Yellow-billed Oxpeckers Research Articles

Feeding ecology and interactions with mammal hosts in a symbiotic genus of birds (Buphagus spp.) in Namibia

As the sole obligate symbiotic birds in Africa, oxpeckers offer a unique model for studying symbiotic relationships. Due to the multitrophic level they occupy and the context dependent foraging behavior they exhibit, the type of symbiotic relationship can be variable. In addition to providing a cleaning service to the host by removing ticks, oxpeckers frequently feed on blood, mucus, and saliva, inflicting potential damage on the host. Here, we used DNA metabarcoding on faecal samples to analyze the taxonomic composition of the trophic interactions of the Yellow-billed Oxpecker (Buphagus africanus) and Red-billed Oxpecker (B. erythrorhynchus) in northeastern Namibia. In contrast to conventional methods, DNA metabarcoding allows for a detailed identification of dietary resources encompassing both mammal hosts and consumed arthropods within the same samples. With this information, we examined differences in the diet composition between oxpecker species and localities, as well as the co-occurrence between host and arthropod species. Our findings revealed that oxpeckers predominantly source their diet from mammals, ticks, and flies; however, ticks and flies rarely co-occur in the diet of an individual. We observed variability among individuals in their feeding ecology, which is strongly correlated with locality and, to a lesser extent, with the mammal host. We noted a high degree of mobility between hosts within relatively short periods, with 32% of the samples showing traces of at least two mammal hosts. This study illustrates the dynamic foraging behavior of these specialized symbiotic birds, shedding light on their potential role in pest control services and disease transmission.

The two oxpecker species reveal the role of movement rates and foraging intensity in species coexistence.

The two Buphagus oxpecker species are specialized passerines that forage for ticks and other food particles on the body of ungulates in the African savannahs. One of their intriguing features is their ability to coexist despite sharing the same, specialized diet. Using co-occurrence data (photographs of giraffes with oxpeckers on them) and approximate Bayesian computing, we demonstrate that yellow-billed oxpeckers changed host faster than red-billed oxpeckers and appeared to displace red-billed oxpeckers from preferred giraffe body parts. Conversely, red-billed oxpeckers exhibited a fuller use of each host and displaced yellow-billed oxpeckers from distal giraffe body parts. These findings highlight that the partition of giraffe hosts in two separate niches was only part of the coexistence story in this species pair. More precisely, the oxpeckers shared the resource by exploiting it at different rates. They engaged in different trade-offs between giving-up density, patch discovery rate and competitor displacement ability. They illustrate the importance of the time frame of interactions.

Rainy season dietary ecology of avian species in semi-refuge habitats in Kano, Nigeria

Birds are important natural field components, and critical to most ecosystems by supporting seeds dispersal, plant pollination and pest control amongst other functions. Data on avian diversity and feeding behavior could be used to enhance habitats and help initiate conservation strategies. Thus, to characterize the diet of local avian fauna, we selected four semi-refuge sites around Kano metropolis, where we established 22 line transects, each 900m long, spaced 150m apart. During May to October, 2017 each site was visited once a month, adding up to 132 transect-visits. Daily surveillance starts between the local hours of 6:30am to 10:30am. We also transect-surveyed tree vegetation for evaluation of the avian habitats. We recorded a total of 22 bird species belonging to 15 families, with ploceidae as the dominant, and the Laughing dove, Streptopelia senegalensis (Family: Columbidae), being the most dominant species. Over 40% of the bird species fed on insects, other arthropods and earthworms; followed in proportion by seed eaters; while only 3.7% were nectar feeders. Goodness of fit test on observed versus expected dietary item frequencies was significant (Chi-Sq=31.49; P=0.000), indicating field cafeteria habits were not random, but selective or, probably even evolutionary. The manner of food search varied amongst the species, with the Yellow-billed oxpecker, Buphagus africanus and Cattle egret, Egretta alba, expending the most continuous foraging time of 30 to 60 minutes. However, some species, e.g., Senegal coucal, Centropus senegalensis, mainly adopted the pick-and-move strategy. The Shanon- Wiener indices of diversity, H, by site, for birds was fair to moderate (1.24 to 2.53) and paralleled those for the trees. In the light of dearth of avian ecological data from the Kano region, we invite motivated ornithologists, bird enthusiasts and public agencies for research into avian movement patterns, and conservation measures that, we believe, must include habitat protection.

