ArticlePDF Available

The moult of the Fan-tailed Warbler

  • Independent researcher - odonatology

Abstract and Figures

First-brood Fan-tailed Warblers may begin nesting activity when only 3–¸4 months old, so that adult males face additional competition for their territory from midsummer. Both of these factors seem to influence the moult strategies shown by the species.
Content may be subject to copyright.
This article was downloaded by: []
On: 25 March 2014, At: 09:39
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number:
1072954 Registered office: Mortimer House, 37-41 Mortimer Street,
London W1T 3JH, UK
Bird Study
Publication details, including instructions
for authors and subscription information:
The moult of the Fan-
tailed Warbler
C. Gauci
& J. Sultana
The Ornithological Society , P.O. Box 498,
Valletta, Malta
Published online: 23 Jun 2009.
To cite this article: C. Gauci & J. Sultana (1981) The moult of the Fan-tailed
Warbler, Bird Study, 28:2, 77-86
To link to this article:
Taylor & Francis makes every effort to ensure the accuracy of
all the information (the “Content”) contained in the publications
on our platform. However, Taylor & Francis, our agents, and our
licensors make no representations or warranties whatsoever as to
the accuracy, completeness, or suitability for any purpose of the
Content. Any opinions and views expressed in this publication are
the opinions and views of the authors, and are not the views of or
endorsed by Taylor & Francis. The accuracy of the Content should
not be relied upon and should be independently verified with primary
sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses,
damages, and other liabilities whatsoever or howsoever caused
arising directly or indirectly in connection with, in relation to or
arising out of the use of the Content.
This article may be used for research, teaching, and private study
purposes. Any substantial or systematic reproduction, redistribution,
reselling, loan, sub-licensing, systematic supply, or distribution in
any form to anyone is expressly forbidden. Terms & Conditions of
access and use can be found at
Downloaded by [] at 09:39 25 March 2014
Volume 28
Part 2
July 1981
The moult of the Fan-tailed Warbler
by Charles Gauci and Joe Sultana
First-brood Fan-tailed Warblers may begin nesting activity when only 3-4
months old, so that adult males face additional competition for their
territory from midsummer. Both of these factors seem to influence the
moult strategies shown by the species.
THE FIRST RECORD OF THE Fan-tailed Warbler
in Malta was in 1967 (De
Lucca 1967); the first nest was discovered there in April 1973, and the species is now
common and widespread (Sultana and Gauci 1974,1975). This warbler frequents the few
'marshy' areas, cereal and clover fields, as well as other cultivated fields where
Hyparrhenia hirta
Avena sterdis
or other grasses grow on sloping waste areas
between terraced fields. In June, birds frequenting cereal fields (which are then harvested)
move down into nearby valleys where grasses, rushes and low shrubs are the predominant
vegetation. Between June and September, Fan-tailed Warblers seem to roost communally
in the low vegetation found in these valley beds and are fairly easy to mist-net.
In the five years period 1976-1980 about 400 moult cards were completed. Most of the
birds were trapped at Ghadira, which was visited at intervals of 2-3 weeks between mid-
June and October for the purpose of recording moult. The birds were trapped in mist-nets
as they came to roost in
Inula crithmoides
Juncus subulatus
(misidentified as
in Maltese floras—E. Lanfranco, pers. comm.) growing in a very thin bed of
Phragmites australis.
Smaller numbers were trapped in other areas, mainly at Chadwick
Lakes, Ghajn Rihana and Xemxija.
Moult was recorded in the standard way, following the criteria described by Snow
(1967). M oulting feathers were given a score from 1 to 4 according to their stage of growth,
old feathers being scored as 0 and new feathers as 5. All but four of the moult cards were
completed by the authors, who often examined each other's birds in order to ensure
uniform recording.
