A preliminary study of bird use of fig Ficus species in
Amurum Forest Reserve, Nigeria
by Barnabas H. DARU1, Kowiyou YESSOUFOU2, Clive NUTTMAN3 & Jacinta ABALAKA4
1Department of Plant Science, University of Pretoria,
Private Bag X20, Hatfield 0028, South Africa. <email@example.com>
2Department of Environmental Sciences, University of South Africa, South Africa
3Tropical Biology Association, Department of Zoology, University of Cambridge,
Downing Street, Cambridge CB2 3EJ, U.K.
4A.P. Leventis Ornithological Research Institute, Laminga, P.O. Box 13404 Jos, Nigeria
Received 17 January 2013; revised 14 December 2014.
While fig trees (Ficus: Moraceae) are acknowledged as keystone resources for
frugivore communities in tropical forests, their detailed use by frugivores is
often poorly understood. In this study, we found over 400 fig trees of 12
species in Amurum Forest Reserve, Nigeria. We analyse bird visits to 12
individual trees of eight Ficus species, observed over a two-year period
(2007–9), during which we recorded 3234 visits by 48 bird species. Different
fig trees received between 23 and 826 visits during our observations; the
diurnal pattern of visits was similar for all fig species, with clear morning
(8h00–9h30, larger) and late afternoon (16h00, lesser) peaks, with a lull in
visits around mid-day. Mean visit duration varied between 2.9 ± 1.8 min. and
20.5 ± 19.2 min. (mean ± SD) at different fig species. Birds ate between 1.7 ±
1.1 and 5.2 ± 4.4 figs per visit at different fig species. Our study provides
preliminary information on Ficus–bird associations and confirms that figs are
important resources for frugivorous birds in Amurum Forest Reserve. We
suggest that at least four Ficus species provide disproportionately important
resources for frugivorous birds: F. lutea, F. ingens, F. thonningii and F.
Étude préliminaire de la consommation par les oiseaux de figues Ficus
spp. dans la Réserve de la Forêt d’Amurum, Nigeria. Bien que les figuiers
(Ficus: Moraceae) soient reconnus comme étant des ressources-clé pour les
communautés de frugivores dans les forêts tropicales, leur consommation par
les frugivores n’est souvent pas connue avec précision. Dans cette étude, nous
2 B.H. Daru et al. Malimbus 37
avons trouvé plus de 400 figuiers dans la Réserve de la Forêt d’Amurum,
Nigeria. Nous analysons les visites par les oiseaux de 12 arbres appartenant à
huit espèces de Ficus, observées sur une période de deux ans (2007–9), durant
laquelle nous avons noté 3234 visites par 48 espèces d’oiseaux. Les différents
figuiers ont reçu entre 23 et 826 visites pendant nos observations; le scénario
diurne des visites était le même pour toutes les espèces de figuiers, avec des
pics évidents pour le matin (8h00-9h30, le plus important) et la fin d’après-
midi (16h00, moins important), avec une pause dans les visites autour de la
mi-journée. La durée moyenne des visites aux différentes espèces de figuiers
variait entre 2,9 ± 1,8 min. (moyenne ± sdv). Les oiseaux consommaient entre
1,7 ± 1,1 et 5,2 ± 4,4 figues par visite aux différentes espèces de figuiers.
Notre étude fournit de premières informations sur les associations Ficus–
oiseaux et confirme que les figues sont des ressources importantes pour les
oiseaux frugivores dans la Réserve de la Forêt d’Amurum. Nous suggérons
qu’au moins quatre espèces de Ficus fournissent des ressources très
importantes pour les oiseaux frugivores: F. lutea, F. ingens, F. thonningii et
Fig trees (Ficus: Moraceae) provide reliable dietary resources for frugivores including
birds in tropical forests (Walker 2007), and birds play important ecological roles
dispersing fig seeds (Peh & Chong 2003), thus contributing to the maintenance of
species diversity (Snow 1981, Wenny & Levey 1998, Holbrook & Smith 2000). Several
criteria have been used to define keystone plant species for frugivores including
phenology (e.g. fructification during periods of general fruit scarcity: White 1994),
reliability of fruit production (Leighton & Leighton 1983, Terborgh 1986), abundance
of fruit produced (Bond 1993, Peres 2000), and most commonly, population size of
frugivores that use specific resources (Peres 2000). Fig trees are well known as a key
component of fruit resources in tropical forests (Lambert & Marshall 1991, Shanahan
et al. 2001, Bleher et al. 2003). Over 10% of the world’s birds and 6% of mammals
consume figs, making Ficus the most widely consumed plant genus (Shanahan et al.
