Incubation behaviour and nesting success of three species of sea ducks in the Swedish archipelago of the Baltic Sea
(2025) BIOM02 20141Degree Projects in Biology
- Abstract
- Nesting phenology in birds has been studied for decades and two different breeding strategies have been identified, income and capital breeding. The nesting behaviour and the breeding strategies of 131 females were studied from three species, the Common eider (Somateria mollissima) (n = 65), known to be a capital breeder and two species the Velvet scoter (Melanitta fusca) (n = 48) and the Red-breasted merganser (Mergus serrator) (n =18). The study is based on data from three breeding seasons (2021-2023). Light and conductivity geolocators were attached to incubating females to measure the time spent away from nest per day and to estimate the date of incubation start. Additionally, the hatching success was monitored, and eggs were counted... (More)
- Nesting phenology in birds has been studied for decades and two different breeding strategies have been identified, income and capital breeding. The nesting behaviour and the breeding strategies of 131 females were studied from three species, the Common eider (Somateria mollissima) (n = 65), known to be a capital breeder and two species the Velvet scoter (Melanitta fusca) (n = 48) and the Red-breasted merganser (Mergus serrator) (n =18). The study is based on data from three breeding seasons (2021-2023). Light and conductivity geolocators were attached to incubating females to measure the time spent away from nest per day and to estimate the date of incubation start. Additionally, the hatching success was monitored, and eggs were counted during field visits. The results reveal interspecific differences in incubation behaviour. Common eiders showed the lowest time spent away from the nest (23 minutes/day), Velvet scoter spent significantly more time (89 min/day) away from the nest meanwhile the Red-breasted merganser showed 121 min/day, which is around five times higher compared to the Common eider. The results clearly indicates that the Common eider relies more on stored energy reserves during breeding than the other species, suggesting that local food availability is more important for the other two species during this part of the breeding period. No interannual variation in time spent away from the nest was found for the Common eider but was found for the Velvet scoter. Signs of interannual variation was present also for the Red-breasted merganser. All species showed high hatching success, between 87% and 92%. There was an indication that Common eider females, with high nesting success spent less time away from the nest per day than those with predated or abandoned nests. The results suggest that resource availability and environmental factors may be of varying importance for breeding females among the three study species, and this may have important implications for conservation efforts. (Less)
- Popular Abstract
- Incubation behaviour and nesting success of three species of sea ducks in the Swedish archipelago of the Baltic Sea
A study of nesting phenology of Common eider (Somateria mollissima), Velvet scoter (Melanitta fusca) and Red-breasted merganser (Mergus serrator) females on the island of Hävringe in the Baltic Sea. I investigated the incubation behaviour and nesting success of these species, and two breeding strategies, energy-storing (capital) and foraging-dependent (income) breeding.
Birds show prominent differences in breeding strategies. Capital and income breeding are often mentioned as the two main strategies and is well-known within bird research. Capital breeders use energy storage and income breeders must get an income i.e.... (More) - Incubation behaviour and nesting success of three species of sea ducks in the Swedish archipelago of the Baltic Sea
A study of nesting phenology of Common eider (Somateria mollissima), Velvet scoter (Melanitta fusca) and Red-breasted merganser (Mergus serrator) females on the island of Hävringe in the Baltic Sea. I investigated the incubation behaviour and nesting success of these species, and two breeding strategies, energy-storing (capital) and foraging-dependent (income) breeding.
Birds show prominent differences in breeding strategies. Capital and income breeding are often mentioned as the two main strategies and is well-known within bird research. Capital breeders use energy storage and income breeders must get an income i.e. forage during incubation. Within the Sea duck (Mergini) subfamily, the Common eider has been widely studied and claimed the capital breeding strategy. Meanwhile, the Velvet scoter and Red-breasted merganser has not been studied in this subject area. All three species are threatened, and the incubation period can be a vulnerable time, and one of the known main negative factors on nesting success is predation. So, what are the differences between the species? Is the Common eider a true capital breeder and what are the other species? What differences appear, does one species have higher nesting success due to a certain breeding behaviour? That’s what I am going to investigate.