Bird Study
28: 77-86, 1981
Downloaded by [] at 09:39 25 March 2014
Aging and sexing
Between March and September most birds can be aged on plumage condition. Adults,
particularly females, are decidedly worn, with abraded and bleached wings and tail. The
central tail feathers are the most affected and, late in the season, they are almost invariably
reduced to two broken shafts. By contrast, first-year birds have fresh and unbleached
remiges and rectrices. After mid-August some birds may be difficult to age since first-year
birds from early broods may already show a good deal of abrasion. However, the tail is
never worn to the same extent as in adults and the wing feathers are never bleached
extensively. Caution has to be taken with females since, as will be seen later, some young
birds develop an incubation patch and could be mistaken for adults on this account.
Adults can be sexed on three points: (a) the presence of a brood patch in females (males
take no part in incubation);
the inside of the mouth is completely jet black in males but
pink, occasionally with slight traces of black on the sides, in females; and
females have
dark brown streaks on the head which in males are much lighter and are buffish-brown
rather than dark brown, making the head appear more uniform. First-year males acquire
the black mouth about two months after fledging and such birds can be encountered from
late April. Birds from last broods do not have any black until after finishing moult and
cannot be sexed. In both adults and first-years most of the black is lost during moult and
only dusky traces remain. Apparently, males average longer wings than females though
there seems to be much overlap (Table I).
Sequence of moult
The sequence of moult is the same in adults and juveniles; the latter undergo a complete
moult in their first calendar year, a feature which has already been noted by Thomas
(1979). The sequence of moult in the various feather tracts is described in relation to the
ten primaries.
Primaries. These moult in the usual way (i.e. descendantly), proceeding sequentially from
primary one to primary ten. Very occasionally the 10th primary, which is reduced, may be
dropped at about the same time as the 6th, 7th or 8th primaries. The first two (rarely three,
and exceptionally four) primaries are dropped in quick succession. The remainder are
shed at regular intervals and (as a rule) not more than two feathers are found growing on
one wing, except when moult is nearing completion when the outer three or four primaries
grow simultaneously (but show different scores). Very occasionally some primaries may
be renewed once again soon after finishing moult, e.g. an adult female which on 31 August
had completed moult was found growing the 6th and 7th primaries (scores 3 and 1
respectively) on both wings on 26 September; it also had the 1st and 5th secondaries
missing on both wings. Some juveniles suspend moult for a short time after renewing up to
six primaries. This is discussed more fully later. Probably all of these birds once again
moult these renewed primaries soon after resumption of moult. Of 15 birds re-examined
Downloaded by [] at 09:39 25 March 2014
after first being caught in suspended moult, 12 remoulted the renewed feathers; while the
other three could have done so undetected since they were retrapped more than five weeks
after first capture. Such birds then show a moult strategy which is similar to that referred
to as eccentric wing moult (Thomas 1977). Symmetry between the two wings is the rule but
slight differences in score are by no means rare.
These do not moult in the usual sequence found in almost all other
passerines (Snow 1967), but follow the order I st-2nd-bth-3rd-5th-4th, with little
variation. Moult thus proceeds in both directions and invariably finishes on the 4th. This
phenomenon was not detected by Thomas (1979) in birds from Portugal. The first
secondary is shed at about the same time as the 5th primary, at an average primary score of
16. Moult of this tract of feathers finishes at the same timeor shortly after the primaries.
In relation to the primaries the tertials are shed with much more variation than
are the secondaries. They moult in the order centre, inner, and outer (i.e. 8th-9th-7th).
Most birds shed the central tertial when the first two primaries are half grown, and tertial
moult is usually completed by a primary score of 26. A large number of birds renew the
central tertial (and rarely the others as well) again after the primaries have progressed half
way or more through the moult. In birds with retrap histories 74% did so, while the rest
could have remoulted one or more tertials at a later stage.
This is usually moulted centrifugally but occasionally either simultaneously or
almost so. Moult starts at an average primary score of 10 and finishes before the
termination of primary moult; however, there is great individual variation.
Wing coverts and alula.
