| 1. |
- Wiktander, Ulf, et al.
(författare)
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Age and reproduction in lesser spotted woodpeckers (Dendrocopos minor)
- 2001
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Ingår i: The Auk. - 0004-8038. ; 118:3, s. 624-635
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Tidskriftsartikel (refereegranskat)abstract
- We examined the influence of female age, male age, and pair-bond duration on start of egg-laying, clutch size, and number of young fledged in the Lesser Spotted Woodpecker (Dendrocopos minor). We also attempted to disentangle the relative influence of individual age and pair-bond duration on reproduction, because the effect of those factors may be confounded. Brooding performance improved with age in that old females started egg-laying earlier and old males raised more young than yearlings, and old pairs both started egg-laying earlier and raised more young than new pairs. Clutch size was not affected by age, but showed a strong negative relation with laying date. Late-laying yearling females experienced a lower survival, and the survival of yearling males showed a positive relation with fledgling production. That differential survival was a likely mechanism explaining the differences in reproductive performance between yearling and old birds. Several analyses suggested that pair-bond duration had independent positive effects on reproduction. Benefit of long-term pair-bonds appeared to depend upon repeated breeding with a particular partner. The mechanisms behind the benefit of remating with a particular partner remain unclear, however. We postulate that much of the patterns of age effects on reproduction in the Lesser Spotted Woodpecker may be caused by constraints posed by the territorial system and effects of territory quality, although effects of individual quality can not be excluded.
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| 2. |
- Brodin, Anders
(författare)
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Hippocampal volume does not correlate with food-hoarding rates in the Black-capped Chickadee (Poecile atricapillus) and Willow Tit (Parus montanus)
- 2005
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Ingår i: The Auk. - 0004-8038. ; 122:3, s. 819-828
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Tidskriftsartikel (refereegranskat)abstract
- Food-hoarding birds use memory to relocate caches, and species that store thousands of scattered food items must have an extraordinary memory capacity to be able to relocate them. Because the hippocampus is important in the functioning of spatial memory, it is logical to assume that the amount of food stored should correlate with hippocampal volume. Previously, food-hoarding capacity has been used as the predictor variable for hippocampal volume. Using the opposite approach, I tested whether hippocampal volume can be used to predict the amount of food stored. The atricapilla complex, a superspecies in the Paridae, has a wide Holarctic distribution, with the Black-capped Chickadee (Poecile atricapillus) in America and the Willow Tit (Parus montanus) in Eurasia. Although they live in similar ecological conditions, the Willow Tit possesses a hippocampus almost twice the size of the Black-capped Chickadee's. I sampled hoarding intensities in Black-capped Chickadees in British Columbia with the same methods I used previously in Willow Tits in Sweden. Contrary to expectation, Black-capped Chickadees stored at the same high rates as Willow Tits, which suggests that both species are large-scale hoarders. I discuss possible explanations for why the difference in hippocampal volume did not translate into differences in food-hoarding rates.
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| 3. |
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| 4. |
- Johansson, Ulf S, et al.
(författare)
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Basal phylogeny of the Tyrannoidea based on comparisons of cytochrome b and exons of nuclear c-myc and RAG-1 genes
- 2002
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Ingår i: The AUK. - 0004-8038 .- 1938-4254. ; 119:4, s. 984-995
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Tidskriftsartikel (refereegranskat)abstract
- The outlines of the phylogenetic relationships within the New World suboscine clade Tyrannoidea were investigated on the basis of nucleotide sequence data from two nuclear genes (c-myc and RAG-1) and one mitochondrial gene (cytochrome b), totaling over 2,400 bp. Representatives of the major tyrannoid lineages were sequenced, including Pachyramphus, Schiffornis, Tityra, and Oxyruncus. The data set with the three genes combined was analyzed under both the parsimony and maximum-likelihood criteria and under different character weighting schemes. The analyses resulted in similar topologies that differed only in poorly supported nodes. The three manakins (Pipra, Manacus, and Chiroxiphia) included in this study were found to be monophyletic, whereas Schiffornis—sometimes also considered to be a manakin—did not group with the manakins, but occurred with Pachyramphus and Tityra in the clade Tityrinae. The two clades Pipromorphinae and Tyranninae are also strongly supported in this analysis and appear as sister groups, thus supporting the monophyly of the tyrant flycatcher assemblage. Phytotoma was placed with the only cotingid species included in this analysis, whereas the position of Oxyruncus was unresolved.
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| 5. |
- Granbom, Martin, et al.
