| 1. |
- Klaassen, Raymond, et al.
(författare)
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Loop migration in adult marsh harriers Circus aeruginosus, as revealed by satellite telemetry
- 2010
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Ingår i: Journal of Avian Biology. - 0908-8857 .- 1600-048X. ; 41:2, s. 200-207
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Tidskriftsartikel (refereegranskat)abstract
- Loop migration among birds is characterized by the spring route lying consistently west or east of the autumn route. The existence of loops has been explained by general wind conditions or seasonal differences in habitat distribution. Loop migration has predominantly been studied at the population level, for example by analysing ring recoveries. Here we study loop migration of individual marsh harriers Circus aeruginosus tracked by satellite telemetry. We show that despite a generally narrow migration corridor the harriers travelled in a distinct clockwise loop through Africa and southern Europe, following more westerly routes in spring than in autumn. We used the Normalized Difference Vegetation Index (NDVI) to identify potential feeding habitat in Africa. Suitable habitat seemed always more abundant along the western route, both in spring and autumn, and no important stopover site was found along the eastern route. Observed routes did thus not coincide with seasonal variation in habitat availability. However, favourable habitat might be more important during spring migration, when the crossing of the Sahara seems more challenging, and thus habitat availability might play an indirect role in the harriers' route choice. Grid-based wind data were used to reconstruct general wind patterns, and in qualitative agreement with the observed loop marsh harriers predominantly encountered westerly winds in Europe and easterly winds in Africa, both in autumn and in spring. By correlating tail- and crosswinds with forward and perpendicular movement rates, respectively, we show that marsh harriers are partially drifted by wind. Thus, we tentatively conclude that wind rather than habitat seems to have an overriding effect on the shape of the migration routes of marsh harriers. General wind conditions seem to play an important role also in the evolution of narrow migratory loops as demonstrated for individual marsh harriers.
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| 2. |
- Larson, Keith W., 1968-, et al.
(författare)
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Inferring the ecology of willow warblers during their winter moult by sequential stable isotope analyses of remiges
- 2013
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Ingår i: Journal of Avian Biology. - 0908-8857 .- 1600-048X. ; 44:6, s. 561-566
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Tidskriftsartikel (refereegranskat)abstract
- We present a comparison of feather stable isotope (δ13C, δ15N) patterns representing the habitat and diet conditions for two subspecies of willow warblers Phylloscopus trochilus that breed in parapatry, but winter in different regions of sub-Saharan Africa. Previous analyses have shown that on average winter moulted innermost primaries (P1) show subspecific differences in δ15N values, although individuals show substantial variation for both δ13C and δ15N within the subspecies. We examined whether corresponding variation in the timing of the winter moult, as reflected by consistent intra-wing correlations for individual's δ13C and δ15N values, could explain some of the previously observed isotopic variation. Further, differential subspecific adaptations to winter precipitation patterns across Africa might result in a variable degree of site fidelity or itinerancy during moult. We found no consistent trend in isotopic values from innermost to outermost primaries, thus inter-individual variation in the timing of moult does not explain the subspecific isotopic variation for P1. Patterns in wing feather δ13C and δ15N values indicated that 41% of the individuals from both subspecies shifted their diet or habitats during winter moult. Importantly, despite well-documented itinerancy in willow warblers during the winter, 59% of the individuals had feather isotope values consistent with stable use of habitats or diets during winter moult. Repeatability analyses suggest that individuals of both subspecies initiate moult in similar habitats from year-to-year while feeding on isotopically similar diets.
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| 3. |
- Berglund, Åsa M. M., et al.
(författare)
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Antioxidant status in relation to age, condition, reproductive performance and pollution in three passerine species
- 2014
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Ingår i: Journal of Avian Biology. - 0908-8857 .- 1600-048X. ; 45:3, s. 235-246
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Tidskriftsartikel (refereegranskat)abstract
- Oxidative stress has been suggested as a mediator in life-history trade-off. By spending more resources on for example reproduction an organism might sacrifice its antioxidant defence. So far, most conclusions on trade-offs between life-history traits and oxidative stress have been drawn from laboratory studies using a few model species and there is a need for studies conducted in natural settings. We investigated associations between markers for antioxidant status (antioxidant enzyme activities and antioxidant levels), body condition, age and reproduction in three species of wild-living passerines. The impact from an anthropogenic stressor (metal pollution) was also assessed. The three bird species showed interspecific variation in their SOD and CAT activities, indicating different pathways to eliminate radicals. The age of females affected both antioxidant status and the breeding performance, indicating the importance of age as a factor in life-history studies. Old birds had lower levels of antioxidants/antioxidant enzyme activities and they produced larger broods/more successful broods, though the latter might be confounded by surviving females having increased fitness. Metal exposure had a negative impact on breeding, and improved breeding outcome was also associated with increased antioxidant defence, but metal exposure was not directly related to the oxidative status of birds, emphasizing that additional stressors might independently affect the same traits. Our results highlight that caution has to be taken when generalizing and extrapolating results to even closely related species. The results support the idea that there is a cost of reproduction, in terms of increased resources spent on antioxidant defence, though this should be confirmed with experimental studies.
