Elizabeth Yohannes

Isotope signatures in winter moulted feathers predict malaria prevalence in a breeding avian host

It is widely accepted that animal distribution and migration strategy might have co-evolved in relation to selection pressures exerted by parasites. Here, we first determined the prevalence and types of malaria blood parasites in a breeding population of great reed warblers Acrocephalus arundinaceus using PCR. Secondly, we tested for differences in individual feather stable isotope signatures (δ13C, δ15N, δD and δ34S) to investigate whether malaria infected and non-infected birds had occupied different areas in winter. We show that birds moulting in Afro-tropical habitats with significantly higher δ13C and δ15N but lower δD and δ34S values were more frequently infected with malaria parasites. Based on established patterns of isotopic distributions, our results indicate that moulting sites with higher incidence of malaria are generally drier and situated further to the north in West Africa than sites with lower incidence of malaria. Our findings are pertinent to the general hypothesis that animal distribution and particularly avian migration strategy might evolve in response to selection pressures exerted by parasites at different geographic scales. Tradeoffs between investment in energy demanding life history traits (e.g. migration and winter moult) and immune function are suggested to contribute to the particular choice of habitat during migration and at wintering sites.

Passerine migration strategies and body mass variation along geographic sectors across East Africa, the Middle East and the Arabian Peninsula

Using the body mass estimates of 12 long-distance migrating Palearctic passerine species monitored at successive sites across the Eastern Africa flyway, we tested whether birds modulate their body mass according to specific seasonal demands across different geographic sectors. We compared body mass estimates across latitudinal distances and geographic sectors in Europe, the desert, Northeast Africa and East Africa. Our results show that, depending on the species and season considered, the average body mass increase or decrease is variable at and among different geographic sectors. By comparing the variation in body mass between different ecological sectors, we were able to show when and where migrants accumulate their migratory fuel reserves during migration.

Advantages of using fecal samples for stable isotope analysis in bats: evidence from a triple isotopic experiment.

RATIONALE Stable isotope analysis in ecological studies is usually conducted on biomaterials, e.g. muscle and blood, that require catching the animals. Feces are rarely used for stable isotope analysis, despite the possibility of non-invasive sampling and short-term responsiveness to dietary changes. This promising method is neglected due to a lack of calibration experiments and unknown diet-feces isotopic difference (Δ(diet-feces)). METHODS To fill this gap, we simulated trophic changes occurring in nature when animals switch feeding habitats, e.g. by moving from freshwater to terrestrial systems, from cultivated areas to forests or changing distance from marine environments. In a controlled experiment, the diet of two bat species (Myotis myotis, Rhinolophus ferrumequinum) was altered to an isotopically distinct one. We measured stable nitrogen, carbon and the rarely used sulfur isotope in feces, and calculated Δ(diet-feces) values. RESULTS The feces acquired the new dietary signature within 2-3 h from food ingestion; thus, they are suited for detecting recent and rapid dietary changes. The Δ(diet-feces) (Δ) did not differ between species or diet (overall means ± standard deviation (sd)): Δ(15)N: 1.47 ± 1.51‰, Δ(13)C: -0.11 ± 0.80‰, Δ(34)S: 0.74 ± 1.10‰. Only Δ(15)N for M. myotis was significantly different from zero and only Δ(13) C differed among the days of the experiment. CONCLUSIONS Fecal stable isotopes can be now further applied in mammalian ecology. This includes a range of applications, such as studying changes in trophic level, resource or habitat use, on a short time-scale. Such information is gaining importance for monitoring rapidly changing ecosystems under anthropogenic influence.

Philopatry of winter moult area in migratory Great Reed Warblers Acrocephalus arundinaceus demonstrated by stable isotope profiles

Stable carbon- (δ13C), nitrogen- (δ15N) and hydrogen (δD) isotope profiles in feathers of migratory Great Reed Warblers Acrocephalusarundinaceus recaptured for 2 or more years in 6 successive years were examined to test whether the isotope profiles of individual warblers appeared to be consistent between years. Similar isotopic signatures in successive years suggested that individual birds tended to return and grow their feathers in Afro-tropical wintering habitats that generate similar δ13C, δ15N and δD signatures. Previous studies have shown that Great Reed Warblers exhibit strong natal and breeding philopatry, with most of the surviving birds returning to the breeding site. The present study of feather δ13C, δ15N and δD isotopic values demonstrate the year-to-year fidelity might also include the African moulting sites in this migratory species.

