Afrotropical Bird Research Articles

Circulation of avian influenza viruses in wild birds in Inner Niger Delta, Mali

Please cite this paper as: Cappelle et al. (2012) Circulation of avian influenza viruses in wild birds in Inner Niger Delta, Mali. Influenza and Other Respiratory Viruses 6(4), 240–244. Background Avian influenza viruses (AIV) have been detected in wild birds in West Africa during the northern winter, but no information is available on a potential year‐round circulation of AIV in West Africa. Such year‐round circulation would allow reassortment opportunities between strains circulating in Afro‐tropical birds and strains imported by migratory birds wintering in West Africa. Objective and Method A 2‐year longitudinal survey was conducted in the largest continental wetland of West Africa, the Inner Niger Delta in Mali, to determine the year‐round circulation of AIV in wild birds. Results and Conclusions Avian influenza virus RNA was detected during all periods of the year. Very low prevalence was detected during the absence of the migratory wild birds. However, a year‐round circulation of AIV seems possible in West Africa, as shown in other African regions. West Africa may hence be another potential site of reassortment between AIV strains originating from both Afro‐tropical and Eurasian regions.

Habitat fragmentation reduces nest survival in an Afrotropical bird community in a biodiversity hotspot

Ecologists have long hypothesized that fragmentation of tropical landscapes reduces avian nest success. However, this hypothesis has not been rigorously assessed because of the difficulty of finding large numbers of well-hidden nests in tropical forests. Here we report that in the East Usambara Mountains in Tanzania, which are part of the Eastern Arc Mountains, a global biodiversity hotspot, that daily nest survival rate and nest success for seven of eight common understory bird species that we examined over a single breeding season were significantly lower in fragmented than in continuous forest, with the odds of nest failure for these seven species ranging from 1.9 to 196.8 times higher in fragmented than continuous forest. Cup-shaped nests were particularly vulnerable in fragments. We then examined over six breeding seasons and 14 study sites in a multivariable survival analysis the influence of landscape structure and nest location on daily nest survival for 13 common species representing 1,272 nests and four nest types (plate, cup, dome, and pouch). Across species and nest types, area, distance of nest to edge, and nest height had a dominant influence on daily nest survival, with area being positively related to nest survival and distance of nest to edge and nest height being both positively and negatively associated with daily nest survival. Our results indicate that multiple environmental factors contribute to reduce nest survival within a tropical understory bird community in a fragmented landscape and that maintaining large continuous forest is important for enhancing nest survival for Afrotropical understory birds.

Using stable isotopes to trace resource acquisition and trophic position in four Afrotropical birds with different diets

(2010). Using stable isotopes to trace resource acquisition and trophic position in four Afrotropical birds with different diets. Ostrich: Vol. 81, No. 3, pp. 273-275.

Does landscape structure affect resource tracking by avian frugivores in a fragmented Afrotropical forest?

Frugivorous species heavily depend on patchy food resources and are believed to track these in space and time, thereby providing an important seed dispersal function that might be critical toward the regeneration of fruiting plants. However, isolation of suitable food patches due to habitat fragmentation or changes in landscape connectivity may hamper food tracking behaviour and adversely affect populations of both frugivores (through starvation) and food plants (through interruption of seed dispersal). We here test whether density fluctuations in four frugivorous Afrotropical bird species were larger and/or matched fluctuations in ripe fruit densities better in study plots embedded in large tracts of indigenous forest than in equally‐sized plots embedded in cultivated lands. We compared these results with those of four non‐frugivorous species (out‐group) which were not expected to track fruit resources. Whereas densities of both frugivores and fruit crops strongly fluctuated in space and time, these fluctuations were not synchronised, nor did the level of synchrony differ in relation to matrix type. For some but not all bird species, lower densities and smaller temporal fluctuations in forest plots surrounded by cultivation may reflect decreased mobility. The observed fluctuations in bird densities most likely reflect exchange with the surrounding landscape matrix, suggesting that small pockets of fruiting trees in farmland may comprise critical food resources for frugivores inhabiting highly fragmented landscapes, apart from increasing connectivity for both bird and seed dispersal.

Where do species' geographic ranges stop and why? Landscape impermeability and the Afrotropical avifauna.

