Red-winged Starling Onychognathus Morio Research Articles

Counting Common Starlings: is Sturnus vulgaris invasive in rural South Africa?

The numbers of Common Starlings Sturnus vulgaris and indigenous starling species, as well as a subset of other common birds, were recorded from October 2006 to January 2020 at 72 point-count sites along four routes (two urban and two rural) in the Eastern Cape Province of South African. In the rural habitat, Common Starlings were localised at buildings; in the urban habitat, there was no clear indication that their presence influenced the occurrence or abundance of the Red-winged Starling Onychognathus morio, a native species which has colonised towns and nests on buildings. In this region there is little evidence that Common Starlings invade areas that have not been heavily modified by human activities.

Pulses of anthropogenic food availability appear to benefit parents, but compromise nestling growth in urban red-winged starlings

The provision of anthropogenic food undoubtedly influences urban bird fitness. However, the nature of the impact is unclear, with both benefits and costs of urban diets documented. Moreover, the influence of short-term fluctuations in food availability, linked to urban weekday/weekend cycles of human presence, is largely unknown. We explored whether breeding red-winged starlings Onychognathus morio in Cape Town, South Africa, altered foraging and provisioning behaviour between days with high human presence (HHP) and days with low human presence (LHP)—i.e. weekdays versus weekends and vacation days. We investigated the relationship between starling diet, adult body mass and nestling development. Breeding adults consumed and provisioned the same quantity of food, but a significantly greater proportion of anthropogenic food on HHP compared to LHP days. Adults apparently benefited from the anthropogenic diet, experiencing significantly greater mass gain on HHP days. However, nestlings experienced a cost, with the number of HHP days during the nestling period associated negatively with nestling size. Adults may, therefore, benefit from the high calorie content of anthropogenic food, while nestlings may be negatively affected by nutrient limitation. The quantity of food available in urban environments may, therefore, benefit adult survival, while its quality imposes a cost to nestling growth.

Role of native avian frugivores in germination facilitation and potential dispersal of invasive American bramble (Rubus cuneifolius) in South Africa

Frugivorous birds are important in the dispersal of many fleshy-fruited plant species, including invasive plants. Consequently, we investigated three native frugivorous avian species’ role in potential dispersal and germination success of the invasive American bramble (Rubus cuneifolius) in South Africa, particularly in terms of amount of fruit ingested, transit time, and their effects on seed germination. Three common species of frugivorous bird species were predicted to positively affect the spread of invasive R. cuneifolius. The bird species (speckled mousebirds Colius striatus, red-winged starlings Onychognathus morio and dark-capped bulbuls Pycnonotus tricolor) were fed R. cuneifolius fruit in captivity and amounts ingested were determined together with transit times. Seeds that were excreted and/or regurgitated by the three bird species, manually extracted seeds, and control whole fruit were then planted and their germination assessed daily. Although the three bird species varied in the amount of fruit consumed (~ 10–30 g), there was no significant difference in amount of R. cuneifolius fruit eaten per gram body mass among the species. Bird-ingested seeds emerged a mean 21–23 days after planting, while the seeds from the whole fruit took longer to emerge (mean 28 days). Germination of seeds ingested by the respective bird species was significantly higher (~ 60–75%) than seeds manually removed from fruits (~ 52%) or seeds in whole fruits (~ 7%). This suggests that removal of pulp and seed coat abrasion by the birds increased germination success. The three bird species all had R. cuneifolius seed transit times greater than 20 min, demonstrating their potential to disperse seeds a distance away from the parent plant. The results showed that the three bird species increased the germination success and suggests they are potentially important dispersers of the invasive R. cuneifolius.

Juggling a “junk-food” diet: responses of an urban bird to fluctuating anthropogenic-food availability

Within highly urban systems, anthropogenic activity often fluctuates cyclically, e.g. between weekdays and weekends. Thus, urban species may regularly experience significant changes in human activity and anthropogenic food abundance over very short time scales. Knowledge of how urban birds cope with such fluctuations may improve our understanding of how some species exploit and thrive in urbanised habitats. In this study, we explore the consequences of highly fluctuating anthropogenic food for Red-winged Starlings Onychognathus morio at the University of Cape Town campus, South Africa. Here, high numbers of students (and therefore anthropogenic food resources) are present during weekdays in term time (high human presence “HHP” days). However, students are largely absent and food outlets closed during weekends and vacation periods (“LHP” days). Using focal observations and morning and evening weights of habituated colour-ringed starlings during the non-breeding season, we investigated how diet, behaviour and daily mass gain differed between HHP and LHP days. We hypothesised that anthropogenic food supply is beneficial to this city-dwelling species. We predicted that on HHP days starlings would consume overall more food and a greater proportion of anthropogenic food items, resulting in less time spent foraging and greater daily mass gain compared to LHP days. We found that on HHP days, starlings consumed more anthropogenic food, however overall food intake, and time budgets were similar to LHP days. Additionally, there was an indication that mass gain was greater on HHP days. Thus, starlings appear to cope with potential food shortage on LHP days by including more natural items in their diet.

