2001
Gulls and terns in Senegal
BREEDING GULLS AND TERNS IN SENEGAL IN
1998, AND PROPOSAL FOR NEW POPULATION
ESTIMATES OF GULLS AND TERNS IN
NORTH-WEST AFRICA
G U ID O O. K E IJL 1, A LLIX B REN N IN K M EIJER2, FRANS J. SC H E PE R S1,
ERIC W.M. STIEN EN 3, JA N V EEN 4 & A B D O U LA Y E N D IA Y E 5
Keiji G.O., Brenninkmeijer, A., Schepers, F.J., Stienen, E.W .M ., Veen, J. & Ndiaye
A. 2001. B reeding gulls and terns in Sengal in 1998, and proposal for new
population estim ates o f gulls and terns in north-west Africa. Atlantic Seabirds 3(2):
59-74. In M ay 1998 breeding gulls a n d terns w ere surveyed in N ational Parks
Langue de B arbarie an d Sine-Saloum Delta, Senegal. This was the fir s t nearcom plete census o f breeding gulls a n d terns in this p a r t o f Senegal. The m ost
num erous breeding species were G rey-headed Gulls L arus cirrocephalus (7565
p a irs), Slender-billed Gulls L. genei (5550 p), R oyal Terns Sterna m axim a (22 693
p ) a n d Caspian Terns S. caspia (>8620 p), while Common Terns Sterna hirundo (70
p ) a n d G ull-billed Terns Gelochelidon nilotica (8 p ) occurred in low numbers. The
fir s t fo u r species were more numerous than expected fro m published accounts, the
latter two occurred in sm aller numbers than expected. Little Tern Sterna albifrons
(35 p ) a n d K elp Guii L arus dom inicanus (1 p ) also bred in low numbers. The
species are discussed, an d a literature review o f num bers breeding in the p a st is
presented. Because Senegal, together with the B anc d'Arguin in M auritania, are the
m ost important areas f o r breeding gulls an d terns in west Africa, a n d while recent
counts are now available fro m both areas, new population estim ates are given and
new 1% -levels proposed. There are several threats to breeding birds, am ong which
eggcollecting a n d overfishing, a n d the n eed fo r p ro p er protection is outlined. Both
the islands along the Senegalese coast an d the B anc d'Arguin in M auritania are o f
m ajor im portance f o r the west African subspecies o f R oyal Tern, o f which alm ost
the entire popula tion breeds in Senegal a n d M auretania. M auritania is o f great
significance f o r the east A tlantic population o f B ridled Tern Sterna anaethetus, a
separate subspecies; this population m ay nowadays comprise as fe w as 100 pairs,
but recent counts are not available.
‘c/o WIWO, P.O. Box 925, 3700 AX, Zeist, The Netherlands, E-mail
guido@hetnet.nl; 2Bureau Altenburg & Wymenga, Postbus 32, 9269 ZR
Veenwouden, The Netherlands; 3Bureau voor Natuurbehoud, Kliniekstraat
25, 1070 Brussel, Belgium; 4Alterra, P.O. Box 23, 6700 AA, Wageningen,
The Netherlands; 5Wetlands International, West Africa Office, P.O. Box
8060, Dakar-Yoff, Senegal.
59
60
K EIJL E T A L .
Atlantic Seabirds 3(2)
INTR O D U CTIO N
T he n o rth -w e st co a st o f A fric a su p p o rts a p ro lific se ab ird co m m u n ity
throughout the year. E specially im portant to seabirds are the shallow areas o f
the Banc d'A rguin in M auritania, the Senegal R iver Delta, Ile de la M adeleine,
the D elta o f the Sine-Saloum , and the m angrove area in G uinea-B issau (e.g.
C ooper et al. 1984; Cram p & Sim m ons 1983; Cram p 1985; B urger & G ochfeld
1996; G ochfeld & B urger 1996). T here are areas, such as the m outh o f the
G am bia river in G am bia, and the C asam ance in the south o f Senegal, that have
n ot been censused yet, but it is likely that they too support seabird colonies.
E ven although m uch attention has been devoted to breeding seabirds in these
areas in the past (for Senegal: de N aurois 1964; L atour 1973; D upuy 1975;
1976; 1983; 1984; E rard 1975; G ow thorpe 1979; D elaporte 1991; for the Banc
d'A rguin: C ooper e t al. 1984; G ow thorpe e t al. 1996), atten tio n has usually
focused on terns, especially R oyal Terns Sterna m axim a, w hile num bers o f non­
target species have been estim ated, often by obscure m ethods.
B ecause o f th e im po rtan ce o f the S eneg alese co ast fo r breed in g
seabirds, and the lack o f recent and detailed data, a census w as carried out in
M ay 1998. C olonies o f gulls and terns w ere visited at the L angue de B arbarie
and the Sine-Saloum Delta. In this paper w e report on the results o f the survey.
Since the m ost im portant areas for breeding gulls and terns in north­
w est A frica are located in M auritania and Senegal (C ram p & Sim m ons 1983;
C roxall et al. 1984; Cram p 1985; N ettleship et al. 1994; del H oyo et al. 1996)
w e feei that, after the census in 1998, it is possible to give a reliable population
estim ate for m ost species breeding along the entire n orth-w est A frican coast
(M orocco to L iberia, including the M adeiran islands, Selvagen islands, Canary
Islands and C ape-V erde Islands). W e also propose new 1% -levels for the gulls
and terns breeding in this area (cf. Rose & Scott 1997).
