Feeding preferences of Oxpeckers in Kruger National Park, South Africa
He said the birds and hippos often share a mutually beneficial relationship, with the oxpeckers helping to free the hippos of ticks and other. Whilst ticks are the main food source for both Oxpecker species, the birds are suggest that the relationship between Oxpeckers and ungulates is primarily Chi-square tests were then used to compare preference index distributions Oxpeckers were also present on Hippopotamus, Plains Zebra and Impala (Figure 1). Here, we investigate general patterns in such relationships at large spatial and .. To test whether a nested structure exists for our set of bird–mammal .. giraffe and hippopotamus, while red-billed oxpecker was most often.
In oxpeckers, however, a nested structure suggests a non-random assignment of birds to their mammal hosts. We also identified some new or rare associations between birds and mammals, but we failed to find several previously described associations.
Furthermore, we found that mammal body mass positively influenced the number and mass of birds observed sitting on them in the full set of species i. We also found a positive correlation between mammal body mass and mass of non-oxpecker species as well as oxpeckers.
Mammal herd size was associated with a higher mass of birds in the full set of species as well as in non-oxpecker species, and mammal species living in larger herds also attracted more bird species in the full set of species. Habitat openness influenced the mass of birds sitting on mammals as well as the number of species recorded sitting on mammals in the full set of species. In non-oxpecker species habitat openness was correlated with the bird number, mass and species richness.
Our results provide evidence that patterns of bird—mammal associations can be linked to mammal and environmental characteristics and highlight the potential role of information technologies and new media in further studies of ecology and evolution. However, further study is needed to get a proper insight into the biological and methodological processes underlying the observed patterns.
The African herbivorous mammals are composed of many phylogenetic lineages with diverse life strategies, including their body masses and tendency to form herds Smith et al. The majority of previous studies investigating patterns in commensalistic—mutualistic interactions between African birds and large herbivores have focused only on single or a small number of species Hart et al. Hence, a large-scale and multitaxonomical approach is useful when investigating patterns in bird—mammal interactions to avoid problems with interpretation and generalization of relationships which may be area- or taxa-specific.
Many types of heterospecific relationships, including both commensalism and mutualism, are depicted as complex webs comprising several interacting species, rather than as isolated interactions between species pairs Bascompte et al.
As a result, the structure of such community networks exhibit a specific arrangement of interactions rather than random inter-specific interactions. However, studies involving birds as interactors have had mixed results.
For instance, while a highly nested structure was found for cleaning associations between birds and their mammal hosts in Neotropical regions Sazima et al. The number and diversity of birds directly interacting with i.Black Rhino & Oxpecker's; A cleaning service.
The only examples of African birds exhibiting obligate mutualistic associations with mammals are the small-bodied passerines, oxpeckers Buphagidaebeing two extant species, yellow-billed oxpecker Buphagus africanus and red-billed oxpecker B. Here, the species association features may differ from other birds since the feeding ecology of oxpeckers and their presence on host species has been found to be strongly correlated with the character of host infestation by ectoparasites Hart et al.
To investigate large-scale patterns of bird—mammal associations, extensive data collection from free online sources may be useful.
During the last decade, the engagement of volunteers in scientific projects, so-called citizen science, has became an integral part of current ecological and evolutionary research Bonney et al. Approaches range from the collection of internet data uploaded by the public to active participation and collaboration with scientists e. Rapid technological development and the expanding access of the public to both internet and recording devices, such as cameras or smartphones, around the world have increased the accessibility, immediacy and extent of data sharing.
Online data collected by the public can represent a useful resource for expansion of scientific knowledge on rare or poorly studied phenomena e.
Despite the increasing number of such studies, material uploaded on the internet by the public is still an underexploited data source for studies in ecology and evolution. Here, we used photos collected using the web-based search engine Google Images to investigate some aspects of commensalistic—mutualistic associations between African birds and herbivorous mammals. In contrast to the majority of previous field studies that focused only on spatially and taxonomically restricted systems e.
Firstly, the structure of the association web between African birds and mammals was visualized and analysed to investigate frequencies of association between particular bird and mammal species and whether bird—mammal interactions were arranged in a nested pattern.
Then, we employed phylogenetically-informed comparative analysis to explore whether patterns in bird visitation of mammals i. Materials and Methods Data searching To collect a large dataset of spatially and taxonomically distributed data on bird—mammal associations, we did an extensive internet search for photos on Google Images.
Moreover, since results of searches using English and scientific names were highly correlated, we decided to search only for English names of birds and mammals, although this could restrict the geographical coverage and decrease the use of records from non-English-speaking countries. We also used this searching phrase for species where few interactions had already been found by a word combination search. However, we used only results revealing new, typically rare, bird—mammal associations, hence avoiding significant bias in the search in favour of common or well-recognized associations.
