The Effect of Different Levels of Selenium in Mineral Mixtures and Salt Licks on Selenium Status in Sheep

This paper describes 3 experiments comparing the effect of 10, 25 and 40 mg Se/kg, as sodium selenite, in mineral mixtures and salt licks fed to sheep. The supplement was given during the indoor season from October to May to 7 different flocks, each consisting of 50 to 100 sheep, in areas with selenium deficiency problems. The average selenium level in the basic diets did not exceed 0.05 mg/kg. Selenium status was monitored in the blood of ewes and lambs, and in milk. Blood selenium in lambs correlated well with blood selenium in their dams (r = 0.85). Selenium levels in milk on day 1 (colostrum) correlated well with selenium levels in dams (r = 0.92) and in offspring (r = 0.87). Statistically significant differences were found between the different flocks. In areas with extreme selenium deficiency, 10 mg Se/kg in mineral mixtures and salt licks proved insufficient. A content of 25 mg Se/kg, providing a daily intake of about 0.4 mg selenium, resulted in selenium levels in ewes’ blood, ewes’ milk and in the offspring that should prevent selenium deficiency disease without causing any toxic effects.     

CuckooCuclus canorus parasitism onAcrocephalus Warblers in Southern Moravia in The Czech Republic

Summary The Reed Warbler,Acrocephalus scirpaceus, in the Lednice area, Southern Moravia in the Czech Republic, was parasitized by the Cuckoo,Cuculus canorus, at a rate of at least 18.0 %. The Cuckoo eggs showed poor mimesis with the Reed Warbler eggs, but showed a greater resemblance to the eggs of other species breeding in the area, including the Great Reed Warbler,A. arundinaceus. This latter species was also parasitized, but we did not find enough nests to obtain a reliable estimate for the rate of parasitism. The parasitized Reed Warblers rejected the Cuckoo eggs at a high rate (42.1 %) and therefore both the hatching success and the breeding success of the Cuckoo was considerably lower than shown by comparable results from Britain. On the background of these results (poor mimesis of the Cuckoo eggs and a high rejection rate by the hosts) the question of the degree of specialization versus generalism in the Cuckoo's host preference is discussed.

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Zusammenfassung Teichrohrsänger im Gebiet von Lednice (Südmähren, Tschechei) waren mindestens zu 18 % vom Kuckuck parasitiert. Die Kuckuckseier glichen jenen der Teichrohrsänger nur wenig, waren jedoch den Eiern anderer im Gebiet brütender Arten einschließlich des Drosselrohrsängers ähnlicher. Drosselrohrsänger waren auch parasitiert; wir fanden jedoch nicht genug Nester, um eine Parasitierungsrate ermitteln zu können. 42,1 % der Kuckuckseier wurden vom Teichrohrsänger nicht angenommen; daher waren Schlüpf- und Ausfliegerate des Kuckucks merklich geringer als in vergleichbaren Ergebnissen aus Großbritannien. Vor dem Hintergrund unserer Ergebnisse — geringe Angleichung der Kuckuckseier und hohe Ablehnungsrate durch die Wirtsart — wird die Frage von Spezialisierung und Generalismus in der Wirtswahl des Kuckucks diskutiert.

     

Breeding success of common cuckoos Cuculus canorus parasitising four sympatric species of Acrocephalus warblers

We investigated the level of parasitism, egg mimicry and breeding success of cuckoos parasitising four sympatric species of Acrocephalus warblers in southern Moravia, Czech Republic. The parasitism rate was highest in the marsh warbler Acrocephalus palustris (44.8%) followed by great reed warbler A. arundinaceus (33.8%), sedge warbler A. schoenobaenus (26.5%) and reed warbler A. scirpaceus (11.6%). Although the cuckoo eggs showed a high level of mimicry the eggs of the marsh warbler this host species rejected 72% of the cuckoo eggs, resulting in a cuckoo breeding success of only 4.3%. Cuckoo eggs laid in great reed warbler and reed warbler nests showed a similar hatching success, but the cuckoo chicks survived better in great reed warbler nests, resulting in a breeding success of 30.4%, as compared to 16.4% in nests of the reed warbler. The relationship between the level of parasitism, host rejection of cuckoo eggs, cuckoo chick survival and breeding success is discussed for the four host species.     

