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- Dänhardt, Juliana, et al.
(författare)
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Optimal departure decisions of songbirds from an experimental stopover site and the significance of weather
- 2001
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Ingår i: Animal Behaviour. - : Elsevier BV. - 1095-8282 .- 0003-3472. ; 62:2, s. 235-243
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Tidskriftsartikel (refereegranskat)abstract
- Recent models have worked with the assumption that birds try to minimize either time, energy or predation risk during migration, or some combination of these. The few empirical studies available have suggested that time minimization may be the most common strategy. One way of distinguishing between strategies is to study the departure decisions of migrating birds. We supplied migrating European robins, Erithacus rubecula, with food ad libitum in the field and monitored their changes in body mass prior to departure. The overall mass gain rate (k(tot), the ratio of daily mass increase to lean mass) of 10 birds using the feeding station was on average 0.05 (range 0.03-0.09). Departure fuel loads (f(dep), the ratio of fuel mass to lean mass) were on average 0.53 (range 0.35-0.66). There was no significant correlation between f(dep) and k(tot), which indicates a strategy of minimizing the energy cost of transport, rather than minimizing time but other aspects of the fuel deposition pattern suggest that time minimization may also be important. Whereas the behaviour of the robins was difficult to interpret in the light of optimal migration strategies, the importance of weather was striking. The robins selected the best weather conditions (tail wind, high air pressure and no precipitation) within the likely period of departure. (C) 2001 The Association for the Study of Animal Behaviour.
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- Green, Martin, et al.
(författare)
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The spring migration of two bar-tailed godwit Limosa lapponica populations in Sweden.
- 2003
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Ingår i: Ornis Svecica. - 1102-6812. ; 13:1, s. 1-15
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The regional distribution and timing of spring passage of the Bar-tailed Godwit Limosa lapponica in Sweden is reported (160,300 observed birds in 1976-1995). Birds were observed in most provinces, with the highest concentrations in southernmost Sweden. Timing of passage was bimodal, with distinct peaks in the middle and end of May, suggesting that two separate populations are passing. The peak in mid-May probably refers to the European population wintering in north-western Europe and bound for breeding areas in Scandinavia, Finland and westernmost Russia. The later peak most likely represents the Afro- Siberian population, on passage from West Africa to northern Siberia. The European birds were recorded over most of Sweden, whereas the Afro-Siberian birds were concentrated to the southern part. More European than Afro-Siberian birds were seen, even though the European population is considerably smaller. Presumably, a higher proportion of European than of Afro-Siberian birds stops in southern Sweden. The time pattern of Bar-tailed Godwit migration is compared with the passage of other arctic migrants previously reported.
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- Hertegård, Stellan, et al.
(författare)
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Cross-linked hyaluronan used as augmentation substance for treatment of glottal insufficiency : safety aspects and vocal fold function
- 2002
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Ingår i: The Laryngoscope. - : Wiley. - 0023-852X .- 1531-4995. ; 112:12, s. 2211-2219
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To examine safety aspects and vocal fold function after vocal fold augmentation with a cross-linked hyaluronan derivative (hylan B gel) as compared with bovine collagen. STUDY DESIGN; A prospective, randomized trial. METHODS: Eighty-three patients with glottal insufficiency were treated with injection augmentation with hylan B gel and bovine collagen and were examined at 1, 6, and 12 months after treatment. Seventy patients with unilateral vocal fold paresis (n = 35) or atrophy (n = 35) were randomly assigned to receive either hylan B gel (n = 47) or collagen (n = 23) injections into one vocal fold. Thirteen patients with glottal insufficiency caused by scar defects or paresis resulting from malignant disease were included in a nonrandomized group and were treated only with hylan B gel. Evaluations were made from patients' subjective ratings (visual analogue scales), digitized videostroboscopic measurements, phonetograms, maximum phonation time, and phonation quotients. RESULTS: Twelve months after injections, the patients' self-ratings were significantly improved for both the hylan B gel and the collagen groups. In addition, the videostroboscopic measurements showed significantly improved glottal closure for both groups. However, for the hylan B gel group, vibration amplitude and glottal area variations were preserved, and this group showed significantly less resorption at the injected vocal fold edge. Furthermore, maximum phonation time had increased significantly for the hylan B gel patients (collagen, nonsignificant). No serious adverse events were observed; three patients injected with hylan B gel had temporary inflammation at the injection site, which resolved without sequelae. CONCLUSIONS: The results showed that both hylan B gel and collagen can be safely used for injection treatment of glottal insufficiency. Both treatments resulted in significantly improved voice as rated by the patients. However, the patients treated with hylan B gel showed better vocal fold status and longer maximum phonation time at 12 months after treatment as compared with patients treated with collagen.
