Flight Speed of Ross's Gull, Rhodostethia rosea, and Sabine's Gull, Larus sabini

I report here for the first time measured flight speeds of Ross's and Sabine's gulls, obtained by optical range finder on the northeast Taymyr peninsula, Siberia. For two flocks of Ross's gulls, airspeeds were 12.2 m/s and 14.6 m/s. Mean airspeed for the Sabine's gulls was 13.9 m/s (SD=3.4 m/s. N=6). A comparison of these measured airspeeds with characteristic speeds predicted from aerodynamic theory showed that the Sabine's gulls were flying significantly faster than predicted minimum power speed, but their speed was not significantly different from maximum range speed. Sabine's gulls adjusted the airspeed in relation to head- and tailwinds, which is in agreement with aerodynamic theory.Je rapporte ici pour la première fois les mesures de vitesse de vol de la mouette rosée et de la mouette de Sabine, prises au télémètre optique dans la presqu'île de Taïmyr en Sibérie. Pour deux volées de mouettes rosées, la vitesse dynamique était de 12,2 m/s et de 14,6 m/s. La vitesse moyenne pour les mouettes de Sabine était de 13,9 m/s (écart-type = 3,4 m/s, N = 6). Une comparaison de ces mesures de vitesse de vol avec les vitesses caractéristiques prédites d'après la théorie aérodynamique montrait que les mouettes de Sabine volaient bien plus vite que la vitesse minimum prédite, mais que cette vitesse n'était pas très différente de la gamme maximum de vitesses. Les mouettes de Sabine ajustaient leur vitesse de vol en fonction des vents de face ou arrière, ce qui correspond à la théorie aérodynamique

Gliding flight in a jackdaw: a wind tunnel study

We examined the gliding flight performance of a jackdaw Corvus monedula in a wind tunnel. The jackdaw was able to glide steadily at speeds between 6 and 11 m s(-1). The bird changed its wingspan and wing area over this speed range, and we measured the so-called glide super-polar, which is the envelope of fixed-wing glide polars over a range of forward speeds and sinking speeds. The glide super-polar was an inverted U-shape with a minimum sinking speed (V(ms)) at 7.4 m s(-1) and a speed for best glide (V(bg)) at 8.3 m s(-)). At the minimum sinking speed, the associated vertical sinking speed was 0.62 m s(-1). The relationship between the ratio of lift to drag (L:D) and airspeed showed an inverted U-shape with a maximum of 12.6 at 8.5 m s(-1). Wingspan decreased linearly with speed over the whole speed range investigated. The tail was spread extensively at low and moderate speeds; at speeds between 6 and 9 m s(-1), the tail area decreased linearly with speed, and at speeds above 9 m s(-1) the tail was fully furled. Reynolds number calculated with the mean chord as the reference length ranged from 38 000 to 76 000 over the speed range 6-11 m s(-1). Comparisons of the jackdaw flight performance were made with existing theory of gliding flight. We also re-analysed data on span ratios with respect to speed in two other bird species previously studied in wind tunnels. These data indicate that an equation for calculating the span ratio, which minimises the sum of induced and profile drag, does not predict the actual span ratios observed in these birds. We derive an alternative equation on the basis of the observed span ratios for calculating wingspan and wing area with respect to forward speed in gliding birds from information about body mass, maximum wingspan, maximum wing area and maximum coefficient of lift. These alternative equations can be used in combination with any model of gliding flight where wing area and wingspan are considered to calculate sinking rate with respect to forward speed

Body frontal area in passerine birds

Projected body frontal area is used when estimating the parasite drag of bird flight. We investigated the relationship between projected frontal area and body mass among passerine birds, and compared it with an equation based on waterfowl and raptors, which is used as default procedure in a widespread software package for flight performance calculations. The allometric equation based on waterfowl/raptors underestimates the frontal area compared to the passerine equation presented here. Consequently, revising the actual frontal areas of small birds will concomitantly change the values of the parasite drag coefficient. We suggest that the new equation S-b = 0.0129m(B)(0.61) (m(2)) where m(B) is body mass (kg) should be used when a value of frontal area is needed for passerines

Climb and flight speeds of shorebirds embarking on an intercontinental flight:Do they achieve the predicted optimal behaviour?

Most Arctic-breeding waders wintering in West Africa cover the first 4000 km of their northward journey in spring by a single flight to western Europe. We examined the extent to which waders economize their night behaviour during departure by comparing climb rates and forward night speeds with predictions based on flight mechanic theory and the relevant morphological measurements made of birds collected on the site. With an optical range finder, we followed 98 wader necks on their departure from Banc d'Arguin in Mauritania, We also measured wind speed and direction at different altitudes by tracking helium-filled balloons and thus were able to deduce airspeeds from groundspeeds of the departing flocks. Of the nine species examined, six showed the predicted negative relationship between climb rate and airspeed, although only one was statistically significant. By normalizing the data, we found a statistically significant negative correlation across all species. Although 17% of the observed climb rates were greater than the predicted theoretical maximum, the average observed climb rate was lower than the predicted optimum and the average observed airspeed was higher. The absolute deviations of climb rates fr om theory may have been because of the existence of pockets of rising and sinking air at the boundary of desert and ocean. That the absolute deviations in average climb rate and airspeed followed the predicted negative relationship is in accordance with the current theory of flight mechanics

Migration Along Orthodromic Sun Compass Routes by Arctic Birds

Flight directions of birds migrating at high geographic and magnetic latitudes can be used to test bird orientation by celestial or geomagnetic compass systems under polar conditions. Migration patterns of arctic shorebirds, revealed by tracking radar studies during an icebreaker expedition along the Northwest Passage in 1999, support predicted sun compass trajectories but cannot be reconciled with orientation along either geographic or magnetic loxodromes (rhumb lines). Sun compass routes are similar to orthodromes (great circle routes) at high latitudes, showing changing geographic courses as the birds traverse longitudes and their internal clock gets out of phase with local time. These routes bring the shorebirds from high arctic Canada to the east coast of North America, from which they make transoceanic flights to South America. The observations are also consistent with a migration link between Siberia and the Beaufort Sea region by way of sun compass routes across the Arctic Ocean

Современные подходы в диагностике и лечении тромбозов системы нижней полой вены

ТРОМБОЗ ВЕНОЗНЫЙ /ДИАГН /ТЕРПОЛАЯ ВЕНА, НИЖНЯЯТРОМБОЭМБОЛИЯЛЕГОЧНАЯ ЭМБОЛИ

Challenging claims in the study of migratory birds and climate change

Recent shifts in phenology in response to climate change are well established but often poorly understood. Many animals integrate climate change across a spatially and temporally dispersed annual life cycle, and effects are modulated by ecological interactions, evolutionary change and endogenous control mechanisms. Here we assess and discuss key statements emerging from the rapidly developing study of changing spring phenology in migratory birds. These well-studied organisms have been instrumental for understanding climate-change effects, but research is developing rapidly and there is a need to attack the big issues rather than risking affirmative science. Although we agree poorly on the support for most claims, agreement regarding the knowledge basis enables consensus regarding broad patterns and likely causes. Empirical data needed for disentangling mechanisms are still scarce, and consequences at a population level and on community composition remain unclear. With increasing knowledge, the overall support (‘consensus view’) for a claim increased and between-researcher variability in support (‘expert opinions') decreased, indicating the importance of assessing and communicating the knowledge basis. A proper integration across biological disciplines seems essential for the field's transition from affirming patterns to understanding mechanisms and making robust predictions regarding future consequences of shifting phenologies