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Partial migration in the common blackbird (Turdus merula) in the south of Sweden

Bengtsson, Jekaterina (2020) BIOK01 20201
Degree Projects in Biology
Popular Abstract
Vacation or staycation?

Seasonal migration is common practice among many different species, including many birds. Birds living in cold climates, such as Scandinavia, experience food shortage during the winter months. Thus, many chose to vacation abroad where the climate is warmer and food is plentiful. However, not all bids in a population make the move – some stay put. This is known as partial migration. So what causes some birds to stay behind?

Multiple explanations of this behaviour exist. Some theories propose that larger individuals can withstand the cold better than small birds as they lose less heat and have slower metabolism – meaning they can survive on less food. Another theory suggests that competition over resources... (More)
Vacation or staycation?

Seasonal migration is common practice among many different species, including many birds. Birds living in cold climates, such as Scandinavia, experience food shortage during the winter months. Thus, many chose to vacation abroad where the climate is warmer and food is plentiful. However, not all bids in a population make the move – some stay put. This is known as partial migration. So what causes some birds to stay behind?

Multiple explanations of this behaviour exist. Some theories propose that larger individuals can withstand the cold better than small birds as they lose less heat and have slower metabolism – meaning they can survive on less food. Another theory suggests that competition over resources drives the smaller and subordinate individuals away as they cannot compete with larger birds. More recently it has been discovered that the state of a bird’s immune system also might influence their decision. However, it is not yet fully understood how the immune system influences migration.

We investigated how a compromised immune system effects migration in the common blackbird. By equipping the birds with small radio tags, we were able to track the birds and determine which individuals overwintered and which chose to migrate and which stayed. I was also interested in what territories the birds occupied when they came back from their journey.

Although previous research suggests immune compromised birds are more likely to overwinter than heathy birds, we were not able show this. However, this does not dispute the importance of immune function but rather suggests that other mechanisms are at play. We did discover that age strongly influences which territories the bird chooses to occupy. Young birds take new territories further away from the ones they occupied in the previous year, which presumably were near their birthplace. This supports the theory that competition for resources forces the less dominant individuals to move.

Partial migration is still a new and developing field. Further research into the effects of immune function can shine a light on mechanisms behind this behaviour. As many bird species decline in numbers, an understanding of partial migration can help when developing conservation strategies as well as help understand how man-made disturbances affects their habitats.

Bachelor’s degree project in Biology 15 cr 2020
Department of Biology, Lund University

Supervisor: Arne Hegemann
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Bengtsson, Jekaterina
supervisor
organization
course
BIOK01 20201
year
type
M2 - Bachelor Degree
subject
language
English
id
9021698
date added to LUP
2020-06-23 15:24:25
date last changed
2020-06-23 15:24:25
@misc{9021698,
  author       = {{Bengtsson, Jekaterina}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Partial migration in the common blackbird (Turdus merula) in the south of Sweden}},
  year         = {{2020}},
}