Wing coverts start at the same time as the primaries or shortly
afterwards. Moult of each primary covert corresponds to that of its primary feather. The
greater coverts are either shed simultaneously or in two or three groups. They finish early,
at an average primary score of 20. The same phenomenon found in the tertials occurs also
in the greater coverts; 55% of retrapped birds moulted up to five (occasionally all) greater
coverts again when primary moult was either nearing completion or after its termination.
The bastard wing feathers are shed between a primary score of 25-35 and moult is
completed by a primary score of 40-45.
Contour feathers.
Head feathers are the first to start, preceding the shedding of the first
primary by 15-30 days. Moult of these feathers is extremely protracted and finishes up to
20 days after the termination of primary moult. The upperparts and underparts generally
start soon after the first primary is dropped. The upperparts finish at about the same time
as the primaries but the underparts are completed up to ten days later.
Rate and duration of moult
There are two principal ways of assessing the rate and duration of moult in a population
of wild birds. One method is based on capture/ recapture data and the other on regression
When all scores were plotted against time for the whole sample of moulting Fan-tailed
Warblers, it became obvious that a regression analysis could not be undertaken because of
the extremely wide scatter of starting dates. A preliminary rate of advance was calculated
from 68 retraps (of mixed age and sex) and resulted in a mean score of 0.70/ day. On this
basis a distribution of starting dates of first-year birds was obtained. The frequency
distribution was divided into three—birds starting between 10 June and 9 July, 10 July
and 9 August, and from 10 August onwards, respectively. These three groups were
Downloaded by [] at 09:39 25 March 2014
Figure I. Primary moult scores plotted against date for adult Fan-tailed Warblers caught more than
once during a single moult. Circles = females, stars = males.
tentatively related to first, second and third brood birds respectively. However, on
examination of sex ratios, it was found that supposed first and second brood birds were
almost exclusively males and third broods females.
Subsequently, birds were divided into four categories: adult males, adult females, first-
year males and first-year females. The primary scores of these four groups are plotted
against date in Figures 1-3; retraps of same individuals are joined by lines. Dotted lines
are used when a bird showed either suspended or eccentric moult at one time or another.
The calculated rates of advance of score and duration of moult (based on retraps) are
listed in Table II.
Age and sex
Mean rate of advance/ day
Standard deviation
Mean duration (days)
92 67
95% confidence range
Downloaded by [] at 09:39 25 March 2014
1Y females
40 -
Figure 2. Primary moult scores plotted against date for first-year male Fan-tailed Warblers caught
more than once during a single moult. Scores joined by dashed lines indicate that the bird showed
evidence of suspended or eccentric moult.
Figure 3. Primary moult scores plotted against date for first-year female Fan-tailed Warblers caught
more than once during a single moult. .Conventions as in Figure 2.
Downloaded by [] at 09:39 25 March 2014
From Figure 2 it is clear that first-year males which start moult between June and early
August almost invariably suspend moult for a short time. Moult is then resumed in late
August or early September. Retraps of birds which were found with suspended or
eccentric moult at one time or another were omitted from the analysis, as were a few which
were suspected to have suspended at some point. Moult suspension seems to be far less
common in females, but retraps suggest that birds starting in July to mid-August moult at
a slower rate than birds starting later.
Timing of moult in relation to breeding season
The date on which each bird started moult was calculated by using the estimated
average rate of advance of primary score for each age/ sex group listed in Table II. The
distributions of starting dates are shown in Figure 4 and the dates are grouped into ten-
day periods to minimise error. First-year males seem to be the first to start moult,
preceeding first-year females by about a month. Most adult males commence between
mid-June and early July while females peak in the second half of July. This difference in
adults is to be expected since males build the outside skeleton of the nest but take no
further part: they neither incubate nor feed the young (pers. obs.). Many males have been
found to be polygamous (Motai 1973, Sultana and Gauci 1976).
The first-year female distribution shows only one peak, in late August. This is perhaps
surprising. To date, the Ornithological Society Nest Record Scheme holds 160 Fan-tailed
Warbler cards, from which first laying dates could be estimated to within ± 2 days. A
distribution of first egg laying dates, grouped into ten-day periods, is shown in Figure 5.
