utilization of mangroves by birds in guinea-bissau - ardeajournal ...

± mean high water
Rhizophora racemosa
& R. harrisonii
UTILIZATION OF MANGROVES BY BIRDS
tanne
- I j
lpossible area for reclamation into ricefields
Elaeis Adansonia
estuarine terrace
Fig.2. Outline zonation of mangrove vegetation in Guinea-Bissau (after Blasco 1983 and SECA/CML 1987).
grove swamp, usually within Avicennia). Though
SCET (1978) mentioned a yearly decrease of c.
20 km 2 , the mangrove area decreased by only
0.7% during 1976-85 (Diemont & Pons 1986).
The estimations of mCN (1983) and Altenburg
(1987) of c. 2,400 km 2 are probably too low, but
roughly comparable with the above-mentioned
figure without tannes and areas with scattered
mangroves. The proportion of the different mangrove
species is unknown. Rhizophora, which
usually forms a wide strip along the seaside,
seems to be the most abundant species. The mangroves
studied (Fig. 1) consisted largely of Rhizophora,
with a narrow - wide strip of Avicennia
on the inland side. Around tannes and on the isolated
island Areias Avicennia was the dominating
species.
Observations
To determine the composition of bird species,
presence and numbers of all species were noted
during field work in or near the mangroves.
Mangrove swamps were divided into three easily
recognizable types: a) on the inland side adjoining
rice fields, b) on the inland side adjoining
"forest" (consisting in the archipelago mostly of
palm trees Elaeis guineensis, and on the mainland
of palm trees, secondary forest and woodland),
c) isolated (the mangrove island Areias, c.
7 km from the mainland in the Canal do Geba).
Subdivisions in Avicennia and Rhizophora
were difficult to make due to a large overlap in
their utilization by birds; the text will give the
most important examples where this overlap was
small. The data do not indicate important differences
between mangroves on the mainland and
those in the archipelago; both areas will therefore
be treated together.
In the three mangrove types observations
were done during field work involving c. 15 days
each. The presence of the majority of the species
could already be determined within 2-3 days; the
observations will therefore give a good idea of
the species composition in the mangroves during
the study period, but will definitely not be complete.
To supplement the observations, birds were
trapped with mistnets in the daytime during c.
30 hours per mangrove type (4-6 days with an
average of 60-90 m mistnets). Trapping took
place at random, in Avicennia, Rhizophora and
above small creeks; the trapping height of the
nets was c. 50-200 cm.
To get an idea of the density in the mangroves
of the most important bird species, apart
from roosting birds, a small number of counts
has been performed. The counts covered the
mangroves from seaside to inland side and thus
from Rhizophora to Avicennia. Because of the
very poor accessibility of the Rhizophora part,
59

62 ARDEA 77 (1989)
and feed in the rice fields from sunset on. Some
seed-eating doves, of which Streptopelia vinacea
was the most common, frequently used the
edges of these mangroves as a base for foraging
flights into the rice fields. The kingfisher Alcedo
cristata was especially common in mangroves
adjoining rice fields, where the species was often
observed hunting.
Numbers
Apart from remarks on some species like
"common", "locally", etc. in various "handbooks"
(Macworth-Praed & Grant 1970 and 1973,
Serle & Morel 1977, Brown et al. 1982, Urban et
al. 1986, Fry et al. 1988), quantitative data on
birds in African mangroves have not been published.
The summary of our observations in Appendix
I gives a rough idea of the relative abundance
of the species, though the registration chance
will have varied. Species which have not been
recorded are probably uncommon or absent in
the mangroves of Guinea-Bissau, at least from
December through February.
Of the c. I million wintering coastal waders
in Guinea-Bissau (Zwarts 1988) several hundred
thousands will have used mangrove trees as a
high tide roost, while most of the remaining birds
roosted on tannes within the mangroves. The greater
part of the large wading birds which feed on
the mudflats had their high-tide roost in the mangroves.
This applied to several thousands of
birds, while their night roosts in mangroves may
have held tens of thousands. Most of the terns
roosted on tannes and beaches and their roosting
in mangroves was limited to hundreds rather than
thousands of birds. We estimate the number of
roosting birds of prey at several thousands for
Gypohierax angolensis and several hundreds for
Pandion haliaetus and Haliaetus vocifer.
Both the mistnet catches (Table 2) and the
sample counts (Table 3) agree with these observations.