2001). Despite the long interest in mutually beneficial fig-frugivore interactions (e.g.
Wheelwright 1985), most fig-frugivore studies have been restricted to the Neotropics
and southeast Asia, commonly with limited sample size (number of fig species
monitored) and observation period (1–2 weeks) (e.g. Shanahan et al. 2001, Ragusa-
Netto 2002, Bleher et al. 2003, Peh & Chong 2003, Tello 2003). In Africa south of the
Sahara, c. 112 Ficus species are recognised, with southern Africa being the centre of
diversity (Berg & Wiebes 1992); but detailed information on fig-frugivore
interactions is scarce. Long-term research might identify keystone Ficus and frugivore
species to be prioritised in conservation efforts (Bleher et al. 2003).
2015 Bird use of figs 3
We report here a two-year study on birds visits to Ficus species in Amurum
Forest, Nigeria. Amurum holds 278 bird species, 31% of the total recorded in Nigeria,
underpinning its status as an “Important Bird Area” and one of Nigeria’s key avian
biodiversity hotspots (Ezealor 2001) and, therefore, a suitable area to explore fig-bird
interactions. We evaluated visit patterns of birds on eight fig species. Our main
objective was to identify key frugivores visiting Ficus species and potentially guide
future conservation programmes in Nigeria. We expected that visitors to a putatively
critical food resource would mainly visit for foraging. Thus, we assessed the
importance of the various fig species by recording all visits by birds, the time spent by
visitors on each tree and the number of figs eaten; we also noted temporal feeding
patterns and visitor behaviour on the tree.
The study was conducted in Amurum Forest Reserve at c. 1300 m altitude on the Jos
Plateau in north-central Nigeria (9°52ʹ30ʺN, 8°58ʹ30ʺE). The reserve, which covers c.
300 ha, is a typical savanna woodland dominated by grasses, with scattered rocky
outcrops, and strips of riparian forest along streams (Vickery & Jones 2002). In the
grassland savanna, common trees and shrubs include Dichrostachys cinerea,
Jasminum dichotomum, Combretum fragrans and Piliostigma thoningii. The rocky
outcrops are characterised by Parkia biglobosa, Acacia ataxacantha and several Ficus
species, whereas the most frequent woody plant species in the forest patches are
Boscia angustifolia, Harungana madagascariensis, Syzygium guineense and Ochna
schweinfurthiana (Gofwen 2009). Temperatures in the region are 8–15°C during the
coldest months (November–February) and rise to 30–38°C during the warm and dry
months (March–April). Mean annual rainfall is 1411 mm, falling mainly between
April and October (Payne 1998).
Of the 278 bird species known from Amurum Forest Reserve, at least 58 are, to
varying extents, fruit feeders. We here follow Snow (1971) in using “fruit” to mean
fleshy fruit. Based on Brown et al. (1982), Fry & Keith (2004) and Fry et al. (1988,
2000), we classified these 58 species into three main categories: obligate frugivores
(18 species) that feed primarily on fruit, partial frugivores (28 species) which have,
beside fruits, other major food items (e.g. invertebrates), and opportunistic fruit-eaters
(12 species) that occasionally eat fruit; in this study we recorded 48 of these 58
species (Table 1). Nomenclature of birds follows Borrow & Demey (2001).
