Association of weather variables with the migration phenology and body conditions of Siberian warblers

László Bozó,Tibor Csörgő,Yury Anisimov

doi:10.51812/of.113447

László Bozó, Tibor Csörgő + Show 1 more

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https://doi.org/10.51812/of.113447

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Abstract

Different elements of weather, such as wind speed, wind direction, precipitation and temperature are very important regulators of bird migration. Weather conditions also play role on the body condition such as body mass and the deposited fat. In this study we selected four warbler species to examine the impact of different weather variables on their spring and autumn migration timing and their body condition in one of the most extreme weather areas of the Earth, at Lake Baikal in Siberia. We also studied the changes in body mass and fat reserves during the spring and autumn migration periods of these species. For the analyses, we used ringing data of 2471 birds from five spring and five autumn seasons during 2015–2019. According to our results, it can be stated that the weather did not have a significant association with the migration timing of the studied warblers, perhaps due to the geographical location of the study site. However, the body mass and the fat reserves of the birds increased during unsuitable weather conditions because of the increased energy requirements. Birds generally migrate with low fat reserves, which is due to the fact that this area is not an important stopover site for these species.

Highlights

The most intense migration occurs in synoptic weather conditions, in the transitional phase on the western side of low-pressure systems and the eastern side of high-pressure areas, when the temperature decreases, the sky clears, the air pressure increases and the wind direction changes (Alerstam 1990)
We examined the impact of different weather variables on bird migration in one of the most extreme weather areas of the Earth, near South Siberia
We examined how much fat the birds had during the different migration periods, and how much the weather associates with the weight and the stored fat reserves of the birds

Summary

Introduction

Birds usually migrate in windless, anticyclonic weather conditions without precipitation or with the support of tailwinds (Alerstam 1990, Gyurácz et al 1997, 2003, Bruderer & Boldt 2001, Erni et al 2002), while cloudy skies, poor visibility, strong head- or crosswinds, and warm or occluded fronts have negative effects on the migration (Åkesson 1993, Pyle et al 1993). The most intense migration occurs in synoptic weather conditions, in the transitional phase on the western side of low-pressure systems and the eastern side of high-pressure areas, when the temperature decreases, the sky clears, the air pressure increases and the wind direction changes (Alerstam 1990). Temperature clearly has an effect on the timing of bird migration. The local temperature on the breeding grounds affected at least the early subsets of the bird populations (Tøttrup et al 2010). As a result of global climate change, more and more migratory bird species return to their breeding grounds earlier in spring, which indicates that temperatures – at least in spring – affect bird migration (Kullberg et al 2015, Bozó & Csörgő 2020)

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