The species which have not been caught
frequently, usually fly higher than the nets (c.
parvus, H. lucida, L. harbarus, M. persicus) or
occur mostly in open Avicennia (A. hypoleucos,
N. phaeopus, N. pulchella) or along the open se-
award edge (c. rudis) where catching is more
difficult. As with sight observations, chances of
catching the species will have varied.
The counts made in six small mangrove plots
(Table 3), though the latter are a negligible proportion
of the total mangrove area of c. 3,000
km 2 , may give an idea of the order of magnitude
of bird densities. The figures in Table 3 are minima.
Both in Tables 2 and 3 the observed densities
vary considerably from place to place; the reason
for this is not known, but is probably related to
factors like food resources, shelter and predators.
When densities as in Table 3 get near the
average for the whole mangrove area of Guinea­
Bissau, for the period December through February
bird numbers of the species in the lower half
of the table may amount at least to thousands,
and in the upper half at least to tens of thousands.
Again with densities as in Table 3, numbers of
the palearctic migrants Acrocephalus scirpaceus,
Hippolais polyglotta and Phylloscopus trochilus
may exceed half a million birds.
DISCUSSION
Species composition
Mangrove swamps are relatively extreme habitats:
they are regularly flooded by salt water
and their variation in food items is small. Neither
Avicennia nor Rhizophora bears a fruit that is
edible by birds; food resources between and above
the mangrove trees are therefore limited to insects
(Cawkell 1964). On and in the ground food
is largely restricted to crabs (especially Uca tangeri)
and mudskippers (Periophtalmus papilio);
macrobenthos is probably neither rich nor varied
in the strongly deoxygenated soil (Macnae &
Kalk 1962, Macnae 1968). In creeks, gullies and
puddles which remain after-high water, food consists
largely of fish, shrimps and water insects.
Descriptions of bird communities found in
mangroves in the different parts of the world
mentioned in the introduction all show that mangroves
are particularly used (apart from roosting
birds) by insect-eating species (especially war-

UTILIZATION OF MANGROVES BY BIRDS 63
Table 2. Mistnet catches in mangroves in Guinea-Bissau, Dec 1986 - Febr 1987. Catching sites d. Fig. 1. The
figures represent the number of birds caught/IO hours/IOO m mistnets. Trapping took place at random (trapping
height of the nets c. 50-200 cm), in Avicennia, Rhizophora and above small creeks during c. 30 hours (Ri 35
hours on 6 days with an average of 59 m mistnets; Fo 29, 4, 75; Is 34, 6, 93). The first half of the table holds the
18 "very frequently" observed species from Table I.
Acrocephalus scirpaceus
Anthreptes gabonicus
Cypsiurus parvus
Eremomela pusilla
Hippolais polyglotta
Hirundo Lucida
Laniarius barbarus
Merops persicus
Nectarinia pulchella
Phylloscopus trochilus
Platysteira cyanea
Sylvia cantillans
Alcedo cristata
Ceryle rudis
Halcyon malimbica
Actitis hypoleucos
Numenius phaeopus
Ploceus cucullatus
Phylloscopus collybita
Caprimulgus climacurus
Mesopicos goertae
Acrocephalus schoenobaenus
Alcedo quadribrachys
Butorides striatus
Merops albicollis
Pogoniulus chrysoconus
Sylvietta brachyura
Cisticola hrachyptera
Dryoscopus gamhensis
Indicator maculatus
Anthus trivialis
Centropus senegalensis
Cossypha niveicapilla
Ispidina picta
lynx torquilla
Lanius senator
Motacilla flava
Ploceus nigricollis
Sylvia atricapilla
Tringa totanus
Zosterops senegalensis
Ri
8.3
6.4
4.9
1.5
1.0
1.0
1.0
3.4
2.0
2.4
1.0
16.1
0.5
0.5
1.0
1.0
2.0
0.5
2.4
0.5
1.0
Fo
1.4
4.1
3.2
0.5
0.9
2.8
4.6
0.9
0.5
8.3
0.9
0.5
0.5
0.9
0.5
Is
9.8
3.2
3.8
0.6
8.9
1.6
3.2
1.6
0.6
0.3
0.3
1.0
0.3
0.3
0.3
0.3
7.0
1.9
0.3
1.0
0.3

64 ARDEA 77 (1989)
Table 3. Mangrove counts in Guinea-Bissau, Jan - Febr 1987. The figures represent densities/1O ha. The first
half of the table holds the 18 "very frequently" observed species from Table 1. Places 1-6 cf. Fig. 1. @ Only singing
males, * palearctic migrant, Ri Rice field, Fo Forest, Is Isolated (Areias). 1,6 Fairly open, 1.5-3 m high
Avicennia; 2,3 Dense, 5 m high Rhizophora, passing into open, 1-3 m high Avicennia; 4 Dense, 3-8 m high
Rhizophora; 5 Fairly open, 5 m high mix of Avicennia/Rhizophora, passing into fairly open, 1.5-3 m high
Avicennia.
