Birds: blowin’ by the wind?

Abstract

Migration is a task that implies a route, a goal and a period of time. To achieve this task, it requires orientation abilities to find the goal and energy to cover the distance. Completing such a journey by flying through a moving airspace makes this relatively simple task rather complex. On the one hand birds have to avoid wind drift or have to compensate for displacements to reach the expected goal. On the other hand flight costs make up a large proportion of energy expenditure during migration and, consequently, have a decisive impact on the refuelling requirements and the time needed for migration. As wind speeds are of the same order of magnitude as birds' air speeds, flight costs can easily be doubled or, conversely, halved by wind effects. Many studies have investigated how birds should or actually do react to winds aloft, how they avoid additional costs or how they profit from the winds for their journeys. This review brings together numerous theoretical and empirical studies investigating the flight behaviour of migratory birds in relation to the wind. The results of these studies corroborate that birds select for favourable wind conditions both at departure and aloft to save energy and that for some long-distance migrants a tail-wind is an indispensable support to cover large barriers. Compensation of lateral wind drift seems to vary between age classes, depending on their orientation capacities, and probably between species or populations, due to the variety of winds they face en route. In addition, it is discussed how birds might measure winds aloft, and how flight behaviour with respect to wind shall be tested with field data.

Migration timing and stopover selection for barnacle geese Branta leucopsis

“…We found that wind conditions (head wind/tail wind and cross wind) en route were not related to the migration timing of the individual Russian and Svalbard geese, which is opposite to previous studies (Erni et al, 2005;Liechti, 2006;Pulido, 2007b). Wind parameters en route at the Russian flyway had high loading on PC3eR, but this PC was not selected by the model.…”

“…Wind speed is probably the most important weatherrelated parameter determining flight speed and flight duration of birds (Erni et al, 2005;Liechti, 2006;Pulido, 2007b). Migrant birds can greatly increase their flight speed by responding appropriately to prevailing wind conditions (Newton, 2008).…”

Flight paths of seabirds soaring over the ocean surface enable measurement of fine-scale wind speed and direction

“…Wind is treated as an important external factor in studies of large-scale seasonal migrations (33)(34)(35) and commuting flights (36-38) of seabirds. Although the migration patterns of seabirds associated with the large-scale wind systems are well documented (33)(34)(35), finer-scale movements in relation to variation of winds in scales of several minutes to hours are still unrevealed due to the lack of wind information relevant to the fine-scale movements of the seabirds. Using the methods outlined in this study, high-resolution wind information experienced by birds throughout their whole flight can be evaluated to investigate bird flight behavior in relation to more finescale turbulence and variation of wind.…”

Indigenous climate knowledge in southern Uganda: the multiple components of a dynamic regional system

“…These conditions could also be associated with small-scale variations in heating that would favor the development of vigorous whirlwinds. Research in other areas has linked shifts in the flowering patterns of trees to El Niño events (Curran et al 1999) and shown that migratory birds often use the movements of fronts to provide them with tailwinds (Liechti 2006). …”