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- Jenni-Eiermann, Susanne, et al.
(författare)
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Fuel use and metabolic response to endurance exercise: a wind tunnel study of a long-distance migrant shorebird
- 2002
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Ingår i: Journal of Experimental Biology. - 1477-9145. ; 205:16, s. 2453-2460
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Tidskriftsartikel (refereegranskat)abstract
- This study examines fuel use and metabolism in a group of long-distance migrating birds, red knots Calidris canutus (Scolopacidae), flying under controlled conditions in a wind tunnel for up to 10 h. Data are compared with values for resting birds fasting for the same time. Plasma levels of free fatty acids, glycerol and uric acid were elevated during flight, irrespective of flight duration (1-10h). Triglyceride levels, the estimated concentration of very-low-density lipoproteins (VLDLs) and beta-hydroxybutyrate levels were lower during flight, while glucose levels did not change. In flying birds, plasma levels of uric acid and lipid catabolites were positively correlated with the residual variation in body mass loss, and lipid catabolites with energy expenditure (as measured using the doubly labelled water method), after removing the effect of initial body mass. The plasma metabolite levels indicate: (i) that the rates of catabolism of lipids from adipose tissue and of protein are higher during flight; (H) that low ketone body concentrations probably facilitate fatty acid release from adipose tissue; (iii) that low triglyceride and VLDL levels do not indicate the use of an additional pathway of fatty acid delivery, as found in small birds; and (iv) that the relationships between energy expenditure, body mass loss and metabolic pattern suggest that a higher individual energy expenditure entails a higher rate of catabolism of both lipids and protein and not a shift in fuel substrate.
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- Jonzén, Niclas, et al.
(författare)
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Climate patterns and the stochastic dynamics of migratory birds
- 2002
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 97:3, s. 329-336
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Tidskriftsartikel (refereegranskat)abstract
- We analyse time series data of 17 bird species trapped at Ottenby Bird Observatory, Sweden, during spring migration 1972-1999. The species have similar demography but respond differently to variation in the North Atlantic Oscillation (NAO) - a strong determinant of winter climate in the northern Hemisphere. Species wintering in northern Europe, compared to species having winter quarters in the Mediterranean area, tend to respond positively to variation in NAO. The variation within each group is high due to wide-ranging winter-distribution in many species, probably smoothing out the effect of spatial variation in NAO. Whereas mild winters (high NAO) are benign for many - but not all - birds wintering in northern Europe, the effect of drier-than-normal conditions in the Mediterranean area during high NAO index winters is uncertain. The work presented here goes beyond simple correlative studies and help identifying which species that are most affected by variation in winter climate. This is a first important step that calls for a more mechanistic approach when analysing possible changes to climate change.
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| 10. |
- Klaassen, M, et al.
(författare)
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Flight costs and fuel composition of a bird migrating in a wind tunnel
- 2000
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Ingår i: The Condor: ornithological applications. - 0010-5422. ; 102:2, s. 444-451
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Tidskriftsartikel (refereegranskat)abstract
- We studied the energy and protein balance of a Thrush Nightingale Luscinia luscinia, a small long-distance migrant, during repeated 12-hr long Eights in a wind tunnel and during subsequent two-day fueling periods. From the energy budgets we estimated the power requirements for migratory flight in this 26 g bird at 1.91 Watts. This is low compared to flight cost estimates in birds of similar mass and with similar wing shape. This suggests that power requirements for migratory flight are lower than the power requirements for nonmigratory Eight. From excreta production during Right, and nitrogen and energy balance during subsequent fueling, the dry protein proportion of stores was estimated to be around 10%. A net catabolism of protein during migratory flight along with that of fat may reflect a physiologically inevitable process, a means of providing extra water to counteract dehydration, a production of uric acid for anti-oxidative purposes, and adaptive changes in the size of Eight muscles and digestive organs in the exercising animal.
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