The Google searches for photos for each combination of bird and mammal taxa were conducted separately, and for each combination we aimed to collect as many photos as possible until the search produced only a small proportion of photos with relevant content. For common species it is virtually impossible to collect all available photos, so this solution represented a trade-off between the number of available relevant photos and the time spent searching for new photos; however, we consider that the proportion of available photos sampled was similar in all species.
We only analyzed photos in which birds were in direct contact with the bodies of a mammal, excluding cases where the birds were only feeding or flying near the mammal. We did not include photos of mammals without birds in our data set, even if such individuals were visible in photos. We focused only on free-living, non-domesticated mammal species in sub-Saharan Africa.
We also excluded photos where birds were observed on captive African mammals outside Africa e. To limit other sources of bias, photos suspected to be shared by multiple sources were briefly checked to see whether they had already been included all photos were collected exclusively by one author, PM, enabling us to do this consistently. We were particularly careful when working with unusual photos that people might prefer to share, e. However, it is still possible that a small number of duplicates remained undetected because we did not cross-check all possible combinations of photos.
On the other hand, such cases were quite rare, and it seems that, for the volume of photos we collected, online sharing of photos would not substantially bias results obtained from a Google search compared to field data.
Similarly, Leighton et al. Although there could be an inherent bias toward photos with larger numbers of birds on mammals caused by a preference for photographers to publish such photos, this should apply to all species and not affect relative differences. Even if only some photographers did this, we again do not expect any consistent bias in our data because photos originated from numerous authors.
Furthermore, the probability of photographing a bird on a mammal may be related to the habitat structure e. Because a substantial proportion of the photos came from amateur photographers we expected less of a bias toward rare species or other unusual occurrences, as compared to professional photographers or researchers see also Dylewski et al. One would assume that the Kenya sites Masai Mara Reserve and Lake Nakuru National Park had a high abundance of large ungulates compared to KNP, hence a marked host preference would only be apparent in lower ungulate densities where interspecific competition is unavoidable.
However, that hypothesis cannot be tested without a measure of ungulate densities from all sites. Surprisingly, the PI results in the present study differed from Grobler and Stutterheim and Stutterheim Optimal foraging strategy Pyke will predict that animals will concentrate on the most abundant and profitable food source. For example, there were fewer White Rhinoceros and Hippopotamus in KNP in the s compared to the present-day population It is therefore reasonable to conclude that as White Rhinoceros and Hippopotamus numbers increased, Red-billed Oxpeckers responded by selecting for these new abundant host species with potentially higher tick loads and less hair to hide the ticks.
Giraffe remained the most preferred host species in both the northern and southern regions of the park. This could also be a detection bias, given that it is possibly easier for flying birds to detect Giraffe compared to other shorter species.
This is further supported by Oxpeckers' preference for White Rhinoceros and Hippopotamus both large ungulatesrecorded as host species in Skukuza. Interestingly, Impala, an abundant, small-sized ungulate, was less preferred as a host species across studies. This surprising contradicts what has been reported by GroblerStutterheim and Stutterheim and Hart et al.
Both Red-billed and Yellow-billed Oxpeckers displayed a preference for the back and head regions of their respective host species. Red-billed Oxpeckers also preferred the necks of Giraffe. Additionally, Oxpeckers prefer feeding on the back regions of a host species since this is easily accessible and provides a stable perch Weeks The head is also preferred since it provides additional food resources other than ticks, i. Exceedingly low occurrences of wound feeding by Red-billed Oxpeckers and the absence of wound feeding in Yellow-billed Oxpeckers suggests that this feeding behaviour is not prevalent in KNP as previously reported in cattle ranches in Zimbabwe Weeks Plantanin her study on both Oxpecker species at Shingwedzi inalso found the prevalence of wound feeding behaviour to be very low 3.
However, she did find that wound feeding was exhibited by Yellow-billed Oxpeckers more than Red-billed Oxpeckers.
Oxpeckers: poor at tick control, great at keeping your wounds open | ScienceBlogs
In the current study, there were instances where ungulates were observed with open wounds and yet Oxpeckers did not tamper with the wounds, but rather continued tick feeding. This observation further suggests that Oxpeckers pose no risk to free-roaming wildlife.
Large ungulates tolerated Oxpeckers more so than medium-sized ungulates. The preferential selection of larger hosts also indicates that reintroductions of Oxpeckers should target areas with high tick loads and substantial, large ungulate populations of the host species that are preferred.
Therefore, even if a large ungulate has many ticks, this does not mean that the Oxpecker will consume those ticks or utilise the host. However, the present study does provide additional insight and understanding of Red-billed and Yellow-billed Oxpeckers' feeding behaviours, particularly in KNP and in terms of wild host species and body-location preferences.
Competing interests The authors declare that they have no financial or personal relationship s that may have inappropriately influenced them in writing this article.