Large mammal declines and the incipient loss of mammal-bird mutualisms in an African savanna ecosystem.

Over the past half-century, large mammal populations have declined substantially throughout East Africa, mainly due to habitat loss and unsustainable direct exploitation. While it has been acknowledged that the loss of large mammals can have direct and cascading effects on community composition and ecosystem characteristics, limited quantitative work has been done on how declines of large herbivore populations impacts the abundance of mutualistic symbionts. Using a space-for-time observational approach, we quantified the large mammal community alongside the densities, host preferences and behaviors of mutualistic red-billed oxpeckers (Buphagus erythrorhynchus), and yellow-billed oxpeckers (Buphagus africanus) in northern Tanzania. At the landscape scale, mammal community composition was substantially less diverse in highly human-dominated areas when compared with more protected areas, with an observed complete loss of large wild mammal species in two study areas. Mirroring this trend, oxpecker densities were lowest in the least protected areas, and highest in fully protected areas. Using resource selection functions implemented via generalized linear models at different scales, we found that oxpeckers (1) were predominantly (67% of red-billed oxpeckers; 70% of yellow-billed oxpeckers) feeding on larger (between 500kg and 1500kg) ungulate host species within the mammal community, (2) usually preferred feeding on larger individuals (adults and males) within a specific host species population, and (3) preferred hosts that were more tolerant of their presence. In particular, cattle were especially intolerant of oxpecker presence and were relatively effective in displacing oxpeckers. We found little evidence that oxpecker feeding was parasitic across all host species; wound feeding was only observed on giraffe, comprising 6% and 4% of feeding behavior in red-billed and yellow-billed oxpeckers respectively. Thus, a loss of large-bodied and oxpecker tolerant host species is a likely explanation for declines of oxpecker populations in human dominated landscapes, which may have further cascading effects.

<b>Record number of Yellow-billed Oxpeckers <I>Buphagus africanus</I> Linnaeus, 1766 (Aves: Passeriformes: Buphagidae) foraging on a single host</b>

In June 2016, we observed a group of Yellow-billed Oxpeckers foraging on a single male Giraffe, in the Savuti area of Chobe National Park, Botswana. From photographic evidence we estimate the Oxpecker group numbered between 51 and 60, the highest number on record for a single host.

Feeding preferences of Oxpeckers in Kruger National Park, South Africa

Oxpeckers reduce tick loads on ungulate hosts, but they are also known to feed on and exacerbate wounds. An understanding of the feeding behaviours and host preferences of these birds is important since they serve as agents of tick control on both domestic and wild ungulates. We conducted an observational study at two sites within the Kruger National Park in South Africa, exploring the feeding preferences of both Red-billed and Yellow-billed Oxpeckers. Oxpeckers’ host preferences, body-location preferences on different hosts, prevalence of feeding and non-feeding behaviours, and frequency of tolerance versus rejection in different hosts were determined. It was found that Yellow-billed Oxpeckers had a smaller range of hosts – typically larger-sized ungulates – and that Red-billed Oxpeckers diversify to smallersized ungulate hosts when in competition with Yellow-billed Oxpeckers. Body-location preferences were generally consistent across sites and across host species. Tick feeding and other host-feeding behaviours (around the eyes, nose, mouth and ears, and anogenital areas) were fairly common. Only six incidents of wound feeding, from a total of 855 observations, were recorded. Tolerance by an ungulate host species was not related to Oxpeckers’ host preferences, suggesting that other factors such as ungulate body size, tick species and tick stages on the host animal may play a significant role in the feeding preferences of Oxpeckers.Conservation implications: It is important to study Oxpeckers’ behavioural feeding preferences so as to better understand their ecology and present distribution, and to determine where they can be reintroduced in future. Reintroduction not only helps with the proliferation of Oxpeckers, but also benefits ungulate hosts through ectoparasite removal and the subsequent control of tick-borne diseases.