(författare)
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Food limitation during breeding in a heterogeneous landscape
- 2006
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Ingår i: The Auk. - 0004-8038. ; 123:1, s. 97-107
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Tidskriftsartikel (refereegranskat)abstract
- Breeding success in birds may be determined by the availability of food that parents can provide to growing nestlings. A standard method for testing the occurrence of food limitation is to provide supplemental food during different parts of the breeding period. If there is spatial variation in the strength of food limitation, the effect of such an experiment should also vary spatially. We investigated whether the strength of food limitation during nestling rearing in the European Starling (Sturnus vulgaris) was related to the management intensity of agricultural landscapes. We fed birds mealworms during the nestling period in landscapes with high or low local availability of pasture, the preferred foraging habitat. Both habitat and food supplementation affected growth and survival of nestlings; the effects of the food-supplementation experiment were generally stronger than those of habitat. Mortality mainly struck the last-hatched chick. Both habitat and food supplementation positively affected nestling growth, measured as nestling tarsus length. In addition, food supplementation positively affected feather growth and asymptotic mass. Contrary to expectation, no interactions existed between effects of habitat and food supplementation, which suggests that breeding success was limited by food availability in both landscapes. Potential reasons for this lack of effect are parental compensation and low statistical power. Also, breeding densities were higher in landscapes with more pastures, possibly equalizing the per-capita availability of food. Thus, our results demonstrate that reproductive success was limited by availability of food when local availability of preferred foraging habitat was either low or high, but fail to demonstrate spatial variation in the strength of food limitation.
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| 6. |
- Nilsson, Anna, et al.
(författare)
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Do partial and regular migrants differ in their responses to weather?
- 2006
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Ingår i: The Auk. - 0004-8038. ; 123:2, s. 537-547
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Tidskriftsartikel (refereegranskat)abstract
- Partial migration is often considered a transitory stage between migration and residency, and whether partial migrants take weather conditions into account during migration is largely unknown. To assess whether partial migrants differ from regular migrants in their responses to weather, we compared the migratory intensity of a partial migrant, the Blue Tit (Cyanistes caeruleus), with more regular migrants in relation to weather at a migratory passage site in southern Sweden (Falsterbo) during the years 1993-2002. The regular migrants in the study were Linnet (Carduelis cannabina), Common Chaffinch (Fringilla coelebs), Brambling (F. montifringilla), and European Robin (Erithactis rubecula). The Blue Tit differed from the regular migrants mainly in showing a striking negative correlation between migratory activity and cloud cover. Also, weather had the highest explanatory power for migratory intensity in the Blue Tit. This suggests that the Blue Tit is more sensitive to weather conditions on migration than the regular migrants and that it preferably awaits days with wholly or partly clear skies before migrating past Falsterbo. As a consequence, Blue Tits usually restrict their migratory flights to the safest occasions, with relatively calm weather, good visibility, and all orientation cues (solar as well as magnetic) available.
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| 7. |
- Ottosson, Ulf, et al.
(författare)
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Nest-attenders in the pied flycatcher (Ficedula hypoleuca) during nestling rearing: A possible case of prospective resource exploration
- 2001
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Ingår i: The Auk. - 0004-8038. ; 118:4, s. 1069-1072
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Tidskriftsartikel (refereegranskat)abstract
- Visits to nest holes by birds other than their owners is a familiar phenomenon for students of breeding biology. In this study, we evaluate that behavior using a transponder reading system. Eighty-five males and females were Fitted with transponders at the end of the incubation period or just after hatching. Nest boxes were fitted with transponder readers from just after hatching until all nestlings fledged. That system revealed 123 visits by birds to nest boxes other than their own, a visit being defined as at least one visit to a separate nest box on a separate day. Males were more often detected at other nests than females (53% of males vs. 29% of females visited) and males on average made more visits than females did (4.8 vs. 2.5 visits). However, both males and females devoted time to visiting other nests while still feeding nestlings, That behavior is more common than previously suspected and is consistent with birds prospecting for future nest sites or investigating patch reproductive success.
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| 8. |
- Sandberg, Roland, et al.
(författare)
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Orientation of nocturnally migrating Swainson's thrush at dawn and dusk: Importance of energetic condition and geomagnetic cues
- 2002
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Ingår i: The Auk. - 0004-8038. ; 119:1, s. 201-209
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Tidskriftsartikel (refereegranskat)abstract
- We studied the early morning cage orientation of nocturnally migrating Swainson's Thrushes (Catharus ustulatus) during three fall migration seasons. The results were compared with earlier free-flight release tests under starry skies and were found to be consistent with continuation of migratory flights in the expected seasonally appropriate direction. Energetic condition proved decisive: fat birds chose directions in accordance with migration across the Gulf of Mexico, whereas lean birds oriented away from the coast, possibly in search of habitats suitable for refuelling. Whereas the orientation of fat Swainson's Thrushes was affected by experimental shifts of the magnetic field, the response during morning tests was larger than expected. A parallel series of orientation cage experiments performed during evening twilight showed a response to deflected magnetic fields that was close to the expected shift, which suggests a difference in integration of directional information between early morning and evening twilight activity. However, within-individual response to deflected magnetic fields was of the same magnitude during both morning and evening tests.
