| 1. |
- Berglund, Åsa M. M., et al.
(författare)
-
Antioxidant status in relation to age, condition, reproductive performance and pollution in three passerine species
- 2014
-
Ingår i: Journal of Avian Biology. - 0908-8857 .- 1600-048X. ; 45:3, s. 235-246
-
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.
|
|
| 2. |
- Brodin, Anders, et al.
(författare)
-
Gene-flow across the European crow hybrid zone - a spatial simulation
- 2013
-
Ingår i: Journal of Avian Biology. - 0908-8857. ; 44:3, s. 281-287
-
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.
|
|
| 3. |
- de la Hera, Ivan, et al.
(författare)
-
Variation in the mechanical properties of flight feathers of the blackcap Sylvia atricapilla in relation to migration
- 2010
-
Ingår i: Journal of Avian Biology. - 0908-8857. ; 41:3, s. 342-347
-
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.
|
|
| 4. |
- Evans, Simon R., et al.
(författare)
-
Seasonality of carotenoid-based plumage coloration : modelling wavelength-specific change through spectral reconstruction
- 2012
-
Ingår i: Journal of Avian Biology. - 0908-8857 .- 1600-048X. ; 43:3, s. 234-243
-
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.
|
|
| 5. |
- Haas, Fredrik, et al.
(författare)
-
Habitat preferences and positive assortative mating in an avian hybrid zone
- 2010
-
Ingår i: Journal of Avian Biology. - 0908-8857. ; 41:3, s. 237-247
-
Tidskriftsartikel (refereegranskat)abstract
- The relatively narrow hybrid zone between hooded and carrion crow is characterised by a high proportion of breeding hybrids, no known intrinsic postzygotic costs, and most likely, high gene flow between populations. It is therefore of interest to identify factors preventing a breakdown of the zone. In this study, we investigate the possibility that habitat choice could create assortative mating in the German-Danish part of the zone. In a GIS analysis, we used two approaches to investigate the role of habitat selection in the maintenance of this zone. We tested if there are 1) any correlations between habitat and the shape of the hybrid zone, and 2) any differences in habitat preferences between territorial individuals of the crow phenotypes. The most extensive habitat, non-irrigated arable land (Habitat 1), which covers almost 50% of the area in the zone was preferred by all three phenotypes (carrion, hooded and hybrid crows), but showed no change in frequency across the zone. Pastures (Habitat 2) and agricultural areas mixed with natural vegetation (Habitat 4) correlated with the shape of the zone, but only H4 differed in preference between the crow phenotypes. H4 was preferred by hybrids and hooded crows, but not by carrion crows. This habitat is present only in 17% of the hooded crow territories, and thus, it is not likely to have a strong influence on the maintenance of the hybrid zone. There was evidence of assortative mating in pure phenotypes, whereas hybrids showed no consistent mating pattern. Because our GIS analyses suggest that species specific habitat preferences are not involved in shaping the assortativeness, we discuss other possible mechanisms.
|
|
| 6. |
- Henningsson, Per, et al.
(författare)
-
How swift are swifts Apus apus?
- 2010
-
Ingår i: Journal of Avian Biology. - 0908-8857. ; 41:1, s. 94-98
-
Tidskriftsartikel (refereegranskat)abstract
- Swifts Apus apus are renowned for their fast flight manner which has fascinated people in all times. However, previous studies of swifts in flight during migration and roosting flights have shown that the birds operate over a narrow range of flight speeds compared with most other birds studied. In this study we have focused on the special flight behavior often called 'screaming parties'. During these flights the birds appear to reach very high speeds and therefore we used a stereo high speed camera setup to measure the flight speeds of the birds during this behavior with high accuracy. The birds were found to fly at much higher speeds during 'screaming parties' than during migration or roosting, on average twice as fast, 20.9 ms-1 (+/- 5.1 ms-1) in horizontal speed. The highest record was 31.1 ms-1 which is the highest measured yet for a swift in self powered flight. Furthermore, the birds were performing steep climbing flights, on average 4.0 ms-1 (+/- 2.8 ms-1) in vertical velocity. A clear trade-off between horizontal speed and vertical speed was found, suggesting that the birds are operating at their maximum.
|
|
| 7. |
- Karell, Patrik, et al.
(författare)
-
Brown tawny owls moult more flight feathers than grey ones
- 2013
-
Ingår i: Journal of Avian Biology. - 0908-8857. ; 44:3, s. 235-244
-
Tidskriftsartikel (refereegranskat)abstract
- The mechanisms by which melanin-based colour polymorphism can evolve and be maintained in wild populations are poorly known. Theory predicts that colour morphs have differential sensitivity to environmental conditions. Recently it has been proposed that colour polymorphism covaries genetically with intrinsic and behavioural properties. Plumage moult is a costly and crucial somatic maintenance function in birds. We used a long-term data set consisting of 761 observations on 307 individuals captured between 1985 and 2010 to examine differences in partial flight feather moult between grey (pale) and brown (pheomelanic dark) colour morphs of the tawny owl. We find that the brown morph consistently moult more primary flight feathers than the grey morph whereas there is no clear difference between colour morphs in the moulting of secondary feathers. Contrary to expectations, the difference in the number of moulted flight feathers between the morphs was independent of environmental conditions, as quantified by the abundance of prey. We discuss the potential physiological and behavioural causes for and costs of the observed difference in maintenance functions between colour morphs.
|
|
| 8. |
- Klaassen, Raymond, et al.
(författare)
-
Loop migration in adult marsh harriers Circus aeruginosus, as revealed by satellite telemetry
- 2010
-
Ingår i: Journal of Avian Biology. - 0908-8857 .- 1600-048X. ; 41:2, s. 200-207
-
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.
|
|
| 9. |
- Larson, Keith W., 1968-, et al.
(författare)
-
Inferring the ecology of willow warblers during their winter moult by sequential stable isotope analyses of remiges
- 2013
-
Ingår i: Journal of Avian Biology. - 0908-8857 .- 1600-048X. ; 44:6, s. 561-566
-
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.
|
|
| 10. |
- Lehikoinen, Aleksi, et al.
(författare)
-
Common montane birds are declining in northern Europe
- 2014
-
Ingår i: Journal of Avian Biology. - 0908-8857. ; 45:1, s. 3-14
-
Tidskriftsartikel (refereegranskat)abstract
- Large-scale multi-species data on population changes of alpine or arctic species are largely lacking. At the same time, climate change has been argued to cause poleward and uphill range shifts and the concomitant predicted loss of habitat may have drastic effects on alpine and arctic species. Here we present a multi-national bird indicator for the Fennoscandian mountain range in northern Europe (Finland, Sweden and Norway), based on 14 common species of montane tundra and subalpine birch forest. The data were collected at 262 alpine survey plots, mainly as a part of geographically representative national breeding bird monitoring schemes. The area sampled covers around 1/4 million km(2), spanning 10 degrees of latitude and 1600 km in a northeast-southwest direction. During 2002-2012, nine of the 14 bird species declined significantly in numbers, in parallel to higher summer temperatures and precipitation during this period compared to the preceding 40 yr. The population trends were largely parallel in the three countries and similar among montane tundra and subalpine birch forest species. Long-distance migrants declined less on average than residents and short-distance migrants. Some potential causes of the current decline of alpine birds are discussed, but since montane bird population sizes may show strong natural annual variation due to several factors, longer time series are needed to verify the observed population trends. The present Fennoscandian monitoring systems, which from 2010 onwards include more than 400 montane survey plots, have the capacity to deliver a robust bird indicator in the climate-sensitive mountainous regions of northernmost Europe for conservation purposes.
|
|
