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ordic Society Oikos
Territory Quality and Feather Growth in the White-Backed Woodpecker Dendrocopos leucotosAuthor(s): Allan CarlsonSource: Journal of Avian Biology, Vol. 29, No. 2 (Jun., 1998), pp. 205-207Published by: Wiley on behalf of Nordic Society Oikos
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8/18/2019 Carlson 1998
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Perrins,
C. M. and
McCleery,
R. H. 1985. The effect
of
age
and
pair
bond
on
the
breeding
uccessof GreatTits
Parus
major.
Ibis
127: 306-315.
Rowley,
I.
1983.
Re-mating
n birds.
-
In:
Bateson,
P.
(ed.).
Mate
Choice.
CambridgeUniversity
Press,
Cambridge, p.
331-360.
Soler,
M. and
Soler,
J. J. 1996. Effects
of
experimental
ood
provisioning
on
reproduction
n
the Jackdaw
Corvus
monedula,
semi-colonial
pecies.
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377-383.
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K. A. 1989. Predation
and starvation:
ge-specific
mortality
n
juvenile
Juncos
Junco
phaenotus).
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Anim.
Ecol. 58: 275-286.
Svensson,
E. and
Nilsson,
J. - A. 1995.Food
supply, erritory
quality,
and
reproductive
iming
in
the Blue Tit
(Parus
caeruleus).
Ecology
76: 1804-1812.
Sxether,
.-E.
1990.
Age-specific
ariation n
reproductive
er-
formance
of birds. - In:
Power,
D.
M.
(ed.).
Current
Ornithology,
Vol.
7,
Plenum
Press,
New
York,
pp.
251-
283.
JOURNAL
OF AVIAN
BIOLOGY29: 205-207.
Copenhagen
998
Territory
quality
and
feather
growth
in the White-backed
WoodpeckerDendrocopos eucotos
Allan
Carlson,
Department
of
Conservation
Biology,
Swedish
University
of Agricultural
Sciences,
Box
7002,
S-750 07
Uppsala,
Sweden.
E-mail: Allan.
During
the last
decades
the
White-backed
Woodpecker
has
shown a
precipitous
decline
in
many regions
of the
western
Palearctic.
In
this
study
I
ask whether
detoriation
of the forest
breeding
habitat
might
have contributed to this
population
de-
cline
and
contraction of the
species'
range.
By
using
the tech-
nique
of
ptilochronology
it
is
shown
that the bird's
condition
reflects
the
quality
of
the
breeding
territory
as estimated
by
the
density
of
dead and deciduous stems.
Feather
growth
bars were
wider on old museum specimens, suggesting that birds living
55-150
years ago experienced
a
forest
landscape
of
better
quality
than birds do
today.
Once
widespread
in
the
boreal
forests
of
Fennoscan-
dia,
the
White-backed
Woodpecker
Dendrocopos
leu-
cotos has
declined
dramatically
during
the second
half
of
this
century
(Tiainen
1990,
Carlson and
Aulen
1992).
Several
reasons
for
the
decline have
been
suggested,
but
attention
has
mainly
focused on
habitat
loss
(Aulen
1988,
Haland
and
Ugelvik
1990,
Virkkala et al.
1993).
The
White-backed
Woodpecker
has
a
highly specialized diet, consisting mainly of
wood-boring
and
bark-living
insects,
collected
in
dead and
decaying
trees
(Aulen
1988,
1991).
Despite
a
great
interest in
the
species
on the
population
level
(Virkkala
et al.
1993),
little is
known
about
possible
effects
of habitat
deterioration
and
fragmentation
on
the
condition of
individual
birds.
Here,
I
use the
technique
of
ptilochronology
(Grubb
1989)
to
ex-
plore
whether
estimates of
territory
quality
are corre-
lated with
the
nutritional
condition of
the
birds
living
in
these
territories.
Furthermore,
this
data set
is
contrasted
to
feather
growth
measured
on
museum
skins
from the period prior to the introduction of
modern
forestry
methods.
The
technique
of
ptilochronology
uses the width
of
feather
growth
bars
to assess the nutritional status
of
a bird
(Grubb
1989).
Experimental
evidence
indicates
that
growth
bar
width reflects the bird's
nutritional
condition at
the time of moult and feather
growth
(Grubb 1995).
Assumptions
and
utility
of
the
method
are
discussed
in
detail in
Murphy
and
King (1991),
Murphy
(1992)
and Grubb
(1992).
During
field
work
in
spring
(1990-1992),
the
right
fourth
rectrix was
sampled
from
nine birds
(3
females
and 6
males)
cap-
tured
at their
breeding
sites
(nine
different
territories).
This
was
done in
two
of the
three Swedish
subpopu-
lations. The method
adopted
was that
outlined
in
Grubb
(1989).
Because
rectrices were worn
and
dirty
it was
often
possible
to discern
only
five
growth
bars.
These five
growth
bars
were
measured,
and their
means were used in the
analysis.