Although understanding large-scale spatial variation in species' distributions is a major goal in macroecology, relatively little attention has been paid to the factors limiting species' ranges. An understanding of these factors may improve predictions of species' movements in response to global change. We present a measure of landscape impermeability, defined as the proportion of resident species whose ranges end in an area. We quantify and map impermeability for Afrotropical birds and use multi-model inference to assess support for a wide suite of hypotheses about its potential environmental correlates. Non-spatial analyses emphasize the importance of broad-scale environmental patterns of energy availability and habitat heterogeneity in limiting species' distributions. Conversely, spatial analyses focus attention on small-scale factors of habitat and topographic complexity. These results hold even when only species from the top quartile of range sizes are assessed. All our analyses highlight that range edges are concentrated in heterogeneous habitats. Global change is expected to alter the nature and distribution of such habitats, necessitating range movement by many resident species. Therefore, impermeability provides a simple measure for identifying regions, where continuing global change and human encroachment are likely to cause profound changes in regional diversity patterns.

Identification of potentially competing Afrotropical and Palaearctic bird species in the Sahel

Areas experiencing a seasonal influx of migrants may be expected to have a high potential for competition between resident and migrant populations. Described differences in foraging behaviour and microhabitat selection between Palaearctic and Afrotropical species have been ascribed to competition between these groups. The first step in the assessment of whether there are any interspecific competitive interactions must be the identification of species with the greatest overlap in habitat selection and foraging method. Our results provide a tool for identifying species with the greatest potential for interspecific competition. These species should be the focus of any further examination of competition within the Sahel.

Experimental evidence of 'floaters' in two isolated populations of an Afrotropical forest bird

We studied the presence of 'floaters', i.e. non-territorial individuals roaming occupied territories awaiting future breeding opportunities, in two separate White-starred Robin (Pogonocichla stellata) populations at the Taita Hills, Kenya, using a removal experiment. Previous vegetation analyses at this site had showed that 'population Ngangao' occupied a high-quality forest fragment, and 'population Chawia' occupied a low-quality one. Using a combination of radio telemetry, dawn calls, visual observations and targetted playbacks in one 16ha plot per fragment, 52 individuals of different territorial status were identified. Ngangao hosted 14 resident and 13 floating males, while Chawia hosted eight residents and two floaters. Population Chawia (but not Ngangao) hosted unmated territorial males. Floating males in Ngangao took over three of seven (i.e. 43%) vacated territories within a few days of the residents' removal. In both populations, no resident neighbouring males expanded their territories or moved to take over the vacant territories following experimental removal of resident males. These results suggest that (1) territorial behaviour is an important factor limiting the number of breeders in Population Ngangao; (2) other factors such as poor habitat quality and female scarcity, most likely associated with the lower bird densities in Population Chawia, can limit numbers of breeders before territorial exclusion becomes a concern.

Taxonomic status and conservation importance of the avifauna of Katanga (south-east Congo Basin) and its environs

A re-appraisal of published knowledge of the birds recorded in Katanga (Democratic Republic of Congo) focussed on the status of 56 taxa, to reveal a high endemism (14 species of a total of at least 642). In addition, 33 taxa were also revealed as possible south-central African endemics but need thorough taxonomic appraisal. All are geographically isolated populations, with ranges restricted within, or centred on, Katanga. These taxonomic enigmas await thorough re-appraisal. The majority of these newly-recognised Katanga endemics were traditionally lumped into polytypic species in classifications based on the Biological Species Concept (BSC). These synonymised taxa have therefore been ignored repeatedly in recent conservation assessments of African birds. This failure illustrates how the BSC can obfuscate patterns of species diversity in its classifications, which lump evolutionarily-distinct lineages into imprecisely-diagnosed taxa. An unfortunate historical legacy is to forget that a distinct population exists, after it has been classified as a subspecies, synonym or race in a polytypic species. These discoveries exemplify the research opportunities that Katanga's birds present for avian systematists. The assessment of any taxon of Afrotropical birds is hamstrung by the fragmented state of taxonomic information in the literature. This constraint impinges on any taxonomic study of any African avifauna and will be removed if an accessible database summarises all published taxonomic information in an exhaustive classification, accounting for synonomy, authority and context of each described taxon. Availability of such a complete taxonomic catalogue is quintessential if phylogeographic and systematic research is to determine precisely which populations have been named, and where these occur. This is critical to compile refined biogeographical knowledge for scientifically-sound conservation plans and actions. Objective evaluation of the endemism of the Katanga avifauna requires complementary datasets for other regional avifaunas across Africa. Their unavailability exemplifies the gravity of this taxonomic impediment, given the immense effort involved in compiling and comparing such fine-grained taxonomic data. Deficiencies aside, the data compiled in this review point to a recent suite of speciation events (most likely late Cenozoic) centred on Katanga. The strident biogeographical signal in these data emphasises the hitherto poorly-appreciated significance of Katanga's unique and rich biodiversity, which ranks alongside better-known sites in Africa of global conservation importance.