Place 1 2 3 4 5 6
Date 04-2 19-1 22-1 26-1 11-1 01-2
Area (ha) 5.4 6.0 4.0 4.0 4.5 4.5
Adjoining Ri Fo Fo Fo Is Is
Acrocephalus scirpaceus* 35 10 23 18 96 162
Anthreptes gabonicus 4 10 30 113 2
Cypsiurus parvus 48
Eremomela pusilla 28 28 8
Hippolais polyglotta* 6 8 5 10 178 51
Hirundo lucida 3 5 9
Laniarius barbarus 6 12 5
Merops persicus 19 7 13 7
Nectarinia pulchella 17 18
Phylloscopus sp.* 4 10 8 28 76 33
Platysteira cyanea@ 2 8 25 131 9
Sylvia sp.* 13 4 3 4 36 2
Alcedo cristata 2 5
Ceryle rudis 6 3 8 5
Halcyon malimbica 11 7 5 5 4
Actitis hypoleucos* 4 5 8 3 2 7
Numenius phaeopus* 9 5 20 3 2
Ploceus cucullatus 52 350 63 50 7
Gypohierax angolensis 10 3 18 4
Motacilla flava* 6 44 9
Centropus senegalensis 4 4 2
Tringa totanus* 3 7 4
Ploceus nigricollis 5 9 9
Turtur afer 5 5 8
Burhinus senegalensis 2 3
Streptopelia semitorquata 3 3
Butorides striatus 6
Coracias abyssinica 4
Nectarinia verticalis 4
Merops pusillus 2
Phalacrocorax africanus 2
Phoeniculus purpureus 8
Pycnonotus barbatus 5
Mesopicos goertae 2
Egretta gularis 10
Tringa nebularia* 3
Psittacus erithacus 3
Tersiphone rufiventer 3
Tockus nasutus 5
Anthus trivialis* 2

iers Sylviidae, t1ycatchers Muscicapidae, shrikes
Laniidae and sunbirds Nectariniidae), fish­
(and insect-) eating species (especially herons
and egrets Ardeidae and kingfishers Alcedidae)
and crab-eating species (some of the waders
Charadriidae). The only two species in Africa
which are largely confined to mangrove swamps
represent these groups: the fish-, crab- and insect-eating
Mangrove Kingfisher Halcyon senegaloides
in East Africa (McNae 1968, Williams
& Arlot 1980) and the insect-eating Brown Sunbird
Anthreptes gabonicus in West Africa (e.g.
Chapin 1954).
The species composition in Guinea-Bissau
corresponds completely with this: insectivorous
and piscivorous species dominate Appendix 1
(all species) and Table 1 (the most numerous species
apart from roosting birds). Seed- and fruiteating
species were usually scarce, often occurring
in a small strip on the inland side only.
These were mainly species found in adjoining
rice fields and forests (doves Columbidae and
weavers Ploceidae + Estrildidae). In the isolated
mangroves of Areias these species were rare or
absent. The only common seed-eater in the mangroves
was Ploceus cucullatus, which used mangrove
trees as a base for foraging flights to adjoining
rice fields. This species was also abundant
in the middle of extensive mangrove swamps,
though less so on the isolated Areias. Possibly its
diet is augmented here with insects or even t10wer
juices (cf. Macworth-Praed & Grant 1970­
73). The weaver Ploceus nigricollis is largely insectivorous
(Cawkell 1964). The less frequently
observed birds of prey were mostly seen hunting
above the mangroves, usually t1ying to or from
adjoining areas. Pandion haliaetus and Haliaetus
vocij"er used high Rhizophora tree tops on the
water's edge as "look-out" and roost. Many
Gypohierax angolensis used Rhizophora as a
high tide roost; some of these birds fed on Uca
and carrion on the mudt1ats, in open Avicennia
and on tannes.