M ETH OD S
In 1998 the follow ing areas w ere visited: Ilot aux O iseaux at Parc N ational
L angue de B arbarie and Parc N ational G uem beul (17 M ay), and the salines at
K aolack (20 M ay), Ile aux O iseaux (18-25 M ay, w ith an additional visit from
21-28 July), Ile de S angom ar (26 M ay), Ile S en g h o r (26 M ay) and the
sandbanks north o f Ile aux O iseaux (26 M ay; F igure 1) at P arc N ational du
D elta du Sine-Saloum . The survey w as carried out in the second h a lf o f M ay
b ecause this appeared to be the m ain breeding period for R oyal T erns (e.g.
D ela p o rte 1991). N ests o f gulls and tern s (i.e. G re y -h e ad e d G uii L arus
cirrocephalus, S lender-billed G uii L. genei, K elp G uii L. dom inicanus, G ull­
billed Tern G elochelidon nilotica, C aspian Tern S. caspia, C om m on Tern
Gulls and terns in Senegal
2001
61
Mauritania
tV.
National Parc
Langue de B arbarie
Senegal
5t. Louis
Atlantic
Ocean
Guinea-Bissau
N ational P arc Sine-Saloum Delta
Bôt aux
O iseaux
Pointe
S angom ar
Be Senghor
5km
Be aux O iseaux
Figure 1. National Park Langue de Barbarie and National Parc Sine-Saloum Delta in
west Africa. Sites with large colonies o f gulls and terns in 1998 are indicated
with asterisks.
Figuur 1. Ligging van Nationaal Park Langue de Barbarie en Nationaal Park SineSaloum Delta in West-Afrika. De grote meeuwen- en sternkolonies in 1998 zijn
met sterretjes aangegeven.
62
Atlantic Seabirds 3(2)
KEHL ETAL.
Table 1. Counted or estimated numbers o f breeding gulls and terns at Langue de
Barbarie (including NationalPark Guembeul) and Sine-Saloum Delta (Ile aux
Oiseaux, Ile Senghor, salines at Kaolack) in Senegal in May 1998.
Tabel 1. Getelde o f geschatte aantallen broedende meeuwen en sterns op Langue de
Barbarie (inclusief Nationaal Park Guembeul) en Sine-Saloum Delta (Ile aux
Oiseaux, Ile Senghor, zoutpannen Kaolack) in Senegal in mei 1998.
Langue de
Barbarie
Sine-Saloum
Total
Grey-headed Guii Larus cirrocephalus
Slender-billed Guii L. genei
Kelp Guii L. dominicanus
3000
2100
0
4565
3450
1
7565
5550
1
Total gulls
5100
8016
13 116
Gull-billed Tem Gelochelidon nilotica
Caspian Tern Sterna caspia
Common Tem S. hirundo
Little Tem S. albifrons
Royal Tem S. maxima
0
>10*
0
35
1650
8
8610
70
0
21 043
8
>8620
70
35
22 693
Total terns
>1695
29 731
>31 426
Species
* 10 fledglings
S. hirundo and Royal Tern) w ere counted one by one. G uii nests o f the previous
year w ere easily recognisable as such and w ere not included. A t L angue de
B arbarie, how ever, C aspian Terns had alm ost com pleted their breeding cycle,
and the m ajority o f young birds had already fledged. Therefore an estim ate o f
the breeding population w as m ade on basis o f the n um ber o f adult and young
birds present, and by counting the em pty nests in the colonies. R oyal Terns were
still breeding, but there w ere also pairs w ith large young. The colony o f G rey­
headed G ulls at L angue de B arbarie w as partly counted, after w hich num bers
w ere extrapolated. For details on counting m ethods on Ile aux O iseaux, w hich
differed according to species, see K eiji et al. (2000).
RESU LTS A N D LIT ER A T U R E REV IEW
A total o f 16 w aterbird species (including herons, egrets and ibises) w as found
breeding in coastal Senegal in 1998. A m ong these w ere three species o f guii and
five species o f tern (Table 1). In 1998, the Langue de B arbarie supported at least
5100 pairs o f gulls and at least 1700 pairs o f terns. In the S ine-Saloum D elta
(including the salines at K aolack) 8016 pairs o f gulls and 29 731 pairs o f terns
w ere counted, giving a grand total o f 44 574 pairs. The m ajority com prised only
four species: G rey-headed Guii, Slender-billed Guii, Caspian and Royal Tern.
