Barriocanal Lozano, Carles

Robson, D.

Revistes Catalanes amb Accés Obert

230 Spring migration in the western Mediterranean and NW Africa
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Range 
The Common Chiffchaff breeds in upper and lower 
middle latitudes of the W Palearctic, including most of 
Europe east as far as E Siberia (Cramp, 1992). It winters 
chiefly in SW Europe around the Mediterranean and in 
a huge area including the northern Afrotropics, Arabia 
and N India (Cramp, 1992). It does not breed on the 
Balearic Islands, in Morocco or at any of the ringing 
sites; however, it is a common wintering species in all 
areas except for the dry Balearics, Els Columbrets, L’Illa 
Grossa and Las Chafarinas, where migrants constitute 
the bulk of captures. 
The recently split Iberian Chiffchaff Phylloscopus 
ibericus breeds in the Iberian Peninsula, S France and 
NW Africa, and winters primarily in tropical Africa 
(Svensson, 2001; Pérez-Tris et al., 2003; Catry et al., 
2005). Records from Catalonia and the Balearics are 
very scarce but our sample from these areas undoubt-
edly includes a very few misidentified Iberian Chiffchaffs 
(since in former years this taxon was not systematically 
told apart). In Morocco, where Iberian Chiffchaffs are 
more common during migration (Gargallo et al., un-
publ.), the number of birds wrongly identified as Com-
mon Chiffchaffs must be slightly higher. 
Migratory route 
Recoveries indicate that the Common Chiffchaff mi-
grates on a broad front through the W Mediterranean 
towards its breeding grounds in C and N Europe, in the 
main heading SW-NE (fig 1; Zink, 1985). Unlike in au-
tumn, the W Iberian Peninsula is largely devoid of birds 
in spring; while passage increases in coastal E Spain and 
the Balearics (present data; Cantos, 1992). An interest-
ing deviation from the main migratory pattern comes in 
the form of a bird ringed in Barcelona in late March and 
recovered one month later in Sardinia (heading E-SE). 
The geographical variation in the frequency of cap-
tures during the standard period gives little information 
in this case, since captures become much scarcer from 
mid-April onwards and data from Morocco may also 
include some Iberian Chiffchaffs (fig. 2). Taking into 
account the full study period, 24% of the birds were 
trapped in three continental wetland sites where the 
species is common both in winter and during migra-
tion: Els Aiguamolls, El Canal Vell and the Llobregat del-
ta. The majority (66%), however, were ringed on three 
insular sites where this warbler is essentially migratory: 
L’Illa de l’Aire, Cabrera and Els Columbrets. It is clear 
from the high number of captures at these sites that 
these islands act as points of attraction for migrants 
needing to rest, and they are also proof that this spe-
cies crosses the Mediterranean in good numbers. This is 
probably also the case for many birds from NW Africa, 
where the species is very common in winter (Cramp, 
231Common Chiffchaff
1992; Isenmann & Moali, 2000; Thévenot et al., 2003; 
Isenmann et al., 2005).
  
Phenology 
Passage begins in February (outside the study period) 
followed by a peak in mid-March. Captures then de-
crease steadily through April, and a few individuals are 
still trapped well into May (fig. 3). The main pattern of 
passage is similar in the Balearics / Els Columbrets and 
Catalonia, although in N Morocco late passing birds 
are somewhat more frequent. Overall, passage through 
the study area is similar to that recorded in spring from 
Gibraltar (Finlayson, 1992), La Camargue (Blondel & 
Isenmann, 1981), the Tyrrhenian islands (Spina et al., 
1993) and Israel (Morgan & Shirihai, 1997). No clear 
age-related differences in phenology are observed. The 
frequency distribution of third primary lengths, how-
ever, indicates a clear temporal segregation of sexes: 
males (distinctly larger; Cramp, 1992) pass during first 
half of March and females mostly from mid-March on-
wards (fig. a). This differential migration has also been 
observed in Eilat (Morgan & Shirihai, 1997) and the C 
Mediterranean (Spina et al., 1993). The early passage 
of male Chiffchaffs seems to be caused by their early 
departure from the wintering grounds and not only by 
a differential speed between sexes during migration 
(Catry et al., 2005). Interestingly, a new wave of larger 
birds (males) passes through the area from mid-April 
onwards (a pattern that may occur also in the C Medi-
terranean; cf. Spina et al., 1993). This new wave may 
reflect the passage of birds belonging to more north-
eastern and late migrating populations (Cramp, 1992), 
perhaps wintering in tropical Africa. Recoveries do not 
reveal any pattern regarding the timing of passage 
and geographical origin because available data is very 
scarce late in the season. 