Table 4 confirms the similarity in species
composition of different African mangrove areas
(Guinea-Bissau, Sierra Leone, Gambia), though
UTILIZATION OF MANGROVES BY BIRDS 65
numbers of observed species vary considerably.
This may be due to differences in observation
time rather than to real differences in species
numbers. Certainly the list for Sierra Leone is
not complete (Field 1968). Observations in mangroves
of Guinea (Altenburg & van der Kamp
1989), situated between Guinea-Bissau and Sierra
Leone, are comparable with those in Table 4.
Importance for birds
In this part of West Africa mangrove swamps
cover at least 11,000 km 2 from Senegal to Sierra
Leone (IUCN 1983). Apart from ensuring coastal
stability and accelerating shore development
(Maltby 1986), which in a way affect the position
and size of mudt1ats and coastal marshes, an important
function of mangroves is their support of
the marine food web by the organic debris produced
by the vegetation (e.g. Lugo & Snedaker
1974). Mangrove swamps enhance the productivity
of mudt1ats and shallow coastal waters, promoting
nursery conditions for invertebrates,
crabs and fish, and are thus essential, though
indirectly, for birds depending on these food
sources (macrobenthos: waders; crabs: waders, at
least partly Threskiornis aethiopica and Gelochelidon
nilotica; fish: wading birds, terns, kingfishers,
Pandion haliaetus, Haliaetus vocifer).
Many species of these groups occur in large
numbers on the mudt1ats and in the mangroves of
Guinea-Bissau in winter. For most of these, especially
the afro-tropical species, the relative importance
of their numbers is unknown because
data on breeding populations, migration or wintering
grounds are lacking. Clear examples of
(groups of) palearctic species on which much
more information is available are:
Waders: Only recently has the international
importance of the mudt1at area from Guinea­
Bissau to Sierra Leone for waders become clear
(Guinea-Bissau, Zwarts 1988; Guinea, Altenburg
& van der Kamp 1988; Sierra Leone, Tye & Tye
1987), by far the largest numbers wintering in
Guinea-Bissau.
Osprey: In Guinea-Bissau alone wintering
numbers of Pandion haliaetus amount to several

66 ARDEA 77 (1989)
Table 4. Bird faunas of the mangroves of Guinea-Bissau (GB), Sierra Leone (SL, after Field 1968) and Gambia
(GA, after CawkeIl1964). The families are arranged in the following groups:
Group A. Mainly insect-eating passerines and non-passerines
Group B. Mainly fish- and/or insect-eating wading birds, terns and kingfishers
Group C. Mainly crab- and macrobenthos-eating waders
Group D. Mainly seed- and fruit-eating passerines and non-passerines
Group E. Birds of prey
number of species number of species
GB SL GA GB SL GA
Group A Group C
Apodidae 2 Burhinidae 1 1
Caprimulgidae 1 Charadriidae 17 5
Coraciidae 3 1
Cuculidae 1 1 total 18 6
Hirundinidae 5 2
Indicatoridae 1
Laniidae 3 3 4 Group D
Meropidae 5 2 Bucerotidae 1 3
Motacillidae 2 2 1 Capitonidae 1 1
Muscicapidae 3 2 2 Columbidae 3 2 2
Nectariniidae 3 4 3 Corvidae 1 1
Oriolidae 1 Estrildidae 3 4 2
Picidae 3 2 Musophagidae 1
Sylviidae 11 9 4 Phasianidae 1
Timaliidae 1 1 Ploceidae 4 2 3
Turdidae 1 2 Psittacidae 1 1
Upupidae 2 Pycnonotidae 1 2
Zosteropidae 1 Stumidae 1 1
total 48 31 15 total 16 18 10
Group B Group E
Alcedidae 5 6 3 Aquilidae 7 5 2
Anhingida¢ 1 1 1 Pandionidae I 1 1
Ardeidae 9 8 12 Strigidae 1
Ciconiidae 1 1
Gruidae 1 total 9 6 3
Laridae 8
Pelecanidae 1 sum totals 125 80 45
Phalacrocciracidae 2
Rallidae 1
Scopidae 1
Threskiornithidae 4
total 34 19 17

nantly winters south of the Sahel (Wammes et
ai. 1983) in forest and woodland savanna (Serle
& Morel 1977). Dowsett et ai. (J 988) suggest that
displacement of this species is to winter regions
roughly south of the breeding areas; their (limited!)
ringing data indicate in this part of coastal
West Africa a wintering population originating
from the British Isles. According to Sharrock
(J 976) British and Irish populations may exceed
3 million pairs. Mangrove forests in Guinea­
Bissau and adjacent countries thus seem to form
an important part of the wintering grounds of
these populations.