An acoustic postconflict display in the duetting tropical boubou (Laniarius aethiopicus): a signal of victory?

BackgroundIn many species of birds, pair bonded males and females precisely co-ordinate their vocalisations to form duets. Duetting behaviour, although still somewhat of an enigma, is thought to function primarily in territorial defence and mate guarding. We identify an additional function of duetting in an afrotropical bird, the tropical boubou (Laniarius aethiopicus), that uses one duet type as a postconflict display probably to advertise victory to other boubous.ResultsWe simulated intrusions into boubou territories in the field in Ivory Coast, West Africa using playbacks of four different types of boubou duets to test the use of the presumptive acoustic victory display before, during and after playbacks. These staged encounters resulted in either retreat of the focal birds during playback or continued presence accompanied by vocal displays after playback had ceased. Losers of encounters never sung after retreating whereas 11 out of 18 pairs sung the presumptive victory duet after the encounter. Analysis revealed that the presumptive victory display was sung significantly more often after than before or during the playback treatment.ConclusionWe conclude that, most likely, the investigated duet type is a postconflict victory display – a novel function of duets. Furthermore the duet is a rare example among birds of a context-specific song. The conspicuousness of the display suggests that it is directed not only to losers of an agonistic encounter but also to other pairs of birds in neighbouring territories.

Gaps in the protected area network for threatened Afrotropical birds

Protected areas established for wildlife conservation (IUCN category I–VI protected areas) or for forest and watershed conservation (forest reserves) across mainland sub-Saharan Africa have high biodiversity values. However, they fail to cover over half of the 106 threatened bird species, and thus leave these vulnerable to extinction. An analysis of Red List bird species that are not represented in existing reserves indicates gaps in the current network of protected areas, namely: Mt. Cameroon-Bamenda highlands (Cameroon), the Angolan scarp (Angola), the Drakensberg Highlands (South Africa), the Highveld (South Africa), the Eastern Arc Mountains (Tanzania), the eastern African coastal forest mosaic (Kenya and Tanzania), the Albertine Rift (Uganda, Rwanda, Burundi, eastern Democratic Republic of Congo and western Tanzania), and the Ethiopian Highlands. The addition of Forest Reserves to the existing protected areas closes some of the reservation gaps for threatened birds in Africa. We suggest that these Forest Reserves should be included within official lists of protected areas, and that National forestry authorities be encouraged to manage these areas. Publication of scientific articles showing the conservation value of Forest Reserves is needed to raise local and international support and funding.

Is ‘nocturnal hypothermia’ a valid physiological concept in small birds?: a study on Bronze MannikinsSpermestes cucullatus

The thermoregulatory capacity and metabolic responses to light–dark cycles under various mild food‐deprivation treatments were measured in Bronze MannikinsSpermestes cucullatus(10–11 g). We measured the response of minimum oxygen consumption to ambient temperature in order to determine the basal metabolic rate (BMR), thermal conductance and limits of thermoneutrality of the Mannikins. In addition, we measured oxygen consumption in response to light–dark cycles and three mild food‐deprivation treatments. Bronze Mannikins have a low BMR (1.67 mlO2/g/h) that isc.50–60% of that predicted from phylogenetically independent allometric curves for all birds. A low BMR resulted in amplitudes of metabolism between the active and rest phases that were double those predicted allometrically from body mass. The reduced nocturnal metabolic rate did not represent torpor. Typically, Mannikins would need to reduce their metabolic rate during the rest phase toc.17% of BMR to attain the average torpor metabolic rate of other birds. The data are, however, consistent with those of other group‐living Afrotropical birds that benefit energetically from group huddling in environments in which moderate seasonality is accompanied by unpredictable climates – and thus unpredictable energy inputs in time and space. When food‐deprived and placed under moderate cold stress (20 °C), Mannikins decreased their rest‐phase metabolic rates to the same magnitude as several small Holarctic birds. We suggest that, in the context of the progress made to quantify and define proximate heterothermic responses in endotherms, such as torpor and hibernation, the term nocturnal hypothermia often applied to moderate nocturnal reductions in metabolic rate is vague, misleading and inappropriate.