Biometry and physical condition
Mean values for third primary lengths range from 43.8 
(S Morocco) to 45.1 (Catalonia; table 1). In most areas 
averages are slightly higher than in the C Mediterra-
nean (overall mean 43.8, n = 1,010; Spina et al., 1993), 
probably due to the inclusion of a higher proportion 
of males (as more early-season data is available). Mean 
values for wing lengths vary from 56.7 (dry Balearics) to 
58.3 (Catalonia), within the range of the nominate race 
in W Europe (Cramp, 1992), but lower than in E Medi-
terranean, where birds from the larger north-eastern 
populations are common (Morgan & Shirihai, 1997). 
The third primary length shows a marked tendency to 
decrease during March, but then in early April the ten-
dency inverts and is slightly upwards (fig. 6). This is a 
similar pattern to that previously found in the C Medi-
terranean (Spina et al., 1993) and reflects the differen-
tial migration of the sexes described above.
Mean fat scores range between 1.2 (Els Colum-
bretes) and 2.8 (S Morocco). Fat is lowest on Els Co-
lumbrets, but otherwise differences between areas 
are not significant. Physical condition is also worst 
on Els Columbrets, but better in N Morocco than in 
Catalonia and the dry Balearics. Birds from the wet 
Balearics also have better physical condition than 
those from the dry Balearics, probably due to a higher 
proportion of wintering birds in the former area and 
its better suitability as a stopover site (it attracts a 
smaller proportion of migrants in poor condition and 
provides better feeding options for gaining mass). Fat 
shows a slight tendency to increase in March and de-
crease in May, reaching a peak in April (fig. 9); in the 
dry Balearics the overall temporal trend is significantly 
negative. Physical condition tends to increase slightly 
with time (fig. 7). 
Mean body mass varies from 7.0 (Els Columbrets) to 
7.6 (N Morocco; table 1). Seasonal variation differs be-
tween study areas, decreasing significantly in Catalonia 
and on Els Columbrets, but increasing in the wet Balear-
ics; it shows no clear pattern in the dry Balearics and Mo-
rocco (fig. 8). Birds from N Morocco are similar to those 
from the wet Balearics, and both are significantly heavier 
than those from Catalonia; birds from Els Columbrets and 
the dry Balearics have the lowest average body mass. Av-
erage mass in N Morocco is somewhat higher than that 
reported by other authors in roughly the same area dur-
ing March (mean 7.1, n = 41; Cramp, 1992) and similar 
to that reported in a very limited sample from N Tuni-
sia (mean 7.6, n = 4; Waldenström et al., 2004). Mean 
values from S Morocco are higher than those reported 
from the nearby areas of Defilia (mean 6.3, n = 17; Ash, 
1969) and Merzouga (mean 7.2, n  =  78; Gargallo et 
al., unpubl.). The overall average body mass (mean 7.2; 
n = 140) is only slightly lower than in N Morocco. Al-
though our data and that from Ash (1969) may include 
some Iberian Chiffchaffs, the body mass of both species 
is very similar in S Morocco (Gargallo et al., unpubl.). Body 
mass in Catalonia is only slightly higher than at Gibral-
tar (mean 7.0, n = 88; Finlayson, 1981) and similar or 
somewhat lower than that reported in Wales and the 
Netherlands further to the north (means 7.5 [n = 101] 
and 8.3 [n = 19], respectively; Cramp, 1992). Averages 
in the dry Balearics and on Els Columbrets are very similar 
to those reported from the C Mediterranean (mean 6.9, 
n = 1,010; Spina et al., 1993). 
Overall, body mass shows very little geographical 
variation across NW Africa and SW Europe and average 
figures are mostly similar to those recorded during the 
breeding season (Cramp, 1992; ICO, 2010). Thus, the 
Chiffchaff seems to move through the area largely by 
means of short bouts of flight interspersed with brief 
stopovers (see also below). Fattening prior to cross the 
Mediterranean seems to be limited even in N Morocco. 
