| 1. |
- de la Hera, Ivan, et al.
(författare)
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How much variation in the molt duration of passerines can be explained by the growth rate of tail feathers?
- 2011
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Ingår i: The Auk. - : Oxford University Press (OUP). - 0004-8038 .- 1938-4254. ; 128:2, s. 321-329
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Tidskriftsartikel (refereegranskat)abstract
- In birds, molt duration is an important trait that can affect plumage functionality and, consequently, the fitness of individuals. However, knowledge about the factors that affect variation in molt speed is sparse, mostly because of the methodological difficulties of studying avian molt. We used a ptilochronology-based approach to estimate the rate at which tail feathers were produced during molt to shed light on the relationship between molt duration and feather growth rate. For that purpose, we used three data sets. First, we tested whether the average molt durations of 22 passerine species were correlated with the mean growth rates of their feathers, using both conventional and phylogenetically corrected statistical procedures. Second, we explored this same association among captive Great Tits (Pants major). And third, we took advantage of the biannual complete molt of Willow Warblers (Phylloscopus trochilus) to examine whether the feathers synthesized during their short summer molt grew faster than those produced during their long winter molt. Feather growth rates were negatively correlated with molt duration in all analyses, revealing that molt duration can be estimated from the growth rate of a single feather. However, predictive power was limited by the fact that molt duration is modulated mainly by molt intensity, which seems to be correlated with ecological constraints in our interspecific approach. We also discuss the implications of our results for the evolution of molt duration, and the potential application of ptilochronology in its study. Received 2 August 2010, accepted 21 December 2010.
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| 2. |
- De La Hera, Ivan, et al.
(författare)
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Inferring the migratory status of woodland birds usisng ringing data: the case of a constant-effort site located in the Iberian highlands.
- 2014
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Ingår i: Ardeola. - : Ardeola. - 0570-7358 .- 2341-0825. ; 61:1, s. 77-95
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the spatiotemporal distribution of birds is crucial for effective management and conservation of their populations. However, we still have only limited knowledge not only of the wintering destinations of many Iberian breeding migrants but also of aspects as general as the migratory behaviour of the populations of many common avian species that breed in the Iberian highlands. We used bird-ringing data to shed light on the migratory status (migratory, partially-migratory or sedentary) of the breeding populations of 13 common species occurring year-round in a woodland located on an Iberian plateau (Garaio,Araba, Spain; 574 m.a.s.l.), where ringing activities have been carried out over the last 20 years. To assess the extent to which birds breeding on this site remain in the area during winter and/or are replaced by conspecifics coming from other areas, we analysed: (1) changes in relative abundance of birds between summer and winter, (2) the frequency of sedentary individuals (birds captured both in summer and winter period in the study area) in relation to the number of individuals captured only in summer (summer visitors) or in winter (wintering birds), and (3) variation in wing length among summer, wintering and sedentary birds. Our results revealed great variation among species in the intensity of migratory behaviour, and a general arrival of foreign conspecifics during the winter for most of the species studied. Likewise, our study represents an illustrative example of how long-term ringing can be used to shed light on the migratory status of bird populations.
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| 3. |
- de la Hera, Ivan, et al.
(författare)
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Structural and Mechanical Differences between Original and Replaced Feathers in Blackcaps Sylvia Atricapilla
- 2010
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Ingår i: Ardeola. - 0570-7358. ; 57:2, s. 431-436
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Tidskriftsartikel (refereegranskat)abstract
- Many bird species are able to replace accidentally lost feathers out of the normal moulting periods, but whether such replaced feathers are able to restore the original mechanical properties of the plumage has not been evaluated before. In this study we analysed the structure and mechanical behaviour of the original and replaced feathers of 12 blackcaps Sylvia atricapilla. Replaced feathers showed wider rachis and greater density of barbs, but were lighter, shorter and less stiff than original feathers. These results suggest that replaced feathers are not able to fully restore the original functionality of feathers.
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| 4. |
- de la Hera, Ivan, et al.
(författare)
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Variation in the mechanical properties of flight feathers of the blackcap Sylvia atricapilla in relation to migration
- 2010
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Ingår i: Journal of Avian Biology. - 0908-8857. ; 41:3, s. 342-347
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Tidskriftsartikel (refereegranskat)abstract
- Migration causes temporal and energetic constraints during plumage development, which can compromise feather structure and function. In turn, given the importance of a good quality of flight feathers in migratory movements, selection may have favoured the synthesis of feathers with better mechanical properties than expected from a feather production constrained by migration necessities. However, no study has assessed whether migratory behaviour affects the relationship between the mechanical properties of feathers and their structural characteristics. We analysed bending stiffness (a feather mechanical property which is relevant to birds' flight), rachis width and mass (two main determinants of variation in bending stiffness) of wing and tail feathers in migratory and sedentary blackcaps Sylvia atricapilla. Migratory blackcaps produced feathers with a narrower rachis in both wing and tail, but their feathers were not significantly lighter; in addition, bending stiffness was higher in migratory blackcaps than in sedentary blackcaps. Such unexpected result for bending stiffness remained when we statistically controlled for individual variation in rachis width and feather mass, which suggests the existence of specific mechanisms that help migratory blackcaps to improve the mechanical behaviour of their feathers under migration constraints.
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| 5. |
- Perez-Rodriguez, Anton, et al.
(författare)
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Evolution of seasonal transmission patterns in avian blood-borne parasites
- 2015
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Ingår i: International Journal for Parasitology. - : Elsevier BV. - 0020-7519. ; 45:9-10, s. 605-611
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Tidskriftsartikel (refereegranskat)abstract
- In temperate regions, many vector-borne parasites maximise their transmission prospects by adjusting reproduction to seasonal cycles of host susceptibility and vector availability. Nevertheless, in these regions there are areas where environmental conditions are favourable throughout the year, so that parasites could benefit from a year-round transmission strategy. We analysed how different transmission strategies (strict summer transmission, extended summer transmission - including spring and autumn, and year round transmission) have evolved among the different genetic lineages of Haemoproteus parabelopolskyi, an avian blood-borne parasite shared by three sibling species of passerine hosts. Our results indicate that the ancestral state of this clade of parasites had a strict summer transmission with the blackcap (Sylvia atricapilla) as the host. Other transmission strategies and switches to the other host species (Sylvia abyssinica and Sylvia born) evolved recently, several times, independently. This suggests that, although year-round transmission is ecologically successful at present, seasonal transmission may have become more stable over evolutionary time. Switches from strict summer to an extended or year-round transmission strategy could have ecological consequences, if they promote the spread of parasites into more distant regions, transported by the migrating bird hosts. Therefore, a deeper knowledge of how different parasite transmission strategies are structured among birds in temperate areas is essential for understanding how disease emergence risks may develop in the future. (C) 2015 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.
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