Spotted Eagle Owl Research Articles

Efficient Evaporative Cooling and Pronounced Heat Tolerance in an Eagle-Owl, a Thick-Knee and a Sandgrouse

Avian evaporative cooling and the maintenance of body temperature (Tb) below lethal limits during heat exposure has received more attention in small species compared to larger-bodied taxa. Here, we examined thermoregulation at air temperatures (Tair) approaching and exceeding normothermic Tb in three larger birds that use gular flutter, thought to provide the basis for pronounced evaporative cooling capacity and heat tolerance. We quantified Tb, evaporative water loss (EWL) and resting metabolic rate (RMR) in the ∼170-g Namaqua sandgrouse (Pterocles namaqua), ∼430-g spotted thick-knee (Burhinus capensis) and ∼670-g spotted eagle-owl (Bubo africanus), using flow-through respirometry and a stepped Tair profile with very low chamber humidities. All three species tolerated Tair of 56–60°C before the onset of severe hyperthermia, with maximum Tb of 43.2°C, 44.3°C, and 44.2°C in sandgrouse, thick-knees and eagle-owls, respectively. Evaporative scope (i.e., maximum EWL/minimum thermoneutral EWL) was 7.4 in sandgrouse, 12.9 in thick-knees and 7.8 in eagle-owls. The relationship between RMR and Tair varied substantially among species: whereas thick-knees and eagle-owls showed clear upper critical limits of thermoneutrality above which RMR increased rapidly and linearly, sandgrouse did not. Maximum evaporative heat loss/metabolic heat production ranged from 2.8 (eagle-owls) to 5.5 (sandgrouse), the latter the highest avian value yet reported. Our data reveal some larger species with gular flutter possess pronounced evaporative cooling capacity and heat tolerance and, when taken together with published data, show thermoregulatory performance varies widely among species larger than 250 g. Our data for Namaqua sandgrouse reveal unexpectedly pronounced variation in the metabolic costs of evaporative cooling within the genus Pterocles.

The 100,000\u201377,000-Year Old Middle Stone Age Micromammal Sequence from Blombos Cave, South Africa: Local Climatic Stability or a Tale of Predator Bias?

In this paper, we present a case study of the micromammal sequence from Marine Isotope Stage 5 (130,000–71,000 YBP) at Blombos Cave on the southern Cape coast of South Africa. Our analyses of the micromammal assemblage from 100,000 to 76,000 YBP shed light on micromammal taxonomic distributions, local palaeoenvironments, and site formation processes at this renowned Middle Stone Age site. Taphonomic analyses indicate that spotted eagle owls (Bubo africanus) were the main predator species responsible for accumulating the micromammals, but with contributions from barn owls (Tyto alba). In addition, the micromammal bones have been subjected to a range of post-depositional processes, some of which are associated with microbial actions likely resulting from human or animal activities in the cave. We have recorded three species in the archaeological assemblage that do not occur in the Blombos area today. These are the Hottentot golden mole (Amblysomus hottentotus), Duthie’s golden mole (Chlorotalpa duthieae), and Laminate vlei rat (Otomys laminatus). The biodiversity indices based on micromammal species suggest that local vegetation consisted of different habitats that could sustain a diverse small mammal population. During MIS 5c/5b, the diversity of species declined, but there was still a mosaic of vegetation habitats present in the local area. On a larger temporal scale, climate conditions were slightly more humid than at present, and winter rainfall was seemingly greater. The amount of winter rainfall would have been similar to locations currently c. 50–150 km further west of Blombos Cave. However, based on micromammal proxies, there were seemingly no major fluctuations visible in climate or vegetation composition during the entire 24,000-year period. We suggest that the explanation could be multifaceted, two potential factors being predator bias derived from the owls’ preference for generalist micromammal species or an actual reflection of local stable climatic and environmental conditions in the Blombos area.