Tracking Diet Preferences of Bats Using Stable Isotope and Fatty Acid Signatures of Faeces

Stable isotope and fatty acid signatures of biomaterials can provide important information about the dietary niche of animals. Stable isotope and fatty acid signatures differ between aquatic and terrestrial food webs, and therefore can be used to assess the aquatic and terrestrial contributions to the diets of species. We studied faecal samples of three co-occurring bat species with known differences in feeding preferences. The aim was to assess whether stable isotope and fatty acid signatures of faeces can be used to determine feeding preferences. We used bat faeces because they can be easily and non-invasively collected. We hypothesised that faeces stable isotope and fatty acid signatures will reveal the terrestrial, aquatic and mixed feeding niches of Myotis myotis, M. daubentonii, and M. mystacinus, respectively. As predicted, the faeces of M. myotis were characterized by higher δ 13C values and higher concentrations of linoleic acid and total ω6 polyunsaturated fatty acids (PUFAs), which are typically higher in terrestrial food webs. The faeces of M. daubentonii had higher δ 15Ν values and higher concentrations of docosahexaenoic acid and total ω3 PUFAs, characteristic features of aquatic systems. Myotis mystacinus faeces had intermediate δ 15Ν values and concentrations of both types of fatty acids. Our results show that analysing stable isotope and/or fatty acid signatures of faeces provides a promising, non-invasive tool to study the feeding ecology of bats and to assess aquatic-terrestrial interactions.

Bone collagen and muscle δ 13 C in relation to the timing of the migration of Garden Warblers Sylvia borin during return migration from Africa

AbstractIn migratory birds, seasonal factors interacting at different stages of the annual cycle can influence individual life histories. These have been well documented for Nearctic-Neotropical birds. Yet, seasonal interactions between the wintering, migration, and breeding periods have not been demonstrated for Palearctic-African passerine migrants. We tested whether variation in long- and short-term dietary choice of the Garden Warbler Sylvia borin can influence events during the subsequent spring migration from the African winter quarters to the Palearctic breeding grounds. Using bone collagen and muscle carbon stable isotope (δ13C) analysis, we assessed the relationships between dietary history, body condition, and migration timing in the Garden Warbler during a return migration from Africa. We predicted that Garden Warblers arriving early will have significantly different muscle and collagen δ13C relative to those arriving later. Whereas muscle δ13C (referring to events in the immediate past) was not related to body condition, we found a strong association between body condition and collagen δ13C signatures (representing the integration of long-term events). Collagen and muscle δ13C indicate that birds passing through later originated from moister or cooler geographic areas. The observed variation in isotope signatures might relate to differences in habitat and geographic/population origin, or in dietary intake.Zusammenfassungδ13C im Knochenkollagen und der Muskulatur von GartengrasmückenSylvia borinin Bezug zum Zugablauf während des Rückfluges aus Afrika Wechselwirkungen saisonaler Faktoren während unterschiedlicher Etappen des Jahreszyklus können bei Zugvögeln deren individuelle Lebensgeschichte beeinflussen. Dies wurde für nearktisch-neotropische Vögel bereits gut belegt. Saisonale Wechselwirkungen zwischen dem Überwintern, dem Zug und der Brutperiode bei in der Paläarktis brütenden und in Afrika überwinternden Singvögeln sind bisher jedoch nicht bekannt. Wir überprüften ob die kurz- bzw. langfristige Nahrungswahl unter Gartengrasmücken Sylvia borin Ereignisse während des folgenden Frühjahrzuges aus den afrikanischen Winterquartieren in die paläarktischen Brutgebiete beeinflusst. Anhand des stabilen Kohlenstoffisotops (δ13C) im Knochenkollagen und in der Muskulatur untersuchten wir Zusammenhänge zwischen der vergangenen Nahrungsaufnahme, der Körperkondition und dem zeitlichen Ablauf des Zuges während des Heimfluges aus Afrika. Nach unserer Voraussage sollten signifikant unterschiedliche δ13C Muster für Knochenkollagen und Muskulatur bei früh und spät ankommenden Gartengrasmücken auftreten. Die δ13C Signatur der Muskulatur (zurückzuführen auf Ereignisse der unmittelbaren Vergangenheit) zeigte jedoch keine Beziehung zur Körperkondition, wohl aber die des Knochenkollagens (zurückzuführen auf Integration langfristiger Ereignisse). δ13C Knochenkollagen und Muskulatur deuten darauf hin, dass später durchziehende Vögel aus relativ feuchteren oder kälteren Gegenden stammen. Die hier beobachtete signifikante Variation in der Isotopensignatur könnte auf Unterschiede in den Habitaten, im geographischen Ursprung (Populationen) oder in der Nahrungsaufnahme zurückgeführt werden.