Adult
White-backed
Woodpeckers
show
a
high
de-
gree of territory fidelity (I. Stenberg and A. Carlson
unpubl.).
Therefore,
I
assume
that
sampled
feathers
had
been
grown
at the
breeding
site
during
the
previ-
ous
moult.
White-backed
Woodpeckers
moult
their
tail in
summer
(Cramp
1988).
The
Museum
of Natural
History (Stockholm)
has a
fairly large
collection of
White-backed
Woodpecker
skins
covering
several
of
the
species'
races.
Eight
skins
were of the
nominate form
leucotos
leucotos and
these were used in
this
study.
Five of
the
skins were
from
Swedish
birds,
and one
skin each from
Norway,
Lithuania and NW
Russia.
These
skins
were collected
between 1832 and 1942, thus being from 55 to 150
years
old.
JOURNAL OF AVIAN
BIOLOGY
29:2
(1998)
205
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8/18/2019 Carlson 1998
3/4
3.0
E 2.5-
2.5
T Ta
2
.0
O
.
1.5
c
0
r-
)
0.5
0.0
I
0
58 117 175 233 292 350
Density
(stems
/ha)
Fig.
1.
Relationship
etween stimates
f
territory uality
and
feather
growth. Regression analysis;
growth
=
1.48
+
3.8
x
10-3
deciduous
stems/ha (broken ine);
F,7=
9.4,
r2
=0.57,
p
<
0.02; growth
=
1.48
+
7.56
x
10-3
dead
stems/ha (solid
line);
F1,7
=
9.01,
r2
=
0.56,
p
<
0.05.
Two
components
of
territory
quality,
density
of dead
stems and
density
of deciduous trees were
quantified
as
follows.
At
intervals of
100
m,
areas
of
20
x
50 m
were
censused for
growing
and dead stems
(standing
or
fallen)
with a
breast
height
diameter
(bhd)
> 10 cm.
This
was done at
10
points along
a north-south transect
and at 10
points
in
an
east-west
transect
centered
on
the
previous year's cavity
tree.
Thus,
for
each
territory
20
plots
of 0.1 ha were censused.
Due
to
the limited
sample
size it was not
possible
to
control for the effect of sex.
Feather
growth
bar width was measured on
eight
55-150
years
old White-backed
Woodpecker
and were
on
average
broader
(3.71
+ 0.41
mm)
than on birds
living today
(2.20
+
0.36
mm;
Mann-Whitney
U-test,
U
=
9,
p
<
0.05).
A linear
regression analysis
revealed a
positive
rela-
tionship
between the densities
of
dead and live decidu-
ous stems found
in
the White-backed
Woodpecker
territories
and
feather
growth (density
of dead trees
r2
=
0.56,
density
of
deciduous trees
r2
=
0.58)
(Fig. 1).
A multiple step-wise regression analysis indicated that
68%
of the variation in feather
growth
bar width was
explained
by
these two
variables
(F2,6
=
6.2,
r2
=
0.68,
p
=
0.03).
The
important
result
of
this
study
is
that the bird's
nutritional
condition,
measured as
feather
growth
bar
width,
was associated
with two
estimates
of
territory
quality, namely
the
density
of
dead
stems and
the
density
of
deciduous
trees. This
result corroborates the
findings
of another
study
in which the
density
of hunt-
ing perches
and habitat
type
influenced feather
growth
in
the
Loggerhead
Shrike Lanius ludovicianus
Josef
and
Grubb 1992, Grubb and Josef 1994). Due to the White-
backed
Woodpecker's specialization
on larvae of wood-
boring
insects
(Aul6n
1988),
it was not
surprising
that
dead stems
affected
the birds'
nutritional condition.
That also
the
density
of
deciduous
trees
can influence
the
birds' nutritional
condition could
likewise
be ex-
pected.
Deciduous
trees,
especially
old
stems,
can
carry
many
dead and
decaying
branches
(Carlson
unpubl.),
and these are
frequently
used
by foraging
White-backed
Woodpeckers (Aul6n 1988).
An
alternative
explanation
for
the
results is that
high
quality
birds are found
in
high quality
territories
while
low
quality
ones reside
in
territories of
poor quality.
Thus,
the observed
relationship
between feather
growth
and
territory quality
may simply depend
on
the
quality
of the individual bird
rather than habitat.
However,
I
have not
assessed the
quality
of individual birds.
On the
museum
skins,
wing lengths
were measured
as an index
of
bird
size.
There was no
indication that
long-winged
birds
grew
feathers with
wider
bars
(r
=
-0.43,
p
=
0.28).
Interestingly,
the
historical
comparison suggests
that
birds were
living
under better
nutritional conditions
in
the
past.
It is a well-known
fact
that
in
today's
man-
aged
forest
landscape
the
density
of
both deciduous
trees
and dead stems
has
been
severely
reduced.
In
the
late
19th
century,
the volume
of
dead
stems
in
Swedish
forests was
approximately
20% while the
corresponding
figure
today
is as
low
as 1%
(Linder
and
Ostlund
1990).
