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Extreme heights and changes in altitude of migrating Great Snipes - Barometer and accelerometer logging put new light on great migrations

Weber, Julia (2019) BION02 20191
Degree Projects in Biology
Abstract
Tracking birds throughout their migratory flights have reached new heights during the last decades, as new technology has made it possible to track birds during with higher accuracy than ever before. In this study, I have used accelerometer and air pressure data to mainly address the questions of altitude selection and changes during long distance non-stop migration in the Great Snipe (Gallinago media). Data was collected for autumn migration in 2016 and 2017, and for spring migration in 2018. During their long-distance non-stop migrations over the Mediterranean Sea and the Sahara Desert they can reach altitudes of 7000 m. Additionally, they perform numerous climbs equivalent to reaching their maximum altitude 5.4 times during the flight.... (More)
Tracking birds throughout their migratory flights have reached new heights during the last decades, as new technology has made it possible to track birds during with higher accuracy than ever before. In this study, I have used accelerometer and air pressure data to mainly address the questions of altitude selection and changes during long distance non-stop migration in the Great Snipe (Gallinago media). Data was collected for autumn migration in 2016 and 2017, and for spring migration in 2018. During their long-distance non-stop migrations over the Mediterranean Sea and the Sahara Desert they can reach altitudes of 7000 m. Additionally, they perform numerous climbs equivalent to reaching their maximum altitude 5.4 times during the flight. The birds were migrating at lower altitudes during the night compared to the day, and started climbing to higher altitudes before the break of dawn. When climbing throughout the non-stop flights, climb rates rarely exceeded 0.5 ms-1. The changes in altitude are discussed to be caused by geographical barriers, wind directions and atmospheric conditions, vision and risk of dehydration and overheating. While avoiding geographical barriers such as mountains may be an obvious explanation, it cannot explain all of the changes in altitude. The birds could be changing altitude to reach favourable winds for migration which can vary in both space and time, and to avoid turbulent air masses during the day. The birds’ ability to see its surroundings may also play a role, as could also the ability to avoid predators by avoiding the airspace at which they seek for prey. Although it proved difficult to draw any certain conclusions, I have been able to elaborate around important pathways for gaining a greater understanding of the patterns in altitude that we see in migrating Great Snipes. I also addressed questions of flight initiation time, where I found a strong correlation between flight initiation time and sunset time. This correlation is discussed to be caused by the birds taking advantage of favourable cues during sunset for calibrating their magnetic and celestial compasses. As the Great Snipe is red listed in Sweden and categorised as “near threatened” by IUCN , there is great value in gaining more knowledge about their migratory behaviour and the sensitivity of their migratory route in order to connect this with possible climatic changes and habitat deterioration at both breeding and wintering grounds. (Less)
Popular Abstract (Swedish)
Stora flygningar av små fåglar: Dubbelbeckasinen når höga höjder – flera gånger om

Flyttfåglar har länge fascinerat människan. Under lång tid visste vi väldigt lite om var fåglarna tog vägen på vintern, och än mindre hur dessa flygningar faktiskt genomfördes. Under det senaste årtiondet har utvecklingen av små mätapparater (”loggar”) gjort att vi nu vet betydligt mycket mer om vart fåglarna tar vägen och hur högt, snabbt och länge fåglarna flyger. Ett exempel är dubbelbeckasinen – där vi med hjälp av dessa loggar fått en större insikt i hur de genomför sina flyttningar från de skandinaviska fjällen till vinterområdena kring Kongofloden.

Dubbelbeckasinen (Gallinago media) är en vadarfågel som häckar i de skandinaviska fjällen. Till... (More)
Stora flygningar av små fåglar: Dubbelbeckasinen når höga höjder – flera gånger om

Flyttfåglar har länge fascinerat människan. Under lång tid visste vi väldigt lite om var fåglarna tog vägen på vintern, och än mindre hur dessa flygningar faktiskt genomfördes. Under det senaste årtiondet har utvecklingen av små mätapparater (”loggar”) gjort att vi nu vet betydligt mycket mer om vart fåglarna tar vägen och hur högt, snabbt och länge fåglarna flyger. Ett exempel är dubbelbeckasinen – där vi med hjälp av dessa loggar fått en större insikt i hur de genomför sina flyttningar från de skandinaviska fjällen till vinterområdena kring Kongofloden.

