Wennerberg, L., Alerstam, T., Holmgren, N., Joensson, P-E. & von Schantz, T. 1998. Genetic structure and migratory strategies of Dunlin Calidris alpina revealed by mtDNA and microsatellite analysis. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 234 - 235.

The Dunlin Calidris alpina shows intraspecific variation in migratory strategies. Variation between populations has been difficult to ascertain, due to morphological overlap between populations which make it difficult to distinguish populations on migration. In addition, gender identification is often difficult, which further complicates studies of migratory strategies. In this study, the genetic composition of various breeding populations on the Eurasian tundra is investigated. Geographic structure of mtDNA lineages was shown previously. Here, more details about distribution and overlap of mtDNA lineages are shown, and results of microsatellite variation are presented. A genetic sex marker is developed and the accuracy of different field methods for sex identification is clarified. Genotypes of migrating Dunlins are compared to breeding populations for identification of breeding origin. The use of different migratory routes is investigated by analysis of birds at various stopover sites. The timing of migration of birds of different genotypes is revealed and the genetic variation is related to the variation in moult pattern. The study shows that genetic analysis improves the possibilities of studying variation in migration patterns, to reveal new aspects of the evolution of migratory strategies.

Key words: mtDNA, microsatellites, population structure, migration, Dunlin

Bergmann, F. 1998. Long-term trends in the timing of autumn migration in European passerines. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 235.

In recent years, possible implications of the ongoing global warming to the timing of bird migration have been of great interest. Increasing air temperature and improved environmental conditions are expected to cause the earlier arrival of migratory birds at their breeding grounds and the delay of the autumn migration period. For many species increasing autumn temperatures could improve the conditions to prolong their stay in the surroundings of the breeding grounds. From 1974 to 1996, the Vogelwarte Radolfzell carried out a standardised trapping programme (Mettnau-Reit-Illmitz-Program), which covers the whole autumn migration period of small passerines at three Central European stopover sites. In some species, long-term trends reveal a remarkable delay in the timing of autumn migration. The migration of Blackbirds, Whitethroats, Lesser Whitethroats, Sedge Warblers, Song Thrushes and Pied Flycatchers is now up to two weeks later than in the 1970s at the Mettnau Peninsula (Lake Constance, Germany). Moreover, in many short- and medium-distance migrants, there are an increasing number of extremely late migrating individuals, which can not be explained by local meteorological factors. Nevertheless, there are considerable intraspecific differences between the three stopover sites. The shift in the timing of autumn migration could be a first hint of the birds' adaptation to changing environmental conditions in recent years.

Key words: timing of bird migration, climatic change, passerines, global warming

Shamoun, J., Yom-Tov, Y. & Leshem, Y. 1998. Development of a real-time warning system for bird movements in the Middle East. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 235.

Collisions between birds and aircraft result in damage costing hundreds of millions of dollars worldwide. Several factors contribute to the fact that the risk of serious bird strikes in Israel is very high. Leshem, Y. & Yom-Tov, Y (1996. Ibis 138: 188-203, 1996. Ibis 138: 667-674, 1998. Ibis 138: 188-203) mapped flight paths, altitudes and chronology of diurnal migration in Israel. The resulting Bird Plagued Zone regulations adopted by the Israeli Air Force (IAF) reduced serious birds strikes by 88% and has saved the IAF an estimated $390 million between 1984 to 1996. However, this bird hazard avoidance system has its limitations. The Real-Time Warning System for Bird Movements in the Middle East presently being developed can be divided into two integral components: a regional bird/weather radar network, and a Geographic Information System (GIS)-based Bird Avoidance Model (BAM). The BAM is being developed with the US Air Force Academy using GIS technology as the key tool to analyse and correlate bird movements with environmental, meteorological and landuse data. This predictive model will provide risk assessments on bird movements to improve flight safety in the region. The system for the Middle East will be based on and be compatible with the BAM being developed by USAF Academy for the coterminous US (Continental US excluding Alaska).

Key words: migration, GIS, birdstrikes, Middle East, radar

Kvist, A., Hedenström, A., Klaassen, M. & Lindström, Å. 1998. Minimum power speed determined from mass loss in birds flying in a windtunnel. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 236.