The
proportion
of deciduous trees
was
probably
around 30%
by
the end of the last
century
(Olsson
1992).
Within the
early
20th
century
distribution
range
of the
species, today
the
proportion
of deciduous trees
in the landscape is 2-4% (Olsson 1992).
To
conclude,
suitable habitat for the White-backed
Woodpecker, old-growth
deciduous
forest
(Carlson
and
Stenberg
1995),
is an
extremely
scarce resource
in
to-
day's rationally managed
forest
landscape.
The results
presented
here
support
the
view
that the observed de-
cline of White-backed
Woodpeckers
in
Sweden
is
caused
by
deterioration
of
the forest
landscape.
Acknowledgements
I thank Dr. T. Part for commentsand
discussion
of
the
manuscript.
The
help
of
Dr.
G.
Frisk at the
Museumof Natural
History
was invaluable.
This
project
was
supported
by grants
from WWF-Sweden
and
the
Swedish
ResearchCouncil orAgriculture ndForestry.Thepaperwas
written
while I
was financed
by
the latter
organization.
References
Aul6n,
G. 1988.
Ecology
and
distribution
of White-backed
Woodpecker
Dendrocopos
eucotos
n
Sweden.
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Swedish
University
of Agricultural
Sciences,
Department
of
Wildlife
Ecology,Report
No. 14.
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1991.
Increasing
nsect abundance
by killing
deciduous
trees:a method
of
improving
he food situation
or endan-
gered
woodpeckers.
Holarct.Ecol. 14: 68-80.
Carlson,
A. and
Aul6n,
G. 1992. Territorial
ynamics
n
an
isolatedWhite-backedWoodpeckerDendrocoposeucotos
population.
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JOURNAL
OF AVIAN
BIOLOGY 29:2
(1998)
This content downloaded from 188.72.96.189 on Sun, 22 Jun 2014 18:14:42 PMAll use subject to JSTOR Terms and Conditions
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8/18/2019 Carlson 1998
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and
Stenberg,
I.
1995.
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hackspett
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Sciences,
Department
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(In Swedish.)
Cramp,
S.
1988.
Handbook of
the
Birds
of Western
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Oxford
University
Press,
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T.
C.,
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1995.
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and
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Power,
D.
M.
(ed.).
Current
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Vol.
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New
York,
pp.
89-114.
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and
Yosef,
R. 1994.
Habitat-specific
utritionalcondi-
tion
in
Loggerhead
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(Lanius
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Evi-
dence from
ptilochronology.
Auk
111:
756-759.
Hiland,
A. and
Ugelvik,
M.
1990. The status
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(Dendrocopos
leuco-
tos)
in
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In:
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A. and
Aul6n,
G.
(eds).
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pp.
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R. and
Grubb,
T. C. 1992.
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JOURNAL OF AVIAN
BIOLOGY 29: 207-208.
Copenhagen
1998
Genetic
confirmationof
non-identical
embryonic
twins in the
House
Sparrow
Passer
domesticus
Simon C.
Griffith
and
Reuven
Stewart,
Department of Zoology, University
of
Leicester,
Leicester,
UK
LE1
7RH.
E-mail:
sg4Oje.ac.uk
During
routine
ornithological
monitoring
of a free-
living
population
of
House
Sparrows
Passer
domesti-
cus on
Lundy
Island,
England,
an
unhatched
egg
from
an otherwise successful
clutch of four
was
found
to
contain two
intact
embryos.
The
embryos
were
comparable
in
size,
and were at an
equally
ad-
vanced
stage
of
development
(estimated
as
being
within
two
days
of
hatching, assuming
an incubation
period
of 11
days
(Seel
1968)).
PCR
amplification
of
extracted
DNA
(Primmer
et
al.
1995)
at three
microsatellite
loci
(Neumann
and
Wetton
1996)
identified the twin
embryos
as full sib-
lings,
but
resulting
from
separate
maternal
gametes
(Fig.
1,
Table
1).
In
addition,
SSCP
analysis
of
a
sex-specific
PCR
product
(Griffiths 1995)
distin-
guished
the
embryos
as of different
sexes.
Twinning
in
birds is rare
(Berger
1953,
Batt et al.
1975)
and is
typically
attributed to
cleavage
during
the
early stages
of
development resulting
in
identical,
monozygotic
twins
(Sturkie
1946).
Clearly,
the
pres-
ence of
dizygotic
House
Sparrow
twins of
different
sexes cannot
be due to
cleavage.
Two
scenarios
Table 1.
Allotypes
of
parents
and
twin
offspring
at three
microsatelliteoci. Alleles
have been
assignedarbitrary
etters
for
illustrative
urposes.
Locus
1
Locus
2
Locus 3
(Pdop3) (Pdo
L4)
(Pdo
gS5)
Male
ab
ef
ij
Female
cd
gh kj
Twin2 ad eh jj
JOURNAL OF
AVIAN
BIOLOGY 29:2
(1998)
207
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