Dubbelbeckasinen (Gallinago media) är en vadarfågel som häckar i de skandinaviska fjällen. Till storleken är den inte mycket större än en koltrast. Trots detta flyger den otroligt långt och snabbt till dess vinterområden. I medelhastigheter på 73 km/h flyger de i under 3 dygn utan att stanna, från Jämtland till söder om Saharaöknen. Under dessa flygningar når de häpnadsväckande höjder. Vissa fåglar når upp till 7000 m över havsytan. Detta beror inte på att de måste flyga över till exempel höga berg. Däremot kan dessa höga flyghöjder förklaras med att det kan finnas fördelaktiga vindar som fågeln vill dra nytta av. Det är definitivt fördelaktigt ur energisynpunkt att flyga på hög höjd om lägre flyghöjder innebär starka mot- eller sidovindar.

Att dubbelbeckasinen når dessa höga höjder är i sig anmärkningsvärt. Dessutom når de inte bara dessa höjder en gång under sin flygning, utan de stiger och sjunker i höjd flera gånger. Totalt sett kan den stiga upp till höjder som motsvarar sin maximala flyghöjd mellan 2.2–5.4 gånger under flygningen. På dagen flyger de på medelhöjder om 3000 m–5600 m, medan de på natten ligger på höjder om 1800 m–3400 m. Det finns troligen flera samverkande förklaringar till varför dubbelbeckasinen ändrar sin flyghöjd så pass mycket. Att det kan skilja flera tusen meter i flyghöjd mellan dag och natt kan möjligen förklaras av att på dagen påverkas de nedre lagren av atmosfären mycket kraftigt av att den underliggande marken värms upp av solen, och i sin tur värmer upp atmosfären. Detta kan orsaka stor turbulens, vilket fåglarna gärna undviker. Dessutom kan det finnas ett värde för dubbelbeckasinen i att flyga på höjder där rovfåglar sällan jagar, för att undvika att bli ett byte. Att flyga på höga höjder kräver dock stora mängder energi, då luften är väldigt tunn, vilket kan förklara att dubbelbeckasinen väljer att flyga på lägre höjder under natten.

Masterexamensprojekt i Bevarandebiologi 45 hp 2019
Biologiska institutionen, Lunds universitet

Handledare: Åke Lindström
Handledarens avdelning/institution: Biodiversitet/Biologiska institutionen (Less)
Please use this url to cite or link to this publication:
author
Weber, Julia
supervisor
organization
course
BION02 20191
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8996972
date added to LUP
2019-10-22 15:21:00
date last changed
2019-10-22 15:21:00
@misc{8996972,
  abstract     = {Tracking birds throughout their migratory flights have reached new heights during the last decades, as new technology has made it possible to track birds during with higher accuracy than ever before. In this study, I have used accelerometer and air pressure data to mainly address the questions of altitude selection and changes during long distance non-stop migration in the Great Snipe (Gallinago media). Data was collected for autumn migration in 2016 and 2017, and for spring migration in 2018. During their long-distance non-stop migrations over the Mediterranean Sea and the Sahara Desert they can reach altitudes of 7000 m. Additionally, they perform numerous climbs equivalent to reaching their maximum altitude 5.4 times during the flight. The birds were migrating at lower altitudes during the night compared to the day, and started climbing to higher altitudes before the break of dawn. When climbing throughout the non-stop flights, climb rates rarely exceeded 0.5 ms-1. The changes in altitude are discussed to be caused by geographical barriers, wind directions and atmospheric conditions, vision and risk of dehydration and overheating. While avoiding geographical barriers such as mountains may be an obvious explanation, it cannot explain all of the changes in altitude. The birds could be changing altitude to reach favourable winds for migration which can vary in both space and time, and to avoid turbulent air masses during the day. The birds’ ability to see its surroundings may also play a role, as could also the ability to avoid predators by avoiding the airspace at which they seek for prey. Although it proved difficult to draw any certain conclusions, I have been able to elaborate around important pathways for gaining a greater understanding of the patterns in altitude that we see in migrating Great Snipes. I also addressed questions of flight initiation time, where I found a strong correlation between flight initiation time and sunset time. This correlation is discussed to be caused by the birds taking advantage of favourable cues during sunset for calibrating their magnetic and celestial compasses. As the Great Snipe is red listed in Sweden and categorised as “near threatened” by IUCN , there is great value in gaining more knowledge about their migratory behaviour and the sensitivity of their migratory route in order to connect this with possible climatic changes and habitat deterioration at both breeding and wintering grounds.},
  author       = {Weber, Julia},
  language     = {eng},
  note         = {Student Paper},
  title        = {Extreme heights and changes in altitude of migrating Great Snipes - Barometer and accelerometer logging put new light on great migrations},
  year         = {2019},
}