r e g u l a r visits, m a in ly in late s u m m e r and a u tu m n , to lakes situated w ith in 30 k m of o u r stu d y area. A bird defined as having eggs or
D isp e rsal of Greylag Geese 23
rtJdingesjönt
Fjallfotasjon ÎBjork>sà Krasjon
K losterviken'
10 km
Total
Lake
P ercentage in n a ta l lake
1. Yddingesjön
10
6
12
28
36
2. B ö rrin g e s jö n
4
6
7
17
24
3. K lo ste rvike n
1
11
15
27
4
4. F jä llfo ta s jö n
0
6
4
10
0
Total
15
29
38
82
18
re a rin g period and the
p ro p o rtio n of
in Lake Yddingesjön, th e lake o ffe rin g
m a le s s u b s e q u e n tly re c r u itin g to t h e i r
th e
n a ta l lake [Table 1, S p e a rm a n r=0.73,
o th e r hand th e r e w a s no su c h te n d e n c y
best fe ed in g th e
c o n d itio n s .
m in o rity
of
On th e
P
