Estimation of the Autumn Migration Pattern of Passerines within the SE European Flyway by Orientation Cage Tests

Abstract

The general migration pattern of passerines can be estimated using a variety of methods. A number of partial analyses based on ringing data, usually limited to a few species, have been published. A very few continent-scale presentations have been offered, as extremely long periods of ringing activity are necessary for passerines. This is especially true for areas where the recovery rate is very low, including vast areas of north-eastern and eastern Europe and the Middle East/Africa. Similarly, radar and moon-watching studies are of limited value for drawing migration patterns within wider areas. Radar studies require good coverage by the radar systems, while weather radar distribution density and the level of evaluation are very uneven. Modern logger and satellite tracking are more applicable to non-passerines, and as yet enable detailed study only of limited numbers of individuals, and not population studies. At the end of the 20th century, a very simple tool was introduced for field studies on the preferred headings of individual birds caught for ringing, i.e. the use of flat orientation cages. This method was introduced as a standard within the SEEN (SE European Bird Migration Network) in 1995. This study presents a preliminary large-scale evaluation of the data collected within this project. The database used contains more than 43,000 orientation tests performed at 45 ringing sites. The area covered stretches from the northern part of western Russia to southern Egypt and from Italy and Poland to Siberia and Armenia. Eight streams of migration are identified within this area, creating a fairly complicated pattern of avian movements.

The European Autumn Migration Pattern of the Garden Warbler, Sylvia borin – A Basic Analysis of Orientation Cage Field Data

“…), ORANGE heads directly to the eastern part of Africa, and YELLOW is directed towards the Middle East/Arabian Peninsula (the last two together are usually called the SE European Flyway), while WHITE heads towards a winter quarters very far eastward. The BLACK heading is surprisingly longitudinal and has never before been described, but mentioned only by Busse (2019)." In the present paper, an additional NAVY stream is defined according to the Garden Warbler data.…”

“…Evaluation of the local heading patterns began with the standard procedure. An example is shown in Figure 2, according to the style described in earlier papers (Busse 2019(Busse , 2020. The results for the sites are presented in Figure 3 and documented in the Appendix -Sites table.…”

“…A new evaluation method was introduced as well (Busse 1995, Busse andTrociñska 1999). Since that time data from more than 43,000 tests on nocturnal migrants have been collected at more than 40 European ringing sites in autumn, mainly by the Operation Baltic and SEEN (SE European Bird Migration Network) (Busse 2019). Evaluation of the test data was discussed in detail by Busse (2018), and the general nocturnal migration pattern of passerines based on the collected data was presented in a subsequent paper by Busse (2019).…”

“…Since that time data from more than 43,000 tests on nocturnal migrants have been collected at more than 40 European ringing sites in autumn, mainly by the Operation Baltic and SEEN (SE European Bird Migration Network) (Busse 2019). Evaluation of the test data was discussed in detail by Busse (2018), and the general nocturnal migration pattern of passerines based on the collected data was presented in a subsequent paper by Busse (2019). First, it was found that at every location studied a few migration streams directed towards different destinations could be defined.…”

“…Previous estimations suggest that the level of precision of directions determined using estimation procedures can be plus/minus 6-11°, which means one of 32 rose-wind sectors. The estimation procedure, after Busse (2019), takes into account mainly the local maxima of the polygon of distribution of headings... For a more quantitative determination of the heading direction (and its 'power' -the number index of the heading vector) we can use not only the local maximum value in the result vector calculation, but also those closely bordering on it (minus one and plus one sector values), and sum up these three values. The result vector will be more precise than previously, and we will have some information about its power (share of the index in the total distribution).…”