In contrast with Phylloscopus trochilus both
Acrocephaius scirpaceus and Hippolais polyglotta
are said to winter in Sahelian Africa north
of the forest belt (e.g. Serle & Morel 1977,
Wammes et al. 1983). However, for both species
West African mangroves could well be a much
more important wintering area than the savanna
zone. This is especially true for Hippolais polyglotta
when considering the fact that the species
is only "assez nombreux" (::; 100,000 pairs) in
France, its main breeding area (Yeatman 1976).
Also for Acrocephalus scirpaceus mangroves
probably constitute a major wintering habitat,
although the winter population, which in this part
of coastal West Africa originates from a large
part of Western Europe (Zink 1973, Dowsett et
al. 1988), is larger than that of the preceding species
(e.g. The Netherlands, Great Britain and
Ireland together 11 0,000-190,000 pairs, Sharrock
1976, SOVON 1988). Wintering in mangroves,
which are much less affected by drought than
other Sahelian habitats, could well account for
the fact that both species show no decline in
West European breeding areas.
ACKNOWLEDGEMENTS
The work in and around the mangroves was part of a
Dutch expedition to the coastal wetlands of Guinea­
Bissau under the auspices of the WIWO Foundation.
The expedition was funded by the Beijerinck-Popping
Fonds, FONA, ICBP, IWRB, Ministerie van Landbouw
en Visserij, Natuurmonumenten, Nederlands
Comite Bescherming Trekvogels, Prins Bernhard
UTILIZATION OF MANGROVES BY BIRDS 69
Fonds, RSPB, Van Tienhoven Stichting, Tour du Valat
and WWF-NL. The cooperation with the Ministerio do
Desenvolvimento Rural and its officers Cipriano
Cassama and Fai Djedjo was highly appreciated. We
thank the members of the expedition - Jan van de
Kam, Jan van der Kamp, Marcel Kersten, Bernard
Spaans, Eddy Wymenga and Leo Zwarts for their help
in collecting the data and for their company, the crew
of the M.S. Knud W (Jan van der Kamp and Bernard
Spaans), Wiebren Planting and Benny Klazenga who
prepared the figures, Jan van der Kamp and Beatrice
Merlet who translated the French summary and Rob
Bijlsma, Jo Ann van Seventer, Eddy Wymenga and
Leo Zwarts who commented on the manuscript.
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SAMENVATTING
Mangroven beslaan wereldwijd tenminste 14
miljoen hectare. Helaas is over het belang ervan
voor vogels nog maar weinig bekend. Dat geldt
zeker voor Afrikaanse mangrovegebieden. Tijdens
een expeditie naar Guinee-Bissau aan de
Afrikaanse westkust (december 1986 - februari
1987) zijn een groot aantal vogelwaamemingen
in mangroven gedaan. Een aanzienlijk dee! van
de in Appendix 1 genoemde 125 soorten betrof
min of meer "toevallige" bezoekers, die maar een
of enkele keren zijn waargenomen en vee! talrijker
zijn in aangrenzende rijstvelden, savanne en
bossen. Naast een aantal wad- en watervogels die
de mangrove vooral gebruiken om er te overtijen,

is slechts een klein aantal soorten heel frequent
op (vrijwel) alle bezochte plaatsen aangetroffen
(Tabel 1, Fig. 3). Mistnetvangsten (Tabel 2) en
gedetailleerde tellingen (Tabel 3) bevestigen dit
beeld.
De soortensamenstelling vertoont grote overeenkomsten
met die in mangroven elders in de
tropen, in het bijzonder in Gambia en Sierra
Leone, beide ook aan de Afrikaanse westkust
(Tabel 4). Dit is ongetwijfeld een direct gevolg
van het voedselaanbod in het relatief extreme
mangrove-habitat, dat goeddeels beperkt is tot
insekten, vis, modderkruipers (Periophtalmus
papilio) en krabben (vooral de wenkkrab Uca
tangeri). Insekteneters (met name zangers, klauwieren,
vliegenvangers en honingzuigers), viseters
(met name reigerachtigen en deels de ijsvogels)
en krabeters (met name Oeverloper en
Regenwulp) vormen het leeuwendeel van de
waargenomen soorten, de overtijers uitgezonderd.