Seed dispersal effectiveness: A comparison of four bird species feeding on seeds of invasive Acacia cyclops in South Africa

Seed dispersal effectiveness (SDE) for vertebrates is determined as a product of quantity (numbers of seeds dispersed) and quality (probability that a dispersed seed becomes a new adult plant) components. There is a limited understanding of seed dispersal effectiveness for different avian vectors in South Africa, yet birds are important for long-distance dispersal for native species, and are implicated in the dispersal of many invasive plant species such as Acacia cyclops. Consequently, SDE was investigated in four bird species that are common seed dispersers in South Africa, of which two are frugivorous species (the Knysna turaco Tauraco corythaix and the red-winged starling Onychognathus morio), and two are granivorous species (the red-eyed dove Streptopelia semitorquata and the laughing dove Streptopelia senegalensis). Individuals of these species were caged and fed mature seeds of A. cyclops to determine quality of seed treatment in the gut. SDE was computed as a product of germination rates of gut-passed seeds of A. cyclops (i.e. quality) and the average bird body mass (i.e. proxy for seed load as quantity component) for the four bird species. Results show that frugivorous birds had significantly greater SDE than the granivorous bird species. SDEs for respective bird species also showed notable differences: the Knysna turaco had highest SDE followed by the non-significantly different red-eyed dove and red-winged starling, while the laughing dove had the lowest SDE of all bird species. However, it is likely that the two ubiquitous dove species, and both the colonial and nomadic red-winged starling, might have higher SDEs associated with large home ranges than the Knysna turaco with its more restricted geographic range. The results highlight the previously overlooked importance of doves and the other birds in mediating the invasion of A. cyclops, and the dispersal processes for the seeds of other plants included in their diet.

Assimilation efficiency of the Red-winged Starling Onychognathus morio fed Strelitzia nicolai arils

There is a paucity of studies investigating the digestive efficiencies of avian frugivores fed fibrous (also referred to as woolly) aril pulp. We fed whole Strelitzia nicolai seeds with arils to captive Red-winged Starlings (Onychognathus morio) to determine daily food and energy intake, digestive transit time and assimilation efficiency. Strelitzia nicolai arils were found to contain a remarkably high lipid content (66.78 %), with a correspondingly low water (7.61 %) and protein (5.79 %) content. Birds generally ate only the aril of S. nicolai seeds, but if they swallowed the seeds whole then they either defecated or regurgitated the seeds without the aril. Red-winged Starlings were found to have fast digestive transit times (approx. 24 min) and very high apparent assimilation efficiencies (approx. 96 %) of the aril of S. nicolai seeds.

Effects of tannins on fruit selection in three southern African frugivorous birds

Tannins are common secondary compounds in plant material and are known for their ability to bind to protein which reduces nitrogen availability in the diet. In fruits, these compounds are responsible for their astringency which is thought to result in reduced food intake. In this study, the repellent effects of tannins were examined in three species of frugivorous birds: red-winged starlings Onychognathus morio, speckled mousebirds Colius striatus and Cape white-eyes Zosterops virens. Birds were fed artificial fruit diets containing varying levels of tannins in paired choice tests with the amount of food eaten by birds used to determine preference. Red-winged starlings were attracted to the control diet, indifferent to the medium tannin diet and deterred by the high tannin diet whereas speckled mousebirds and Cape white-eyes were not deterred at all concentrations. The discrepancy in the results was attributed to differences in taste sensitivity, tolerance levels and detoxification mechanisms of secondary compounds between species. Because fruit selection and ultimately fruit removal rates affect plant community composition, the disparity in the results suggests that frugivorous birds do not contribute equally to plant community dynamics. However, plant secondary compounds in fruits are diverse and their effects are similarly diverse and there is potential that different groups of secondary compounds generate disparate effects. Similar studies on other types of secondary compounds may thus contribute towards a broader understanding of the role of secondary compounds in mediating fruit-frugivore interactions.

Songs of two starling species: common traits versus adaptations to the social environment

We analysed, for the first time, songs of the African Red-winged Starling Onychognathus morio and compared their general characteristics with those of the European Starling Sturnus vulgaris. Both species are gregarious during the non-breeding season, but European Starlings tend to nest in colonies, form unstable pair-bonds and are occasionally polygynous, whereas Red-winged Starlings form long-term pair-bonds and occupy exclusive nesting territories. Red-winged Starlings produced the same basic song categories as European Starlings: warbles and whistles. These two categories appeared to be involved in similar social interactions in the two species. However, several aspects of song behaviour differed between the two species: Red-winged Starlings, breeding in isolated nests, preferentially used whistles for long-distance communication and showed a simpler organization of warbling song. Whistles in the Red-winged Starling were mostly shared between birds and, in contrast to the European Starling, were not indicators of individual identity. Also in contrast to the European Starling, female song in Red-winged Starlings appeared very important throughout the breeding period. Our results suggest that some song characteristics in the two species are phylogenetically conserved whereas others are affected by the distinct social systems of the two species.