The histogram is biased in favour of later broods. Fan-tailed Warblers start laying from
mid-February but, since the majority of first brood nests are situated in cereal fields or
clover fields overgrown with wild oats, access to many of them is impossible, with the
result that they are unrecorded on cards. However, it seems likely that a genuine peak
exists between mid-May and mid-June. Several first-year females develop an incubation
patch at this time. A ringed bird known to have fledged on 11 March showed both
suspended moult and an incubation patch when retrapped on the following 31 July. Some
of the incubation patches examined on these first-year birds were clearly vascularised and
there seemed to be little doubt that at the time they were in fact incubating eggs. This
possibility had already been suggested for Bearded Reedlings
Panurus biarmicus
in Buker
1975). In July and the first half of August a number of first-year males were
found showing suspended primary moult; most of these birds had renewed the innermost
2-3 primaries. It seems probable that birds from the earliest broods start moult in late
May, June and early July, and suspend for a short period during which time they seem to
start breeding activity. During this period males can be heard singing and seen chasing
females as well as carrying nesting material. It is reasonable to assume that these are first-
year birds since most adult males are in active moult at this time. Juvenile males with
suspended moult also have "he characteristic jet black mouth of breeding adults while
moulting adults lose most of the black.
In Figure 6, the estimated starting date of moult is plotted against the hatching date for
nestlings subsequently caught when fledged and in moult. The birds shown circled were in
suspended moult when first retrapped and could have started moult at an earlier date than
shown. Though the number of ringed nestlings subsequently caught in moult is small, two
features show clearly in the figure:
males start moult earlier than females irrespective of
the time of fledging, and
the young hatched in the latter part of the season commence
moult at an earlier age than those coming from early broods.
Downloaded by [] at 09:39 25 March 2014
Figure 4. Percentage frequency distributions of estimated dates of moult commencement for
different age/ sex classes of Fan-tailed Warblers. Data grouped into 10-day periods to minimise error.
June July Aug
Figure 5. Date of laying of first egg in Fan-tailed Warblers in Malta. Data grouped into 10-day
Downloaded by [] at 09:39 25 March 2014
Figure 6. Estimated date of moult onset in first-year Fan-tailed Warblers; lines fitted by eye. Open
squares = females; solid squares = males; circled squares = birds showing moult suspension. Right
hand line joins same dates to show closing of gap between hatching and moult onset for young from
late broods.
Fan-tailed Warblers have been reported previously to moult in 43 days (Thomas 1979).
The present, more comprehensive, study indicates a considerably longer duration.
Females moult more quickly than males. The slower moult in adult males may be an
adaptation that enables them to defend their breeding territories against first-year birds
from early broods. When adult males start moulting, females are still incubating or
feeding young, and a number of first-year birds in breeding condition invade the
territories. A slower rate of moult thus appears to enable adult males to spend less time
feeding and more time defending territory. The average of 67 days for adult females
appears to be normal for a resident species. First-year males are the first to start moult,
and suspension is common until late August (Figure 2); during this time these birds sing,
contest territories and construct nests. Moult suspension is far less common in females but
it appears almost certain that at least some birds from first broods breed in their first
calendar year when about three months old.
The variability in moult rate from bird to bird is considerable, especially in first-years.
This is also found in other species, e.g. Tree Sparrow
Passer montanus
(Bibby 1977), and
is usually attributable to slower rates at the start and end of the moult cycle when fewer
feathers are growing. In the case of first-year Fan-tailed Warblers it could also result from
birds suspending moult undetected for an undetermined period between two captures.
