Some Physical Limitations on Migration

Yapp, W. B.

doi:10.1111/j.1474-919x.1962.tb08630.x

Cited by 101 publications

(4 citation statements)

References 12 publications

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“…Berger &Hart (1974) stated that net water loss via respiration alone can exceed 350-400°/o over water production at ambient temperatures of 35-37"C, with a net loss of 5-8% of body weight per hour; at 20°C the losses range between 0.4% and 2% of body weight per hour. Yapp (1956Yapp ( , 1962 and Biesel & Nachtigall (1987) pointed out that in most cases flight distance is limited by dehydration rather than by lack of fuel. Nachtigall (1987Nachtigall ( , 1990 stated (for homing pigeons flying in wind tunnels) that the metabolic water produced by burning fat at optimal flight speeds in ambient temperatures below 7°C equals the water which is necessary for evaporative cooling (i.e.…”

Section: Discussionmentioning

confidence: 99%

Altitude choice by night migrants in a desert area predicted by meteorological factors

Bruderer

Underhill

Liechti

1995

Ibis

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The height distribution of nocturnal migrants in southern Israel was determined by con‐ically scanning the sky with the pencil‐beam of an X‐band radar at different elevation angles. Altitudinal profiles of meteorological parameters were derived from radio sondes launched at midnight and from pilot balloons launched every 4 h. A model to predict the height distribution of birds by means of meteorological variables was developed by assuming that the observed proportions of birds within a height zone, compared with the neighbouring height zones, reflect the degree of the birds' preference for that height zone. Only one among the variables included in the multiple regression analysis proved to have a significant influence on the height distribution of migrants: the difference of tailwind speed between height zones. Simulations with 1000 birds choosing altitudes by means of the night's altitudinal profile of tailwind speed closely traced the observed distributions. The fact that all the other meteorological factors which were previously suggested to have an influence on the flight range in trans‐desert migration were not selected as relevant factors is discussed. The following basic information on nocturnal bird migration in the Negev is provided as a background for the statistical analysis: Directions of migration are within very narrow limits. During the first hour after take‐off, 60% of autumn migrants and 75% of spring migrants are climbing, with vertical speeds of 0.1–2 m per s and 0.1–4 m per s, respectively. During the rest of the night, climbing and descending birds are in nearly equal proportions. Thus, there is a high potential of sampling atmospheric conditions at different altitudes. Height distributions in spring and autumn show the influence of the trade wind situation, autumn migrants making use of the northerly winds at low levels in spite of high temperatures, while spring migrants tend to reach the southwesterly winds at higher levels.

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Section: Discussionmentioning

confidence: 99%

Altitude choice by night migrants in a desert area predicted by meteorological factors

Bruderer

Underhill

Liechti

1995

Ibis

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“…The accumulation of fat reserves before migration has been much studied, and several authors have considered the problem of predicting how far a migrant bird should be able to fly on a given amount of fuel (Odum, Connell & Stoddard 1961, Yapp 1962, Lasiewski 1962, Nisbet 1963, Raveling & LeFebvre 1967. All have recognized that this depends both on the speed at which the bird flies and on the rate at which it uses up fuel.…”

Section: Introductionmentioning

confidence: 99%

The Mechanics of Bird Migration

Pennycuick

1969

Ibis

321

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Summary A theory is presented for calculating the relation between mechanical power required to fly and forward speed, for a bird flying horizontally. The significance of this for migration is explained, and quick methods are given (and summarized in the Appendix) for calculating key points on the curve. Speed ranges and effective lift: drag ratios are calculated for a number of different flying animals. Factors affecting migration range are discussed, and the effects of head‐ and tailwinds are considered. Still‐air range depends on effective lift: drag ratio, but not on size or weight as such. The relation of power required to that available from the muscles is considered. Small birds have a greater margin of power available over power required than large ones, and tend to run their flight muscles at a lower stress, or lower specific shortening, or both. There is an upper limit to the mass of practicable flying birds, represented approximately by the Kori Bustard Ardeotit kori. The effect of adding extra weight (food or fuel) is to increase both minimum‐power speed, and maximum‐range speed, in proportion to the square root of the weight, and to increase the corresponding powers in proportion to the three‐halves power of the weight. Birds up to about 750 g (fat‐free) can double their fat‐free mass, and still have sufficient power to fly at the maximum‐range speed. Larger birds are progressively more severely limited in the maximum loads they can carry, and this reduces their range. Many large birds migrate by thermal soaring, thus economizing on fuel at the expense of making slower progress. During a long flight both speed and power have to be progressively reduced as fuel is used up. A formula is given for calculating the still‐air range of a bird which does this in an optimal fashion. The only data required are the effective lift: drag ratio, and the proportion of the take‐off mass devoted to fuel. Increase of height has no effect on the still‐air range, but the optimum cruising speed (and power) is increased. The optimum cruising height is reached when the bird can absorb oxygen just fast enough to maintain the required power. The optimum height increases progressively as fuel is used up. No range is lost as a result of the work done in climbing to the cruising height.

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“…Some researchers believe that energy reserves are a limiting factor in avian migration , while others argue that water reserves could impose a limit on longdistance Hights (Yapp 1962, Berger & Hart 1974, Blem 1980, Carmi et al 1992. Most studies of physical condition of migrating birds have focused on species that migrate using powered flight, such as passerines (Moreau & Dolp 1969.…”

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Fat, hydration condition, and moult of Steppe Buzzards Buteo buteo vulpinus on spring migration

Gorney

Yom‐Tov

1994

Ibis

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Physical condition of migrating Steppe Buzzards Buteo buteo vulpinus was determined during spring migration at Elat, southern Israel, 1984–1988. An index based on measurements of body mass, wing‐length and culmen was used to estimate fat content, based on fat extraction from nine buzzards. In addition, hydration condition was measured in 1988 and moult was checked in 1985–1988. More immatures (1001) than adults (459) were trapped, and a greater percentage of immatures (19.8%) than adults (8.4%) was retrapped during the same season. Adults had significantly greater fat reserves (4.5% of body mass) than immatures (3.8%). Most adults were in some stage of interrupted moult: however, active primary moult was noted only in immatures (10%). These findings suggest that different age groups use different migration strategies. Most of the buzzards trapped in this study could not have completed their entire migration using only stored fat: thus, hunting was probably necessary to replenish their energy reserves. No indication of water stress was found in the spring of 1988.

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Some Physical Limitations on Migration

Cited by 101 publications

References 12 publications

Altitude choice by night migrants in a desert area predicted by meteorological factors

Altitude choice by night migrants in a desert area predicted by meteorological factors

The Mechanics of Bird Migration

Fat, hydration condition, and moult of Steppe Buzzards Buteo buteo vulpinus on spring migration

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