| 1. |
- Green, Martin, et al.
(författare)
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Do Arctic waders use adaptive wind drift?
- 2004
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Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857 .- 1600-048X. ; 35:4, s. 305-315
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Tidskriftsartikel (refereegranskat)abstract
- We analysed five data sets of night directions of migrating arctic waders ill relation to,winds, recorded by tracking radar and optical range finder, in order to find out if these birds compensate for wind drift, or allow themselves to be drifted by winds. Our purpose was to investigate whether arctic waders use adaptive wind drift strategies or not. The data sets were collected in Siberia (two sets) and Canada during post-breeding (autumn) migration, and in Mauritania and South Sweden during pre-breeding (spring) migration. Both significant drift and compensation effects were found in three of the data sets, Canada, Mauritania and South Sweden. Almost no compensation was found in birds departing in easterly directions from the Siberian tundra (complete drift), while no drift effect was found in birds departing in westerly directions (complete compensation). There were indications that at least some populations of waders may use an adaptive drift strategy consisting of drift at high altitude and/or in high wind speed combined with compensation at low altitude and/or in lower wind speeds, but support for this idea was rather weak and not consistent. Our results were instead more in accordance with the adaptive drift theory that predicts initial drift during the migratory journey, followed by compensation during later stages as the birds are approaching their destinations. Such a strategy implies that arctic waders, at least adult birds, have the capacity of true navigation. A comparison with earlier studies of migrating arctic waders from different parts of the world show that all results so far may be interpreted in accordance with this general adaptive drift strategy An element of non-adaptive drift can, however, not be completely ruled out.
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| 2. |
- Hedenström, Anders
(författare)
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Flying with holey wings
- 2003
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Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857 .- 1600-048X. ; 34:4, s. 324-327
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Sunde, Peter, et al.
(författare)
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Diurnal exposure as a risk sensitive behaviour in tawny owls Strix aluco?
- 2003
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Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857 .- 1600-048X. ; 34:4, s. 409-418
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Tidskriftsartikel (refereegranskat)abstract
- Tawny owls Strix aluco generally roost in cryptic locations during the day. To test the hypothesis that this cryptic behaviour is an effort to avoid mobbers or avian predators, we measured diurnal behaviour and cause-specific mortality of radio-tagged birds. Non-breeding adults (assumed to be well fed individuals, optimising their own survival) roosted in less exposed locations than adults with young and newly independent juveniles. Parents roosted in the most exposed sites when their young were immature and vulnerable to depredation, probably to guard offspring. Newly independent juveniles apparently selected roosting sites in exposed places to get access to food, as this behaviour was associated with lower perching heights and higher prey abundance beneath their roosting sites. They also perched in more exposed sites, closer to the ground, in summers with low prey abundance compared to summers with high prey abundance. After previous encounters with goshawks Accipiter gentilis, dependent juveniles roosted in less exposed places compared to other young. The increased risk of being mobbed was highly significant with increasing roosting exposure. Once an owl was mobbed, the intensity of the mobbing correlated positively with the mass of the mobbers, but mobbing birds never killed any owls. In contrast, diurnal raptors caused 73% of natural owl deaths (n = 15) and the depredation rate by raptors was 3.8 times higher in population classes that generally roosted in more exposed locations than did non-breeding adults. We therefore suggest that depredation by diurnal raptors is the main factor shaping the diurnal behaviour of tawny owls.
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| 4. |
- Zehnder, Susanna, et al.
