1) Corsican pine seeds are an important food source for the Corsican nuthatch, especially in winter. 2) Cone and seed production in Corsican pine forests varies greatly between years and locations. Forests at higher altitudes tend to have lower and more variable production. 3) To survive, a pair of Corsican nuthatches needs access to an area producing at least 1300 cones per year, or around 10 hectares in most forests. Forest disturbances can negatively impact the food availability for nuthatches.

1. Pasquale MONEGLIA,
EPHE, CEFE (UMR 5175)

3. Seeds pine are an abundant and energetic source of food for generalist seed
predators and specialist seed predators.
But, in Pinus, cone and seed production have interannual and spatial variations,
also seeds and cones characteristics are variables.
The forest’s granivorous develop specific adaptations to their habitat and food. But,
these adaptations create a dependency that may be restricting, in case of
disturbances affecting the productivity of trees (logging, fire,…)
The Corsican nuthatch is sedentary and remains in an area of only a few hectares
throughout the years, at altitudes above 900 m. Nuthatch develop specific
adaptations to their habitat and food, specifically important in winter when laricio
seeds are the essential of the diet of nuthactches

4.  Quantify the relationship between the Corsican nuthatch and
Corsican pine seed :
1. the energy needs of the bird
2. energy intake of the seeds
3. availability / accessibility of the resource
 Description of Corsican pine seed and cone production :
1. Quantitative aspects of cone crop,
2. Cone and seed caracteristics
3. Spatio-temporal variation of cone crop
4. Dendrometric and fire severity variables influence cone crop

6. Cones and seeds characteristics
1. Cone harvested before seed dispersal
2. Cones were placed at a temperature
of 35°C for twelve hours to trigger the
opening and release the seeds
3. Measures
i. Diameter at breast height (DBH)
ii. Full and empty seed number
iii. Seed weight
Cone production
1. Monitoring during 3 years :
2004-2005-2006
2. Study area :
8 pinewoods, elevations 150-1400 m.
3. Visual counting
4. 3 diameter classes : 20-49, 50-79, ≥80 cm

7. %U%U%U%U
%U%U
%U
%U%U%U%U%U
%U%U%U%U
%U
%U%U%U%U%U
%U
%U
%U%U%U%U%U%U
%U%U
%U%U%U%U
%U%U%U%U%U
%U%U
%U
4
2
3
6
1
5
7
8 1 – Tartagine
2 – Aitone-Lindinosa
3 – Vizzavona
4 – Vallée d’Asco
5 – Basse vallée du Golo
6 – Restonica
7 – Basse vallée du Tavignano
8 – Petrapiana – Poggio di Nazza
- light green : pinewood at low
altitude (altitude below 1000 m)
- dark green : homogeneous stands
of altitude (altitude above 1000 m)

8. To assess the availability of seeds for nuthatches, we quantify four parameters :
 Field metabolic rates of Corsican nuthatches: it represents the total daily
energy requirement for an animal in the wild.
Equation relating FMR for birds to body weight :
FMR (kJ/day) = 10,4×(weight)0,68
 Metabolizable energy: it depends on characteristics of both the food and the
organism eating it.
ME = GE × AE
where:
ME = Metabolizable energy (e.g., in kj/g)
GE = Gross energy (e.g., in kcal/g) is the total energy content of a food
AE = Assimilation efficiency by animal : AE = 0.75 for the passerines
eating seeds
 Energy value of Corsican pine seeds, measured with a bomb calorimeter
 Cone production/ha

9. Variation in cone production
Seeds and cones characterists
Variation in number and weight of seed per cone
Food needs of the nuthatch
Estimation pinewood area required to maintain a pair of Nuthatch

10. Cone production is highly variable :
1. The number of cones produced by trees varies according to the year
2. Production varies according to location of trees :
i. production varies from one forest to another for the same years
ii. production varies within forest
iii. production varies between the altitudes
3. Cone production depends strongly on the diameter of pins

11. Effect of geographical area according to
year, on the cone production
0
20
40
60
80
100
120
140
160
180
NS1 NS2 NS3 NS4
Conenumberpertree
Forest
2004
2005
2006
NS1 Vallée d’Asco
NS2 Forêt de Petrapiana-Poggio di Nazza
NS3 Forêt d’Aitone-Lindinosa
NS4 Forêt de Vizzavona
0
100
200
300
400
500
600
300 600 900 1200 1500
Conenumberpertree
Elevation (m)
Année 2006
D=40cm
D=60cm
D=80cm
Effect of altitude and diameter of the tree on
the cone production in 2005 and 2006
0
100
200
300
400
500
600
300 600 900 1200 1500
Conenumberpertree
Elevation (m)
Année 2005
D=40cm
D=60cm
D=80cm

12. We have also seen that :
1. Pines with larger diameters are more productive.
2. In the pine forests of altitude(alt.>1000 m.), there are many small producers
and few large producers. But large producers produce a large number of
cones constituting the majority of production. They may even be the only
producers.
3. Change in proportion of non-producing trees at altitudes above 1000
meters : between 13 and 64% depending on the year.
The years of low cone production correspond to the years of low frequency
of producing trees when production is low, it is concentrated on a few
trees.
And, the proportion of non-producers trees is higher in high altitude
during the years of low production. However, during the good years, the
proportion of non-producers trees was the same regardless of altitude.