2001
Gulls and terns in Senegal
63
G r ey -h ea d ed G uW Larus cirro ce p h a lu s In 1998, 7565 nests w ere counted
along the Senegalese coast. T he species also breeds on the B anc d'A rguin,
M auritania, w ith 50 pairs in 1984; c. 25 pairs during 1984-1985 and 10-20 pairs
in 1995 (C am predon 1987; Lam arche 1988; G ow thorpe et al. 1996). A part from
the colonies in Senegal, there are apparently no breeding sites holding large
num bers along the entire south and w est A frican coast (C ooper et al. 1984;
N ettleship et al. 1994; G atter 1997; H afner et al. 1998; B rooke et al. 1999). O ur
results show that the population estim ate for G rey-headed G uii in w est A frica
given by Cooper et al. (1984; T able 3) is m uch too low. M oreover, even though
m ost o f the G rey-headed G ulls breed from m id-M ay onw ards, the species
apparently has an extended breeding season, w ith pairs possibly starting as early
as M arch, w hile others are still seen w ith sinaii young as late as July (w ardens
o f Ile aux O iseaux pers. com m ). W e estim ate that the n o rth -w est A frican
population presently holds about 10 000 pairs, corresponding to a 1% -level o f
300 individuals.
S le n d e r -b ille d G u ii L a ru s g e n e i In 1998, 5550 n ests w ere co u n ted .
Interestingly, C ooper et al. (1984) m entioned 2850 pairs in w est A frica (Table
3; num bers based on D upuy 1976; T rotignon et al. 1976 and G ow thorpe 1979),
w h ile in the sam e y ear D upuy (1984) rep o rted th e species to b e "on the
increase" and estim ated the population at the L angue de Barbarie, in the SineSaloum D elta, and at K alissaye (S-Senegal) com bined at 5000 pairs. In contrast
to G rey-headed G uii, the entire population o f S lender-billed G ulls appears to
breed sim ultaneously in M ay-June. In 1998, 1776 w ere counted on the Banc
d'A rguin (H afner et al. 1999). The (derived) estim ate o f Rose & Scott (1997) is
3333 breeding pairs. T he p resen t estim ate for the entire n o rth -w est A frican
population is 7500 pairs, w ith a 1% -level o f 225 individuals.
K elp G uii L aru s dom in ican u s D uring our visit (18-25 M ay) there w ere up to
four (sub) adult K elp G ulls present on Ile aux O iseaux. A nest w as found on 25
M ay, close to a C aspian Tern subcolony. It contained one chick o f one day old,
one recently hatched ('w et') chick and one egg (photo on p. 27 in K eiji et al.
2000). This is the third breeding record o f this species in Senegal. The first nest
was found betw een 26-30 June 1980 on Ile T érém a (a sm all island close to Ile
aux O iseaux) and probably belonged to a m ixed pair o f K elp G uii and Lesser
B lack-backed Guii L. [fuscus] graellsii (D upuy 1984). A second nest w as found
on Ile aux O iseaux betw een 28-30 M ay 1983 (Erard et al. 1984). T his p air o f
K elp G ulls is probably the only one breeding in the northern hem isphere, and is
the northernm ost one in A frica (cf. Burger & G ochfeld 1996).
64
KEHL ETAL.
Atlantic Seabirds 3(2)
G u ll-billed Tern G elochelidon n ilotica O nly eight nests o f G ull-billed Terns
w ere found at the salines near K aolack. It is possible that the n um ber w ould
have increased further in the course o f the season, because som e tens o f adults
present in the area could have been birds that had not started breeding yet (cf.
B row ne 1981; H afner et al. 1999). O n the other hand, it is also possible that
G ull-billed Terns declined considerably since the early 1970s. O utside Senegal,
G ull-billed T erns in N orth-A frica breed only in the M editerranean, possibly a
few pairs every year (G lutz von B lotzheim & B auer 1982; M eininger et al.
1994), and in M auritania; on the B anc d'A rguin 1600 pairs bred in 1978, on
A ftout es Sahéli, Toum bos, an other 1850 pairs bred in Septem ber 1987; and 80
kilom etres south o f N ouakchott there w ere c. eight m ore pairs (Trotignon 1980
in B row ne 1981; L am arche 1988). M ore recently, num bers in M auritania have
apparently b een low er; after a m inim um o f 250 pairs in 1994 on the Banc
d'Arguin, 660 pairs w ere counted there in 1995; and in the same year there were
15 pairs near N ouakchott (G ow thorpe et al. 1996). In 1972 and 1973 G ull-billed
Terns bred w ith 200 and 300 pairs respectively at the m outh o f the Senegal river
(L atour 1973), but we have no inform ation on the present situation or on the
intervening period. H afner et al. (1999) did not m ention G ull-billed Terns as a
breeding species during their recent census on the Banc d'Arguin. The colony at
K aolack is the southernm ost one in A frica (C ooper et al. 1984). R ose & Scott
(1997) give 12,000 individuals for w est-E urope and north-w est A frica together,
corresponding to 4000 breeding pairs. In w est E urope there are presently about
2000 breeding pairs (B iber 1994; G ochfeld & B urger 1996); this leaves 2000
pairs for the entire A frican continent {i.e. north-w est and north A frica). We
estim ate that the north-w est A frican population presently holds 800 pairs, w hich
corresponds to a 1% -level o f 24 individuals.
C aspian Tern Stern a caspia C aspian Terns seem to have increased m arkedly
during the past decade; in 1991 the num ber w as estim ated at 4700 pairs on Ile
aux O iseaux (D elaporte 1991), but in 1998 w e counted 8600 pairs. O n Langue
de B a rb arie, it w as n o t p o ssib le to m ake even a ro u g h estim ate o f the
population, as the breeding season w as already finished and only som e large
fledglings w ith adults w ere present. T he colony num bered at least 10 pairs.