(författare)
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Nocturnal autumn bird migration at Falsterbo, South Sweden
- 2001
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Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857 .- 1600-048X. ; 32:3, s. 239-248
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the patterns of nocturnal bird migration in autumn 1998 at a coastal site on the Falsterbo peninsula in south-western Sweden, by means of a passive infrared device. In total 17 411 flight paths, including track direction and altitude, of migrating birds were recorded for 68 nights from August to October. Mean migratory traffic rate per night varied between 6 and 6618 birds km1 h1, with an average of 1319 birds km1 h1. Migration at Falsterbo showed a similar seasonal pattern to that reported for central Europe, with pronounced peaks of migration and intermittent periods with relatively low migratory intensities. Weather factors explained two thirds of the variance in the intensity of bird migration. During nights with intense migration, associated with weak winds, the mean track direction was close to that in central western Europe (225). Birds usually maintained a constant heading independent of wind directions and, in consequence, were drifted by the wind. The mean orientation clearly differed from that of the nearest coastline, suggesting that the birds did not use the topography below to compensate for wind drift.
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| 5. |
- Ådahl, Emma, et al.
(författare)
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Can intraspecific brood parasitism be detected using egg morphology only?
- 2004
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Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857 .- 1600-048X. ; 35:4, s. 360-364
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Tidskriftsartikel (refereegranskat)abstract
- Intraspecific brood parasites lay their eggs in the nests of conspecifics. There are a number of methods for detecting intraspecific brood parasitism (IBP) in birds based on egg morphology. Here we test Eadie's (1989) method, which calculates the Euclidean distances between eggs in a given clutch in a three-dimensional space (weight, length and width). A parasitised clutch is predicted to contain an egg (or eggs) that is significantly different from the clutch's other eggs. Data from three species were analysed. Our captive zebra finch Taeniopygia guttata clutches did not include any instances of IBP, the wild jackdaw Corvus monedula data were unlikely to contain any, and for the goldeneye Bucephala clangula data set we had an observational estimate of IBP. We simulated IBP in the zebra finch, jackdaw and goldeneye data to test whether the method reliably detects an experimentally 'parasitised' clutch. We show that the distributions of the test statistics greatly overlap in 'parasitised' and unmodified clutches, and are dependent on the clutch size. We therefore conclude that the method can only be used with caution, after calibrating it for a given population.
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| 6. |
- Irestedt, Martin, et al.
(författare)
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Phylogenetic relationships of woodcreepers (Aves: Dendrocolaptinae) - incongruence between molecular and morphological data
- 2004
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Ingår i: Journal of Avian Biology. - : Blackwell. - 1600-048X .- 0908-8857. ; 35:3, s. 280-288
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Tidskriftsartikel (refereegranskat)abstract
- The woodcreepers is a highly specialized lineage within the New World suboscine radiation. Most systematic studies of higher level relationships of this group rely on morphological characters, and few studies utilizing molecular data exist. In this paper, we present a molecular phylogeny of the major lineages of woodcreepers (Aves: Dendrocolaptinae), based on nucleotide sequence data from a nuclear non-coding gene region (myoglobin intron II) and a protein-coding mitochondrial gene (cytochrome b). A good topological agreement between the individual gene trees suggests that the resulting phylogeny reflects the true evolutionary history of woodcreepers well. However, the DNA-based phylogeny conflicts with the results of a parsimony analysis of morphological characters. The topological differences mainly concern the basal branches of the trees. The morphological data places the genus Drymornis in a basal position (mainly supported by characters in the hindlimb), while our data suggests it to be derived among woodcreepers. Unlike most other woodcreepers, Drymornis is ground-adapted, as are the ovenbirds. The observed morphological similarities between Drymornis and the ovenbird outgroup may thus be explained with convergence or with reversal to an ancestral state. This observation raises the question of the use of characters associated with locomotion and feeding in phylogenetic reconstruction based on parsimony.
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| 7. |
- Arnold, KE, et al.
