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Northern wheatears (Oenanthe oenanthe) decrease oxidative stress at stop-over during spring migration

Winslott, Erica (2019) BIOM02 20191
Degree Projects in Biology
Abstract
During migration birds are exposed to several challenges, one of these are the potential threat of getting oxidative stressed. Oxidative stress can be defined as when free radicals are produced in a vastly amount so antioxidants cannot detoxify them. This is the case at higher metabolic rate such as migratory flight, and probably during hyperphagia at stop-over. The aim of this paper was to investigate the oxidative condition in northern wheatears (O. oenanthe) at stop-over. Does oxidative stress decrease at stop-over, and what could this potential decrease depend on? Could it depend on an upregulation in antioxidant capacity? Or is it possible that wheatears do not increase ROS at hyperphagia and therefore that rest i.e. lower metabolic... (More)
During migration birds are exposed to several challenges, one of these are the potential threat of getting oxidative stressed. Oxidative stress can be defined as when free radicals are produced in a vastly amount so antioxidants cannot detoxify them. This is the case at higher metabolic rate such as migratory flight, and probably during hyperphagia at stop-over. The aim of this paper was to investigate the oxidative condition in northern wheatears (O. oenanthe) at stop-over. Does oxidative stress decrease at stop-over, and what could this potential decrease depend on? Could it depend on an upregulation in antioxidant capacity? Or is it possible that wheatears do not increase ROS at hyperphagia and therefore that rest i.e. lower metabolic rate could be responsible for the decrease? Wheatears were caught at Helgoland, a German offshore island, during spring migration and kept in cages with ad libitum amount of food. Two blood samples were taken with two days in-between. The results show new and intriguing data about how birds cope with oxidative stress at stop-over. There was a significant decrease in lipid damage (MDA), however no change in non-enzymatic antioxidants (AOX) between the blood samples. Wheatears do not seem to suffer from increased ROS production during hyperphagia since MDA nor AOX correlated with fuel deposition rate or total food intake. The change in MDA was not related to change in AOX. Taken together, the decrease in MDA seems to depend on rest due to lower metabolic rate rather than an upregulation in antioxidants. In addition, there was an among individual variation where wheatears that arrive in poor oxidative state can decrease their MDA concentration substantially. This result shows that birds arriving in poor oxidative condition can improve well enough for oncoming flight. Oxidative stress is seldom considered in the area of migration, however new knowledge in this field could perhaps explain some migratory behaviour, e.g. using poor stop-over sites. (Less)
Popular Abstract
Resting allows migrating birds to recover

Migration is an activity that many different animals undertake - from butterflies to fish to birds. It comes with challenges though, for birds’ long flights and rapid refueling at stopovers are physically demanding. In this project we wanted to provide more information about how birds cope with a specific physical challenge, oxidative stress, when arriving to stop-over after a migratory flight session.

Oxidative stress is experienced when free radicals are produced in such large amounts that the defense mechanisms in the body (antioxidants) cannot detoxify them. Free radicals are dangerous in high concentrations since they can damage proteins, fat and DNA. These are formed in higher... (More)
Resting allows migrating birds to recover

Migration is an activity that many different animals undertake - from butterflies to fish to birds. It comes with challenges though, for birds’ long flights and rapid refueling at stopovers are physically demanding. In this project we wanted to provide more information about how birds cope with a specific physical challenge, oxidative stress, when arriving to stop-over after a migratory flight session.

Oxidative stress is experienced when free radicals are produced in such large amounts that the defense mechanisms in the body (antioxidants) cannot detoxify them. Free radicals are dangerous in high concentrations since they can damage proteins, fat and DNA. These are formed in higher quantities e.g. during intensive metabolic activity or when eating an excessive amount of food (hyperphagia), at least in mammals. During migration, birds are both exposed to high metabolic activity, flying, and hyperphagia at stop-over sites when refueling. Previous research has shown that birds increase oxidative stress during migratory flight, and upregulate antioxidants compared to non-migratory conspecifics, but overall the oxidative system has received little attention.