Causes of admission to a raptor rehabilitation centre and factors that can be used to predict the likelihood of release

AbstractAdmission records of rescued birds are an important source of information for tracking the prevalence of human‐related threats to wildlife. In this study, we used admission records from January 2015 to December 2016 to review the causes for raptor admissions to a raptor rehabilitation centre in Pietermaritzburg, South Africa, and to determine factors that can be used to predict the outcome of rehabilitation. During the study period, 242 raptors were admitted to the centre, representing 33 species. The major causes of admission were collision‐related injuries (52%), grounded birds (12%) and orphaned chicks (10%). The most common casualties were spotted eagle‐owl Bubo africanus (23%), yellow‐billed kite Milvus migrans aegyptius/parasitus (12%), jackal buzzard Buteo rufofuscus (10%) and western barn owl Tyto alba (10%). The rehabilitation centre had a release rate of 48%. Reason for admission was a significant predictor of the outcome of rehabilitation while other variables were not. Raptors with no severe injuries such as orphaned chicks and grounded birds were more likely to have successful rehabilitation treatment than raptors suffering from collision injuries. Wildlife rehabilitators can use the results of the present study to develop triage guidelines for raptors admitted to rehabilitation centres.

Micromammal and macromammal stable isotopes from a MIS 6 fossil hyena den (Pinnacle Point site 30, south coast, South Africa) reveal differences in relative contribution of C4 grasses to local and regional palaeovegetation on the Palaeo-Agulhas Plain

Proxy records dating to marine isotope stage 6 on the south coast of South Africa are rare. This study presents integrated micromammal and macromammal stable isotope palaeoenvironmental proxy data from one of the few MIS 6 fossil occurrences in the region, a fossil brown hyena (Parahyena brunnea) den, Pinnacle Point 30 (PP30). Two predators with significantly different foraging ranges aggregated the large and small mammal components of the PP30 fossil assemblage. The large mammal specimens were brought to PP30 by Parahyena brunnea with an expansive daily foraging radius that focused on the Palaeo-Agulhas Plain. The micromammal taxa were deposited at the site primarily by the spotted eagle owl, Bubo africanus, with a foraging radius of ∼3 km, and would have sampled the ecotone between the Palaeo-Agulhas Plain and the Cape coastal lowlands. The large and small mammal components of the PP30 assemblage thus sample palaeovegetation at different geographic scales; micromammal stable isotope data act as a proxy for local conditions, while macromammal data integrate information at a broader scale. Comparison of the stable carbon isotope data obtained from the micromammal and macromammal fossil specimens suggests that these two assemblage components intersected vegetation with differing proportions of C4 grasses. Micromammal δ13C proxy data indicates that, immediately local to the site, a C3 dominated vegetation was present, while the large mammal δ13C proxy data shows evidence of a vegetation community with a greater C4 grass component that likely occurred somewhat more distant from the site itself on the Palaeo-Agulhas Plain.

Acanthocephalans, Including the Description of a New Species of Mediorhynchus (Gigantorhynchidae) and a Redescription of Centrorhynchus clitorideus (Centrorhynchidae) from Vertebrate Hosts from South Africa

Forty-seven individuals comprising 4 species of birds, Tockus leucomelas, Crecopsis egregia, Turdus smithi, and Bubo africanus; 4 species of mammals, Otolemur crassicaudatus, Gerbilliscus leucogaster, Mus minutoides, and Mus sp.; and 1 species of reptile, Varanus albigularis, all from South Africa were examined for acanthocephalans. Centrorhynchus clitorideus, Mediorhynchus mokgalongi n. sp., Masticophis taeniatus, Moniliformis acomysi, Moniliformis sp., Plagiorhynchus (Prosthorhynchus) cylindraceus, and a putative new genus of the Oligacanthorhynchidae were found. Additional characters of C. clitorideus were described. The new species of Mediorhynchus differs from all congeners by a suite of characters, including a proboscis armature of 125–156 hooks arranged in 24–26 longitudinal rows of 24–26 hooks and 30 rows of 5–6 spines. The putative new genus has a total of 24 hooks arranged in 12 longitudinal rows of 2 hooks. All are new host and locality records.

Syntopy and co‐utilization of a “roosting area” by the barn owl (Tyto alba) and spotted eagle owl (Bubo africanus) in Tanzania

Syntopy and co‐utilization of a “roosting area” by the barn owl (<i>Tyto alba</i>) and spotted eagle owl (<i>Bubo africanus</i>) in Tanzania

Dietary Overlap of Co-Occurring Barn OwlTyto albaScopoli and Spotted Eagle OwlBubo africanusTemminck in Urban and Rural Environments