(författare)
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Sex-biased hatching sequences in the cooperatively breeding Noisy Miner
- 2001
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Ingår i: JOURNAL OF AVIAN BIOLOGY. - : MUNKSGAARD INT PUBL LTD. - 0908-8857. ; 32:3, s. 219-223
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Tidskriftsartikel (refereegranskat)abstract
- The Noisy Miner Manorina melanocephala (Meliphagidae) is a cooperatively breeding bird species in which sons often remain on their natal home ranges and help one or both of their parents. In a population of Noisy Miners in SE Queensland, Australia, a mole
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| 8. |
- Eggers, S
(författare)
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Compensatory frugivory in migratory Sylvia warblers: geographical responses to season length
- 2000
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Ingår i: JOURNAL OF AVIAN BIOLOGY. - : MUNKSGAARD INT PUBL LTD. - 0908-8857. ; 31:1, s. 63-74
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Tidskriftsartikel (refereegranskat)abstract
- Seasonal shifts in the diets of Garden Warblers Sylvia borin, Blackcaps S. atricapilla and Lesser Whitethroats S. curruca at a North German site were studied from samples obtained by flushing the digestive tract of the birds. The significance of seven spe
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| 9. |
- Ericson, Per G P, 1956-, et al.
(författare)
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Evolution, biogeography, and patterns of diversification in passerine birds
- 2003
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Ingår i: Journal of Avian Biology. - 0908-8857 .- 1600-048X. ; 34:1, s. 3-15
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Tidskriftsartikel (refereegranskat)abstract
- This paper summarizes and discusses the many new insights into passerine evolution gained from an increased general interest in avian evolution among biologists, and particularly from the extensive use of DNA sequence data in phylogenetic reconstruction. The sister group relationship between the New Zealand rifleman and all other passerines, indicates the importance of the former southern supercontinent Gondwana in the earliest evolution of this group. Following the break-up of Gondwana, the ancestors of other major passerine groups became isolated in Australia (oscines), South America (New World suboscines), and possibly, the then connected Kerguelen Plateau/India/Madagascar tectonic plates (Old World suboscines). The oscines underwent a significant radiation in the Australo-Papuan region and only a few oscine lineages have spread further than to the nearby Southeast Asia. A remarkable exception is the ancestor to the vast Passerida radiation, which now comprises 35% of all bird species. This group obviously benefitted greatly from the increased diversity in plant seed size and morphology during the Tertiary. The lyrebirds (and possibly scrub-birds) constitute the sister group to all other oscines, which renders “Corvida” (sensu Sibley and Ahlquist 1990) paraphyletic. Sequence data suggests that Passerida, the other clade of oscines postulated based on the results of DNA–DNA hybridizations, is monophyletic, and that the rockfowl and rock-jumpers are the most basal members of this clade. The suboscines in the Old World (Eurylamides) and the New World (Tyrannides), respectively, are sister groups. A provisional, working classification of the passerines is presented based on the increased understanding of the major patterns of passerine evolution.
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| 10. |
- Green, Martin, et al.
(författare)
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Flight speeds and climb rates of Brent Geese: mass-dependent differences between spring and autumn migration
- 2000
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Ingår i: Journal of Avian Biology. - 0908-8857. ; 31:2, s. 215-225
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Tidskriftsartikel (refereegranskat)abstract
- Aerodynamic theories of bird flight predict that horizontal flight speed will increase with increasing load whereas vertical Eight speed will decrease. Horizontal flight speed for birds minimizing overall time on migration is predicted to be higher than flight speed for birds minimizing energy expenditure. In this study we compare flight speeds of Brent Geese Branta b. bernicla recorded by tracking radar and optical range finder during spring and autumn migration in southernmost Sweden, testing the above-mentioned predictions. Geese passing Sweden in spring are substantially heavier than in autumn and there might also be a stronger element of time-selection in spring than in autumn. Recorded airspeeds were significantly higher in spring (mean 19.0 m s(-1)) than in autumn (mean 17.3 m s(-1)), the average difference bring slightly larger than predicted due to the mass difference alone. The effects on airspeed of wind, vertical speed, flock size and altitude were also analysed, but none of these factors could explain the seasonal difference in airspeed. Hence, the results support the hypothesis of mass-dependent flight speed adjustment. The difference between the two seasons was not large enough to corroborate the hypothesis of a stronger element of time-selection in spring, but this hypothesis cannot be rejected. Vertical flight speeds were lower in spring than in autumn, supporting a negative effect of load on birds' Right power margin.
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