MUTUALISM OR PARASITISM? USING A PHYLOGENETIC APPROACH TO CHARACTERIZE THE OXPECKER‐UNGULATE RELATIONSHIP

With their striking predilection for perching on African ungulates and eating their ticks, yellow-billed (Buphagus africanus) and red-billed oxpeckers (B. erythrorhynchus) represent one of the few potentially mutualistic relationships among vertebrates. The nature of the oxpecker-ungulate relationship remains uncertain, however, because oxpeckers are known to consume ungulate tissues, suggesting that the relationship between oxpeckers and ungulates may also be parasitic. To examine this issue further, we obtained data on oxpecker preferences for different ungulate species, the abundance of ticks on these ungulates, and ungulate hide thickness. In support of the mutualism hypothesis, we found that both species of oxpeckers prefer ungulate hosts that harbor a higher abundance of ticks. We found no evidence that hide thickness-a measure of the potential for parasitism by oxpeckers-predicts oxpecker preferences for different ungulate species. Oxpeckers also prefer larger-bodied ungulates, possibly because larger animals have more ticks, provide a more stable platform upon which to forage, or support more oxpeckers feeding simultaneously. However, the preference for ungulates with greater tick abundance was independent of host body mass. These results support the hypothesis that the relationship between oxpeckers and ungulates is primarily mutualistic.

Oxpeckers in north-eastern Namibia: recent population trends and the possible negative impacts of drought and fire

Both redbilled oxpeckers ( Buphagus erythrorhynchus) and yellowbilled oxpeckers ( Buphagus africanus) have experienced recent population decreases in southern Africa largely as a result of cattle dipping against ticks, their primary source of food. In Namibia, oxpeckers are confined largely to the Caprivi region in the north-east and the yellowbilled oxpecker is classified as a Namibian Red Data species. Counts in 1983–1984 estimated populations of 2285–3780 redbilled oxpeckers and 2062–2613 yellowbilled oxpeckers on cattle in East Caprivi. In this study, three counts of oxpeckers were made in 1997–1998. Bird numbers had not increased in proportion with cattle numbers, the primary host which had increased three-fold in the last 15 years. Current redbilled oxpecker numbers (3627–4902) were similar to those in the 1980s. Too few yellowbilled oxpeckers were observed to derive robust population estimates, but our counts suggest a decline to about 330 birds. There have been no official cattle dipping programmes in Caprivi, and private tick control is virtually non-existent. We suggest that the current dry conditions, in combination with the increasingly widespread and more frequent practice of veld burning are having a substantial, differential effect on some of the tick species favoured by the two species of oxpeckers. We hypothesise that these two factors act as a control mechanism on ticks favoured by yellowbilled oxpeckers, so precipitating the dramatic decline of this species. If current trends continue, yellowbilled oxpecker will soon disappear from Caprivi.

Host preferences and behaviour of oxpeckers: co-existence of similar species in a fragmented landscape

The host preferences and behaviour of red-billed and yellow-billed oxpeckers (Buphagus erythrorynchus and Buphagus africanus) were studied at two locations in Kenya and combined with previously published data from East and South Africa. Red-billed oxpeckers are generally more common and have a greater niche breadth with respect to host preferences than yellow-billed oxpeckers, possibly due to the behavioural dominance of the latter. Otherwise, the host preferences are remarkably similar: both prefer larger species of ungulates and are found predominantly on species with manes. There are also no significant differences in the time–activity budgets of the two species controlling for site and host species, and differences in the proportion of time spent on different body parts of hosts are small in absolute magnitude even when statistically significant. Despite these and other basic ecological similarities, no evidence for competitive displacement was detected by comparing host preferences in areas of sympatry with areas of allopatry, even though each species appears to depress the population size of the other when sympatric. Traditional single-community competition theory cannot explain the geographical ecology of these two species. Instead, co-existence appears to be dependent on the patterns of extinction and colonization characterized by metapopulations distributed among a fragmented habitat.