Mass loss (excluding faeces) at different flight speeds was measured in Thrush Nightingale Luscinia luscinia, Teal Anas crecca and Red Knot Calidris canutus in a windtunnel. Mass loss showed a U-shaped relationship to flight speed. Evaporation of water is the major contributor to mass loss. There are two reasons why the speed associated with minimum mass loss should equal minimum power speed: (1) Less power means less oxygen is required, hence a lower ventilation rate is needed and thus less water is lost through respiration, (2) Less power also means less heat is produced and hence less evaporation is needed to remove heat from the body. Minimum mass loss speed in all three species studied indicate a higher minimum power speed than previously predicted from aerodynamic models. The discrepancy can be resolved if body drag is significantly lower than previously thought. Available estimates of the body drag coefficient in the region of 0.4 are mainly from measurements on dead birds. Our minimum mass loss speeds indicate a body drag coefficient of about 0.05. This means that previous estimates of optimal flight speeds and migration ranges are, in general, too low.

Key words: flight, windtunnel, body drag, minimum power speed, mass loss

Ward, S., Moeller, U., Jackson, D.M., Rayner, J.M.V., Nachtigall, W., Speakman, J.R. 1998. Measurement of the power requirement for flight by digital thermography. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 236.

The power requirement for flight is technically difficult to measure by established methods. We propose a novel technique, digital thermography, which allows instantaneous measurement of body surface temperature from an infrared image of a flying bird. We recorded images of starlings Sturnus vulgaris flying in a wind tunnel. The head, legs and proximal portion of the ventral surface of the wing were the hottest parts of the body. The body surface superficial to the pectoral muscles was relatively cool. A flying starling dissipated around 8 W by convection and 0.2 W by radiation. Metabolic rate during flight calculated from 8.2 W heat transfer and a 17% conversion efficiency from metabolic to mechanical power was 9.6 W, close to the 10 to 12 W obtained from the same birds by mask respirometry. Flight costs calculated by digital thermography are much less sensitive to the value of efficiency used than estimates based on aerodynamic models because thermography measures approximately 80% of metabolism, to which around 20% must be added, whilst aerodynamic models predict 20% of metabolic costs from which the remaining 80% must be extrapolated.

Key words: flight, energetics, Sturnus vulgaris, European Starling, thermoregulation

Nudds, R.L. 1998. The energetic cost of 'trivial' flight in birds. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 236 - 237.

Take-offs and ascents and descents at low speeds, are often major components of short flights in birds. These apparently 'trivial' flights have been overlooked by most flight energetics studies, but two studies have suggested that trivial flight in birds may be more energetically costly than indicated by existing models. In this study the doubly labelled water method was used to determine the energetic cost of trivial flight. Zebra Finches Taeniopygia guttata were trained to fly in bouts between perches 5.4 m apart and their flight duration was measured. Control finches remained perching during flight bouts of experimental finches, whilst activities between flight bouts were identical for both groups. Therefore, the difference in energy expenditure between the two groups was mainly attributable to flight. The results show that the energetic cost of trivial flight in birds may be more than double the cost estimates derived from existing models. This has important implications for a wide body of work, but particularly flight aerodynamics theory. Is it just trivial flight that is more costly than predicted, or are aerodynamics models using unrealistically high conversion figures for converting mechanical power into chemical power and therefore, systematically under-estimating flight costs?

Key words: energetics, ‘trivial’ flight, doubly labelled water, Zebra Finch, Taeniopygia guttata

Williams, E.V., Gordon, R. & Rayner, J.M.V. 1998. Wingbeat kinematics and wake structure in take-off in the European Starling Sturnus vulgaris. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban. Ostrich 69: 237.

Initial forces to accelerate the body during take-off are produced by the legs, but the bulk of energy gain is provided by lift from the wings. The relationship between lift production and wingbeat kinematics and the constraints on maximum lift generation during take-off remain unclear. A high-speed (200-fps) video camera was used to film eight starlings taking off over barriers which were set at four increasing heights to manipulate lift production. A mirror gave synchronous side and ventral views in the same image. Positions of the beak, wing and tail were digitised, and take-off speed, angle and energy gain per wingbeat were calculated and related to the movements of the wings and tail throughout the first three wingbeats of take-off. Flow visualisation experiments of the wake were analysed by 3-D particle tracking velocimetry to reveal the wake structure and to calculate the energy (induced drag) contributed by the wings in take-off. These results are compared to the detailed kinematic analyses to determine how kinematics relates to wake structure.

Key words: flight, take-off, kinematics, visualisation, wake