African Red-winged Starlings prefer hexose sugar solutions, but do not like them too sweet

Globally, two bird–pollination systems have been recognised, involving specialist and occasional nectar-feeding birds. Whether avian pollinators place selective pressure on the plants they feed on, in terms of flower morphology and nectar traits, is still debated. While considerable research exists that examines the sugar preferences, concentration preference and digestive ability of specialist nectar-feeding birds, there is little known about these parameters for occasional nectar-feeding birds, as most previous studies have not controlled for the energetic value of solutions employed in choice experiments. Birds of the Sturnidae–-Muscicapoidea lineage lack sucrase and are intolerant of solutions or fruit above 11–15% sucrose content. African Red-winged Starlings Onychognathus morio are occasional nectarivores that play a role as pollinators of several plant groups, particularly aloes, which produce large amounts of dilute floral nectar. We confirmed that these birds, like other members of their lineage studied outside of Africa, are unable to digest sucrose. In laboratory trials, they strongly preferred hexose (1:1 glucose:fructose) over sucrose solutions in paired equicaloric choice tests at a range of concentrations (5–20%) and maintained energy balance at these concentrations. However, they were unable to maintain body mass when given a choice between sucrose and hexose solutions at the highest concentration (25%) and showed no sugar preference at this level, suggesting that high concentration solutions may place physiological stress on starlings. Starlings preferentially consumed lower concentration solutions, when simultaneously offered four hexose solutions of varying concentrations (10–25%). These results suggest that starlings impose pollinator-mediated pressure for low concentration, hexose-rich nectar in the plants they pollinate.

The birds of Sehlabathebe National Park, Lesotho

A total of 117 bird species has been recorded in Sehlabathebe National Park, south-east Lesotho, consisting of 29 vagrants, 18 visitors and 70 breeding and probable breeding residents. For each species status was determined and abundance roughly estimated. Quantitative studies on breeding bird communities were carried out by means of the line transect method on four transects with the total length ca 30 km in the park and on two transects with the total length of ca 20 km outside the park. In the park, dominant species were represented by the Stonechat Saxicola torquata, Ayres’ Cisticola Cisticola ayresii, Yellow-rumped Widow Euplectes capensis and Wailing Cisticola Cisticola lais. Outside the park dominants were represented by Cape Weaver Ploceus capensis, Cape Sparrow Passer melanurus, Cape Canary Serinus canicollis, Common Quail Coturnix coturnix, Stonechat, Cape Bunting Emberiza capensis and Drakensberg Siskin Pseudochloroptila symonsi. Characteristic, high-altitude species in the park included Drakensberg Siskin, Mountain Pipit Anthus hoeschi, Orange-breasted Rockjumper Chaetops auriantius, Banded Martin Riparia cincta and Sentinel Rock Thrush Monticola explorator. Species such as the Laughing Dove Streptopelia senegalensis, Sicklewinged Chat Cercomela sinuata, Mountain Chat Oenanthe monticola, Thick-billed Lark Galerida magnirostris, Red-winged Starling Onychognathus morio, Alpine Swift Apus melba Cape Sparrow, Grey-headed Sparrow Passer diffusus, Red Bishop Euplectes orix and Golden Bishop Euplectes afer were absent or occurred in very low densities in the park, although they are widespread and common in the Maluti/Drakensberg grasslands (including areas neighbouring to the park). The lack of trees and shrubs for nesting, the lack of cultivated fields as feeding places and competition with related species both for food and nesting sites, may partly play a role in this regard.

NESTING OF SYMPATRIC REDWINGED AND PALE WINGED STARLINGS

Summary Craig, A. J. F. K., Hulley, P. E. & Walter, G. H. 1989. Nesting of sympatric Redwinged and Pale-winged Starlings. Ostrich 60:69-74. Observations were made over four breeding seasons at Cradock, South Africa, where Redwinged Starlings Onychognathus morio and Palewinged Starlings O. nabouroup nest on the same cliffs. Nests were not accessible, and the stage of breeding was determined by the behaviour of the birds. Both species reuse the same nest sites, and only the females incubate, but both sexes feed the young. The timing of breedingMaybe more variable in the Palewinged Starling. A review of the available data on nest site selection and nest construction shows apparent species-specific differences: Redwinged Starlings usually nest on ledges, often on buildings, and use mud in the nest base; Palewinged Starlings favour vertical crevices, and do not use mud.