Migratory and wintering behaviour of the Baltic Lesser Black-backed Gull (Larus fuscus fuscus)
(2025) BION02 20242Degree Projects in Biology
- Abstract
- GPS tracking technologies are essential to follow long-distance migratory species throughout their annual cycle and identify the threats they encounter at large geographical scales. Information on the “lost” years of juvenile individuals of many species is lacking and it is vital to uncover their movements during these critical early stages. The Baltic Lesser Black-backed Gull (L. f. fuscus), a long-distance migratory seabird, is now classified as endangered and its populations have been decreasing in the last decades as a result of food shortages in the Baltic and pesticide contamination in its wintering grounds. A total of 70 adult and 39 young Baltic gulls from Swedish colonies were equipped with GPS trackers to compare the movement... (More)
- GPS tracking technologies are essential to follow long-distance migratory species throughout their annual cycle and identify the threats they encounter at large geographical scales. Information on the “lost” years of juvenile individuals of many species is lacking and it is vital to uncover their movements during these critical early stages. The Baltic Lesser Black-backed Gull (L. f. fuscus), a long-distance migratory seabird, is now classified as endangered and its populations have been decreasing in the last decades as a result of food shortages in the Baltic and pesticide contamination in its wintering grounds. A total of 70 adult and 39 young Baltic gulls from Swedish colonies were equipped with GPS trackers to compare the movement behaviour of adults versus juveniles in autumn migration, of adults in autumn versus in spring migration and of adults versus juveniles in their wintering grounds in Africa. This tracking data revealed that adults spent less time on migration and migrated at a faster speed than juveniles during autumn migration as a result of reduced time spent at stopovers. Adults also spent less time on migration and migrated at a faster speed during autumn migration than during spring migration due to the use of a shorter migration route, faster flight speeds and a reduced time spent at stopovers. Adults were also found to occupy larger core ranges and move larger distances within their wintering range than juveniles. Age differences in autumn migration speeds likely occur because juveniles achieve lower fuelling rates than adults at stopovers. Seasonal differences in adult migration may be a result of tailwinds encountered during autumn migration and headwind-driven detours in Africa plus a weather-dependent timed arrival at breeding grounds in spring. Previous knowledge on the wintering range landscape might facilitate the roaming of larger areas and distances in adults in winter compared to naïve juveniles. Our identification of the main wintering sites in Baltic gulls could provide support for the implementation of conservation actions tackling potential pesticide contamination in these areas. Further research on migratory connectivity and habitat use in wintering grounds is recommended to identify the specific contact zones between Baltic gulls and pesticides. (Less)
- Popular Abstract
- A study on the migratory and wintering behaviour of the Baltic Lesser Black-backed Gull (Larus fuscus fuscus)
Tracking technologies have the potential to uncover the locations of long-distance migrants throughout their annual cycle. This is of vital importance for the conservation of species that face threats at large geographical scales and to pinpoint where those threats occur. The Baltic Lesser Black-backed Gull (Larus fuscus fuscus) is a long-distance migrant and is currently considered as endangered since its populations have been declining due to food shortages in its breeding grounds and pesticide contamination in Africa, where it spends the winter.
GPS tracking was used to monitor 109 gulls, 70 adults and 39 juveniles, from... (More) - A study on the migratory and wintering behaviour of the Baltic Lesser Black-backed Gull (Larus fuscus fuscus)
Tracking technologies have the potential to uncover the locations of long-distance migrants throughout their annual cycle. This is of vital importance for the conservation of species that face threats at large geographical scales and to pinpoint where those threats occur. The Baltic Lesser Black-backed Gull (Larus fuscus fuscus) is a long-distance migrant and is currently considered as endangered since its populations have been declining due to food shortages in its breeding grounds and pesticide contamination in Africa, where it spends the winter.
GPS tracking was used to monitor 109 gulls, 70 adults and 39 juveniles, from Swedish colonies. These gulls were tracked to their wintering grounds in Africa and back to their breeding grounds in Scandinavia for several seasons. The study focused on comparing how adult and young gulls migrate in autumn, how adult migration differs between spring and autumn, and how wintering behaviors vary between age groups.
The first main finding was that adults migrate faster in autumn. Adult gulls used spent a shorter amount of time at stopovers. This was likely to happen because juveniles are still learning how to refuel efficiently on their first journey to Africa. The second main finding was that adults took longer to migrate in spring than in autumn. The main reasons for this are possibly that gulls encounter challenging headwinds over the Sahara in spring and need to time their arrival to favourable climatic conditions at breeding areas. The third main finding was that adults typically wintered farther south, often around Lake Victoria in East Africa, and roamed larger areas. Young birds, on the other hand, wintered closer to the Mediterranean and were less mobile. This suggests that adults, familiar with the landscape, can exploit resources more broadly, while naïve younger gulls limit their movements to a local scale.
These findings shed some light on the migration routes and behaviour of Baltic gulls and also pinpoint some wintering locations that need protection in Africa. Pesticide use and the ways in which gulls have contact with the agents should be further investigated in these regions.
Master’s Degree Project in Biology – Animal Ecology, 45 credits, 2025
Department of Biology, Lund University
Supervisors: Susanne Åkesson and Liam Langley (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9215017
- author
- Estrada, Joan
- supervisor
-
- Susanne Åkesson LU
- Liam Langley LU
- organization
- course
- BION02 20242
- year
- 2025
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9215017
- date added to LUP
- 2025-11-06 14:56:19
- date last changed
- 2025-11-06 14:56:19
@misc{9215017,
abstract = {{GPS tracking technologies are essential to follow long-distance migratory species throughout their annual cycle and identify the threats they encounter at large geographical scales. Information on the “lost” years of juvenile individuals of many species is lacking and it is vital to uncover their movements during these critical early stages. The Baltic Lesser Black-backed Gull (L. f. fuscus), a long-distance migratory seabird, is now classified as endangered and its populations have been decreasing in the last decades as a result of food shortages in the Baltic and pesticide contamination in its wintering grounds. A total of 70 adult and 39 young Baltic gulls from Swedish colonies were equipped with GPS trackers to compare the movement behaviour of adults versus juveniles in autumn migration, of adults in autumn versus in spring migration and of adults versus juveniles in their wintering grounds in Africa. This tracking data revealed that adults spent less time on migration and migrated at a faster speed than juveniles during autumn migration as a result of reduced time spent at stopovers. Adults also spent less time on migration and migrated at a faster speed during autumn migration than during spring migration due to the use of a shorter migration route, faster flight speeds and a reduced time spent at stopovers. Adults were also found to occupy larger core ranges and move larger distances within their wintering range than juveniles. Age differences in autumn migration speeds likely occur because juveniles achieve lower fuelling rates than adults at stopovers. Seasonal differences in adult migration may be a result of tailwinds encountered during autumn migration and headwind-driven detours in Africa plus a weather-dependent timed arrival at breeding grounds in spring. Previous knowledge on the wintering range landscape might facilitate the roaming of larger areas and distances in adults in winter compared to naïve juveniles. Our identification of the main wintering sites in Baltic gulls could provide support for the implementation of conservation actions tackling potential pesticide contamination in these areas. Further research on migratory connectivity and habitat use in wintering grounds is recommended to identify the specific contact zones between Baltic gulls and pesticides.}},
author = {{Estrada, Joan}},
language = {{eng}},
note = {{Student Paper}},
title = {{Migratory and wintering behaviour of the Baltic Lesser Black-backed Gull (Larus fuscus fuscus)}},
year = {{2025}},
}