Diet of co-occurring Barn Owl and Spotted Eagle Owl has been studied by means of pellet contents analysis in urban and rural environments in the Highveld of South Africa. In urban environment, diet of both owl species was dominated by murid rodents (mainly Otomys, Mastomys and Rhabdomys). In rural environment, Barn Owl diet was also dominated by murid rodents, but in the diet of the Spotted Eagle Owl higher proportion of birds and non-murid rodents was recorded. Although in the rural environment the breadth of diet niche was wider in Spotted Eagle Owl (DB = 35.41) than in Barn Owl (DB = 12.67), there was almost total dietary overlap (DO = 0.98) between these two co-occurring owl species. For contrast, there was only slight food niche overlap (DO = 0.12) between these owl species co-occurring in the urban environment, but the diet breadth here was also wider in Spotted Eagle Owl (DB = 29.02) than in Barn Owl (DB = 17.90). In the urban environment diet breadth of the Spotted Eagle Owl is, therefore, slightly wider than in rural environment, while in the case of the Barn Owl the reverse is true. Probably there is lower abundance of available prey in urban and rural areas in the Highveld, in comparison with more natural habitats. This may force both species to resort to a more diverse diet to meet their energy requirements. Both species show, therefore, high plasticity of foraging.

Mammal and Bird Road Mortalities on the Upington to Twee Rivieren Main Road in the Southern Kalahari, South Africa

Road ecology is becoming an increasingly important aspect of conservation biology. Carcasses lying on the road often confront visitors travelling to the Kgalagadi Transfrontier Park between Upington and the Twee Rivieren Rest Camp. This study investigated the species killed, the factors contributing to their deaths, and suggested solutions to curtail these mortalities. Twelve surveys to record mammal and bird road mortalities were conducted on the R360 main road between Upington and Twee Rivieren (261 km) from January to September 2007. One hundred and eighty four carcasses were recorded from 22 species, and the most common taxa killed were the bat-eared fox (n = 47) and spotted eagle owl (n = 10). The road mortality rate on the R360 road was very high, 5.44 mammals and 1.14 birds per 100 km. Birds were predominantly killed in summer. Notably more nocturnal mammals were killed than diurnal and ‘indistinct’ species. A mammal hotspot was identified along the 91 km of road that traversed the Gordonia duneveld. Since the nine roadside traffic warning signs erected on the R360 road had no measurable impact on road mortalities, it is recommend that three rumble strip sections with accompanying signage be erected in the hotspot to slow down vehicles and curtail mortalities.

Mammal and bird road mortalities on the Upington to Twee Rivieren main road in the southern Kalahari, South Africa

Road ecology is becoming an increasingly important aspect of conservation biology. Carcasses lying on the road often confront visitors travelling to the Kgalagadi Transfrontier Park between Upington and the Twee Rivieren Rest Camp. This study investigated the species killed, the factors contributing to their deaths, and suggested solutions to curtail these mortalities. Twelve surveys to record mammal and bird road mortalities were conducted on the R360 main road between Upington and Twee Rivieren (261 km) from January to September 2007. One hundred and eighty four carcasses were recorded from 22 species, and the most common taxa killed were the bat-eared fox (n = 47) and spotted eagle owl (n = 10). The road mortality rate on the R360 road was very high, 5.44 mammals and 1.14 birds per 100 km. Birds were predominantly killed in summer. Notably more nocturnal mammals were killed than diurnal and ‘indistinct’ species. A mammal hotspot was identified along the 91 km of road that traversed the Gordonia duneveld. Since the nine roadside traffic warning signs erected on the R360 road had no measurable impact on road mortalities, it is recommend that three rumble strip sections with accompanying signage be erected in the hotspot to slow down vehicles and curtail mortalities.

Environmental implications of micromammals accumulated close to the MIS 6 to MIS 5 transition at Pinnacle Point Cave 9 (Mossel Bay, Western Cape Province, South Africa)