Using stable isotopes to trace resource acquisition and trophic position in four Afrotropical birds with different diets

(2010). Using stable isotopes to trace resource acquisition and trophic position in four Afrotropical birds with different diets. Ostrich: Vol. 81, No. 3, pp. 273-275.

Multiple isotope analyses of the pike tapeworm Triaenophorus nodulosus reveal peculiarities in consumer-diet discrimination patterns.

Previous studies of dietary isotope discrimination have led to the general expectation that a consumer will exhibit enriched stable isotope levels relative to its diet. Parasite-host systems are specific consumer-diet pairs in which the consumer (parasite) feeds exclusively on one dietary source: host tissue. However, the small numbers of studies previously carried out on isotopic discrimination in parasite-host (ΔXP-HT) systems have yielded controversial results, showing some parasites to be isotopically depleted relative to their food source, while others are enriched or in equilibrium with their hosts. Although the mechanism for these deviations from expectations remains to be understood, possible influences of specific feeding niche or selection for only a few nutritional components by the parasite are discussed. ΔXP-HT for multiple isotopes (δ13C, δ15N, δ34S) were measured in the pike tapeworm Triaenophorus nodulosus and two of its life-cycle fish hosts, perch Perca fluviatilis and pike Esox lucius, within which T. nodulosus occupies different feeding locations. Variability in the value of ΔXP-HT calculated for the parasite and its different hosts indicates an influence of feeding location on isotopic discrimination. In perch liver ΔXP-HT was relatively more negative for all three stable isotopes. In pike gut ΔXP-HT was more positive for δ13C, as expected in conventional consumer-diet systems. For parasites feeding on pike gut, however, the δ15N and δ34S isotope values were comparable with those of the host. We discuss potential causes of these deviations from expectations, including the effect of specific parasite feeding niches, and conclude that ΔXP-HT should be critically evaluated for trophic interactions between parasite and host before general patterns are assumed.

Isotopic evidence for dietary niche overlap between barking deer and four-horned antelope in Nepal

BackgroundMorphologically similar sympatric species may have a high degree of niche overlap. Barking deer Muntiacus vaginalis and four-horned antelope Tetracerus quadricornis are solitary ungulates of the Indian sub-continent. Limited information is available regarding their trophic ecology, particularly of the endemic four-horned antelope. We present stable carbon (δ13C), nitrogen (δ15N), and sulphur (δ34S) isotopic values, and nitrogen content (%N) of faeces from barking deer and four-horned antelope living in lowland Nepal to assess trophic niche differentiation of these herbivores along the browser-grazer continuum. We also describe trophic differences between those two species in ecological niches and seasonal effects on their diets.ResultsWe found that the barking deer and four-horned antelope consumed C3 plant sources exclusively. The niche partitioning in their diet was reflected by δ34S values. Some seasonal effects observed were: δ13C and δ15N were significantly lower in the dry season diet of four-horned antelope than that of barking deer, while δ34S values were significantly higher in the winter diet; monsoon diet was similar for both species. Faecal N levels for barking deer and four-horned antelope were similar throughout all the seasons, indicating that both species adapted their feeding behaviour so as to maximize protein intake, in accordance with season and environment.ConclusionsBarking deer and four-horned antelope both are browsers; their dietary sources overlapped during monsoon but differed during the dry season. Conservation actions focused on resource management during the dry season to reduce food scarcity and competition over limited resources is likely to be the most effective.

Moulting and Wintering Grounds of Marsh Warblers Acrocephalus palustris : Evidence from Stable Isotopes and Ring Recoveries

Abstract. We analysed stable carbon (&dgr;13C) and nitrogen (&dgr;15N) isotope ratios in Marsh Warbler Acrocephalus palustris feathers sampled in Europe and Africa to assess non-breeding habitat selection and location of wintering grounds of different breeding populations. Feather &dgr;13C values showed that Marsh Warblers occupy a biome dominated by C4 vegetation during the stopover in northeastern Africa, whereas C3 habitats are used during the complete moult in southern Africa. East European Marsh Warblers differed in their stable isotope profiles from other European regions, suggesting a certain level of population segregation in southern Africa. A dual-isotope assignment approach confirmed this difference and helped us restrict the autumn staging areas to lower elevations of the Ethiopian Highlands west of the Rift valley. Available ring recoveries, however, suggested high levels of population mixing both on migration through East Africa and in the final wintering grounds.