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| 4. |
- Evans, Simon R., et al.
(författare)
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Seasonality of carotenoid-based plumage coloration : modelling wavelength-specific change through spectral reconstruction
- 2012
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Ingår i: Journal of Avian Biology. - 0908-8857 .- 1600-048X. ; 43:3, s. 234-243
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Tidskriftsartikel (refereegranskat)abstract
- Plumage coloration has provided important model systems for research on signal expression. Whilst it had previously been assumed that moulting provided the only mechanism to change plumage coloration, recent studies have shown plumage colours to be seasonally dynamic, with implications both for the quantification of expression and for any signalling role. However, the mechanistic processes underlying such change remain uncertain. Here, we describe within-moult shifts in expression of a carotenoid-based colour trait the yellow ventral plumage of the great tit Parus major over a nine-month timespan. We report that plumage chromaticity (colour) but not achromaticity (brightness) exhibits a marked seasonal decline, independent of sex, age or body condition, and at a constant rate across twelve environmentally heterogeneous plots within our study site. To gain a greater understanding of the mechanisms underlying this change we employed a spectral reconstruction approach, that generates predicted spectra for any timepoint within the sampling period. By comparing spectra for both early and late in the moult we show that the seasonal decline in chromaticity is driven by both a marked reduction in ultraviolet (UV) reflectance and, to a lesser extent, loss of active carotenoid pigments. Thus, our study shows that seasonal loss of chromaticity in the great tit is driven by altered reflectance primarily in the UV section of the spectrum, a finding made possible by the use of spectral compartmentalisation and multi-parallel modelling to produce reconstructed spectra. Whether change in plumage coloration influences signal function will depend on the dynamics of the signalling system but it could clearly inflate patterns such as assortative mating and should be considered in studies of colour expression.
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| 5. |
- Low, Matthew
(författare)
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Impact of temperature on the breeding performance and selection patterns in lesser kestrels Falco naumanni
- 2012
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Ingår i: Journal of Avian Biology. - 0908-8857 .- 1600-048X. ; 43, s. 472-480
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Tidskriftsartikel (refereegranskat)abstract
- Adjusting breeding phenology to climate fl uctuations can be problematic for migratory birds as they have to accountfor local environmental conditions on the breeding grounds while migrating from remote wintering areas. Predictinggeneral responses to climate change is not straightforward, because these responses vary between migrant species due to thespecies-specifi c ecological drivers of breeding behaviour. Th erefore more information is needed on species with diff erentecological requirements, including data on heritability of migration, factors driving phenological changes and how climateaff ects selection pressures.Here, we measure heritability in settlement dates and the eff ect of local climate at the breeding grounds on settlementdates, reproductive success and selection patterns in a French population of a trans-Saharan migratory insectivorous raptor,the lesser kestrel Falco naumanni , monitored and ringed since 1996.Heritability of settlement dates was low (0.07 0.03), indicating a weak evolutionary potential. Nevertheless,plasticity in settlement dates in response to temperatures allowed earlier settlement when early spring was warmer thanaverage. Reproductive success and selection patterns were strongly aff ected by temperature during settlement and chickrearing respectively. Warmer spring decreased selection for earlier settling and warmer early summer increased reproductivesuccess. Interestingly, selection for earlier settling was more intense in cooler springs, contrasting with patterns frompasserines lagging behind food peaks.Altogether, these results suggest a positive eff ect of warmer temperatures on breeding performances of lesser kestrelsmost likely because the French population is at the coolest boundary of the species European breeding range.
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| 6. |
- Morales, Judith, et al.
(författare)
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Variation in eggshell traits between geographically distant populations of pied flycatchers Ficedula hypoleuca
- 2013
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Ingår i: Journal of Avian Biology. - 0908-8857 .- 1600-048X. ; 44:2, s. 111-120
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Tidskriftsartikel (refereegranskat)abstract
- The expression and impact of maternal effects may vary greatly between populations and environments. However, little is known about large-scale geographical patterns of variation in maternal deposition to eggs. In birds, as in other oviparous animals, the outermost maternal component of an egg is the shell, which protects the embryo, provides essential mineral resources and allows its interaction with the environment in the form of gas exchange. In this study, we explored variation of eggshell traits (mass, thickness, pore density and pigmentation) across 15 pied flycatcher populations at a large geographic scale. We found significant between-population variation in all eggshell traits, except in pore density, suggesting spatial variation in their adaptive benefits or in the females' physiological limitations during egg laying. Between- population variation in shell structure was not due to geographic location (latitude and longitude) or habitat type. However, eggshells were thicker in populations that experienced higher ambient temperature during egg laying. This could be a result of maternal resource allocation to the shell being constrained under low temperatures or of an adaptation to reduce egg water loss under high temperatures. We also found that eggshell colour intensity was positively associated with biliverdin pigment concentration, shell thickness and pore density. To conclude, our findings reveal large- scale between-population variation of eggshell traits, although we found little environmental dependency in their expression. Our findings call for further studies that explore other environmental factors (e.g. calcium availability and pollution levels) and social factors like sexual selection intensity that may account for differences in shell structure between populations.