Ook bij de meest talrijke soorten (Tabel 1)
gaat het vrijwel uitsluitend om deze groepen.
Op grond van de tellingen zijn schattingen
gemaakt van de dichtheden van de verschillende
soorten (Tabel 3). Wanneer deze dichtheden representatief
zijn voor het gehele mangrovegebied
van Guinee-Bissau, gaat het om tenminste
1O.OOO-en exemplaren bij de in Tabel 1 genoemde
meest algemene soorten. Bij de palearctische
zangers Fitis, Kleine Karekiet en Orpheusspotvogel
zou het dan om tenminste een half miljoen
vogels gaan.
Mangroven zijn van groot belang voor de
productiviteit van wadden en ondiepe kustwateren
en dus voor vogelsoorten die afhankelijk
zijn van voedsel uit deze gebieden (vooral steltlopers,
reigerachtigen, stems en Visarend). Deze
groepen komen in grote aantallen voor in het
kustgebied van Guinee-Bissau en waarschijnlijk
langs een groot deel van de mangrovekust van
Senegal - Sierra Leone. Voor steltlopers, Lachstem
en Visarend betreft het hier intemationaal
gezien belangrijke aantallen. Verder heeft het
mangrovegebied een belangrijke functie als relatief
veilige overtijingsplaats voor lOO.OOO-en
steltlopers en als resp. broed-, slaap- en overtij-
UTILIZATION OF MANGROVES BY BIRDS 71
ingsplaats voor belangrijke aantallen grote waadvogels
(reigers, aalscholvers, lepelaars, ibissen).
Veel van de genoemde soorten en groepen
vinden buiten de mangroven hun voedsel. In de
mangroven zelf komt maar een zeer beperkt aantal
soorten in belangrijke aantallen voor. De afrotropische
soorten uit Tabel 1 zijn voor zover bekend
algemeen in grote delen van West-Afrika.
Alleen de Bruine Honingzuiger Anthreptes
gabonicus is beperkt tot de mangrovezone van
Gambia tot Zaire.
Voor een aantal palearctische trekvogels zijn
de Westafrikaanse mangroven waarschijnlijk van
groot belang als overwinteringsgebied, met name
voor Regenwulp, Kleine Karekiet en Orpheusspotvogel.
Eerstgenoemde soort overwintert kennelijk
in veel grotere aantallen in de mangroven
dan op het wad. De beide zangvogels overwinteren
in grote aantallen in de mangroven. Dit is
misschien de belangrijkste reden dat ze niet, zoals
zovele andere Sahel-overwinteraars onder de
zangvogels, sterk zijn achteruitgegaan in de
Westeuropese broedgebieden.
RESUME
In n'existe que peu de donnees sur l'importance omithologique
de la foret de mangrove couvrant au moins
14 million d'hectares mondialement. Cela vaut certainement
pour les zones de mangroves en Afrique. Au
cours d'une expedition en Guinee-Bissau (Fig. 1) situee
ala cote ouest-africaine (decembre 1986 - fevrier
1987) un grand nombre d'observations ont ete faites
dans la mangrove. Panni les 125 especes mentionnees
dans I'Appendice 1 figure un nombre considerable de
visiteurs plus ou moins accidentels; leur presence est
beaucoup plus importante dans les rizieres, la savane
et les forets attenantes. A part les oiseaux d'eau de la
zone intertidale qui utilisent la mangrove principalement
pour y passer la periode des marees hautes, seul
un petit nombre d'especes est signale tres ftequemment
dans (presque) tous les endroits visites (Tableau 1, Fig.
3). Les captures al'aide de filets (Tableau 2) ainsi que
des recensements detailles (Tableau 3) cortfinnent cette
image.