Impact of Red Deer Cervus elaphus Grazing on Bilberry Vaccinium myrtillus and Composition of Ground Beetle (Coleoptera, Carabidae) Assemblage

We studied the role of red deer Cervus elaphus L. as ecosystem modifier in boreal forest (Tingvoll municipality, 62°52′ N, 8°20′ E, Norway), during early summer of 2001. The effect of grazing by red deer on ground beetles (Carabidae) abundance and diversity was investigated across a gradient of grazing pressures. We trapped ground beetles by pit-fall traps from three homogeneous winter grazing areas (ungrazed, medium grazed, heavily grazed). Bilberry Vaccinium myrtillus (the main winter food for red deer) was sampled and its dry weight was measured for the three locations. Gradient analyses showed that grazing by red deer affects carabid species composition. Grazing significantly affected the amount of bilberry, which correlated with species variation. According to our predictions, we found a higher abundance of carabids in the heavily grazed location, but the species richness and the diversity indices were similar for the three areas. This study shows that overall species composition is altered along a gradient as consequence of red deer winter grazing and that red deer act as ecosystem engineer, by reducing the bilberry heather which dominates the field layer in early summer.     

Rejection of artificial cuckoo (Cuculus canorus) eggs in relation to variation in egg appearance among reed warblers (Acrocephalus scirpaceus)

Passerines that are exposed to brood parasitism can evolve reduced intraclutch variation in egg appearance to facilitate recognition and rejection of the parasitic egg. This has been shown to be true for European passerine species that are assumed to have participated in an evolutionary arms race with the cuckoo (Cuculus canorus). However, few investigations have been carried out with the aim of finding out whether there is a relationship between these two traits within a species. In this study, we compare the level of intraclutch variation in egg appearance and the rejection of an unlike parasitic egg within a population of reed warblers (Acrocephalus scirpaceus) in the south-eastern part of the Czech Republic. We parasitized reed warbler nests with an artificial non-mimetic cuckoo egg, and then monitored the reaction of the hosts. In 27 out of 48 nests (56.3%) the parasitic egg was rejected. The rejecter pairs had a statistically significantly lower intraclutch variation in egg appearance than the acceptor pairs. We discuss possible explanations for the observed relationship between rejection of unlike eggs and intraclutch variation in egg appearance within this population of reed warblers. The results are consistent with the evolutionary arms race hypothesis, but the intermediate rejection rate found in this population could also be maintained by an equilibrium between acceptors and rejecters due to rejection costs.     

Nest defence,enemy recognition and nest inspection behaviour of experimentally parasitized Reed Warblers Acrocephalus scirpaceus

Capsule Reed Warblers in a regularly parasitized population do not recognize Cuckoo Cuculus canorus as a special enemy and do not change their behaviour at nest immediately after being parasitized.

Aims To assess if an intruder near the nest influences the behaviour of the Cuckoo host.

Methods Host responses to Cuckoo, control Pigeon dummies and human intruder were observed. Host behaviour at 71 nests was video-recorded for 30 minutes at four experimental groups of nests: Cuckoo dummy, Cuckoo dummy + Cuckoo egg, Pigeon dummy, human intruder.

Results Reed Warblers did not respond differently to the Cuckoo and the control species. The experimental procedure had no significant effect on the behaviour of hosts during the study period. We were unable to find any differences in the time spent at the nest, clutch inspection behaviour and nest defence behaviour between morning and afternoon experimental groups. Our results do not support the hypothesis that afternoon laying by the Cuckoo is maintained by a selection pressure from the host. We observed no ejection or egg-pecking during the 30-min period after the experimental parasitism.

Conclusions Low aggression and non-specificity of host responses in our study area are in line with the fact that the Reed Warbler is an intermediate rejecter of Cuckoo eggs as expected from the spatial habitat structure hypothesis.     