Biogeographical patterns of endemic terrestrial Afrotropical birds

Abstract.Biogeographical zones are described for terrestrial bird species endemic to the Afrotropics using up‐to‐date distributional data and multivariate statistical techniques. This provides an objective basis for a hierarchy of subregions, provinces and districts, based on a set of rules. Results are compared to previous studies at continental and regional scales. Biogeographical zones for passerines and non‐passerines are compared and found to be similar. Peaks of species richness and narrow endemism are described for the six major subdivisions (subregions) identified by the cluster analysis. Coincidence of peaks of species richness and narrow endemism is found to be low, such that areas selected to represent high species richness tallies will often fail to represent narrow endemics. Strong regionalization of Afrotropical birds indicates the need to use a biogeographical framework in conservation priority setting exercises to ensure that unique, but species‐poor, avifaunas are not neglected.

Patterns of species richness and narrow endemism of terrestrial bird species in the Afrotropical region

AbstractGeographical patterns and peaks of species richness and narrow endemism (defined by range‐restrictedness and range‐size rarity) are described for terrestrial Afrotropical birds and subsets thereof based on residency, endemism, and taxonomy. Species richness for residents and Afrotropical endemics (species globally restricted to sub‐Saharan Africa) peaks along the mountains and adjacent lowlands of eastern and southern Africa. Isolated mountains in central and western Africa and the lowlands of the north‐eastern Congo Basin (Ituri) are highlighted to a lesser degree. Peaks of narrow endemism occur in these areas as well as in the Ethiopian Highlands (particularly for non‐passerines), Somalia (particularly for passerines), and the Angolan Escarpment. Within residents, patterns of species richness vary greatly between Afrotropical endemics (which concentrate in forests on mountains and adjacent lowlands, and the southern Brachystegia woodlands) and non‐endemic residents (which concentrate in Sudanian woodlands and the Ethiopian Highlands). Patterns of species richness of residents (species that breed in the Afrotropics) and non‐breeding migrants (non‐breeding visitors to the Afrotropics) also show notable differences. The latter concentrate in areas close to the Palaearctic, which forms their distributional range centres. Patterns of species richness and narrow endemism for Afrotropical endemics show broad‐scale coincidence within mountains or mountain–lowland complexes, particularly the Cameroon–Bamenda Highland system, East African rift system and Eastern Arc mountains. However, fine‐scale coincidence of peaks of species richness and narrow endemism within these complexes is low. Narrow endemism peaks occur in areas of topographical complexity, which may have conferred localized climatic stability over short‐, medium‐, and long‐term climatic cycles (sensu Fjeldså, 1994; Fjeldsået al., 1997), allowing these areas to act as ‘species pumps’. Species accumulate in areas of high productivity. Lack of fine‐scale coincidence of narrow endemism and species richness peaks have implications for conservation prioritization exercises.

Distribution, abundance and niche breadth of birds: scale matters

AbstractWe used local habitat niche breadth, local abundance and body size of non‐passerine afrotropical birds in Tsavo East National Park (Kenya) to predict species distributional ranges in Kenya and across Africa. Univariate analysis revealed a significant positive correlation between local abundance and distribution only on the scale of Kenya. Performing a multiple regression analysis, local abundance, local habitat niche breadth and body size explained a significant part of the variance in bird distribution, again only on the Kenyan scale. From these results, we speculate that on continental scales distributions may be more influenced by macroclimatic conditions and historical factors, whereas distributions on regional scales are predominantly influenced by ecological factors.