232 Spring migration in the western Mediterranean and NW Africa
Stopover 
The proportion of birds remaining at ringing sites is 
low and the mean minimum stopover length is only 
3-5 days in most areas (table 2,  fig. 5). There are 
no retraps from N Morocco in spite of the relatively 
large sample size. Birds are unable to gain mass in 
any area and fuel deposition rates are only marginally 
significant in the dry Balearics (negative) and the wet 
Balearics (positive) when considering retraps of more 
than one day. Stopover length is significantly longer 
in Catalonia and the wet Balearics than in the dry Bal-
earics, moreover birds staying in the first two of these 
areas do not have significantly lower initial body mass 
than those not trapped again (as is the case in the dry 
Balearics). Birds from Els Columbrets seem to act in a 
similar manner to the dry Balearics; however, retraps 
are also too scarce at this site to be conclusive. The 
presence of wintering birds early in the season may 
explain part of these site-related differences, since 
they are common in Catalonia and the wet Balearics 
and all but absent from the other areas. Using only 
data from the standard period (16 April to15 May), 
when the vast majority of captures undoubtedly in-
volve migrants, the pattern of fuel deposition –but 
not stopover length– shows similar but not significant 
differences (albeit with a much smaller sample size: 
63 retraps in the dry Balearics vs. 19 in Catalonia). 
Data, however, show again that at isolated sites with 
unsuitable habitats birds that stay tend to be in poor-
er initial body condition, indicating that these sites do 
not offer good opportunities for refuelling.
Figure a. Frequency distribution of the third primary length in fortnightly periods.
Fr
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38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53
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Fr
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b
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Third primary length
     1st March
     1st May
     1st April
     2nd March
     2nd April
     2nd May
38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53
38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53 38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53
38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53
38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53
233Common Chiffchaff
Figure 1. Map of recoveries 
of birds captured in the 
study area during the study 
period (March to May). 
Table 1. Mean (± SD), range and sample size of main biometric parameters according to area.
 n Wing Third primary Body mass Fat score
Catalonia 2,187 58.3 ± 3.1 (52.0-68.0)  45.1 ± 2.6 (39.0-54.0)  7.5 ± 0.8 (4.8-12.5)  2.7 ± 1.2 (0-6) 
Columbrets 661 58.2 ± 3.5 (50.0-69.5)  44.7 ± 2.9 (39.0-54.5)  7.0 ± 0.8 (5.0-9.9)  1.2 ± 1.1 (0-6) 
Balearics (dry) 3,157 56.7 ± 2.9 (50.0-69.0)  43.8 ± 2.4 (39.0-55.0)  7.1 ± 0.8 (4.6-13.6)  2.5  ± 1.2 (0-8) 
Balearics (wet) 139 57.8 ± 3.1 (51.0-65.5)  44.6 ± 2.4 (39.0-51.0)  7.5 ± 0.8 (5.3-9.8)  2.3 ± 1.1 (1-5) 
Chafarinas 6  44.8 ± 1.8 (42.0-47.0)  7.3 ± 1.0 (6.3-9.1)  1.5 ± 1.9 (0-5) 
N Morocco 82 57.7 ± 3.0 (51.0-64.0)  43.9 ± 2.5 (39.0-51.0)  7.6 ± 1.0 (5.0-10.3)  2.6 ± 1.4 (0-6) 
S Morocco 43 57.9 ± 2.8 (54.0-64.0)  43.8 ± 2.2 (40.0-48.0)  7.6 ± 1.2 (5.0-10.3)  2.8 ± 1.5 (1-7)  
Table 2. Variation in fuel deposition rate (g / day) according to area and type of retraps involved (mean ± 95% CI and sample size are given).
 Catalonia Columbrets Balearics (dry) Balearics (wet) Chafarinas N Morocco
All retraps -0.06 ± 0.04 (299) -0.08 ± 0.13 (30) -0.12 ± 0.05 (243) 0.09 ± 0.11 (20)    
Retraps >1 day -0.01 ± 0.03 (214) -0.04 ± 0.10 (18) -0.05 ± 0.04 (130) 0.04  ± 0.04 (18)    
234 Spring migration in the western Mediterranean and NW Africa
Figure 2. Relative
frequency of captures and 
mean daily numbers
according to site during 
the standard period 
(16 April to 15 May). 
Figure 3. Frequency of 
captures during the  
study period. 