C ooper et al. (1984) reported 2400 pairs for the entire north-w est A frican coast,
and G ochfeld & B urger (1996) estim ated the population at 5000 pairs. Although
the situation on the Banc d'A rguin is obscure, because b reeding takes place
continuously from February until June (H afner et al. 1999; this is also the case
in Senegal), the M auritanian population num bers at least 4000 pairs. (H afner et
al. 1999 give a total o f 10 903 breeding pairs, but this seem s a sum m ation o f all
num bers counted on eight occasions betw een 23 February and 8 June 1998.)
South o f Ile aux O iseaux C aspian Terns bred in the past w ith about 1500 pairs in
2001
Gulls and terns in Senegal
65
G am bia and the Casam ance, and 400-600 pairs in G uinea-B issau (Britton 1986),
although B renninkm eijer et al. (1998) counted only 84 nests there in N ovem ber
1992. R ose & Scott (1997) give a b reeding p o pulatio n o f 4000 pairs. W e
estim ate the present north-w est A frican population at 13 500 breeding pairs, and
a 1%-level o f 405 individuals.
Caspian Tem R euzenstem (photo Frans Schepers).
C om m on Tern S te rn a h irundo We estim ated the population on Ile Senghor at
45 pairs and the one on Ile aux O iseaux at 25 pairs. N um bers at Ile Senghor
w ere difficult to estim ate though, because the entire colony w as plundered by
fisherm en im m ediately prior to our visit. T he num ber o f C om m on Terns at Ile
aux O iseaux w as difficult to estim ate as w ell, because the nests w ere scattered
along the edge o f the entire guii colony. B ecause o f predation by gulls, the tim e
spent near the C om m on Tern nests was kept to a m inim um . T he hundreds o f
pairs o f Com m on T ern in the S ine-Saloum D elta, m entioned by de N aurois
(1964), have probably largely disappeared. E rard (1975) counted 'som e dozens'
on Ile aux O iseaux in June 1974; w hile G ow thorpe (1979) counted only eleven
nests on the same island a few years later. Even though D upuy ( 1984) noted that
the species increased along the S enegalese coast, D elaporte (1991) found only
28 nests in the S ine-Saloum Delta. The only other location in Senegal w here
C om m on Terns are know n to breed is the C asam ance. E lsew here along the
66
K eIJL ETAL.
Atlantic Seabirds 3(2)
n o rth -w est A frican coast breed in g sites are found on th e B anc d'A rguin,
M auritania, w ith approxim ately 200 pairs in 1974 (Trotignon 1976), and (in
unknow n num bers) in W estern S ahara, G uinea-B issau , N ig eria and L ibya
(Britton 1986). On the Banc d'Arguin, how ever, the species w as not encountered
during the m ost recent censuses (H afner et al. 1998; 1999, but note that these
w ere conducted b y aeroplane). There are no indications for breeding in Libya at
present (cf. M ein in g er et al. 1994). R ose & Scott (1997) give a b reeding
population o f 400 pairs for the entire A frotropical region. W e estim ate the
present north-w est A frican population at 200 pairs and the 1% -level for north­
w est A frican breeding birds at six individuals.
L ittle Tern S te r n a a lb ifro n s In 1998, adult L ittle T erns w ere seen only at
Langue de B arbarie and near Pom te de Sangom ar, Sine-Saloum D elta, but no
nests w ere found. The species breeds every year in G uem beul w ith 35-50 pairs,
and w ith c . 35 pairs on Langue de B arbarie (M baye D iop pers. com m .), but
breeding starts som ew hat later in the season. On the Banc d'A rguin, the num ber
w as estim ated at 25-50 pairs in 1974 (T rotignon et al. 1976). T here are no
recent indications o f breeding in M auritania (H afner et al. 1998; 1999, but note
that these censuses are done from aeroplanes, and breeding L ittle T erns are
notably difficult to count because they often breed solitarily, and pairs m ay be
spread over a large area). T here is no population estim ate for this species in
Rose & Scott (1997). W e propose a population estim ate for north-w est A frica
(excluding the M editerranean) o f 100 pairs and a 1% -level for individuals o f
three.
