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Competition for nectar is expected to result in feeding niche differentiation. Here, we targeted the sexually size-dimorphic Volcano Sunbird (Cinnyris preussi) on Mount Cameroon. We investigated whether males and females feed on different plant species, whether females with shorter bills than males prefer shorter flowers, and whether larger dominant males visit more energetic flowers that produce higher amounts of nectar sugars. We also asked whether feeding niches were spatially separated along the elevation gradient and whether this separation varied between the two contrasting seasons. We collected data on the frequency of visits to individual plant species and analyzed the male-to-female ratios in the mist-netted dataset. In addition, we estimated production of nectar sugar in individual habitats and seasons. Despite the large dataset collected, encompassing 6476 bird–plant interactions, our findings did not provide evidence of differences in the spectra of the visited plant species. In addition, females did not visit flowers with shorter tubes, nor did males visit flowers that produced higher amounts of sugars. However, we observed a sex-specific dispersion of sunbirds during the wet season. During the dry breeding season, both males and females feed mainly in nectar-rich montane and submontane forests. In the wet season, the production of nectar sugar in these habitats decreased dramatically, and females largely disappeared. In contrast, female activity increased in the lowest and highest parts of the altitudinal range. Our findings on elevational movements are important in the current context, in which species face potential threats from habitat destruction and climate change. [ABSTRACT FROM AUTHOR]

Differences in interaction specializations between nectarivorous birds and plants across continents serve as common examples of evolutionary trajectory specificity. While New World hummingbird-plant networks have been extensively studied and are considered highly specialized, knowledge on the network specialization of their Old World counterparts, sunbirds (Nectariniidae), remains limited. A few studies from tropical Africa indicate that sunbird-plant networks are rather generalized. Unfortunately, these studies are limited to dry seasons and high elevations at the tree line, environments where niche-based hypotheses also often predict lower resource partitioning. In our study, we explored the specialization of sunbird-plant networks and their spatiotemporal variability on Mt. Cameroon (Cameroon). Using a combination of automatic video recordings and personal observations, we constructed eight comprehensive sunbird-plant networks in four forest types at different elevations in both the dry and wet seasons. As reported in previous studies, the montane forest plants, birds and whole networks were highly generalized. Nevertheless, we observed a much higher specialization in forests at lower elevations. Except at the lowest altitude, the wet season was also characterized by higher specialization. While less specialized flowering trees dominated in the dry season networks, more specialized herbs and shrubs were visited by birds during the wet season. As our findings do not support the generally accepted assumption that Old World bird-plant networks are rather generalized, we need further studies to understand the differences in bird-plant specializations on individual continents. [ABSTRACT FROM AUTHOR]

Motion-activated cameras ("camera traps") are useful for recording plant–animal interactions that are difficult to observe using conventional means. We used camera traps to document interactions between animal flower visitors and the orchid Satyrium neglectum subsp. woodii and used mesh exclosures which selectively exclude access of larger animals to flowers to test the importance of bird visits for pollination. Camera footage revealed that the orchid is visited by two sunbird species (amethyst and greater double-collared) which carry pollinaria on the upper mandible of their beaks. Plants which could only be accessed by bees and other small insects had few pollinaria removed and set very few fruits relative to plants which could also be accessed by larger animals such as sunbirds. The sturdy inflorescence stem, and thick fleshy perianth tissue, orange–red colour of the flowers, low scent production and large viscidia, are traits shared with other, distantly related bird-pollinated Satyrium species and can therefore be considered likely to play a functional role in bird pollination. We previously made anecdotal observations of sunbird visits to this orchid species in south-central Africa, and this study conducted in populations in South Africa confirms that sunbird pollination is consistent across the highly disjunct distribution of the taxon. [ABSTRACT FROM AUTHOR]

There are two alternative hypotheses related to body size and competition for restricted food sources. The first one supposes that larger animals are superior competitors because of their increased feeding abilities, whereas the second one assumes superiority of smaller animals because of their lower food requirements. We examined the relationship between two unrelated species of different size, drinking technique, energy requirements and roles in plant pollination system, to reveal the features of their competitive interaction and mechanisms enabling their co-existence while utilising the same nectar source. We observed diurnal feeding behaviour of the main pollinator, the carpenter bee Xylocopa caffra and a nectar thief, the northern double-collared sunbird Cinnyris reichenowi on 19 clumps of Hypoestes aristata (Acanthaceae) in Bamenda Highlands, Cameroon. For comparative purpose, we established a simplistic model of daily energy expenditure and daily energy intake by both visitor species assuming that they spend all available daytime feeding on H. aristata. We revealed the energetic gain-expenditure balance of the studied visitor species in relation to diurnal changes in nectar quality and quantity. In general, smaller energy requirements and related ability to utilise smaller resources made the main pollinator X. caffra competitively superior to the larger nectar thief C. reichenowi. Nevertheless, sunbirds are endowed with several mechanisms to reduce asymmetry in exploitative competition, such as the use of nectar resources in times of the day when rivals are inactive, aggressive attacks on carpenter bees while defending the nectar plants, and higher speed of nectar consumption. [ABSTRACT FROM AUTHOR]

