Nocturnal hypothermia as a migratory strategy in passerines
(2024) BION02 20232Degree Projects in Biology
- Abstract
- Involving a controlled reduction of body temperature (lowering of 3 - 10 °C), nocturnal hypothermia is a common strategy among birds to manage the high energy expenditure required for body temperature regulation, particularly during periods of elevated metabolic demands. In this study, I investigated whether migrating passerines generally use controlled nocturnal hypothermia as a migratory strategy at stopovers by implanting subcutaneous PIT tags to measure nocturnal body temperature change in 148 migrating birds across 22 passerine species. I found that the average drop in body temperature among the birds was 3.92±1.36 °C (mean ± SD), and 73.65% of the birds showed a decrease in nocturnal body temperature of 3 °C or more, indicating that... (More)
- Involving a controlled reduction of body temperature (lowering of 3 - 10 °C), nocturnal hypothermia is a common strategy among birds to manage the high energy expenditure required for body temperature regulation, particularly during periods of elevated metabolic demands. In this study, I investigated whether migrating passerines generally use controlled nocturnal hypothermia as a migratory strategy at stopovers by implanting subcutaneous PIT tags to measure nocturnal body temperature change in 148 migrating birds across 22 passerine species. I found that the average drop in body temperature among the birds was 3.92±1.36 °C (mean ± SD), and 73.65% of the birds showed a decrease in nocturnal body temperature of 3 °C or more, indicating that they were using hypothermia during the night. Birds with lower fat score, lower body mass, and those exposed to lower ambient temperatures showed greater drops in nocturnal body temperature, with fat reserve having the strongest effect. The results support my main hypothesis that nocturnal hypothermia is a widespread energy saving strategy among migrating passerines at stopover sites. My findings highlight the critical role of energy reserves for migratory birds and how environmental conditions can impact energy management strategies during avian migration. (Less)
- Popular Abstract
- Migrating birds reduce body temperature at night to save energy
During periods with high energy demands, birds commonly drop their body temperature below the normal resting level to save energy, but do they apply this strategy during migration?
During each year's autumn migration, billions of birds depart from their breeding sites to journey to their wintering habitats. Birds are expected to spend seven times as long at stopover sites as their actual flight time, and they use twice the amount of energy at stopovers as they do during flight. A major part of this energy is used to maintain body temperature, which is also considered to be one of the biggest energy expenditures throughout their migration.
To reduce the energy cost... (More) - Migrating birds reduce body temperature at night to save energy
During periods with high energy demands, birds commonly drop their body temperature below the normal resting level to save energy, but do they apply this strategy during migration?
During each year's autumn migration, billions of birds depart from their breeding sites to journey to their wintering habitats. Birds are expected to spend seven times as long at stopover sites as their actual flight time, and they use twice the amount of energy at stopovers as they do during flight. A major part of this energy is used to maintain body temperature, which is also considered to be one of the biggest energy expenditures throughout their migration.
To reduce the energy cost at stopover sites, bats have been found to drop their body temperature dramatically at night during migration. This brings up the question of whether birds also adopt similar strategies during their migratory journeys. While a few bird species have been observed using it, we still don’t fully know whether birds, in general, lower their body temperature more at night to assist their migration.
To test this hypothesis, I measured bird body temperature change by implanting tiny temperature-sensitive transponders (PIT tags) under the skin of 148 migrating birds across 22 passerine species. This is a minimally invasive approach that causes very little harm to birds and is highly reliable. Data loggers automatically recorded the birds' body temperature during the experimental nights.
My results show that 73.65% of the birds lowered their body temperature below normal levels during the night, suggesting they were using this strategy to help with their migration. Birds with less body fat, lower body weight, and those exposed to colder temperatures dropped their body temperature more at night, with body fat having the biggest impact.
My findings emphasize how important energy reserves are for migratory birds and how their energy management can be affected by environmental conditions. Since changes in habitat quality can reduce food availability at stopover sites and climate change can cause temperature fluctuations, it’s likely that birds' ability to drop body temperature at night and to use this strategy to save energy during migration will be significantly influenced in this changing environment. Future research could focus on investigating the long-term effects of climate change and habitat loss on bird migration success and bird populations.
Master’s Degree Project in Biology, 45 credits, 2024
Department of Biology, Lund University
Advisor: Fredrik Andreasson & Andreas Nord
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9176026
@misc{9176026,
abstract = {{Involving a controlled reduction of body temperature (lowering of 3 - 10 °C), nocturnal hypothermia is a common strategy among birds to manage the high energy expenditure required for body temperature regulation, particularly during periods of elevated metabolic demands. In this study, I investigated whether migrating passerines generally use controlled nocturnal hypothermia as a migratory strategy at stopovers by implanting subcutaneous PIT tags to measure nocturnal body temperature change in 148 migrating birds across 22 passerine species. I found that the average drop in body temperature among the birds was 3.92±1.36 °C (mean ± SD), and 73.65% of the birds showed a decrease in nocturnal body temperature of 3 °C or more, indicating that they were using hypothermia during the night. Birds with lower fat score, lower body mass, and those exposed to lower ambient temperatures showed greater drops in nocturnal body temperature, with fat reserve having the strongest effect. The results support my main hypothesis that nocturnal hypothermia is a widespread energy saving strategy among migrating passerines at stopover sites. My findings highlight the critical role of energy reserves for migratory birds and how environmental conditions can impact energy management strategies during avian migration.}},
author = {{Yao, Yao}},
language = {{eng}},
note = {{Student Paper}},
title = {{Nocturnal hypothermia as a migratory strategy in passerines}},
year = {{2024}},
}