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| 9. |
- Alerstam, Thomas, et al.
(författare)
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Great-Circle Migration Of Arctic Passerines
- 2008
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Ingår i: The Auk. - : Oxford University Press (OUP). - 0004-8038 .- 1938-4254. ; 125:4, s. 831-838
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Tidskriftsartikel (refereegranskat)abstract
- Birds can save distance and time on their migratory journeys by following great circles rather than rhumblines, but great-circle routes require more complex orientation with changing courses. Flight directions at different places along the route and in relation to the destination can be used to test whether birds migrate along great circles or rhumblines. Such data have indicated great-circle migration among shorebirds at high latitudes, but no critical tests have been made for passerines. Using tracking radar on board the icebreaker Oden in August 2005, we recorded westerly flight directions of passerine migrants over the Chukchi Sea. The main sector of migratory directions was 237-311 degrees centered oil a mean heading direction of 274 degrees. The most likely species to participate in this westward trans-Beringia migration, mainly departing from Alaska, were Eastern Yellow Wagtail (Motacilla Ischutschensis), Arctic Warbler (Phylloscopus borealis kennicotti), Northern Wheatear (Oenanthe oenanthe), and Bluethroat (Luscinia svecica); all except the Bluethroat were recorded from the ship. Observed flight directions agreed with predicted great-circle courses but not with rhumbline courses for three of these four species with winter quarters in Southeast Asia; no definite conclusion could be drawn for the Northern Wheatear (wintering in East Africa). These results support great-circle migration among passerines traveling between Alaska and Old World winter quarters, though the long-distance precision and orientation mechanisms are Still unknown. The relative importance of different evolutionary causes-such as circumvention of geographic barriers, retracing of ancient colonization ways, or distance reduction by great-circle migration-to complex bird migration routes with changing courses remains to be understood. Received 24 August 2007, accepted 6 March 2008.
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| 10. |
- Alström, Per, Professor, et al.
(författare)
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Morphology, vocalizations, and mitochondrial DNA suggest that the Graceful Prinia is two species
- 2021
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Ingår i: Ornithology. - : Oxford University Press (OUP). - 0004-8038 .- 2732-4613 .- 1938-4254. ; 138:2
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Tidskriftsartikel (refereegranskat)abstract
- Prinias (Cisticolidae:Prinia) are resident warblers of open areas across Africa and Asia and include many polytypic species whose species limits have not been seriously reevaluated recently. Based on an integrative taxonomic analysis of morphology, song, and mitochondrial DNA (mtDNA), we suggest that 2 species should be recognized in the Graceful Prinia (Prinia gracilis) complex. In addition, our morphological analyses show the existence of a well-marked undescribed form in southeastern Somalia, which we name herein as a new subspecies. Prinia gracilisis a small, drab, long-tailed species with streaking above and plain pale underparts that has been suggested to fall into 2 groups: the southwestern nominate group (from Egypt to Oman) and the northeastern lepida group (from Turkey through India). However, the characters presented to justify this grouping are variable and show a mosaic pattern, and whether genetic and vocal differences exist is unknown. We found consistent between-group song differences, with the nominate group giving consistently longer inter-phrase intervals, whereas the members of the lepida group sing an essentially continuous reel. An mtDNA tree suggests a deep split between the nominate and lepida groups, with a coalescence time between these clades of similar to 2.2 million years ago. Vocal and mtDNA analyses provided evidence that the northeastern Arabian Peninsula taxon carpenteri belongs to the lepida group. We found that, of all the morphological characters proposed, only proportions and tail barring and spotting relatively consistently distinguish the 2 groups. However, these characters strongly suggest that the eastern Arabian Peninsula is populated by taxa of both the gracilis and lepida groups, in different areas, but we lack genetic and bioacoustic data to corroborate this. Although further study is needed in potential contact zones, we suggest that 2 species should be recognized in the P. gracilis complex, and we propose the retention of the English name Graceful Prinia for P. gracilis sensu stricto, while we suggest that P. lepida be known as Delicate Prinia.
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