Autumn Movements of Willow Warblers ringed in the British Isles

Norman, S. C.; Norman, William C.

doi:10.1080/03078698.1985.9673849

Cited by 15 publications

(13 citation statements)

References 16 publications

(18 reference statements)

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“…The fat contents of Bardsey birds would have enabled the majority to fly direct to France, even the Loire region; indeed France is a major site for the recovery of British ringed birds in autumn (Spencer & Hudson 1981). However, Norman & Norman (1985) conclude, partly from the pattern of ringing recoveries and partly from live weights, that the movement of British Willow Warblers to France in autumn is not a direct one. The discrepancy between the two studies could arise if Willow Warblers killed at Bardsey were not of British origin; the dates of collection (Table 1) suggest continental birds (Norman & Norman 1985).…”

Section: Willow Warblermentioning

confidence: 86%

“…However, Norman & Norman (1985) conclude, partly from the pattern of ringing recoveries and partly from live weights, that the movement of British Willow Warblers to France in autumn is not a direct one. The discrepancy between the two studies could arise if Willow Warblers killed at Bardsey were not of British origin; the dates of collection (Table 1) suggest continental birds (Norman & Norman 1985). However, if British in origin Bardsey birds may have differed in their migratory behaviour.…”

Section: Willow Warblermentioning

confidence: 86%

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The fat contents and flight ranges of four warbler species on migration in North Wales

Baggott

1986

Ringing & Migration

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1986. The fat contents and flight ranges of four warbler species on migration in North Wales. . The fat contents of four warbler species killed during a migratory flight in N. Wales are reported for both spring and autumn. From the fat content and the wingspan the potential still-air flight range and flight times are calculated for individual birds by the formulae of Pennycuick (1975) : the inaccuracies of these predictions are discussed in relation to attainable range. For three of the warbler species examined (Willow Warbler, Sedge Warbler and Whitethroat) the ranges predicted are consistent with the known migratory destinations of these species in autumn. The ranges predicted for the fourth species, the Grasshopper Warbler, indicate that in autumn some birds are capable of reaching S. France in a single migratory flight. In spring, potential flight ranges of the Willow Warbler, Grasshopper Warbler and Whitethroat suggest that these birds could reach destinations only within the British Isles. However, some Sedge Warblers had sufficient fat to reach Norway in a single flight in still air. In both spring and autumn the times required to fly the predicted still-air ranges are mostly less than 24 hours. The Willow Warbler, Sedge Warbler and Whitethroat are species that scale in an isometric manner; the Grasshopper Warbler is not similarly proportioned as it has a short wingspan for its body weight. A method based on isometric scaling is developed for the prediction of relative flight ranges. All species had markedly larger wingspans in the spring compared with the autumn.

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Section: Willow Warblermentioning

confidence: 86%

Section: Willow Warblermentioning

confidence: 86%

The fat contents and flight ranges of four warbler species on migration in North Wales

Baggott

1986

Ringing & Migration

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“…The latter place is close to the areas of the few winter recoveries of British ringed Willow Warblers (Norman & Norman 1985). In order for Willow Warblers to have sufficient resources to make a trans-Saharan crossing from Western Iberia a 'fat' loading of about 63% (based on projection of Figure 1) of mean dawn weights giving dusk take off weights of around 13.4 g and an arrival weight of 8.2 g. As shown by Baggott ( 1986) tail winds would increase the range substantially and as Moreau (1961) stated that winds are more favourable in the autumn for a transSaharan crossing then it may possible for a 'fat' loading of 52% to be sufficient for Willow Warblers to make the journey safely to their winter quarters.…”

Section: Discussionmentioning

confidence: 99%

“…These include the analysis of body weights of live birds (Pepler & Pepler 1972, Langslow 1976, Thomas 1979, ringing recovery data (Hope Jones 1975, da Prato & da Prato 1983, Norman & Norman 1985, investigation of lipid deposition and flight muscle hypertrophy (Evans 1969, Fry, Lees & Dowse« 1972, Baggott 1975, the fat contents present in the carcass of birds (Baggott 1986) or visual estimates of fat contents in conjunction with live weights (Pettersson& Hasselquist 1985) and also the study of migratory restlessness (Berthold 1984).…”

Section: Introductionmentioning

confidence: 99%

Body weights of Willow Warblers during autumn migration within Britain

Norman¹

1987

Ringing & Migration

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The relationship between weights of Willow Warblers and the autumn migration strategy of the species was investigated by examination of weights of first-autumn birds captured at two coastal and two inland sites in Britain over the period 16 July to 30 September. The migration 'season' was divided into two periods and the data from each compared. No account was taken of the sex of birds and only individuals which had completed moult were used. Capture times throughout the season were standardised and actual weights were used Mean overnight weight-loss was found to be about 8% of total body weight and mean diurnal weight-gain about the same over the first period of the season, slightly more over the latter period. Results implied that this order of increase was needed by birds to meet overnight metabolic requirements and, that they migrated at weights virtually equivalent to normal roosting levels, A migration strategy is proposed based on the findings of Baggott (1975Baggott ( , 1986) that approximately 13% of total wet weight of first-autumn Willow Warblers comprises fat deposits. It is suggested that the majority of Willow Warblers use normal evening weight levels for successive short-stage migratory flight (<300 km) through Britain, and that about 5% of body fats is held available in reserve for the funding of additional energy demands which might be imposed should adverse weather conditions be encountered. Estimates of the 'fat' loadings birds would require to traverse France and for transSaharan flight from Iberia are discussed. S. C.

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“…Norman and Norman (1985) described how young British Willow Warblers Phylloscopus trochilus undertook local random dispersal within 25 km of the nest-site before beginning southwards emigration when they were around 60 days old, this emigration period coinciding with completion of their postjuvenile moult (Norman 1981).…”

Section: Discussionmentioning

confidence: 99%

Post‐fledging dispersal of British Pied WagtailsMotacilla alba yarrellii

Dougall¹

1992

Ringing & Migration

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Autumn Movements of Willow Warblers ringed in the British Isles

Cited by 15 publications

References 16 publications

The fat contents and flight ranges of four warbler species on migration in North Wales

The fat contents and flight ranges of four warbler species on migration in North Wales

Body weights of Willow Warblers during autumn migration within Britain

Post‐fledging dispersal of British Pied WagtailsMotacilla alba yarrellii

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