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- Monti, Flavio, et al.
(författare)
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Migration distance affects stopover use but not travel speed : contrasting patterns between long- and short-distance migrating ospreys
- 2018
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Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857. ; 49:10
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Tidskriftsartikel (refereegranskat)abstract
- The development of migratory behaviour is a continuous process which is not only determined by genes, but also moulded by individual differences based on life-history variations occurring at each ontogenetic stage. Assessing consistency and plasticity in migratory traits between long distance (LDM) and short distance migratory (SDM) populations within the same species that may express dissimilarities in the leeway of annual schedules is essential to understand the evolution and ontogeny of migratory strategies. We studied the migration strategies in autumn regarding flight speed and the use of stopovers (number and duration of stop-overs across the whole journey) at the intra-specific level, by tracking with GPS loggers the intercontinental migration of 43 adult and juvenile ospreys Pandion haliaetus from both LDM and SDM populations. LDM ospreys travelled distances five times larger than SDM ospreys, but their total migration speed was 2.4 times slower. While daily distance travelled did not differ between populations, the reduced total migration speed by LDMs was due to higher stopover use compared to SDM birds. SDM birds used more direct routes, crossing open sea at higher flight speeds, even though both populations largely benefitted from wind assistance across their journey. Across populations, adult birds travelled longer distances per day and displayed less sinuous migratory paths than juveniles, suggesting that migratory capabilities improve with age and experience of the bird. Overall, the time constraint related to total migration distance was not the main driver of the total migration speed, and other factors such as physiological needs to rest and refuel at stopover sites may play an important role. Our study underlines the importance of investigating variability in migration strategies in partially migratory species, for a better understanding of avian migratory ecology.
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| 3. |
- Sumasgutner, Petra, et al.
(författare)
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Integument colouration and circulating carotenoids in relation to urbanisation in Eurasian kestrels (Falco tinnunculus)
- 2023
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Ingår i: Science of Nature. - 0028-1042. ; 110
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Tidskriftsartikel (refereegranskat)abstract
- Urbanisation is one of the biggest environmental challenges of our time, yet we still lack an integrative understanding of how cities affect behaviour, physiology and parasite susceptibility of free-living organisms. In this study, we focus on carotenoids, strictly dietary micronutrients that can either be used as yellow-red pigments, for integument colouration (signalling function), or as antioxidants, to strengthen the immune system (physiological function) in an urban predator, the Eurasian kestrel (Falco tinnunculus). Kestrels are specialised vole hunters but shift to avian prey in cities where diurnal rodents are not sufficiently available. This different foraging strategy might determine the quantity of carotenoids available. We measured integument colouration, circulating carotenoids in the blood and ectoparasite burden in kestrels along an urban gradient. Our results showed that nestlings that were raised in more urbanised areas displayed, unrelated to their ectoparasite burden, a paler integument colouration. Paler colours were furthermore associated with a lower concentration of circulating carotenoids. These findings support the hypothesis that the entire urban food web is carotenoid deprived and only prey of low quality with low carotenoid content is available (e.g. fewer carotenoids in urban trees, insects, small birds and finally kestrels). The alternative hypothesis that nestlings allocate carotenoids to reduce physiological stress and/or to cope with parasites rather than invest into colouration could not be supported. Our study adds to existing evidence that urban stressors negatively affect carotenoid production in urban areas, a deficiency that dissipate into higher trophic levels.
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