La composition des especes est a peu pres identique
a celie des autres zones tropicales, particulierement
en Gambie et en Sierra Leone situees egalement
sur la cote ouest-africaine (Tableau 4). Ceci est sans

72 ARDEA 77 (1989)
doute la consequence directe de la disponibilite alimentaire
propre al'habitat de mangrove assez extreme,
se composant essentiellement d'insectes, poissons, 10ches
(Periophalmus papilio) et crabes (surtout Uca
tangeri). Les oiseaux insectivores (notamment les fauvettes,
cisticoles etc. (Sylviidae), les pies-grieches, les
gobe-mouches et les soui-mangas), piscivores (notamment
les herons et aigrettes et partiellement les martins-pecheurs
et martins-chasseurs) et crabivores (notamment
Ie Chevalier guignette et Ie Courlis corlieu)
constituent la grande majorite des especes observees,
hors les especes 'intertidales'. Aussi chez les especes
les plus nombreuses (Tableau 1) il s'agit presque exc1usivement
de ces groupes.
Tableau 3 donne une idee de l'ordre de densites des
diverses especes. Si ces densites seraient approximatiyes
a celles de la zone de mangrove entiere de la
Guinee-Bissau, il s'agit de dizaines de milliers d'oiseaux
au minimum chez les especes les plus communes.
Le Pouillot fitis, la Rousserole effarvate et la
Hippolals polyglotte (passerines palearctiques) representeraient
alors un demi-million d'oiseaux au minimum.
La mangrove est d'une grande importance pour la
productivite alimentaire des zones intertidales et des
mers peu profondes; par consequence elle l'est aussi
pour des especes d'oiseaux se nourrissant aux depends
de ces aires (surtout limicoles, herons, aigrettes, sterries
et Balbuzard pecheur). Ces groupes sont tres nombreux
et, concernant les limicoles, la Sterne hansel et
Ie Balbuzard pecheur, presents en effectifs importants
au niveau mondial, dans la zone c6tiere dela Guinee­
Bissau et probablement dans une grande partie de celie
attenante a la mangrove entre Ie senegal et la Sierra
Leone. La fonction de reposoir amaree haute relativement
sur pour des centaines de milliers de limicoles
est egalement importante. De meme les qualites de
lieu de nidification, dortoir etreposoir a maree haute
pour des nombres importants d'echassiers (herons, aigrettes,
spatules, ibis) et de cormorants sont asouligner.
Toutes ces fonctions concernent des especes qui
s'alimentent generalement hors de la mangrove. Dans
la mangrove elle-meme on ne trouve qu'un petit nombre
d'especes en effectifS importants. Les especes afrotropicales
du Tableau 1 sont, dans l'etat des connaissances
actuelles, communes en grandes parties de
I'Afrique occidentale. Seul Ie Soui-manga bron
Anthreptes gabonicus se limite ala zone de mangrove
entre la Gambie et Ie ZaIre. Pour un nombre de migrateurs
palearctiques la mangrove ouest-africaine parait
etre d'un interet enorme en tant que zone d'hivernage,
notamment pour Ie Courlis corlieu, la Rousserole effarvate
et la Hippolais polyglotte. La premiere de ces
trois hiverne dans la zone de mangrove en nombres
beaucoup plus grands que ceux presents dans la zone
intertidale. Les deux autres especes hivernent en nombres
impressionants dans la mangrove; cela pourrait
bien expliquer pourquoi leur effectifs, a l'oppose de
beaucoup d'autres passerines qui ont souffertdes periodes
de secheresse dans les annees soixante-dix et
quatre-vingt, n'ont pas fortement diminue dans les aires
de nidification ouest-europeennes.

UTILIZATION OF MANGROVES BY BIRDS 73
Appendix 1. Presence of bird species in mangroves in Guinea-Bissau, December 1986 - February 1987.
Mangroves are divided in those adjoining rice fields (Ri), forested areas (Fo) and isolated mangroves (the island
Areias, Is). The most important observation sites are shown in Fig. 1. Within the groups names and order of species
follow Serle & Morel (1977) except for Merops persicus (Fry et al. 1988), Hirundo lucida/rustica
(Mackworth-Praed & Grant 1970, 1973) and Circaetus gallicus (Brown et al. 1982).
+ frequently observed, . once or occasionally observed, c caught with mistnets only, * palearctic migrant, (*) probably
palearctic/afro-tropical mixture in unknown proportions. Information on food and origin after Mackworth­
Praed & Grant (1970, 1973), Brown et al. (1982), Urban et al. (1986) and Fry et al. (1988).
Ri: Rio Geba, Rio Mansoa; c. 50-1,000 m wide, by the seaside a wide strip of Rhizophora, by the landside a small
strip of Avicennia. Fo: Bijagos, Rio Grande de Buba, Rio Tombali; c. 10-2,500 m wide, by the seaside a small ­
wide strip of Rhizophora (Rio Tombali also Laguncularia), by the landside id. Avicennia. Is: Ilha das Areias; c.