At Gibraltar there is evidence of passage: several birds have been found carrying fat
deposits, and 'high flying' resembling that of Bearded Reedlings (Pearson 1975) has been
recorded there in July and early August (Finlayson 1979). The same behaviour has been
Downloaded by [] at 09:39 25 March 2014
observed frequently at Xemxija in Malta, most commonly in May. Small groups of
juveniles would fly high into the air, calling repeatedly, and disappear out of sight, though
sometimes they ret6ned after a few minutes. This behaviour is most common about two
hours after sunrise. While 'high flying' in Bearded Reedlings is associated with eruption,
there appears to be no similar connection in Maltese Fan-tailed Warblers. The birds at
Xemxija always flew due north and probably went on to nearby Mistra Valley (2 km
away) to feed. Before the Fan-tailed Warbler started breeding in Lunzjata Valley, on
Gozo, birds were often observed arriving there early in the morning to feed. No Fan-tailed
Warblers have been specifically examined for fat deposits in Malta, but weights appeared
to remain constant throughout the year. Though Fan-tailed Warblers show no migratory
or eruptive behaviour, there appears to be a good deal of local roaming. In juveniles this
may be interpreted as dispersal, but adults are also involved, particularly females. One
trapped at Buskett on 8 July was controlled at Ghadira (13 km NW) on 31 July when it was
in moult. Another trapped at Ghajn Rihana on 4 August 1976 was trapped at Ghadira (8
km NNW) on 21 August 1978, back at Ghajn Rihana on 15 July 1979 (when it was
accompanying a party of newly fledged young) and again at Ghadira 16 days later!
Another adult female ringed at Chadwick Lakes on 2 July was controlled while in moult at
Lunzjata on Gozo (21 km NW) the following 12 September.
Both adults and juveniles undergo a complete moult between June and November,
though it seems possible that a very few birds from extremely late nests undergo only a
partial moult. On 19 October 1979 two individuals were found with moult on the teritials,
wing coverts and body only, while another bird showed no sign of moult. Evidence is
accumulating slowly that in a number of species which are resident (or partial migrants) in
southern Europe, many juveniles also have a complete moult in their first autumn. This
has already been found in Goldfinches
Carduelis carduelis
from Sicily and Iberia (Newton
1968), Moustached Warblers
Acrocephalus melanopogon
(Svensson 1975), and in first
brood Sardinian Warblers
Sylvia melanocephala
from Malta (Gauci and Sultana 1979).
At least some juvenile Spectacled Warblers
S. conspicillata
in Malta also undergo a
complete moult in their first calendar year (pers. obs.).
We are grateful to the following ringers and trainees who, on various occasions, helped in catching
the birds: J. Azzopardi, S. Balzan, G. Bonett, V. Cilia, R. Galea, M. V. Gauci, J. Grech, J. W. Perry
and R. Testa. Robert Hudson suggested valuable improvements to an earlier draft of the paper.
Fan-tailed Warblers, both adults and juveniles, have a complete moult in autumn, mainly between
June and October. Adult males moult in about 92 days while adult females average 67 days. First-
year birds moult in 75 days (females) and 81 days (males). From spring to early autumn birds can be
aged according to the abrasion of wing and tail feathers. Adults, as well as some juveniles, can also be
sexed. Primaries moult in the normal way, i.e. descendantly, but moult of the secondaries proceeds in
both directions and finishes on the 4th. Many birds moult the tertials and some of the greater coverts
twice—at the beginning and at the end of moult. This phenomenon has apparently not been
encountered previously in other Palearctic passerines studied. Exceptionally, some primaries and
secondaries may also be moulted twice. Head feathers take longest to moult. Adult males start
moulting about two weeks before females. Many juveniles, especially males, suspend moult and show
breeding behaviour. When moult is resumed the renewed feathers are moulted once again. First-year
females from early broods develop brood patches. Young hatched in the latter part of the season start
to moult at an earlier age than those fledging from early broods.
Downloaded by [] at 09:39 25 March 2014
BIBBY, c. .j
1977. Observations on the moult of the Tree Sparrow.
Ringing and Migration
I: 148-157.
1975. Post-juvenile moult of the Bearded Tit in Zuidelijk Flevoland, the
23: 169-179.
C. 1967.
Cisticola juncidis
in Malta.
109: 623.
1979. Movements of the Fan-tailed Warbler
Cisticola juncidis
at Gibraltar.