Nectar-feeding birds are important pollinators in fire-prone regions of the world, but the impact of fires on these bird communities has seldom been studied. Nectar-feeding bird communities were censused during peak flowering, before and after fire in the Cape fynbos of South Africa. The abundance and species richness of nectar-feeding birds decreased at all sites. In a controlled experiment, two common bird-pollinated plants, which flower profusely after a fire, were presented in floral arrays in burnt and unburnt vegetation. Birds visited flowers only in the unburnt areas. The results are surprising given the large number of bird-pollinated plants that have fire-stimulated flowering. [ABSTRACT FROM AUTHOR]

A total of 170 wild birds from Senegal, belonging to 48 species and 9 orders, were searched for lice in 2005 and 2007. Chewing lice were found on 58 birds of 18 species and 5 orders (Columbiformes, Cuculiformes, Coraciiformes, Galliformes and Passeriformes). Twenty-two species of chewing lice of 13 genera were determined. Other nine samples of chewing lice that represent a new host-parasite association were determined at generic level only, because only one sex or nymph of these lice were found. Our records represent the first louse records from passerines Camaroptera brachyura (Cisticolidae), Chalcomitra senegalensis (Nectariniidae), Corvinella corvina (Laniidae), Laniarius barbarus (Malaconotidae), Prinia erythroptera (Cisticolidae) and Turdus pelios (Turdidae). Descriptions and illustrations are given for Brueelia chalcomitrae Najer et Sychra sp. nov. ex Chalcomitra senegalensis (Nectariniidae), Brueelia priniae Najer et Sychra sp. nov. ex Prinia subflava (Cisticolidae), and Philopteroides terpsiphoni Najer et Sychra sp. nov. ex Terpsiphone viridis (Monarchidae). [ABSTRACT FROM AUTHOR]

Plasma glucose concentrations in birds are much higher than those in mammals of similar body mass, and they are thought to be kept more or less constant. We investigated plasma glucose concentrations of Malachite Sunbirds ( Nectarinia famosa) to determine whether there was a circadian rhythm in plasma glucose and whether plasma glucose concentrations rose at lower temperatures. We explored the possibility that glycogenolysis and gluconeogenesis might be used by birds before daylight to generate body heat during arousal from torpor or from overnight adaptive heterothermy. Plasma glucose concentration of Malachite Sunbirds were relatively high, between 13.6 and 21.4 mmol/L. Plasma glucose concentrations were higher at 5°C than at 25°C, and generally lower during the scotophase, particularly in the early hours of the morning. Therefore, it appears that Malachite Sunbirds are not increasing plasma glucose concentrations during arousal from torpor or to increase scotophase body temperature levels to photophase levels. It is apparent that these nectarivorous birds have a circadian variation in plasma glucose concentrations that is affected by ambient temperature and feeding patterns. [ABSTRACT FROM AUTHOR]

Differentiation in floral traits among clusters of related species may reflect a process of pollinator-driven evolution. Pollination systems in the morphologically diverse southern African genus Syncolostemon (Lamiaceae) were investigated by means of field observations of floral visitors and analysis of their pollen loads. Among the five study species, those with short corolla tubes ( S. parviflorus, S. ramulosus) were pollinated solely by bees, while those with long corolla tubes were pollinated by a broader array of visitors, primarily long-proboscid flies in S. rotundifolius and S. macranthus and sunbirds in S. densiflorus. The predominately insect-pollinated taxa have lax inflorescences, but S. densiflorus has a compact terminal inflorescence, which facilitates feeding by sunbirds from a single perching position. Experimental hand-pollinations involving three taxa ( S. macranthus, S. densiflorus, and S. rotundifolius) showed that these possess a genetic self-incompatibility system. Production of fruits and seeds per fruit was pollen-limited in S. densiflorus and S. rotundifolius, but not in S. macranthus. [ABSTRACT FROM AUTHOR]

Nectarivorous birds encounter varying nectar concentrations while foraging on different food plants and must adjust their consumption to maintain constant energy intake. We determined how rapidly captive whitebellied sunbirds ( Cinnyris talatala) adjust their volumetric intake and feeding patterns after changes in diet concentration. On four consecutive days, birds were fed sucrose diets alternating between a standard diet of 16% w/w and test diets of 2.5, 8.5, 16 or 30% w/w, respectively, for 1.5 h periods. Feeding events were recorded with an infrared photo-detection system and food intake and body mass were monitored continuously by electronic balances interfaced to a computer. Generally, birds demonstrated a measurable increase in feeding frequency and food intake within 10 min after a decrease in sucrose concentration. However, individuals responded differently to the most dilute diet (2.5%): while most increased their food intake, others stopped feeding for a short while, appearing to dislike this diet. Furthermore, the number and duration of feeding events increased in the first 5 min after the switch from 2.5% back to 16%, as the birds attempted to compensate for previous reduced sugar intake. Daily sugar intake was lower when birds alternated between 2.5 and 16% diets than on other test days, but birds were able to maintain body mass, presumably through behavioural adjustments. [ABSTRACT FROM AUTHOR]