Royal Tern S te rn a m a xim a In 1998 we counted alm ost 23 000 breeding pairs,
o f w hich over 21 000 on Ile aux O iseaux. T ogether w ith M auritania, w here a
m axim um o f 11 041 w as counted in M ay-June 1998 (H afner et al. 1998), at
least 34 000 pairs w ere b reeding in w est A frica in 1998. (In June 1999,
how ever, there w ere about 43 000 pairs on Ile aux O iseaux - pers. obs.) Betw een
1960 and 1998, Royal Terns have been found breeding at the B anc d'A rguin,
M auritania, at the Langue de B arbarie, P ointe de Sangom ar, Ile aux O iseaux,
and in the C asam ance (all in Senegal), in G am bia, and in G uinea-B issau, but
apparently did not breed every year on every site. In W estern Sahara the species
did not breed in the 1950s (V alverde 1957), but there is no inform ation before
and after this period. In 1974; Erard (1975) saw three displaying pairs on Ile aux
O iseaux, w hile in the same year D upuy (1975) found 10 000 chicks on the south
point o f Pointe de Sangom ar, Sine-Saloum D elta. In G am bia and the Casam ance
(south Senegal) the species bred in th e early 1960s (M orel & Roux 1966), but
we have no inform ation from these areas from recent years. D e N aurois (1964)
and M orel & R oux (1966) nam ed several o f the above m entioned locations o f
2001
Gulls and terns in Senegal
67
breeding in w est A frica, but not the S ine-Saloum D elta, so either this site w as
n o t v isited by them in the 1960s or, m ore likely, the species w as n o t breeding
there. T he R oyal T erns reg u larly shift b etw een breed in g sites, resu ltin g in
seem in g ly large flu ctu atio n s at any site; in M a u ritan ia fo r in stan ce, the
population fluctuated betw een 3000 and 16 911 pairs during 1984-1998 (H afner
et al. 1999; although this m ay have been due also to variation in counting dates
betw een years, coverage o f the area, or differences in census m ethods). The
reaso n fo r sh iftin g o f b ree d in g site is u n clear. T he n o rth -w e st A fric an
population was recently estim ated at only 25 000 pairs by G ochfeld & B urger
(1996), but this seem s very low, as D elaporte (1991) found m any m ore in 1991:
2650 on L angue de B arbarie and 27 500 on Ile aux O iseaux. R ose & Scott
(1997) gave a population estim ate o f 16 667 pairs. W e estim ate the population
at 43 000 pairs, w ith a 1% -level o f 1290 individuals.
O ther gu ii and tern species A part from the above m entioned species, B lack­
head ed G uii L. rid ib u n d u s, L aughing G uii L. atricilla, F ran k lin 's G uii L .
p ip ix ca n , Sooty Tern S. fu sc a ta and B ridled T ern S. anaethetus have (possibly)
b red on the S enegalese coast, but w ere not found b reed in g in 1998. T he
breeding o f the three guii species is highly erratic (D upuy 1983; E rard.1984;
M baye Diop pers. comm.).
A nest o f a Sooty T ern w as found on 9 July 1954 on Ile D iam anio,
Sine-Saloum D elta (de N aurois 1969). Tw o nests w ere found betw een 1977 and
1980 on L angue de B arbarie, and one in M ay-June 1979 in the S ine-Saloum
D elta, after w hich the species returned for a few m ore years (D upuy 1979). On
22 M ay 1998 one adult w as observed on Ile aux O iseaux, and in July 1998 two
w ere seen on the same site, but there w ere no indications o f breeding.
U ntil 1999, B ridled Terns unsuccessfully attem pted to breed in Senegal
(E rard 1975; B ritton 1986). The species bred in M auritania, w ith 1200-1800
pairs betw een 1959 and 1965 and only 100 pairs in 1995 (de N aurois 1969;
G ow thorpe et al. 1996).
D ISCU SSIO N
Senegal is very im portant for breeding seabirds in w est A frica, especially for
G rey-headed G uii, Slender-billed Guii, R oyal T ern and C aspian T ern, and the
1% -levels given by R ose & Scott (1997) are greatly exceeded for these species
at p resen t (T able 2). F or several species h ow ever there are no p o p ulation
estim ates available. W ith at least 37 000 pairs o f gulls and terns, Ile aux O iseaux
hosts the largest seabird colony along the Senegalese coast. A lth o u g h it is
tem pting to com pare num bers w ith those found in the past (de N aurois 1964;
L atour 1973; D upuy 1975; 1976; E rard 1975; G ow thorpe 1979; D elaporte
68
Atlantic Seabirds 3(2)
KEIJL ETAL
Table 2. 1%-levels fo r gulls and terns breeding in north-west Africa (Rose & Scott
1997; first column) and the time this number was exceeded in Senegal in
1998 (second column). Also, a proposal fo r new 1%-levels fo r breeding
populations in north-west Africa is presented. Gulls and terns that have never
been found breeding in Senegal, but do breed in north-west Africa (Yellow­
legged Gulls Larus m. michahellis, L. m. atlantis, Roseate Terns Sterna
dougallii; Zino & Biscoito 1994) are not included. - = no population estimate
available, + = present, but comparison not possible.
Tabel 2. l%>-normen voor in Noordwest-Afrika broedende meeuwen en sterns (Rose
& Scott 1997; eerste kolom) en het aantal keer dat dit getal werd overtroffen
in Senegal in 1998 (tweede kolom). Een voorstel voor een nieuwe 1%-norm
staat in de laatste kolom. Meeuwen en sterns die nog nooit in Senegal hebben
gebroed, maar dit wel elders in N oordw est-Afrika doen (beide
Geelpootmeeuwen Larus m. michahellis en L. m. atlantis en Dougalls Stern
Sterna dougallii; Zino & Biscoito 1994) worden hier niet behandeld. - = geen
populatieschatting bekend, + = aanwezig, maar vergelijking niet mogelijk.