Patterns and Correlates of Bird Migrations in Sub-Saharan Africa

SummaryThe common mode of migration among Afrotropical birds is movement from tropical to temperate areas to breed usually coinciding with the onset of summer and the rainy season. The proportion of species that are migratory can be predicted with considerable accuracy from the average temperature of the coldest month of the year. Once this exceeds 20°C, 90% or more of breeding species will be non-migratory. The likelihood of any one species being migratory is strongly influenced by diet, foraging mode as influenced by the behaviour of prey and vegetation geography. Insectivores are disproportionately well represented among the migrants whereas, at the other extreme, frugivores are almost exclusively sedentary. Within the insectivore guild, the greatest migratory tendencies are found among those groups that exclusively hunt aerial insects above the canopy (e.g. swallows, swifts and nightjars), perch-hunters that depend on large, active insect prey (e.g. halcyonid kingfishers and rollers) and taxa heavily dependent on the larvae of flying insects (cuckoos). Insectivores that hunt or glean small invertebrates (volant or not) within the canopy or glean relatively sessile prey from the ground are much less likely to be migratory. This gradient, linking prey attributes and hunting behaviour to migratory behaviour, is probably mediated by a parallel gradient in seasonal prey availability. In marked contrast to the Neotropics and the Orient, many Afrotropical birds undertake polarised migrations, with part of the population moving north, and part south, of the tropics. The explanation of this is hypothesised to lie in the spatial symmetry and large extent of savannas both north and south of the tropics, coupled with a lack of north-south dispersal barriers. These conditions are not replicated in either the Neotropics or the Orient.

Distribution of waterfowl in the wetland of Northern Nigeria

Agbelusi, E.A. & Afolayan, T.A. 2000. Distribution of waterfowl in the wetland of Northern Nigeria. Ostrich 71 (1 & 2): 73. Nigeria with a land area of 923 850 km2 has approximately 24 000 km2 of wetland. These wetlands are scattered all over the country and include the man-made lakes. The wetlands of northern Nigeria are important breeding sites for Afrotropical duck and also serve as the winter refuge for Palearctic birds from Europe. About 13 sites have been identified as the actual habitat and concentration points for waterfowl in the wetlands of northern Nigeria. Among these areas, the Hadeija-Nguru wetland represents one of the most productive and ecologically significant wetlands in Nigeria. This area supports about 58 000 waterbirds, belonging to about 376 species, which consist mostly of Palearctic and Afrotropical migratory birds. Some of the important bird species that are associated with the wetland of northern Nigeria are Black Crowned Crane, Pintail, White Pelican, White-faced Tree Duck, Knob-billed Goose, Spur-winged Goose, Gull-billed Tern and Saddle-billed Stork. The paper also discusses the management implications for waterfowl conservation and tourism in Nigeria.

Training Kenyan bird ringers

Jackson, J. 2000. Training Kenyan bird ringers. Ostrich 71 (1 & 2): 342. Capturing and ringing birds is a fundamental ornithological field technique, and one that underlies much bird conservation research. In several countries, particularly in Britain and parts of western Europe, ringing is largely an amateur activity. Enthusiasts ring birds in their free time and take part in national surveys, enabling the effective monitoring of bird populations and movements. Until recently ringing in Kenya has been undertaken almost entirely by a handful of expatriate researchers and enthusiasts. Over the last 1CL15 years, it has also been largely confined to one site: Ngulia in Tsavo West National Park. Ringing effort has targeted Palaearctic migrants, mainly ignoring Afrotropical birds. The number of amateur and professional Kenyan ornithologists is fast increasing, but only a handful have any ringing experience. The remainder lack the resources to obtain the necessary equipment or the opportunity to undergo the long training required to become a qualified ringer. In June 1994, the, Nairobi Ringing Group was formed, based at the Department of Ornithology, National Museums of Kenya, Nairobi. The Group provides an opportunity for interested Kenyans to train as amateur ringers to a high standard, using departmental equipment and expertise. Ringing takes place twice weekly at the Nairobi Museum grounds and monthly at a constant effort site in a forest near Nairobi. Excursions have been made to other sites including Lake Magadi, for training in ringing waders, and Ngulia. The Group has a core of seven to ten members and a further 30 have taken part to varying degrees. Over 2 500 birds have been ringed so far and much learned about the identification, ageing and moult of the commoner species.