13. Year
Number of
cones
measured
Variables Mean min - max
2004 263
Length cone (mm) 53,3 31,7 - 82,1
n seed empty 22 0-57
n seed full 20 1-83
n seed 42 1-97
% seed empty 54 0-98
weight of seeds
/cone
299,26 7,7-1542,4
2005
348
Length cone (mm) 54,4 30,5-81,6
n seed empty 15 0-49
n seed full 29 0-69
n seed 44 7-79
% seed empty 36 0-100
weight of seeds
/cone
418,81 0-1361
46 number of scales 43 26-58
Without being able to identify
the precise reasons, we observed
that could coexist :
1. full seeds
2. empty seeds
3. scales without seeds
developed where only the
wing was present

14. Full seeds
Empty seeds, with marks of
invertebrates

15. Sample 1:
Asco forest
Elevation > 1000 m
February 2003
495 cones from 36 trees
1. The individual weight seed (WGP) varied between the cones and the trees.
2. The individual weight seed (WGP) was influenced by :
• DBH,
• the number of empty seeds per cone
• the total number of seeds per cone

16. 12,0
13,0
14,0
15,0
16,0
17,0
18,0
19,0
20,0
20 40 60 80 100
WGP
D
NTG=12
NTG=32
NTG=52
NTG=72
12,0
13,0
14,0
15,0
16,0
17,0
18,0
19,0
20,0
20 40 60 80 100
WGP
D
NTG=12
NTG=32
NTG=52
NTG=72
12,0
13,0
14,0
15,0
16,0
17,0
18,0
19,0
20,0
20 40 60 80 100
WGP
D
NTG=32
NTG=52
NTG=72
12,0
13,0
14,0
15,0
16,0
17,0
18,0
19,0
20,0
20 40 60 80 100
WGP
D
NTG=32
NTG=52
NTG=72
Effect of diameter (D) on the seed weight (WGP) according to number of empty seeds per cone (NGV) and
total number of seeds per cone (NTG)
NGV=0 NGV=11
NGV=22 NGV=32
…but the effect of the diameter depends on the total number of seeds and the
number of empty seeds :

17. The weight of seeds per cone (=food quantity per cone) varied between the forests
and the years.
The weight of seeds per cone (=food quantity per cone) was influenced by :
• the total number of seeds per cone  a positive effect
• the number of empty seeds per cone  a negative effect
• the length of the cone  a positive effect
• the year  2005 good year
• the size of the cone  a positive effect
Sample 2 : Forest
Elevation
(m)
2004 2005
Number
of trees
Number of cones
harvested
Number
of trees
Number of cones
harvested
Vizzavona 1150 9 74 10 83
Petrapiana 1150-1500 9 68 12 89
Asco
1300 6 59 10 97
800 4 34 0 0
440 3 28 10 80

18. Our knowledge suggest that, at least during the 3 months of winter, the nuthatch
eats almost exclusively some seeds.
 It means that a pair needs at least 50.000 seeds (more than 2 500 cones) per
year, that is to say more than 250 seeds/bird/day.
These quantities are to be compared to the one observed on forest Tits (passerine
with a body weight and a trophic ecology comparable to the nuthatch). Indeed, the
seed availability for nuthatches is clearly limited by competition with other
granivores  in Corsican pine forest, the main competitor is Coal tit (Parus ater).

19. Parus ater
Field Metabolic rate = 46.3 Kj/day,
but seeds only a third of the diet
 seeds provide only 15.4 Kj/day
Need food = 80 seeds/day/ind.
7 198 seeds/year/ind
215 954 seeds/year/10ha
Density =15-21 pairs/10ha
Corsican Nuthatches with densities of
only 1 pair/10 ha, collect only
587 seeds/day/10ha
Sitta whiteheadi
Field Metabolic rate = 56.7 Kj/day
Need food = 294 seeds/day/ind.
26 446 seeds/year/ind
52 892 seeds/year/10ha
Density = 1 pair/10ha .
Coal tits collect more than
2 400 seeds/day/10ha
10 ha  1 pair of nuthatch and 15 pairs of tit needs at least 13 443 cones/year

20. 10 ha (nuthatch
density = 1 pair/10ha),
1300 cones are
required to maintain 1
pair of Nuthatch, and
15 pairs of Coal tit
Area of the stand to feed the Corsican nuthatches and
Coal tits, depending on the production of cones

21. Area of the stand to feed the Corsican nuthatches and Coal tits,
depending on the production of cones

22. Territory
Sitta
Altitude
(m)
Number of cones
per ha
Minimale area
(ha)
2005 2006 2005 2006
X8 1067 34 272 25 377 0,4 0,5
ZA7 1086 22 616 15 116 0,6 0,9
V10 1110 29 052 17 131 0,5 0,8
T14 1200 31 343 11 640 0,4 1,2
ZD9 1240 21 950 6 494 0,6 2,1
O23 1285 8 345 1 870 1,6 7,2
V16 1310 21 772 4 146 0,6 3,2
W15 1310 24 219 4 490 0,6 3,0
P21 1315 16 481 3 066 0,8 4,4
R22 1330 28 475 4 727 0,5 2,8
N24 1337 22 534 3 495 0,6 3,8
S20 1400 37 267 3 886 0,4 3,5
H25 1465 7 988 487 1,7 27,6
year 2005 : NC = 3,42 + 0,02(D) + 0,002(ALT) - 0,0001(ALT²/100)
year 2006 : NC = 3,37 + 0,15(D) + 0,006(ALT) - 0,0005(ALT²/100)
0,0
2,0
4,0
6,0
8,0
10,0
1067
1086
1110
1200
1240
1285
1310
1310
1315
1330
1337
1400
1465
Minimalearea(ha)
Altitude of the territory (m)