121: 487-489.
1979. Moult of the Sardinian Warbler.
20: 1-13.
1973. Male behaviour and polygamy in
Cisticola juncidis. Misc. Rep. Yamashina Inst. Orn.
7: 87-103.
1968. The moulting seasons of some finches and buntings.
Bird Study
15: 84-92.
1975. Moult and its relation to eruptive activity in the Bearded Reedling.
Bird Study.
22: 205-227.
1967. A guide to moult in British birds.
BTO Field Guide II.
Cisticola juncidis
breeding in Malta. Ibis
116: 373-374.
and C.
1975. The Cetti's Warbler and Fan-tailed Warbler colonizing new areas.
1976. Polygamy in
Cisticola juncidis. Il-Merit!
17: 28-29.
L. 1975.
Identification Guide to European Passerines.
2nd edition. Stockholm.
1977. Wing moult in the Saves Warbler.
Ringing and Migration
I: 125-130.
1979. Wing moult in the Fan-tailed Warbler.
Ringing and Migration
2: 118-121.
C. Gauci and J. Sultana, The Ornithological Society, P.O. Box 498, Valletta, Malta.
(Revised MS. received 5 December 1980)
Downloaded by [] at 09:39 25 March 2014
... The only proven example (of which I am aware) of a bird arresting its moult when a breeding opportunity arose is that of a captive male rook Corvus frugilegus studied by Richards (1976). This apparent strategy of interrupting moult in order to make a further breeding attempt is not restricted to adults since there is evidence that some juvenile Fan-tailed Warblers Cisticola juncidis suspend their post-juvenile moult in order to make a breeding attempt in their first autumn (Gauci & Sultana 1981). ...
... If this hypothesis turns out to be correct, moult interruption in juvenile House Sparrows will be analogous to the moult suspension in juvenile Fan-tailed Warblers mentioned above. It is interesting that moult interruption appears to be more frequent among juvenile males of both species (see Gauci & Sultana 1981), a trend which might reflect sex differences in the costs of precocious breeding. An alternative hypothesis to account for moult interruption in juvenile House Sparrows is that it occurs during the intense competition for potential nest-sites which occurs in colonies during the autumn (pers. ...
This note records ten cases of moult interruption in three species of passerines resident in Britain: Robin Erithacus rubecula, House Sparrow Passer domesticus and Greenfinch Carduelis chloris. In addition previous records of moult interruption are reviewed and possible functions discussed. The importance of distinguishing between cases of “arrested” and “suspended” moult is stressed; many published records of moult interruption do not do so.
... A few individuals of many species may moult S 6 before S 5 (Jenni & Winkler 1994). A very similar pattern was reported by Gauci & Sultana (1981) for the Zitting Cisticola, with a sequence of S 1 -S 2 -S 6 -S 3 -S 5 -S 4 . Descendant and ascendant is a common sequence for the secondary moult in non-passerines, especially in species with many secondaries, such as gulls and kingfishers (Baker 1993); the adaptive role of this sequence strategy for the Graceful Prinia is not clear. ...
Full-text available
The moult pattern of the Graceful Prinia Prinia gracilis, a resident cisticolid warbler of the Middle East region of the Western Palaearctic, is poorly known. Characterising moult strategies in the avian life cycle is important for understanding population processes and dynamics and, therefore, we have analysed the timing, sequence, extent and duration of post-juvenile moult of Graceful Prinia in Israel. The extent of post-juvenile moult was either complete or partial (but extensive), depending on the dates of hatching and the start of moult. Compared to most European passerines, the long breeding period (February–November) in this region allows a relatively long moult period (79.3 ± 4.7 days) for this resident species, which facilitates considerable variability in the extent of post-juvenile moult.