Aiguamolls
Llobregat
Canal Vell
Alfacada
Punta de la Banya
Columbrets
Illa de Colom
Albufera d’Es Grau
Illa de l’Aire
Albufera d’Alcudia
Dragonera
Cabrera
Conillera
Formentera
Illa Grosa
Chafarines
Kerbacha
Larache
Sidi Bou Rhaba
Fguig
Jorf
Mean daily number of captures
0              0.5              1               1.5             2               2.5 
0              20              40              60             80             100
Frequency
       Relative frequency                           Mean daily captures
                                    March                             April                            May
                      13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30
Pentad
                              Total (median date = 19/3; n = 8,176)   
20
18
16
14
12
10
8
6
4
2
0
%
 C
ap
tu
re
s
 Relative frequency                     Mean daily captures
235Common Chiffchaff
Figure 4. Variation in body 
mass and fat score 
according to site during
 the standard period 
(16 April to 15 May).
Figure 5. Variation in body 
mass by trapping status, 
minimum stopover length 
and frequency of retraps 
according to area.
Aiguamolls (n = 62)
 Llobregat (n = 32)
Canal Vell (n = 83)
Alfacada (n = 19)
Punta de la Banya (n = 11)
Columbrets (n = 411)
Illa de Colom (n = 9)
 Albufera d’Es Grau (n = 6)
Illa de l’Aire (n = 282)
Albufera d’Alcudia
Dragonera (n = 67)
Cabrera (n = 245)
Conillera (n = 53)
Formentera (n = 13)
Illa Grosa (n = 5)
Chafarines (n = 6)
Kerbacha
Larache (n = 24)
Sidi Bou Rhaba (n = 9)
Fguig (n = 40)
Jorf
Fat score (± 95% CI)
0                  1                  2                  3                4    
 5              6              7              8             9            10
Body mass (±  95% CI)
       Body mass
8.5
8
7.5
7
6.5
6
     Catalonia    Columbrets  Balearics (d)  Balearics (w) Chafarinas   N Morocco
   13.4% (2,314)    3% (1,081)     8.3% (3,463)  13.2% (151)         0% (6)              0% (86)
Area
% of retraps (sample size)
B
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(m
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 ±
 9
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C
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18
16
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8
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St
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 9
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 Fat score                     Body mass
 Not retrapped                    Retrapped (1st capture) 
  Stopover duration         Retrapped  (last capture)
236 Spring migration in the western Mediterranean and NW Africa
Figure 6. Temporal 
variation of third primary 
length according to area.
Figure 7. Temporal 
variation of physical 
condition according 
to area.
                                        March                            April                             May  
  13    14   15    16    17    18    19    20    21    22    23    24    25    26    27   28    29    30
Pentad  
      Catalonia          Columbrets            Balearic Is (dry)             Balearic Is (wet)
      Chafarinas         N Morocco            S Morocco
 T
h
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 p
ri
m
ar
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le
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g
th
 (
m
m
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48
47
46
45
44
43
42
                                          March                        April                            May
  13    14   15    16    17    18    19    20    21    22    23    24    25    26    27   28    29   30
Pentad  
     Catalonia         Columbrets            Balearic Is (dry)             Balearic Is (wet)
     Chafarinas        N Morocco            S Morocco 
Ph
ys
ic
al
 c
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d
it
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0.22
0.21
0.20
0.19
0.18
0.17
0.16
0.15
0.14
Catalonia                      Colu brets     l ric Is. (dry)        Balearic Is. (wet)
Chafarinas                     N orocco      
Catalonia                      Columbrets     Balearic Is. (dry)        Balearic Is. (wet)
Chafarinas                     N Morocco     S Morocco
237Common Chiffchaff
Fa
t 
sc
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4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
                                       March                            April                              May
  13    14   15    16    17    18    19    20    21    22    23    24    25    26    27   28    29    30
Pentad  
     Catalonia          Columbrets            Balearic Is (dry)             Balearic Is (wet)
     Chafarinas         N Morocco            S Morocco
Figure 8. Temporal 
variation in body mass 
according to area.
Figure 9. Temporal 
variation in fat score 
according to area.
B
o
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y 
m
as
s 
(g
r)
9.5
9
8.5
8
7.5
7
6.5
6
                                      March                           April                                May
  13    14   15    16    17    18    19    20    21    22    23    24    25    26    27   28    29   30
Pentad  
      Catalonia          Columbrets            Balearic Is (dry)             Balearic Is (wet)
      Chafarinas         N Morocco            S Morocco 
t l i                       Colu brets     Balearic Is. ( r )        l i  I . ( et)
f ri              N orocco     S Moroc o
Catalonia                      Columbrets     Balearic Is. (dry)        Balearic Is. ( et)
Chafarinas                     N Morocco     S Morocco


Common Chiffchaff (Phylloscopus collybita)

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Revistes Catalanes amb Accés Obert