We determined Ficus density and diversity in 25 plots of 200 × 200 m (Fig. 1),
selected across the reserve using computer-generated random numbers. In each plot,
Ficus trees were photographed and identified to species level (where possible), the
number of trees of each species was counted, and their geographical coordinates taken,
allowing us to map their spatial distribution. Keay (1989) and the Fig Web
(<www.figweb.org>) were used for species identification.
4 B.H. Daru et al. Malimbus 37
Figure 1. Map of Amurum Forest Reserve showing Ficus species richness. The
Reserve is the diamond-shaped area. Depth of shading reflects interpolated
values of fig species richness from high (dark) to low (light) derived from species
richness in the 25 plots using Ordinary Kriging with a 12-cell neighbourhood.
The 25 plots are indicated and locations of the 12 Ficus trees observed for bird
frugivory are shown. Inset: the reserve’s position in Plateau State and Nigeria.
Over a two-year period March 2007 to June 2009, we observed bird–fig
interactions at 12 individual trees of eight fig species (four trees of F. lutea, two of F.
sycomorus, and one each of F. abutilifolia, F. thonningii, F. ingens, F. ovata, F.
platyphylla and an unidentified Ficus species) when they were found fruiting during
this period (Fig. 2). Each focal tree was found in fruit once during the study period
and observations commenced when the tree was first noted to be fruiting. Hence, we
could not be certain of the overall length (in days) of fruiting period, nor did we
estimate the number of figs produced by each tree during a fruiting event. For all
birds visiting a tree, we recorded the following: species identity and number, time
spent in the tree (including eating, perching and moving within the tree), number of
figs eaten and handling behaviour. Independence of observations was not assured as
birds were not marked:individual birds repeatedly revisiting the same tree would
have been classed as different observations. We acknowledge that this may have
caused pseudo-replication, but judging from observations of different individuals
visiting concurrently, and considering the extended study period, we believe the data
2015 Bird use of figs 5
Figure 2. Chronology of observation of bird-fig interactions in Amurum Forest
Reserve, Nigeria. The perpendicular lines mark first and last observation day for
each tree, and their length is arbitrary to enable legibility. N days in brackets are
total observation days on each tree.
on fruit-feeding behaviour to be reliably indicative of true patterns. Visitation was
recorded by scan-sampling from a concealed position using binoculars and telescope.
Observations consisted of 12 h sessions (6h00–18h00), lasting from the time of
ripening of figs on an individual tree through to consumption of the last figs on it,
following the method of Tello (2003). We collected quantitative data on visit time
(seconds spent on a tree) and fig consumption (number eaten per visit), and also
recorded the temporal patterns of visits and the behaviour of visiting birds.
A preliminary analysis showed that foraging activity of frugivores occurred
mainly between 6h00-11h00 and 13h00-18h00, with lower activity in the afternoon.
We therefore explored the differences between morning (6h00–11h00) and afternoon
(13h00–18h00) in the number of figs eaten, time spent on each tree, and number of
visits to each tree, using the non-parametric two-sample Kolmogorov-Smirnov test.
We also investigated intra-specific differences among individual trees of Ficus lutea
by analysis of variance (ANOVA), contrasting mean time spent per visit, mean
number of figs eaten per visit and number of visits by different bird species, between
individual trees (n = 135, 229, 302, 308 for the four trees; sample sizes are the subsets
of visits where fig consumption was observed) using Tukey’s honest significant
difference (HSD). To assess whether these three variables were correlated, we
calculated the correlation coefficient and determined its significance using Pearson’s
product-moment method. Prior to this correlation test, variables were log10-
transformed to meet the assumptions of normality and homogeneity of variance.
6 B.H. Daru et al. Malimbus 37
Finally, we explored the temporal dynamics of tree usage by frugivores. All analyses
were carried out using R (<http://www.R-project.org> consulted 2013). All mean
values are reported as mean ± 1 standard deviation.
We recorded 412 fig trees of 12 species in the 25 sampled plots with more species
recorded in the central parts of the reserve (Fig. 1). Ficus lutea (122 trees), F.
thonningii (96), F. abutilifolia (78), F. ovata (39), F. sycomorus (19) were the most
abundant species, with F. platyphylla, F. ingens and the unidentified species
represented by one tree found each; the four other Ficus species found, at which we
did not make frugivory observations, were F. sur (17 trees), F. umbellata (17), F.
glumosa (13), F. polita (1). The overall density of the combined Ficus population in
the reserve was 1.35 trees/ha.