... Other explanations for the sexual difference in timing of molt could be that die male for some reason values die current brood less than the female, e.g., because of a lowered realized paternity caused by extra-pair fertilizations (Kempenaers et aL, 1992; Mailer and Birkhead, 1993) or because of greater future life-expectancy as a consequence of higher male than female overwinter survival (Breitwisch, 1989). Finally, in many sedentary birds such as die blue tit, there is often a strong density-dependent competition over territories in early autumn when die juveniles of die year try to establish themselves in die local population (Gaud and Sultana, 1981;Tinbergen et aL, 1985). Since males are more active in territory defense, they might have to start molt earlier than die females to have full-grown flight feathers early and be prepared for autumn territorial contests (Dhondt, 1973). ...
Full-text available
Breeding activities and molt are generally thought to be mutually exclusive in birds since both are energetically costly and are normally separated in time. However, sometimes molt overlaps with breeding to some degree. A trade-off between adult somatic maintenance functions (feather renewal) and parental care is then to be expected. The consequences of this are largely unknown, and there are few studies that have shown any fitness costs of molt-breeding overlap. We investigated the consequences of molt-breeding overlap by removing first clutches of blue tit Parus caeruleus pairs, thereby inducing late repeat clutches. Among the delayed pairs, a high proportion of males and some females started their molt already during incubation or nestling feeding. Molting males fed their nestling to a lesser extent than non-molting ones, and nestling mortality increased as a direct result of the early timing of male molt. Furthermore, the ability to raise an experimentally enlarged brood was negatively coupled to the molt stage of the male. Our data thus protide evidence that molt-breeding overlap leads to fitness costs, and we discuss the results within the context of sexual conflict and the implications for optimization of avian reproductive decisions.
Wing and tail morphology strongly affect flight performance which may consequently decline during feather moult due to the creation of feather gaps in the flight‐surface. Hence, the size and shape of moult‐related gaps may directly affect flight capacity. Here, I examined the divergent rectrix moult sequence compared to the more common distal moult sequence. In the divergent moult, the focus of rectrix moult is shifted from the tail centre (R1; rectrices numbered distally from mid‐tail outward) to another rectrix (R2 or R3), and then rectrices are moulted bidirectionally, towards the tail centre and outwards. The result of this moult sequence is the splitting of the tail gap into multiple smaller gaps. Using a large moult database including 5,669 individuals of 47 Western Palaearctic passerine species, I found evidence of divergent moult sequence for only seven species. Using comparative and experimental approaches, I found that the divergent rectrix sequence is correlated with higher moult speed and lower aerodynamic cost. Furthermore, the divergent rectrix sequence is more common among adults than juveniles. This work focused on the feather moult sequence ‐ a seldom studied aspect of the avian life‐history. I propose that moult‐related aerodynamic costs may be an important evolutionary factor not only in moult speed, but also in moult sequence. This article is protected by copyright. All rights reserved.
Full-text available
In the Fan-tailed Warbler population, males were found to have significantly longer wings than females. There was no overlap, except two adult males with the shortest wings and one female with the longest ones, contrary to the observations of Gauci & Sultana (1981). The same was also true for juveniles, there was no overlap. There were also significant differences in body weight and bill length between adult males and females, however, these measurements were not used for sexing because of overlapping. In juveniles, body weight and bill lenght did not differ significantly between the sexes.
During a two-year study in Malaysia, I recorded molt in 117 adult Fantail Warblers (Cisticola juncidis) to examine the annual molt pattern in relation to the population's breeding seasons. Adult male warblers that were molting primaries were recorded only during January, September, and October, while females in primary molt were recorded in every month except July. Molt in the secondaries, rectrices, and head and body followed similar schedules. There appears to be just one molt annually, unlike the pattern in most other parts of the species' range. Adult male warblers begin to molt synchronously at the end of the summer breeding season; most complete their primary molt before territory establishment and courtship activity in the winter breeding season. The females' postbreeding molt is less synchronous because many females in this polygynous population are caring for fledglings weeks after males stop breeding. Thus, many female birds enter the winter breeding season still in molt. Rather than risk losing a breeding opportunity, these birds apparently delay, or interrupt, their molt to begin breeding, and then complete molting after the winter breeding season. The flexible molt schedule of birds in this population is a facultative response to the seasonal availability of nesting cover and food, and enables the warblers to exploit valuable, brief opportunities for breeding.