PP9C is a coastal cave situated on the south coast, Pinnacle Point, Mossel Bay, and contains both archeological deposits, as well as fossil micromammal accumulations. Micromammals were analyzed from facies accumulated close to the transition from MIS (Marine Isotope Stage) 6 to MIS 5, between 130 ± 9 and 120 ± 7 ka. The taphonomy of the assemblages indicates that the majority of micromammals became associated with the site when they were deposited in Spotted eagle owl or Barn owl pellets. Modern comparative studies suggest that these two predator species select a very similar suit of prey species from the available micromammal population and the fossil micromammal assemblages they produce are comparable when tracing palaeoenvironmental change. The fossil assemblages suggest that the period during which the micromammals accumulated was warm and wet, and that the vegetation within the hunting range of the owls accumulating the micromammal assemblages was relatively dense. There is, however, some evidence that at the time of deposition of the older assemblages, conditions were colder, relatively grassier, and may reflect a rather more open environment. This difference may indicate the change from glacial MIS 6 to inter-glacial MIS 5e climatic conditions. These conclusions are supported both by the habitats and habits of the micromammal faunas, as well as by multivariate analysis. E. edwardii and A. namaquensis appear only in the earliest fossil assemblages at PP9C, and their general scarcity suggests that the rocky and open habitat preferred by these two species was never available on a wide scale at Pinnacle Point. The Pinnacle Point fossil sites indicate that the soricid, C. flavescens, was a common component of the local micromammal fauna and occurred in the area during some of MIS 6, and into MIS 5, suggesting that this species was able to adapt to glacial/interglacial cycles, and may utilize drier habitats than commonly reported in the literature. The fossil evidence indicates that C. cyanea, S. infinitesimus and Saccostomys campestris are relative latecomers to the Mossel Bay region. S. campestris appears only in PP9C in surface sediments, and confirms previous suggestions that the arrival of this species to the southern Cape occurred sometime within the Holocene.

Diet of sympatric African grass owl (Tyto capensis) and spotted eagle owl (Bubo africanus) in the Bamenda Highlands, NW Cameroon

Diet of sympatric African grass owl (Tyto capensis) and spotted eagle owl (Bubo africanus) in the Bamenda Highlands, NW Cameroon Jan Riegert*, Ondřej Sedlacek and Rainer Hutterer Department of Zoology, Faculty of Biological Sciences, University of South Bohemia, Branisovska 31, CZ-370 05 Ceske Budějovice, Czech Republic, Department of Ecology, Faculty of Science, Charles University in Prague, Vinicna 7, CZ-128 44 Praha, Czech Republic and Section of Mammals, Zoologisches Forschungsmuseum Alexander Koenig, Adenauerallee 160, D-53113 Bonn, Germany

Sexual dimorphism of four owl species in South Africa

Sexual dimorphism was studied in four South African owl species (African Grass-Owl Tyto capensis, Barn Owl T. alba, Marsh Owl Asio capensis and Spotted Eagle-Owl Bubo africanus) by examining specimens of intact owl carcasses found killed by vehicles along a national road in Gauteng province, South Africa. Females were significantly heavier and larger than males for most species. The body mass and length of T. capensis, and body mass and tail length of A. capensis, were significantly different, with females being larger than males. Body, wing, tail and tarsus length for T. alba males were significantly different to females. For B. africanus, only tarsus length was found to be significantly different among genders. These findings were reiterated further when applying a dimorphism index to the same morphometric measurements. This study contributes to morphometrics distinguishing the sexes of the four southern African owl species, especially T. capensis, which has a Vulnerable IUCN status.

Taphonomic implications of roosting behavior and trophic habits in two species of African owl

As some of the most common predators of micromammals, owls are implicated in the formation of many fossil assemblages. Actualistic research on owl-accumulated assemblages has tended to focus on owls roosting in caves. Comparatively few data are available on the roosting behavior, and prey preference of owls in open habitats. This paper presents observations on the roosting and prey habits of two sympatric species of owl in the Serengeti region of northern Tanzania, the Barn Owl, Tyto alba affinis, and the Spotted Eagle Owl, Bubo africanus. The Barn Owl and Spotted Eagle Owl are found to segregate by roosting habit, with Barn Owls occupying cavity roosts and Eagle Owls appearing on the ground or in tree crowns. Previous studies comparing these two species suggested a close similarity in trophic habits. A comparison of large samples (MNI = 1012) at cavity and exposed roosts shows identical taxonomic representation, though differences are found in the relative abundance of some taxa and significant differences in prey body mass.

Taphonomy of Micromammals from Cave Deposits at Kabwe (Broken Hill) and Twin Rivers in Central Zambia

Samples of Middle Pleistocene micromammals from cave deposits at Kabwe (Broken Hill) and Twin Rivers in Zambia were analysed according to Andrews's (1990) methods. In addition, behavioural and ecological data relating to possible predator species were examined for corrobation or contradiction of the mechanical evidence. Interpretation of the Kabwe sample is complicated by its unknown history since recovery and the possibility that the paucity of cranial remains results from their selective post-recovery removal from the sample. However, the combined evidence suggests that it was collected by barn owls whereas the Twin Rivers material perhaps accumulated at a spotted eagle owl nest site.

