Activity and migratory flights of individual free‐flying songbirds throughout the annual cycle: method and first case study

Abstract

We describe a method and device ( 1.2 g) for recording, processing and storing data about activity and location of individuals of free-living songbirds throughout the annual cycle.Activity level was determined every five minutes from five 100 ms samples of accelerometer data with 5 s between the sampling events. Activity levels were stored on an hourly basis throughout the annual cycle, allowing periods of resting/sleep, continuous flight and intermediate activity (foraging, breeding) to be distinguished. Measurements from a light sensor were stored from preprogrammed key stationary periods during the year to provide control information about geographic location.Successful results, including annual actogram, were obtained for a red-backed shrike Lanius collurio carrying out its annual loop migration between northern Europe and southern Africa. The shrike completed its annual migration by performing  66 (max. 73) nocturnal migratory flights (29 flights in autumn and  37, max. 44, in spring) adding up to a total of  434 (max. 495) flight hours. Migratory flights lasted on average 6.6 h with maximum 15.9 h. These flights were aggregated into eight travel episodes (periods of 4-11 nights when flights took place on the majority of nights). Daytime resting levels were much higher during the winter period compared to breeding and final part of spring migration. Daytime resting showed peaks during days between successive nocturnal flights across Sahara, continental Africa and the Arabian Peninsula, indicating that the bird was mostly sleeping between these long migratory flights.Annual activity and flight data for free-living songbirds will open up many new research possibilities. Main topics that can be addressed are e.g. migratory flight performance (total flight investment, numbers and characteristics of flights), timing of stationary periods, activity patterns (resting/sleep, activity level) in different phases of the annual cycle and variability in the annual activity patterns between and within individuals.

Migration of red‐backed shrikes from the Iberian Peninsula: optimal or sub‐optimal detour?

“…Our trackings also confirm that the eastward migration is in short almost daily flights, whereas from the southeast Europe, the birds cross the barrier relatively fast (Supplementary material Appendix 1, Fig. A1 and Table A1, see also Bäckman et al ). The spring route northwards from the wintering grounds via the Horn of Africa is also similar both spatially and temporally until the birds turn abruptly westwards over the Arabian Peninsula and travel along the north Mediterranean.…”

Timing avian long-distance migration: from internal clock mechanisms to global flights

“…For example, in the study of Bäckman et al 21 (see Fig. 1), a year-around recording of a free-flying red-backed shrike (Lanius collurio)…”

“…Recently, first data have become available that allow comparisons of year-around activities of wild and captive conspecifics 21 ( Figure 1). This opens intriguing possibilities to compare the timing of migration studied with such different methods, and shows the complementary information that can be generated by combining these approaches.…”

Wind tunnel as a tool in bird migration research

“…The rapid development of new miniature data loggers allows not only tracking of migratory routes, but also using on‐board instrumentation for measurements of additional parameters such as acceleration due to flight (Shepard et al , Hedenström et al , Bäckman et al ), air pressure and even physiological measures (Gumus et al ). These devices often require calibration before deployment on free‐ranging migrants, and here wind tunnels once again may prove crucial.…”