This paper contains the commencement, sequence, extent and duration of moult, and body weights during moult in first‐year Sylvia warblers. Lesser Whitethroats, Whitethroats and Blackcaps moulted the five feather areas in the same sequence but Garden Warblers differed in the sequence of wing‐covert moult. Extent of moult was similar, except for wing‐coverts, which differed both within and between species with Lesser Whitethroats moulting the most feathers and Garden Warblers the least. Variations in duration of moult were also present with Garden Warblers the first to start and finish moult and Blackcaps the last.Mean body weights (in all species) followed similar patterns with higher mean weights when in mid‐moult suggesting that energy demands were highest when the greatest number of feathers were growing. Body weights for birds in fresh plumage are discussed speculatively.
Full-text available
Full-text available
This paper considers the rate and season of moult in the Fan-tailed Warbler Cisticola juncidis in southern Portugal. An estimate of 43 days for the duration of primary moult of peak season juveniles is obtained, though four retraps predicted 66 days.
1. The breeding behavior particularly of the male Cisticola juncidis was studied in 1967 at Chikuma River basin, Nagano prefecture.2. The observation data were obtained by '2-hour observation' between 8-10 a. m.3. The chief behaviors of the male are singing and nest-building.4. The male sings two kinds of song, the air and perch songs, and both the frequency and length of the songs are greater in the air song.5. The male sings through the breeding season from early April to middle September, and the frequency and the length of the songs per hour were 12.9 times and 12 minutes 37 seconds in average respectively.6. The male constructs the outer wall of the nest and the female works for inside lining. One male constructed 20 nests during a breeding season, of which 8 were used by different females.7. The nesting behavior was recorded on 66 days (84.6%) of the 78 days observation between April 25 and September 11. Average 6.6 days were required for construction of one nest.8. The male abandoned the nests which were not used by females and may take their material for construction of a new nest.9. The above two sustained behaviors of the male, the continuous singing and nesting, have definitive roles in functioning its polygomous breeding system, for accepting the females successfully.
This paper reports on the rate and timing of the autumn moult of the Tree Sparrow Passer montanus. Primaries were replaced in about 60 days, adults probably moulting slightly faster than juveniles. The variation in moult-rate between individual juveniles was considerable and strongly associated with their gain of weight. Moult started between early July and early September; adults starting earlier than juveniles. First-brood young seemed to remain near the breeding areas while moulting. Later young appeared to roam in flocks away from the natal areas and probably had a low chance of being recruited into the next season’s breeding population because they were still moulting while the early birds were claiming sites for the next breeding season. The speed of moult is compared with a few other species and the energetics are briefly discussed.
Moult and its relation to eruptive activity in the Bearded Reedling Bird Study A guide to moult in British birds. BTO Field Guide II. Tring. SULTANA. J. and C. GAUCI. 1974. Cisticola juncidis breeding in Malta
  • D J Pearson
PEARSON, D. J. 1975. Moult and its relation to eruptive activity in the Bearded Reedling. Bird Study. 22: 205-227. SNOW. D. W. 1967. A guide to moult in British birds. BTO Field Guide II. Tring. SULTANA. J. and C. GAUCI. 1974. Cisticola juncidis breeding in Malta. Ibis 116: 373-374.
  • C Gauci
  • J Sultana
GAUCI, C. and J. SULTANA. 1979. Moult of the Sardinian Warbler. ll-Merill 20: 1-13.
Polygamy in Cisticola juncidis
  • J Sultana
SULTANA, J. and C. GAUC1. 1976. Polygamy in Cisticola juncidis. Il-Merit! 17: 28-29.
The Cetti's Warbler and Fan-tailed Warbler colonizing new areas
  • J Sultana
SULTANA, J. and C. GAUC1. 1975. The Cetti's Warbler and Fan-tailed Warbler colonizing new areas. II-Merill 15: 2-3.