100-700 m wide, by the seaside a small strip of Rhizophora, by the "Iandside" a wide strip ofAvicennia.
A. Mainly insect-eating
(non-)passerines
Ri
Centropus senegalensis +
Caprimulgus climacurus
Apus apus *
Cypsiurus parvus + +
Merops apiaster *
Merops persicus + +
Merops albicollis
Merops pusillus
Merops gularis
Coracias abyssinica
Coracias cyanogaster
Eurystomus glaucurus
Upupa epops (*)
Phoeniculus purpureus
Indicator maculatus
lynx torquiquilla *
Campethera maculosa
Mesopicos goertae .
Hirundo lucida + +
Hirundo rustica * .
Hirundo daurica (*)
Hirundo spi/odera +
Psalidoprocne obscura
Motacillaflava *
Anthus trivialis * +
Dryoscopus gambensis
Laniarius barbarus + +
Lanius senator *
Griolus nigripennis
Cossypha niveicapilla
Acrocephalus schoenobaenus *
Fo
+
c
c
+
+
c
Is
+
Ri
Acrocephalus scirpaceus * +
Hippolais polyglotta * +
Sylvia atricapilla * .
Sylvia cantillans * + +
Phylloscopus trochilus * +
Phylloscopus collybita *
Cisticola brachyptera
Cisticola juncidis
Eremomela pusilla + +
Sylvietta brachyura c
Platysteira cyanea + +
Tersiphone rufiventer
Tersiphone viridis
Anthreptes gabonicus +
Nectarinia verticalis
Nectarinia pulchella +
Zosterops senegalensis
Ploceus nigricollis
B. Mainly fish and/or insecteating
wading birds,
kingfishers and terns
Pelecanus rufescens +
Phalacrocorax africanus +
Phalacrocorax carbo
Anhinga rufa .
Nycticorax nycticorax (*) +
Butorides striatus +
Egretta alba + +
Egretta intermedia .
Egretta ardesiaca .
Egretta gClrZetta (*) .
Egretta gularis + +
Fo Is
+ +
+ +
c
+
+ +
+
c
+
+
+ +
+
+
+
c

74 ARDEA 77 (1989)
Ri Fo Is Ri Fo Is
Ardea cinerea (*) D. Mainly seed and fruit-
Ardea goliath
Scopus umbretta
+ eating, (non-)passerines
Ciconia episcopus Streptopelia semitorquata +
Threskiornis aethiopica + Streptopelia vinacea +
Bostrychia hagedash
Plegadis falcinellus
Turtur afer + +
* Psittacus erithacus
Platalea alba Tockus nasutus
Gallinula chloropus (*) Pogoniulus chrysoconus c
Balearica pavonina . Lamprotornis splendidus
Gelochelidon nilotica (*) Corvus albus
Sterna caspia (*) Pycnonotus barbatus
Sterna hirundo (*) Ploceus cucullatus + +
Sterna maxima (*)
Sterna bengalensis
+ Vidua chalybeata
* Sterna sandvicensis
Vidua orientalis
* Sterna leucoptera
+
Estrilda bengala
* Sterna hybrida
Lagonosticta senegala
* Lonchura cucullata .
Sterna albifrons (*) +
Ceryle rudis + +
Alcedo quadribrachys E. Birds of prey
Alcedo cristata + +
Ceyxpicta
Halcyon malimbica+
Gypohierax angolensis
Circus aeruginosus
+ + +
*
+ +
Polyboroides radiatus
Circaetus gallicus (*)
C. Waders Haliaetus vocifer
Pandion haliaetus
+
* +
Burhinus senegalensis Falco cuvieri
Vanellus senegaJlus .
Pluvialis squatarola
Falco ardosiaceus
* Charadrius hiaticula
+ + + Otus scops (*)
*
Charadrius alexandrinus *
Numenius phaeopus * Numenius arquata
+ + +
*
Limosa limosa *
Limosa lapponica *. +
Tringa nebularia * .
Actitis hypoleucos
+
* Tringa totanus
+ + +
*
+
Arenaria interpres
+ +
* Calidris ferruginea
+
* Calidris alpina
+ + +
*
Calidris canutus *
Calidris minuta *
Calidris alba *