Anting in Afrotropical birds: a review

Craig, A.J.F.K. 1999. Anting in Afrotropical birds: a review. Ostrich 70 (3&4): 203–207. Passive anting has been recorded from four non-passerine species in Africa, the Rock Kestrel Falco tinnunculus, the African Finfoot Podica senegalensis, the African Hoopoe Upupa epops and the Whitebacked Mousebird Colius colius. Active or passive anting has been recorded from 21 passerine species in 10 families in the wild, and in captive birds in a further 27 species of 3 families. Although such behaviour may have been overlooked or misinterpreted, the rarity of observations implies that in most species anting is likely to be infrequent. In all cases in which the ants have been identified, they were members of the sub-family Formicinae. It appears unlikely that any single functional explanation can account for the observed occurrences of this behaviour.

Evidence for organism-wide asymmetry in five bird species of a fragmented afrotropical forest

Empirical evidence for between-trait correlation in fluctuating asymmetry (FA) at the individual level is generally lacking or contradictory. Yet the assumption of organism-wide asymmetry, estimated by the asymmetry of any given trait, is inherent to most studies that use FA as a measure of developmental stability (DS). A commonly assumed reason for this weak between-trait correlation is the low repeatability of individual, single-trait asymmetry. In this paper we describe high repeatability and significant between-trait correlation in population- and individual-level FA in five afrotropical bird species inhabiting a fragmented cloud forest. Absence of anti-symmetry and of between-trait correlation in signed FA levels permits us to translate the observed patterns into the presumed underlying DS, using the concept of hypothetical repeatability. This correction, which has not been applied before in this context, proved adequate as it yielded correlations comparable to those found at the population level.

Interpreting biogeographical boundaries among Afrotropical birds: spatial patterns in richness gradients and species replacement

Summary Aim We analyse the geographical distribution of 1911 Afrotropical bird species using indices of three simple biogeographic patterns. The first index, the frequency of species with range edges (Te), is formulated to map directly the density of species distribution limits, for comparison with the results of traditional biogeographical classification and ordination procedures, in order to show variations in the strength and breadth of transition zones. The other two indices are formulated to seek to distinguish as directly as possible between two components within these transition‐zone patterns: contributions from gradients in species richness (Tg); and contributions from replacements among species (Tr). We test the ability of these indices to discover the same boundaries among Afrotropical bird faunas as one popular procedure for classifying areas (TWINSPAN) and then use them to look for geographical trends in the different kinds of transition zones. Location The analysis is restricted to the sub‐Saharan or Afrotropical region, excluding the Arabian Peninsula, Madagascar and all offshore islands. Methods We record the presence of each species in 1961 1°×1° grid cells of the map. To apply the three indices, each (core) grid cell in turn is compared with its neighbouring eight cells in the grid. The range edges index (Te) counts the number of species with range edges between the core cell and the surrounding cells. The richness gradients index (Tg) counts the largest difference in species richness measured diametrically across the core cell in any direction when there is a consistent trend in richness along this line of three cells. The species replacements index (Tr) counts the number of species pairs recorded within a nine‐cell neighbourhood that are not corecorded within any of the cells. Values for each of the 1961 grid cells are calculated and used to produce colour‐scale maps of transition zones. Results Large‐scale spatial patterns of variation in density of range edges (Te) are consistent with classifications of the same data and with most previous biogeographical classifications proposed for the region. Variation in richness gradients (Tg) and species replacements (Tr) explain different parts of this pattern, with transition zones around humid forests in the equatorial region being dominated by species replacement, and transition zones around deserts (most extensive in the north and south) being dominated by richness gradients. Main conclusions The three indices distinguish the spatial arrangement and intensity of different kinds of transition zones, thereby providing a first step towards a more rigorous mechanistic understanding of the different processes by which they may have arisen and are maintained. As an example of one such pattern shown by our analyses of Afrotropical birds, there is evidence for a broad latitudinal trend in the nature of transition zones in faunal composition (following the latitudinal distribution of the different kinds of habitat transitions), from being dominated by species replacements near the equator to being dominated by richness gradients further from the equator.