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| 7. |
- Podmokla, Edyta, et al.
(författare)
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Avian malaria is associated with increased reproductive investment in the blue tit
- 2014
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Ingår i: Journal of Avian Biology. - 0908-8857 .- 1600-048X. ; 45:3, s. 219-224
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Tidskriftsartikel (refereegranskat)abstract
- Haemosporidians causing avian malaria are very common parasites among bird species. Their negative effects have been repeatedly reported in terms of deterioration in survival prospects or reproductive success. However, a positive association between blood parasites and avian fitness has also been reported. Here, we studied a relationship between presence of malaria parasites and reproductive performance of the host, a hole-breeding passerine - the blue tit Cyanistes caeruleus. Since the malaria parasites might affect their hosts differently depending on environmental conditions, we performed brood size manipulation experiment to differentiate parental reproductive effort and study the potential interaction between infection status and brood rearing conditions on reproductive performance. We found individuals infected with malaria parasites to breed later in the season in comparison with uninfected birds, but no differences were detected in clutch size. Interestingly, infected parents produced heavier and larger offspring with stronger reaction to phytohemagglutinin. More importantly, we found a significant interaction between infection status and brood size manipulation in offspring tarsus length and reaction to phytohemagglutinin: presence of parasites had stronger positive effect among birds caring for experimentally enlarged broods. Our results might be interpreted either in the light of the parasite-mediated selection or terminal investment hypothesis.
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| 8. |
- Väli, Ulo, et al.
(författare)
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Microsatellites and single nucleotide polymorphisms in avian hybrid identification : a comparative case study
- 2010
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Ingår i: Journal of Avian Biology. - 0908-8857 .- 1600-048X. ; 41:1, s. 34-49
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Tidskriftsartikel (refereegranskat)abstract
- The correct identification of hybrids is essential in avian hybridisation studies, but selection of the appropriate set of genetic markers for this purpose is at times complicated. Microsatellites and single nucleotide polymorphisms (SNPs) are currently the most commonly used markers in this field. We compare the efficiency of these two marker types, and their combination, in the identification of the threatened avian species, the greater spotted eagle and the lesser spotted eagle, as well as hybrids between the two species. We developed novel SNP markers from genome-wide distributed 122 candidate introns using only sympatric samples, and tested these markers successfully in 60 sympatric and allopatric spotted eagles using Bayesian model-based approaches. Comparatively, only one out of twelve previously described avian nuclear intron markers showed significant species-specific allele frequency difference, thus stressing the importance of selecting the proper markers. Twenty microsatellites outperformed selected nine SNPs in species identification, but were poorer in hybrid detection, whereas the resolution power of ten microsatellites remained too low for correct assignment. A combination of SNPs and microsatellites resulted in the most efficient and accurate identification of all individuals. Our study shows that the use of various sets of markers could lead to strikingly different assignment results, hybridisation studies may have been affected by too low a resolution power of used markers, and that an appropriate set of markers is essential for successful hybrid identification.
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| 9. |
- Brodin, Anders, et al.
(författare)
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Gene-flow across the European crow hybrid zone - a spatial simulation
- 2013
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Ingår i: Journal of Avian Biology. - 0908-8857. ; 44:3, s. 281-287
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Tidskriftsartikel (refereegranskat)abstract
- In hybrid zones populations that are otherwise allopatric meet and produce hybrids. One of the most well-known hybrid zones occurs throughout much of Europe between the hooded and carrion crows. Even though these species (or subspecies) of crows look very different, genetic differentiation is weak, and introgression seems to be common. In a spatial simulation that was based on empirically estimated values, we investigated how introgressing alleles that would confer some fitness advantage would flow across the zone. The advantage was assumed to be some unknown factor that enhanced survival for carriers relative to non-carriers. We varied the yearly survival advantage between 0 to 10% and recorded how this would affect zone shape and position. In the simulation we cycled yearly' events such as reproduction, mortality and juvenile dispersal. We started the simulation by equipping all individuals of one crow type outside the zone with a homozygotic set of the beneficial allele. At all levels of advantage the allele first rapidly became fixed in the donator crow type, then transgressed into the receiving type more slowly and finally became fixed in all individuals. The time until fixation varied from around 176 yr for a 10% advantage to around 20 000 yr for 0% advantage. An exciting discovery was that the position of the zone would move during the introgression but then stop. The reason is that the beneficial allele would be common in the donating type but not in the receiving type during the introgression event. At large the crow hybrid zone appears to have been stable for a long time but there have been small recent northward movements of carrion crows in both Scotland and Denmark. We suggest that introgression by itself is a factor that should be considered as an explanation for why hybrid zones move temporarily.
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| 10. |
- 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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