Functional morphology of the pecten oculi in the nocturnal spotted eagle owl (Bubo bubo africanus), and the diurnal black kite (Milvus migrans) and domestic fowl (Gallus gallus var. domesticus): a comparative study

AbstractThe pecten oculi is a highly vascularized and pigmented organ that overlies the optic disc and projects into the vitreous body in the avian eye. First reported over 300 years ago, its function(s) remains a puzzle to ornithologists, ophthalmologists and anatomists. Morphometric study of this unique organ was undertaken in birds exhibiting apparently different visual acuities, namely two species of diurnal birds (the ground‐dwelling domestic fowl Gallus gallus var. domesticus and a highly active predator bird, the black kite (Milvus migrans) and a nocturnal bird (the spotted‐eagle owl Bubo bubo africanus). The volume of the owl's eye was 4.8 and 2.2 times larger than that of the fowl and the kite, respectively. However, the pecten of the fowl consisted of more pleats (16–18) compared to the kite (12–13) and the owl (5–6). The volume of the pecten of the kite was 1.4 and 2.7 times larger than that of the fowl and the owl, respectively (P &lt; 0.05). Similarly, the surface area of the pecten of the kite was 2.6 and 4 times larger than that of the fowl and owl, respectively (P &lt; 0.05). The volume density of blood vessels (lumen and wall) in the pecten of the kite, fowl and owl comprised 67.7%, 66.9% and 62.6%, respectively, the pigmented tissue constituting the rest. Both the volume density and the volume of the blood in the pecten were higher in the diurnal birds (kite, fowl) than the owl (P &lt; 0.05). The surface area of the capillary luminal surface was 1.7 and 5.3 times higher in the kite than in the fowl and the owl, respectively (P &lt; 0.05). These results suggest that the functional morphology of the pecten correlates with the life‐style of the bird and with functional need, and lends further support to the nutritive role of the pecten.

Cryptococcus neoformans var neoformans isolated from droppings of captive birds in Nigeria.

The yeast, Cryptococcus neoformans, was found in apparently healthy birds at the Jos Wildlife Park and Zoo in Jos, Nigeria. Cryptococcus neoformans var neoformans was isolated from feces of four captive bird species. Five isolates belonged to serotype A while two were serotype D. Serotype A of C. neoformans was isolated from a white face duck (Dendrocygna viduata), eagle owl (Bubo africanus cinerascene) and peacock (Pavo cristatus). The other two (serotype D), were isolated from a spotted eagle owl.

FATAL HERPESVIRUS INFECTION IN A CAPE EAGLE OWLBUBO CAPENSZSAND A SPOTTED EAGLE OWLBUBO AFRZCANUS

Summary Williams, M.C. & Nesbit, J.W. 1996. Fatal herpesvirus infection in a Cape Eagle Owl Bubo capensis and a Spotted Eagle Owl Bubo africanus. Ostrich 67:50-62 Fatal, systemic herpesvirus infection was reported in a Cape Eagle Owl Bubo capensis and a Spotted Eagle Owl Bubo africanus. This is believed to be the first report of systemic herpesvirus infections in owls in South Africa. Post mortem examinations revealed multifocal necrosis in the liver and spleen. Histologically, intranuclear inclusion bodies were present, particularly in cells at the periphery of necrotic foci. Typical herpesvirus virions, demonstrable by transmission electron microscopy, were present. Viral isolations were unfortunately not undertaken.

FOSSIL OWLS FROM EARLY MAN SITES OF OLDUVAI GORGE, TANZANIA

Summary Brodkorb, Pierce & Mourer-Chauviré, Cécile. 1984. Fossil owls from Early Man Sites of Olduvai Gorge, Tanzania. Ostrich 54:17-27. Three species of owl have been recognized among the fossil bird remains of Olduvai. Bubo leakeyae n. sp. seems to be the immediate ancestor of the recent Spotted Eagle Owl Bubo africanus. The other forms are Giant Eagle Owl Bubo cf. lacteus and Barn Owl Tyto alba. These three forms indicate a landscape of lightly wooded savanna.