Factors influencing host selection by yellow-billed oxpeckers at Matobo National Park, Zimbabwe

Factors influencing host selection by yellow-billed oxpeckers at Matobo National Park, Zimbabwe

Interactions between impala and oxpeckers at Matobo National Park, Zimbabwe

SummaryIn order to better understand the symbiotic relationship of the oxpecker‐mammal association and the role that oxpeckers play in controlling their hosts' tick burdens, interactions between yellow‐billed oxpeckers (Buphagus africanus) and impala (Aepyceros melampus) were investigated at Matobo National Park, Zimbabwe during the wet and dry seasons. Oxpeckers devoted 30–35% of attendance time to foraging upon impala hosts. The ears were preferred for foraging above all other body regions, and foraging sessions directed to the ears were longer than sessions on other areas, apparently due to high tick infestation on host ears. Two‐thirds of adult ticks (mostly the blue tick Boophilus decoloratus) collected from impala females were from the ears, and heavy infestations of immature ticks on the ears were common. The majority of oxpecker foraging (71–74%) was directed to the ear, head, and neck area where impala are unable to self‐oral groom. Most adult ticks (75–77%) were found on the ears, head, and neck of sampled impala, indicating that oxpeckers foraged so as to maximize adult tick intake. Adult tick abundance in the vegetation, and presumably on impala, was much greater in the wet season than in the dry season. Oxpeckers spent significantly less time foraging upon impala in the wet season compared with the dry season, reflecting the presumed greater abundance of adult ticks on hosts during this time. Impala hosts tolerated oxpeckers 86% of the time, and 42% of oxpecker‐tolerant impala accommodated foraging activity by lowering an ear, inclining the head, or standing still. An interaction was apparent between the tick‐removal strategies of oxpeckers and their impala hosts in that impala reduced their grooming rate when oxpeckers foraged upon them to 11–36% of their grooming rate in the absence of oxpeckers, thereby reducing the cost of tick control.RésuméPour mieux comprendre la relation symbiotique de l'association pique‐boeufsmammifères et le rôle que jouent les pique‐boeufs dans le contrôle des tiques de leurs hôtes, on a analysé les interactions entre les pique‐boeufs à bee jaune (Buphagus africanus) et les impalas (Aepyceros melampus) au Pare National de Matobo, au Zimbabwe, en saison sèche et en saison des pluies. Les pique‐boeufs consacraìent de 30 à 35% de leur temps d'attention à se nourrir sur des impalas. Ils préféraient les oreilles à toute autre partie du corps et le temps consacréå se nourrir sur les oreilles était plus long que sur toute autre partie du corps, ceciétant dû semble‐t‐il à un plus haut degré d'infestation des oreilles des hôtes par les tiques. Les deux tiers des tiques adultes (surtout la tique bleue Boophilus decoloratus) recoltées sur les impalas femelles provenaient des oreilles, et de fortes infestations des oreilles par des tiques immatures sont communes. La plus grande part des recherches de pique‐boeufs (71 à 74%) se faisait au niveau des oreilles, de la tête et du cou, là où les impalas sont incapables de se toiletter eux‐mêmes. On trouvait la plupart des tiques adultes (75 à 77%) sur les oreilles, la tête et le cou des animaux analysés, ce qui indique que les pique‐boeufs se nourrissaient à ces endroits pour maximaliser la prise de tiques adultes. L'abondance de tiques adultes dans la végétation, et probablement sur les impalas, était bien plus grande pendant la saison des pluies que pendant la saison sèche. Les pique‐boeufs passaient significativement moins de temps à se nourrir sur les impalas en saison des pluies qu'en saison sèche, ce qui reflétait l'abondance probablement plus grande de tiques adultes sur leurs hôtes pendant cette saison. Les impalas hôtes toléraient la présence des pique‐boeufs 86% du temps, et 42% des impalas consentants facilitaient l'activité de nourrissage en abaissant l'oreille, en baissant la tête ou en restant tranquilles. Il semblait done exister une interaction entre les stratégies des pique‐boeufs pour enlever les tiques et les impalas hôtes, en ceci que les impalas réduisaient leur temps de toilettage jusqu' à 64 à 89% de ce qu'il aurait été en l'absence de pique‐boeufs, ce qui réduit d'autant le cout du contrôle des tiques.