Visitation to Ficus spp.
We observed 3234 individual bird visits, representing 48 bird species visiting the 12
Ficus trees monitored (Table 1). Ficus lutea received the most bird species (38
species cumulatively for four individuals, which received 11, 17, 28 and 26 species
each: mean species per tree = 20.5), followed by F. abutilifolia (19 species), F.
thonningii and F. sp. (17 species each), F. ingens (15 species), F. ovata (14 species),
F. sycomorus (18 species cumulatively for two individuals, which received 7 and 16
species each: mean species per tree = 11.5) and F. platyphylla (5 species).
More than half of the total number of bird visits (1665) were observed on the four
trees of F. lutea, followed by F. abutilifolia, F. ingens, F. sp. and F. sycomorus, the
three remaining species each receiving < 5% of visits (Table 2).
The majority of bird visitors (> 55%) swallowed figs whole. We also observed birds
perching and occasionally pecking out parts of the figs (29% of visits). The least
frequent behaviour (5% of visits) consisted of birds (three species only, described as
opportunistic frugivores and marked with asterisks in Table 1) eating insects rather
Several bird species visited multiple fig species (Table 1). Among the obligate
frugivores, the Common Bulbul and the Yellow-fronted Tinkerbird were recorded on
all eight Ficus species, and the Speckled Mousebird was recorded on seven of them.
Opportunistic and partial frugivores were recorded in up to six species (Table 1).
The longest mean visit times were observed on Ficus ingens, followed by F. ovata
and F. sycomorus (Table 2).
Table 1. The total number of visits by each bird species to the eight Ficus species studied in Amurum Forest Reserve, Nigeria:
Fa, Fi, Fl, Fo, Fp, Fsp, Fsy, Ft correspond to F. abutilifolia, F. ingens, F. lutea, F. ovata, F. platyphylla, F. sp., F. sycomorus and
F. thonningii respectively. The birds’ frugivory category (see Methods) also indicates species that visited but ate only insects
in the trees (marked *) and species that visited but did not eat figs or insects (i.e. perched without appearing to feed, marked †).
Frugivory Visits to Ficus species
category Fa Fi Fl Fo Fp Fsp Fsy Ft
Scopus umbretta Hamerkop opportunistic† 0 0 1 0 0 0 0 0
Falco biarmicus Lanner Falcon opportunistic† 0 0 1 0 0 0 0 0
Streptopelia hypopyrrha Adamawa Turtle Dove opportunistic 0 0 2 0 0 0 0 0
S. senegalensis Laughing Dove opportunistic 0 0 1 0 0 0 0 0
S. vinacea Vinaceous Dove opportunistic 0 0 1 4 0 0 0 0
Turtur abyssinicus Black-billed Wood Dove opportunistic 0 0 3 0 0 0 0 0
Treron waalia Bruce’s Green Pigeon obligate 1 0 244 0 0 0 0 0
Musophaga violacea Violet Turaco obligate 41 0 96 0 0 2 0 0
Crinifer piscator Western Grey Plantain-eater obligate 32 0 95 2 0 0 17 1
Centropus senegalensis Senegal Coucal opportunistic 0 0 0 0 0 0 1 0
Colius striatus Speckled Mousebird obligate 113 189 326 73 0 55 80 5
Merops bulocki Red-throated Bee-eater opportunistic* 0 0 2 0 0 0 0 0
Tockus erythrorhynchus Red-billed Hornbill partial 0 0 10 0 0 0 0 1
T. nasutus African Grey Hornbill obligate 4 1 157 0 0 19 9 1
2015 Bird use of figs 7
Frugivory Visits to Ficus species
category Fa Fi Fl Fo Fp Fsp Fsy Ft
Pogoniulus chrysoconus Yellow-fronted Tinkerbird opportunistic 4 1 3 1 2 1 2 1