The aim of this experiment was to investigate if northern wheatears (Oenanthe oenanthe) decrease oxidative stress at stop-over during spring migration, and what this decrease could depend on. The birds were caught at their stop-over site, Helgoland, and kept in indoor cages where they had ad libitum access to food during the daytime. Two blood samples were taken with two days apart, and lipid damage and antioxidants were further extracted in the lab. The potential decrease in lipid damage could be due to an upregulation in antioxidant capacity, or perhaps it is possible that wheatears do not increase production of free radicals at hyperphagia and therefore that rest i.e. lower metabolic rate could be responsible for the decrease? The general assumption and theory behind this is that under decreased metabolic rate the production of free radicals is decreased.

A little bit of rest could be the answer
The results revealed that wheatears decreased their oxidative damage at stop-over. In addition, individuals in poor oxidative state at arrival decreased lipid damage substantially in comparison with those in better oxidative condition at arrival, providing all migratory birds to reset their physiology to a similar default level. The concentration of antioxidants was not upregulated, and the wheatears did not seem to suffer from hyperphagia during refuelling. Further, the change in oxidative damage between the two blood samples was not related to the change in antioxidants. Therefore, the results support that wheatears probably decrease oxidative stress due to rest (reduced production of free radicals) rather than an upregulation of antioxidants. However, the set-up of the experiment could have influenced the results; such as no predation pressure i.e. higher survival for birds in poor condition in the cages, and only one food source which took away the ability for the birds to choose food rich in antioxidants.

In the field of migration, oxidative stress is seldom considered. However new research, such as this experiment, shows that it is an important physiological factor to study when trying to understand migratory behaviours, as stopping at a seemingly poor stop-over sites.

Master’s Degree Project in Biology 30 credits 2019
Department of Biology, Lund University

Supervisors: Caroline Isaksson and Cas Eikenaar
Lund University, Evolutionary Ecology and Wilhelmshaven, Institute of Avian Research (Less)
Please use this url to cite or link to this publication:
author
Winslott, Erica
supervisor
organization
course
BIOM02 20191
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8989813
date added to LUP
2019-07-03 15:32:11
date last changed
2019-07-03 15:32:11
@misc{8989813,
  abstract     = {During migration birds are exposed to several challenges, one of these are the potential threat of getting oxidative stressed. Oxidative stress can be defined as when free radicals are produced in a vastly amount so antioxidants cannot detoxify them. This is the case at higher metabolic rate such as migratory flight, and probably during hyperphagia at stop-over. The aim of this paper was to investigate the oxidative condition in northern wheatears (O. oenanthe) at stop-over. Does oxidative stress decrease at stop-over, and what could this potential decrease depend on? Could it depend on an upregulation in antioxidant capacity? Or is it possible that wheatears do not increase ROS at hyperphagia and therefore that rest i.e. lower metabolic rate could be responsible for the decrease? Wheatears were caught at Helgoland, a German offshore island, during spring migration and kept in cages with ad libitum amount of food. Two blood samples were taken with two days in-between. The results show new and intriguing data about how birds cope with oxidative stress at stop-over. There was a significant decrease in lipid damage (MDA), however no change in non-enzymatic antioxidants (AOX) between the blood samples. Wheatears do not seem to suffer from increased ROS production during hyperphagia since MDA nor AOX correlated with fuel deposition rate or total food intake. The change in MDA was not related to change in AOX. Taken together, the decrease in MDA seems to depend on rest due to lower metabolic rate rather than an upregulation in antioxidants. In addition, there was an among individual variation where wheatears that arrive in poor oxidative state can decrease their MDA concentration substantially. This result shows that birds arriving in poor oxidative condition can improve well enough for oncoming flight. Oxidative stress is seldom considered in the area of migration, however new knowledge in this field could perhaps explain some migratory behaviour, e.g. using poor stop-over sites.},
  author       = {Winslott, Erica},
  language     = {eng},
  note         = {Student Paper},
  title        = {Northern wheatears (Oenanthe oenanthe) decrease oxidative stress at stop-over during spring migration},
  year         = {2019},
}