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Arizaga J.,Institute For Vogelforschung Vogelwarte Helgoland | Barba E.,University of Valencia | Alonso D.,Oficina de Anillamiento de Aranzadi | Vilches A.,Oficina de Anillamiento de Aranzadi | Vilches A.,University of Navarra
Ardeola | Year: 2010

Fuel management and stopover duration are parameters of great interest for the understanding of bird migration strategies. Our aim was to study the stopover of bluethroats Luscinia svecica cyanecula in northern Iberia. Data were collected at Badina de Escudera lagoon (reedbeds), Villafranca (42° 16' N 01° 42' W), Ebro Valley. Systematic mist-netting was performed during the autumn migration period between 2003 and 2006. The timing of passage did not vary between age and sex classes, with the bulk of migrants being captured in September. The stopover duration was very long (nearly 30 days) compared to that reported from other stopover sites. Main causes explaining these results could be: (i) an atypical September with unfavourable meteorological conditions, and (ii) the interference of apparently wintering specimens. Apart from a small fraction of birds with very large fuel loads, a mean fuel load of nearly 15 % over lean mass suggests that, if a fraction of migrants stopping-over in Badina overwinter in tropical Africa, they must refuel in areas further south to gain sufficient fuel before crossing the Sahara. Conversely, we cannot rule out that these less loaded birds overwintered within the circum-Mediterranean region. Adults were more fuel loaded than juveniles, but this was not due to a higher fuel deposition rate (mean 0.08 g/day). Bluethroats recaptured from 6 to 10 days after the first capture showed a higher mass deposition rate than those recaptured after 10 days or more. This suggests that birds with long stopovers were not true fuelling migrants, but more probably wintering specimens with balanced energy budgets. A long initial lost of mass (5 days) agrees with both the high competition and the interference of wintering specimens hypotheses. In conclusion, Badina de Escudera, in northern Iberia, is an area used by a true, stopping-over population, as well as by apparently wintering specimens.

Benito M.M.,University of Barcelona | Gonzalez-Solis J.,University of Barcelona | Becker P.H.,Institute For Vogelforschung Vogelwarte Helgoland
Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology | Year: 2011

Carotenoids, as pigments with antioxidant and immunoregulatory properties, play a crucial role in developing chicks. Carotenoids must be acquired through diet and are relatively scarce, suggesting that their availability is a limiting factor leading to a trade-off between colour displays and physiological functions. However, potential differences in this trade-off between male and female chicks have been little studied. We manipulated carotenoid availability in 9 days old common tern Sterna hirundo chicks by supplementing their fish diet with four carotenoids during 9 days. Our aim was to examine sex-specific responses to the experimental increase of dietary carotenoids on plasma circulation, physiological and condition variables and successful fledging. Furthermore, to explore the functional and evolutionary basis of the trade-off, we studied the relationships among carotenoid concentration, mediated immune response and foot colouration. After treatment, control chicks showed decreasing plasma levels for most carotenoid types, whereas supplemented chicks had strong increases. Colour luminosity and saturation increased in both treatment groups, while hue only changed significantly towards redder feet in supplemented females. Supplemented chicks presented neither different T-cell-mediated immunity nor other differences compared to control chicks. Nevertheless, supplemented females showed tendencies towards decreased immune responses and increased δ15N signatures, and supplemented males towards greater body mass. Our results indicate colouration may have, in females, a signalling function as to compensate for immunological costs. In males, additional availability of carotenoids may contribute to improve the body condition. This study suggests that trade-off responses to carotenoid availability are sex-specific in tern chicks. Thus, parental carotenoid supply to chicks may be an unrecognised component in sex allocation. © 2010 Springer-Verlag.

Benito M.M.,University of Barcelona | Schielzeth H.,Bielefeld University | Gonzalez-Solis J.,University of Barcelona | Becker P.H.,Institute For Vogelforschung Vogelwarte Helgoland
Journal of Avian Biology | Year: 2013

Adaptive sex allocation has frequently been studied in sexually size dimorphic species, but far less is known about patterns of sex allocation in species without pronounced sexual size dimorphism. Parental optimal investment can be predicted under circumstances in which sons and daughters differ in costs and/or fitness returns. In common terns Sterna hirundo, previous studies suggest that sons are the more costly sex to produce and rear. We investigated whether hatching and fledging sex ratio and sex-specific chick mortality correlated with the ecological environment (laying date, clutch size, hatching order and year quality) and parental traits (condition, arrival date, experience and breeding success), over seven consecutive years. Population-wide sex ratios and sex-specific mortality did not differ from parity, but clutch size, mass of the father, maternal breeding experience and to some extent year quality correlated with hatching sex ratio. The proportion of sons tended to increase in productive years and when the father was heavier, suggesting the possibility that females invest more in sons when the environmental and the partner conditions are good. The proportion of daughters increased with clutch size and maternal breeding experience, suggesting a decline in breeding performance or a resources balance solved by producing more of the cheaper sex. No clear patterns of sex-specific mortality were found, neither global nor related to parental traits. Our results suggest lines for future studies on adaptive sex allocation in sexually nearly monomorphic species, where adjustment of sex ratio related to parental factors and differential allocation between the offspring may also occur. © 2013 The Authors. Journal of Avian Biology © 2013 Nordic Society Oikos.

Korner-Nievergelt F.,Schweizerische Vogelwarte | Huppop O.,Institute For Vogelforschung Vogelwarte Helgoland
Vogelwarte | Year: 2010

Publishing ornithological data requires the application of adequate statistical methods. With the improvement of methods, software requirements are arising, but available proprietary programs are often far beyond the financial limits of the users. The statistic package R is a free but nevertheless very sophisticated alternative. Regrettably, it is not easy to get started with R since it is not clickable and needs the typing of code. This article is a step by step introduction for R-beginners. The reader can experience the input of data, their handling and visualisation at his computer. We guide the user through a t-test and develop a simple linear model including analysis of residuals. Finally, we suggest books for further reading. © DO-G, IfV, MPG 2010.

Saino N.,University of Milan | Ambrosini R.,University of Milan Bicocca | Rubolini D.,University of Milan | Von Hardenberg J.,CNR Institute of Neuroscience | And 8 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2011

Climate is changing at a fast pace, causing widespread, profound consequences for living organisms. Failure to adjust the timing of life-cycle events to climate may jeopardize populations by causing ecological mismatches to the life cycle of other species and abiotic factors. Population declines of some migratory birds breeding in Europe have been suggested to depend on their inability to adjust migration phenology so as to keep track of advancement of spring events at their breeding grounds. In fact, several migrants have advanced their spring arrival date, but whether such advancement has been sufficient to compensate for temporal shift in spring phenophases or, conversely, birds have become ecologically mismatched, is still an unanswered question, with very few exceptions. We used a novel approach based on accumulated winter and spring temperatures (degree-days) as a proxy for timing of spring biological events to test if the progress of spring at arrival to the breeding areas by 117 European migratory bird species has changed over the past five decades. Migrants, and particularly those wintering in sub-Saharan Africa, now arrive at higher degree-days and may have therefore accumulated a 'thermal delay', thus possibly becoming increasingly mismatched to spring phenology. Species with greater 'thermal delay' have shown larger population decline, and this evidence was not confounded by concomitant ecological factors or by phylogenetic effects. These findings provide general support to the largely untested hypotheses that migratory birds are becoming ecologically mismatched and that failure to respond to climate change can have severe negative impacts on their populations. The novel approach we adopted can be extended to the analysis of ecological consequences of phenological response to climate change by other taxa. © 2010 The Royal Society.

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