Lybius dubius Bearded Barbet obligate 8 4 179 0 0 1 33 23
L. vielloti Vieillot’s Barbet partial 0 0 57 0 0 10 0 7
Dendropicos fuscescens Cardinal Woodpecker opportunistic 0 0 4 1 0 2 1 0
Mesopicos goertae Grey Woodpecker opportunistic 0 0 1 0 0 0 0 0
Pycnonotus barbatus Common Bulbul obligate 51 46 62 11 10 48 52 16
Chlorocichla flavicollis Yellow-throated Leaflove obligate 1 4 49 0 0 0 0 4
Turdus pelios African Thrush opportunistic 45 4 41 13 0 12 20 0
Myrmecocichla cinnamomeiventris Mocking Chat opportunistic 11 1 6 0 0 23 0 0
Melaenormis edolioides Northern Black Flycatcher opportunistic 0 1 1 0 0 0 0 0
Eremomela pusilla Senegal Eremomela opportunistic 17 5 4 0 0 1 1 0
Sylvietta brachyura Northern Crombec opportunistic 1 0 0 0 1 0 0 1
Phylloscopus trochilus Willow Warbler opportunistic 0 1 7 0 0 0 0 0
Sylvia borin Garden Warbler opportunistic 6 0 0 0 0 11 0 0
S. communis Common Whitethroat opportunistic 1 25 18 2 0 1 13 0
Camaroptera brachyura Grey-backed Camaroptera opportunistic 0 0 5 0 0 0 0 0
Prinia subflava Tawny-flanked Prinia opportunistic 0 9 0 2 0 0 8 3
Batis senegalensis Senegal Batis opportunistic 0 0 0 0 0 0 0 2
8 B.H. Daru et al. Malimbus 37
Elminia longicauda Blue Flycatcher opportunistic* 0 0 1 0 0 0 0 0
Terpsiphone viridis Paradise Flycatcher opportunistic* 0 0 0 0 0 0 0 3
Turdoides plebejus Brown Babbler opportunistic 0 0 13 0 0 0 1 0
Anthoscopus parvulus Yellow Penduline Tit opportunistic 0 0 0 0 0 0 0 1
Chalcomitra senegalensis Scarlet-chested Sunbird opportunistic 4 1 27 3 0 0 15 0
Nectarinia venusta Variable Sunbird opportunistic 0 0 1 1 0 0 0 0
Zosterops senegalensis Yellow White-eye partial 0 4 12 2 0 6 22 4
Onychognathus morio Neumann’s Starling obligate 15 0 1 0 0 0 0 0
Lamprotornis purpureus Purple Glossy Starling obligate 0 0 183 0 1 40 61 0
Cinnyricinclus leucogaster Violet-backed Starling obligate 0 0 25 0 0 0 0 0
Passer griseus Grey-headed Sparrow opportunistic 0 0 0 0 0 0 0 1
Ploceus heuglini Heuglin’s Masked Weaver opportunistic 0 0 1 0 0 0 0 0
P. cucullatus Village Weaver opportunistic 9 0 0 4 0 0 87 0
Estrilda caerulescens Lavender Waxbill opportunistic† 31 0 24 1 9 3 1 0
Lagonosticta sanguinodorsalis Rock Firefinch opportunistic† 0 0 1 0 0 1 0 0
L. senegala Red-billed Firefinch opportunistic† 0 0 0 0 0 0 0 1
Total visits 395 296 1665 120 23 236 424 75
Number of species visiting 19 15 38 14 5 17 18 17
2015 Bird use of figs 9
10 B.H. Daru et al. Malimbus 37
Table 2. Summary of Ficus species visited by birds during the study period. Fig
sizes (mm) are reported as mean syconium length (first value) and width (second
value). Habitat types: SW = savanna woodland; GF = gallery forest; RO = rocky
Ficus species Fig size Habitat Total visits Time spent n figs eaten
in mm (n) types per tree per visit (min.) per visit
abutilifolia 22.9 x 12.1 (44) SW 395 9.1 ± 10.9 3.9 ± 5.2
ingens 5.0 x 4.5 (30) SW 296 20.5 ± 19.2 4.8 ± 3.9
lutea 23.1 x 21.7 (80) GF, SW 416.25* 12.2 ± 26.0 3.6 ± 5.5
ovata 27.5 x 28.8 (15) RO 120 15.5 ± 31.7 2.3 ± 1.7
platyphylla 14.0 x 13.1 (16) RO 23 2.9 ± 1.8 1.7 ± 1.1
sp. indet. 20.1 x 18.2 (30) RO 236 6.3 ± 5.6 3.9 ± 5.5
sycomorus 38.5 x 36.1 (23) RO, SW 212* 15.2 ± 17.0 2.9 ± 2.4
thonningii 8.3 x 6.5 (40) RO 75 7.4 ± 5.8 5.2 ± 4.4
*Means of the visit numbers to the four F. lutea (826, 229, 302, 308 visits) and two F.