The effect of the removal of buffaloSyncerus caffer(Sparman 1779) on the host selection of yellow-billed oxpeckersBuphagus africanusLinnaeus 1766 in Zimbabwe

Past studies of yellow-billed oxpeckers Buphagus africanus Linnaeus 1766 have shown that buffaloes Syncerus caffer (Sparrman 1779) are their preferred hosts. Yellow-billed oxpeckers were successfully introduced into the Matobo National Park, Zimbabwe, in 1975. In 1986, all the buffalo were removed from the park. The oxpecker population shifted their host selection onto other ungulates present in the park, and continued to breed successfully.

Range Expansion of the Yellowbilled Oxpecker <i>Buphagus africanus</i> into the Kruger National Park, South Africa

The Yellowbilled Oxpecker, long believed extinct as a breeding species in the Republic of South Africa has been recorded regularly in the Kruger National Park since 1979. The first definite indication of breeding was recorded in January 1984, and final confirmation of breeding was observed in December 1985. The recovery of the ungulate populations of the park, in particular buffalo, from overhunting and rinderpest during the long period of absolute protection stretching from 1902, has ensured a suitable habitat for the immigrant Yellowbilled Oxpeckers. Circumstantial evidence indicates that the birds have colonised in the park from the population of the Gonarezhou National Park in south-eastern Zimbabwe. The movement of the birds across the 50 km Sengwe area separating the two parks is explained by the cessation of cattle dipping and the movement of buffalo out of Gonarezhou from 1977 onwards. These events were a direct consequence of the hostilities in Zimbabwe at that time.

Past and present ecological distribution of the yellowbilled oxpecker in South Africa

The South African records of the yellowbilled oxpecker Buphagus africanus are reviewed and acceptable ones mapped. No evidence for breeding between 1907 and 1941 or after 1942 has been found though vagrants may enter the country from the north. The extinction is largely due to the inaccessibility of the preferred prey, Acarine ticks of the genera Rhipicephalus and Amblyomma, following the collapse of populations of buffalo and rhinoceros spp. coupled with eating poisoned prey due to arsenical dipping of domestic stock starting at the turn of the century. We recommend that yellowbilled oxpeckers be reintroduced to game reserves in which they used to live.

The re-introduction of oxpeckers Buphagus africanus and B. erythrorhyncus to the Rhodes Matopos National Park, Rhodesia

Two species of oxpeckers occur in Rhodesia, Buphagus africanus and B. erythrorhyncus, both of which are now restricted to large game areas and some large ranches. As a conservation measure 47 B. africanus and 12 B. erythrorhyncus were introduced to the Rhodes Matopos National Park from Wankie National Park. The B. africanus have become established and have increased in numbers whereas the introduction of B. erythrorhyncus has been unsuccessful, although at least one pair is still in the release area. Birds were captured on donkeys and then transported directly by air to the Matopos for immediate release. Host selection by the birds is discussed with brief notes on competition from other species.