The study area is in the Baltic Sea on the coast of Sweden on the island of Hävringe. In the study, light and conductivity geolocators were used to analyse the incubation behaviour of the females. The geolocators were attached and taken off during incubation. They were attached to the females legs for 1-2 years recording parts of 2-3 incubation periods. Specifically, the conductivity data (when the females come in contact with salt or brackish water) was used for investigating when females were away from the nest, referred to as time spent away from nest per day. This in combination with the light data which was examined using graphs (figure 1). The key variables that could be taken from the conductivity data was incubation start, time spent away from nest, hatching date and duration of the incubation period. Interannual differences per species and interspecific differences in time spent away from nest were then investigated. Furthermore, nesting success was studied within species with three different nest fate categories, Hatched, Abandoned and Predated and the time spent away from nest was used to compare the three categories. In addition to that, eggs per female in relation to incubation start was studied to understand if earlier incubation start was correlated to larger clutches.
Is the incubation behaviour and nesting success different between the species?
The Common eider as expected spent the least amount of time away from nest (median 23.3 min/day) and had no variation between the years, suggesting it to be a capital breeder. Meanwhile, Velvet scoter showed variation between years and a median time of 88.9 minutes per day, almost 4 times the amount of the Common eider. Furthermore, the Red-breasted merganser had the highest time spent away from nest (120.6 min/day), however no significant difference between the years. This could suggest that the Red-breasted merganser is the most dependent, out of the three species, to forage during the incubation period which could suggest that it is an income breeder. When comparing these three species, the Velvet scoter comes between the other two species, however as it is closer to the Red-breasted merganser I would still suggest that the Velvet scoter is an income breeder.
Nesting success was high with 87%, 88% and 92% for Common eider, Velvet scoter and Red-breasted merganser, respectively. There was not a significant difference between the nest fate categories Hatched, Predated and Abandoned, however an indication for the Common eider females, the females on hatched nests, spent less time away from nest per day than the Abandoned and Predated nests. Eggs per female in relation to incubation start did not show any significance.
To further investigate nesting phenology, a combination with biometric (e.g. weight, wingspan, tarsus length) data and bigger sample sizes could get a more precise answer on what breeding strategy is used by each species. Furthermore, the high nesting success shows that the decline of these three species might not be due to failed incubation, therefore other parts of the nesting period might be of importance to investigate.
Master’s Degree Project in Biology with specialization in Animal ecology 30 credits 2024
Department of Biology, Lund University
Superpvisor: Fredrik Haas, Lund university, Department of Biology
Co-supervisors: Johan Månsson, Swedish University of Agricultural Sciences and Niklas Liljebäck, Swedish hunting association (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9185154
- author
- Öhlund, Andreas
- supervisor
- organization
- course
- BIOM02 20141
- year
- 2025
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9185154
- date added to LUP
- 2025-02-13 13:39:21
- date last changed
- 2025-02-13 13:39:21
@misc{9185154,
abstract = {{Nesting phenology in birds has been studied for decades and two different breeding strategies have been identified, income and capital breeding. The nesting behaviour and the breeding strategies of 131 females were studied from three species, the Common eider (Somateria mollissima) (n = 65), known to be a capital breeder and two species the Velvet scoter (Melanitta fusca) (n = 48) and the Red-breasted merganser (Mergus serrator) (n =18). The study is based on data from three breeding seasons (2021-2023). Light and conductivity geolocators were attached to incubating females to measure the time spent away from nest per day and to estimate the date of incubation start. Additionally, the hatching success was monitored, and eggs were counted during field visits. The results reveal interspecific differences in incubation behaviour. Common eiders showed the lowest time spent away from the nest (23 minutes/day), Velvet scoter spent significantly more time (89 min/day) away from the nest meanwhile the Red-breasted merganser showed 121 min/day, which is around five times higher compared to the Common eider. The results clearly indicates that the Common eider relies more on stored energy reserves during breeding than the other species, suggesting that local food availability is more important for the other two species during this part of the breeding period. No interannual variation in time spent away from the nest was found for the Common eider but was found for the Velvet scoter. Signs of interannual variation was present also for the Red-breasted merganser. All species showed high hatching success, between 87% and 92%. There was an indication that Common eider females, with high nesting success spent less time away from the nest per day than those with predated or abandoned nests. The results suggest that resource availability and environmental factors may be of varying importance for breeding females among the three study species, and this may have important implications for conservation efforts.}},
author = {{Öhlund, Andreas}},
language = {{eng}},
note = {{Student Paper}},
title = {{Incubation behaviour and nesting success of three species of sea ducks in the Swedish archipelago of the Baltic Sea}},
year = {{2025}},
}