sycomorus (29, 395 visits) trees observed: sample sizes for behavioural measures are
the “total visits” column, except for F. lutea (n = 1665) and F. sycomorus (n = 424).
We found no strong correlation between mean number of figs consumed per visit
and fig size (maximum dimension) (r = –0.48, P = 0.23, n = 8), although the two
species with the smallest figs, F. ingens and F. thonningii, had the greatest mean
number of figs eaten per visit (Table 2). There was also no significant correlation
between the number of bird species that visited a tree and fig size, nor between total
number of visits to a tree and fig size.
There was a general similarity in the daily pattern of use of the eight fig tree
species by birds (Fig. 3), with most feeding activity occurring from 6h30 to 10h00 and
the morning peak falling roughly between 8h00 and 9h30 (a little later in F.
platyphylla). No visitors were seen on trees between noon and 13h00. There was a
lesser period of activity from around 14h00 to 18h00, with its peak around 16h00
The mean time spent per visit on each tree was similar among the four individuals
of Ficus lutea (Tukey HSD test: P > 0.05; Fig. 4), but the numbers of visits by birds
of different species and mean figs eaten per visit differed significantly between the
four trees, in four and five of the six pairwise combinations, respectively (Tukey HSD
tests, both P < 0.05; Fig. 4).
There was a strong correlation between mean length of visit and mean number of
figs eaten per visit at each fig species (r = 0.57, P < 0.001, n = 8) and significant but
weaker positive relationships between number of visits and mean number of figs eaten
per visit (r = 0.17, P < 0.001, n = 8) and between number of visits and mean duration
of the visit (r = 0.12, P < 0.001, n = 8).
2015 Bird use of figs 11
Figure 3. Daily feeding patterns on eight Ficus species, as the frequency of bird
visits for every hour of the day. Grey bars signify overlap between black and white.
Figure 4. Intra-specific differences in visitation pattern between individuals of
Ficus lutea. The box ends mark the first and third quartiles, the median is
indicated by the horizontal line, the range by the vertical dashed line, and
outliers (points > 1.5 x the interquartile range) by circles. Data points on central
graph are numbers of visitors of different bird species, whereas all species are
grouped for visit times (left) and number of figs eaten (right).
12 B.H. Daru et al. Malimbus 37
Differential attractiveness of Ficus species has previously been reported for African
frugivores: for example, Bruce’s Green Pigeon was said to favour Ficus platyphylla
(Morel et al. 1986), although in the present study it was not noted on F. platyphylla but
fed almost exclusively on F. lutea. Plant species that attract a diverse community of
frugivores may similarly be important for frugivore survival (Peres 2000). The relation-
ships observed in our study between birds and fig trees may reflect bird preferences for
certain Ficus species. For example, F. lutea was the most visited fig species (per tree), in
terms of both number of bird species and number of visits. The longest visit durations
were on F. ingens, F. ovata, F. sycomorus and F. lutea, and the most fruits eaten per
visit on F. thonningii, F. ingens, F. abutilifolia and F. sp., respectively. Of the three
most abundant fig species in Amurum, F. lutea, F. abutilifolia and F. thonningii, the
former two received the most visits per tree, whereas F thonningii received relatively
few visits although its small fruits had the highest removal rate (mean figs removed per
mean visit time) of all species (Table 2). The somewhat scarce F. ingens received many
long visits but showed relatively low levels of fruit removal than more common species.