1% Rose &
Scott 1997
Grey-headed Guii L. cirrocephalus
Slender-billed Guii L. genei
Kelp Guii L. dominicanus
Gull-billed Tem G. nilotica
Caspian Tern Sterna caspia
Common Tem S. hirundo
Little Tem S. albifrons
Royal Tem S. maxima
Bridled Tem S. anaethetus
Sooty Tem S. fuscata
-
33
-
20
40
4
167
45
400
number x 1%
in Senegal
1998
1% breeding
population
NW Africa
+
167
+
0.4
216
17.5
+
128
100
75
1
8
135
2
1
400
1
2
-
-
1991), this is not done because o f differences in survey m ethodology. A lso,
there is no inform ation about m ovem ent o f breeding birds betw een the various
lo cations along the w est A frican coast; rendering a co m parison even m ore
difficult.
T h rea ts and p ro tec tio n C ooper e t al. (1984) concluded that m ost seabird
p o p u la tio n s in w est A frica have in c re ase d sin ce th e 1960s. S ince th eir
publication, num bers appear to have increased further, although there are large
differences, both betw een locations and betw een species. O ne explanation for
num erical increase could be the m arked grow th in com m ercial fishery and the
resu lting change in the fish com m unity (cf. F urness 1984). T here have been
m an y studies em phasizing the close relatio n sh ip b etw een fish p o p ulations,
2001
Gulls and terns in Senegal
69
Table 3 Comparison o f several estimates in the literature o f breeding pairs o f gulls
and terns along the north-west African coast, that breed in Senegal, or have
bred there in the past. The numbers given by Cooper et al (1984, first
column) are based on census results dating from 1972-1975. Gulls and terns
that have been recorded breeding in north-west Africa but not in Senegal
(Yellow-legged Gulls Larus m. michahellis, L. m. atlantis, Roseate Terns
Sterna dougallii/ Zino & Biscoito 1994) are not considered here. + = present
but not counted; - = absent.
Tabel 3. Vergelijking van het aantal in Noordwest-Afrika en Senegal broedende
paren meeuwen en sterns tussen verschillende literatuurbronnen. De
aantallen die door Cooper et al. (1984, eerste kolom) worden gegeven zijn
afkomstig uit de jaren 1972-1975. Meeuwen en sterns die nog nooit in
Senegal hebben gebroed, maar dit wel elders in Noordwest-Afrika doen
(beide Geelpootmeeuwen Larus m. michahellis en L. m. atlantis en Dougalls
Stern Sterna dougallii; Zino & Biscoito 1994) worden hier niet behandeld. +
= aanwezig maar niet geteld, - afwezig.
Species
Grey-headed Guii L. cirrocephalus
Slender-billed Guii L. genei
Kelp Guii L. dominicanus
Gull-billed Tem G. nilotica
Caspian Tem S', caspia
Common Tem S. hirundo
Little Tem S. albifrons
Royal Tern S. maxima
Bridled Tem S. anaethetus
Sooty Tem S. fuscata
Cooper et al.
1984
Urban et al.
1986
600-700
2850
1800
2400
400
150
10 500
1500
2
3000
1
1700-2100
3500-4300+
200-900+
100s
15 000-21 000
1700+
-
-
del Hoyo et
al. 1996
+
6000-7000
-
2000
5000
+
few 100s
25 000
+
+
seabird populations and com m ercial fisheries (e.g. A shm ole 1963; C raw ford &
Shelton 1981; Furness & Cooper 1982; Safina & B urger 1985; H unt et al. 1986;
Schaffner 1986; C airns 1988; H eubeck 1989; M onaghan et al. 1992a, b, Clapp
et al. 1993; N ettlesh ip et al. 1994). I f w e co n sid er all fish -ea tin g b ird
populations in w est A frica (such as corm orants P h ala cro co ra xspp., Red-billed
T ro p icbird P h a eto n a e th e re u s, pelicans P e le c a n u s spp., hero n s and egrets
A r d e i d a e , storks Ciconiidae, A fric a n F ish -e a g le H a lia e e tu s v o c ife r and
kingfishers Alcedinidae) there are no indications for increases on the B anc
d'A rguin. On the contrary, the num bers o f corm orants, herons, egrets, gulls and
te rn s h av e d ec reased in the m id -1 9 9 0 s afte r an in c re ase in th e 1980s
(G ow thorpe et al. 1996; H afner et al. 1999). On Ile de la M adeleine, Senegal,
the num bers o f G reat Corm orants P halacrocorax carbo lucidus, how ever, have
increased greatly (Schepers et al. 1998). F or the other species or species groups
70
KEHL ETAL
Atlantic Seabirds 3(2)
there are no data, either for the Sine-Saloum D elta, for the rem ainder o f Senegal
or elsew here in w est Africa.
O ther im portant, m ore direct threats to seabird colonies in Senegal are
to u rism , h a b ita t d estru c tio n , c o lle c tin g o f eggs, h u n tin g o f b ird s, and
(introduction of) ground predators (e.g. Stienen e t al. 1998). M en have collected
seabird eggs for hundreds o f years (e.g. D ragesco 1961). P resently how ever, at
least som e o f the colonies are over-exploited by egg-collectors. The birds are
restricted in their choice o f breeding locations, w hile the hum an population has
in creased and continues to do so. In addition tran sp o rtatio n has im proved,
m aking it possible for people to easily visit every seabird colony.