UV reflectance as a cue in egg discrimination in two Prinia species exploited differently by brood parasites in Taiwan

Birds are capable of seeing the ultraviolet light (UV) spectrum and as a consequence have evolved UV‐reflective structures with signalling functions. Avian eggs also reflect in the UV spectrum but the importance of UV egg matching in egg rejection decisions has been equivocal. Here we conducted egg rejection experiments in the congeneric and sympatrically breeding Yellow‐bellied Prinia Prinia flaviventris and Plain Prinia Prinia inornata in Taiwan to assess the role of UV as a cue in egg discrimination. Yellow‐bellied Prinia is a host of Oriental Cuckoo Cuculus optatus, whereas Plain Prinia is not. We coated one prinia egg in the experimental clutches with a cream containing a UV‐blocking agent, while the rest of the eggs were coated with cream only. We also experimentally parasitized prinias with non‐mimetic model eggs with reduced UV reflectance. Yellow‐bellied Prinia and Plain Prinia rejected their own UV‐blocked eggs in 18.2 and 8.3% of the experiments, respectively, and the difference was not significant. However, Yellow‐bellied Prinia rejected 100% of the non‐mimetic eggs, whereas the Plain Prinia rejected only 5%. Hence, UV reflectance alone is a cue in egg discrimination, but the importance of reflectance outside the UV spectrum in these two prinia species is much more responsive to selection as a consequence of brood parasitism.     

Extra-pair paternity in relation to regional and local climate in an Arctic-breeding passerine

Reproductive processes are affected by local and regional climate variation. Birds breeding in the Arctic may experience strong energetic constraints, which will affect their reproductive output. Recent research has emphasized the importance of extra-pair copulation as a means of improving reproductive output. In this paper, we explore ecological and climatic determinants that may explain variation in extra-pair paternity (EPP) in an arctic-breeding passerine, the snow bunting Plectrophenax nivalis. EPP occurred in 10.8 % of the young and 20.9 % of the broods sampled from 1999 to 2003. We found that the proportion of extra-pair young in a nest was positively related to the body size and age of the social male and weakly negatively related to the local average minimum temperature prior to the onset of egg laying. These results suggest that older and larger males lost a larger share of paternity than smaller and younger males, and that the relative loss of paternity decreased with cold weather during the female’s fertile period. Large and old males spend less time mate guarding compared to small and young males and may allocate more time towards extra-pair forays, and thus lose more paternity in their own nest. Climatic conditions most likely constrain the total energy budget with less energy available for extra-pair activity in cold weather.     

The role of moose <Emphasis Type="Italic">Alces alces</Emphasis> L. in boreal forest – the effect on ground beetles (Coleoptera,Carabidae) abundance and diversity

The indirect effect of moose Alces alces browsing on ground beetle's abundance and diversity was investigated by pitfall trapping in a mixed coniferous forest in Vestfold County (59°19′ N, 9°50′ E, Norway), during the summer of 2002. Three areas with different browsing pressures, ranging from non- to medium- and heavily browsed were chosen and dry weight of bilberry Vaccinium myrtillus and humidity at ground level were measured in the three locations. As predicted, the gradient analyses showed that browsing by moose influenced the composition of carabid fauna, and that browsing intensity and humidity covaried with the most important gradient in carabid species composition found across the three locations. Species that live in light stands with rather dry soil, were more often captured in the browsed areas, whereas shade tolerant and hygrophilous species were more abundant in the non-browsed area. The carabid abundance increased significantly with increasing browsing pressure. According to our predictions, the diversity at trap level (α-diversity) was higher in the highly browsed area. Conversely, species turnover (β-diversity) decreased with browsing intensity. On the other hand, the rarefaction analysis showed that the regional species richness (γ-diversity) was considerably higher in the medium browsed area than in the heavily browsed one, which is consistent with the intermediate disturbance hypothesis. This study indicates that moose, by reducing the bilberry that constitutes the field layer in summer, affect carabid species composition and might be capable to reshape the whole ecosystem in our study area by a cascade effect.     

Reproductive success is strongly related to local and regional climate in the Arctic snow bunting (Plectrophenax nivalis)

Polar Biology - Global climate change is regarded as one of the major threats to biodiversity. Both local and regional climate parameters can have strong effects on ecological processes affecting...