Hence, the drivers of consumption are likely to be factors other than tree density.
Factors driving the usage of a particular fig species might include tree density,
fruiting phenology, fig colour, fig nutritive value and fig size (Korine & Kalko 2000,
Githiru et al. 2002, Herrera 2002, Bleher et al. 2003, Lord 2004). There was great
variation in fig size between the eight Ficus species (Table 2; cf. Berg & Wiebes
1992), which could account for some of the variation in fig species attractiveness. But
although species with small fruits are presumably accessible to a larger range of bird
species, we found no significant relationships between fig size and visit frequency or
number of bird species visiting.
For F. lutea, there were significant differences between the four trees in number
of visitors and mean number of figs eaten per visit, although the numerical difference
in the latter was slight. These intra-species differences indicate that the conclusions on
interspecific differences below, based on only a single tree for most species, must be
treated as preliminary.
There was a general similarity in temporal feeding patterns on all fig species, with
heavy activity in the morning, except that activity on F. platyphylla occurred slightly
later in the morning (but not in the afternoon) compared to other fig species. One
possible reason could be that frugivores prefer the other species and later move onto
F. platyphylla when the fruits that ripened overnight on the other species are depleted.
Supporting this, F. platyphylla had a low number of birds visiting, and the lowest rate
of fruit removal. As such, F. platyphylla may represent a “backup resource” relative
to more preferred species. Choice tests could examine this possibility. The overall
pattern of greatest visitation before 10h00 conforms to a common pattern of avian
foraging and Breitwisch’s (1983) finding at a Ficus in Cameroon.
2015 Bird use of figs 13
Visitation in the morning was nearly three times higher to F. thonningii than to all
other tree species, with a peak slightly later than all other trees except F. platyphylla;
in the evening, the latter part of the afternoon peak in visitation to F. thonningii
occurred when bird activities started declining on other fig trees (Fig. 3). F. thonningii
appears to be an important food resource in Amurum; it is found at high density, and
although visit times are relatively short, the heavy morning usage pattern and high
fruit removal rates (with no figs dropped) suggest it is a preferred food for frugivorous
birds. Bleher et al. (2003) found that F. thonningii provided the most reliable
resources for birds in Oribi Gorge Nature Reserve in South Africa.
Our Ficus trees were utilized by some opportunistic frugivores which foraged for
insects but were not seen to consume figs (Red-throated Bee-eater, Blue Flycatcher,
Paradise Flycatcher). Additionally, a number of birds used focal trees for perching but
not feeding at all, e.g. Hamerkop, Lanner Falcon, Lavender Waxbill, Red-billed
Firefinch, and the Nigerian endemic Rock Firefinch.
Overall, our data on Ficus–bird associations show that figs are important
resources for frugivorous birds in Amurum Forest Reserve. Ficus lutea, F. ingens, F.
thonningii and F. abutilifolia in particular appear to be the most important fig
resources for birds, though we remain cautious in this conclusion because our sample
size was limited. The site harbours a high density of fig trees of a variety of species
that are used by a large and diverse assemblage of visitors. Longer-term research
should focus on the reproductive phenology as well as temporal and spatial
availability of figs. This will help identify critical resources and potential keystone
species that will inform conservation planning. Reforestation programs should not
only consider species rarity and vulnerability but also give priority to plant species
that are especially useful in sustaining bird diversity and ultimately ecosystem
We are grateful to the A.P. Leventis Ornithological Research Institute, Jos, for study
permission and overall support. Thanks to Simon van Noort for assistance with tree
identification and Arin Izang, Useh Damburam and Mary Maisaini for fieldwork. This
work was supported by Rufford Small Grant (U.K.) reference 32.12.07. We thank two
reviewers for their comments on earlier drafts.
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