T he n o rth -w est A frican countries have h igh resp o n sib ility for the
conservation o f several species m entioned in Table 2, especially Royal T em and
Bridled Tern. The A frican Royal Terns are separated from the N orth A m erican
pop u lation as a different subspecies S. m. albididorsalis. This m eans that the
w orld population o f this subspecies occurs only in north-w est Africa.
The w est A frican B ridled Terns seem to be com pletely isolated from
the other A tlantic populations, and they are som etim es considered to belong to a
separate subspecies S. a. m elanoptera In the east A tlantic, there is a sm all
population in M auritania, w hile other colonies are found only on Ile V irginie,
W estern Sahara, w here 400 pairs w ere counted in 1960 (H eim de B alsae &
M ayaud 1962), and on Pagalu (or A nnobon) in the G u lf o f G uinea w ith 200
pairs (Fry 1961; B ritton 1986). Rose & Scott (1997) estim ated the w est A frican
b reeding p o pulation at 1500 pairs, but this seem s too high. It is n o t know n
w hether B ridled Terns still breed in W estern Sahara, w hile they seem to have
disappeared from the G u lf o f G uinea (cf. W illiam s 1984; G ochfeld & B urger
1996). T he w est A fric an B rid led T erns are th e re fo re am o n g st th e m ost
threatened seabirds in the world.
ACKNOW LEDGEM ENTS
T his study was carried out under the auspices o f F oundation W orking G roup International
W aterbird- and W etland R esearch (W IW O), the Institute o f Forestry and N ature Reserve (IBNDLO, presently A lterra), and the D irection des Parcs N ationaux du Sénégal (DPNS). Financial
support was obtained from W etlands International (W I) and Alterra. Logistic support w as received
by DPNS, WI and IUCN-Senegal. M any people assisted before, during and after the fieldwork, and
w e w ould like to thank especially dr. Seydina 1. Sylla, Tim and Jennifer Dodm an, W im and Geny
M ullié, Kees K offijberg, W im Fokker and Sjoerd Dirksen for their support. M any local people,
am ong which hotel m anagers and fisherm en in Senegal, assisted in various ways. Tom van Spanje
provided some literature on Mauritania.
A special w ord o f appreciation goes to Robert Brasseur, Abdoulaye Diop, M baye Diop,
A liou Gano, Insa Goudiaby, Effolem ing M anga, W im M ullié, Jacques Rigoulot, Em anuel Sagna,
M am adou Sali, Ibrahim a Sarr, and Landing Traore, for their excellent com panionship throughout
the field period. W ithout them, the project would not have been so successful.
2001
Gulls and terns in Senegal
71
B RO E D E N D E M EE U W E N E N ST E R N S I N SENEG AL IN 1998, E N
VOORSTEL VOOR N IE U W E POPULA TIESCHA TTING EN VAN M EE U W E N
E N ST E R N S I N N O O R D W EST-AFRIKA
In 1998 zijn broedende meeuwen en sterns g eteld langs de Senegalese kust. H et was de eerste
volledige telling van alle soorten meeuwen en sterns in Senegal; in het verleden concentreerden
onderzoekers zich m eestal vrijw el geheel op K oningssterns Sterna maxima, o f op enkele soorten
sterns, en werden in het gunstigste geval schattingen gegeven van andere soorten. E r zijn twee
belangrijke gebieden m et grote kolonies, nam elijk N ationaal P ark Langue de Barbarie, in het
noorden van het land, en N ationaal P ark Sine-Saloum Delta, ju is t ten noorden van Gambia. In
to taal werden 13.116 p a a r m eeuw en en (ten m inste) 31.426 p a a r sterns g e te ld (tabel 1). De
bela n g rijkste so o rten waren D unbekm eeuw L arus genei, G rijskopm eeuw L. cirrocephalus,
R eu zen stem S. caspia en Koningsstérn. K elpm eeuw L. dom inicanus, Lachstern Gelochelidon
nilotica, V isdief S. hirundo en Dwergstern S. albifrons broedden in lage aantallen.
H oew el het verleidelijk is om de in 1998 getelde aantallen te vergelijken met die van
eerdere tellingen, w ordt een directe vergelijking niet gem aakt om dat van eerdere tellingen vaak
onduidelijk is hoe de aantallen tot stand zijn gekom en. Wel worden de oude populatieschattingen
gegeven. Tevens w ordt een voorstel gedaan voor nieuwe schattingen en voor nieuwe 1%-normen
(tabel 2). D it is m ogelijk om dat van alle genoem de soorten vrijw el de gehele W est-Afrikaanse
populatie uitsluitend in Senegal en op de Banc d'Arguin in M auretanië broedt.
Grijskopm eeuw was met ruim 7500 p a a r de talrijkste meeuw. De vorige West-Afrikaanse
populatieschatting was 600-700 p a a r (tabel 3). In M auretanië broeden enkele tientallen paren, ook
elders langs de g ehele W est-Afrikaanse kust komen geen grote kolonies voor. Tot nog toe waren
geen tellingen u it W est-Afrika beschikbaar. D e nieuw e sc hatting bedraagt 10.000 paar. Van
D unbekm eeuw werden 5550 pa a r geteld. In M auretanië werden recent bijna 2000 p a a r geteld. D e
oude populatieschatting voor W est-Afrika bedroeg 3300 paar, voorstel voor een nieuwe schatting is
7500 paar. Van Kelpm eeuw werd een nest gevonden m et tw ee jo n g en en een uitkom end ei. D it is het
derde broedgeval van deze soort in Senegal en verm oedelijk het enige op het noordelijk halfrond.
Van Lachstern werden slechts acht p a a r gevonden in zoutpannen bij Kaolack. M ogelijk vestigden
zich later in het seizoen nog nieuwe paren. D e grootste aantallen broeden in M auretanië; recent
werden daar bijna 700 p a a r geteld. In het verleden werden in het noorden van Senegal 200-300
p a a r geteld, m aar hier is geen recente informatie over. D e oude populatieschatting bedroeg 2000
paar, de nieuw e 800. Van R euzenstem vonden wij in 1998 ten minste 8600 paar, vrijw el alle op Ile
aux Oiseaux. In de Langue de Barbarie was het broedseizoen a l voorbij en werden slechts enkele
vliegvlugge jo n g en gezien. Op de Banc d'Arguin broedde recent ten minste 4000 paar, terwijl ten
zuiden van het in 1998 bezochte geb ied recent ruim 2000 pa a r zijn geteld. D e populatieschatting
van 4000 p a a r voor N oordwest-Afrika is daarom naar 13.500 paar. Van V isdief werden 70 paar
geteld, m aar een exacte telling was moeilijk, om dat in een kolonie ju is t voor ons bezoek alle eieren
door vissers geraapt waren. In een andere kolonie zaten de Visdieven verspreid langs de rand van
de m eeuw enkolonie. Om predatie van meeuwen tot een m inim um te beperken w erd daarom een
snelle, globale telling gehouden. In M auretanië broedden in de ja re n 70 nog 200 paar, maar uit de
ja re n daarna zijn ons geen aantallen bekend. Voorheen w erd de totale W est-Afrikaanse populatie
geschat op 400 paar. Onze schatting bedraagt 200 paar. Van Dwergstern werden geen broedende
vogels aangetroffen, m aar bew akers in N ationaal P ark Langue de B arbarie meldden dat daar
ja a rlijks 35 p a a r broeden, zij het iets later in het seizoen. In het naburige p a rk Guem beul broeden
ja a rlijks 35-50 paar. In M auretanië broedden in de ja re n 70 25-50 paar, maar uit later ja re n zijn
ons geen getallen bekend. D e soort is notoir m oeilijk te tellen, om dat zich vaak solitaire paren in
afgelegen gebieden vestigen. Wij schatten de Noordw est-A frikaanse populatie voorzichtig op 100
paar. Van Koningsstérn telden wij bijna 23.000 paar, waarvan m eer dan 21.000 in een kolonie op
Ile aux Oiseaux. Tellingen van de Banc d'Arguin wijzen uit dat de aantallen jaarlijks enorm kunnen
72
KEIJL ETAL.
Atlantic Seabirds 3(2)
flu ctu eren . D e oude schatting voor W est-Afrika bedroeg 17.000 paar. Wij schatten de huidige
populatie op 4 3 .0 0 0 paar.
Behalve bovengenoemde soorten zijn in het verleden m ogelijke o f zekere broedgevallen
vastgesteld van K okm eeuw L. ridibundus, Lachm eeuw L . atricilla, F ranklin 's M eeuw L. pipixcan.
B onte Stern S. fuscata en B rilstern S. anaethetus. D eze laatste soort broedde in het verleden in
Spaanse Sahara en op A nnobon in de G o lf van Guinee. N a de ja re n 1960 is geen informatie over de
eerste broedlocatie, m aar de broedvogels op de tweede zijn m ogelijk verdwenen. D e populatie in
M auretanië is derhalve de laatste in het O ost-A tlantische gebied. D e oude sc hatting voor de
populatie bedroeg 1500 paar, m aar een recente schatting kwam niet verder dan 100 paar.
H et lijkt a ls o f de aantallen meeuw en en sterns in W est-Afrika zijn toegen omen. Een
m ogelijke verklaring hiervoor zou de sterk toegenomen visserij kunnen zijn. Op de B anc d'Arguin
lijken de aantallen echter eerder af- dan toegenomen te zijn. Van Senegal weten we alleen zeker dat
de A alscholvers P halacrocorax carbo lucidus op Ile de la M adeleine zijn toegenomen; van alle
overige viseters (aalscholvers, R oodsnavelkeerkringvogel Phaethon aethereus, pelikanen, reigers,
ooievaars, A frikaanse V isarend H aliaeetus vocifer en ijsvogels) zijn geen populatietrends bekend.
E en reeks van andere bedreigingen w ordt genoem d, w aaronder eierrapers, invoer van grondpredatoren, biotoopvernietiging en jacht. Z ow el M auretanië ais Senegal hebben een belangrijke
verantwoordelijkheid voor de bescherming van deze vogels en hun biotopen.
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