Advanced

Migration strategy and winter area use of common swift (Apus apus) breeding in the Netherlands – using combined GeoLight and FlightR approach

Chen, Xier (2020) BION02 20192
Degree Projects in Biology
Abstract
Migration is an adaptation for birds to exploit the resources that change temporally and spatially. The recent development of miniature light level geolocators has revealed this previously poorly known aspect of birds. From light intensity data together with time recorded by geolocators, we can infer the positions of the birds, i.e. latitudes and longitudes, using a threshold method or a curve-fitting method. The focal species of this study, the common swift (Apus apus), is a long-distance migrant in Palearctic-Africa. Previous studies by geolocation has revealed the annual cycle of swifts from Sweden, Germany and the Netherlands, using the threshold method alone. In this study, we analyzed geolocator data of 15 individuals of common... (More)
Migration is an adaptation for birds to exploit the resources that change temporally and spatially. The recent development of miniature light level geolocators has revealed this previously poorly known aspect of birds. From light intensity data together with time recorded by geolocators, we can infer the positions of the birds, i.e. latitudes and longitudes, using a threshold method or a curve-fitting method. The focal species of this study, the common swift (Apus apus), is a long-distance migrant in Palearctic-Africa. Previous studies by geolocation has revealed the annual cycle of swifts from Sweden, Germany and the Netherlands, using the threshold method alone. In this study, we analyzed geolocator data of 15 individuals of common swifts from two colonies breeding in the Netherlands. We reconstructed the annual cycle of their migration and nonbreeding activities using a threshold method, GeoLight, and a curve-fitting method, FlightR. We found that the two methods gave consistent results on the migration route and schedule, as well as major stationary sites during the wintering period. Swifts in spring migration were found to make longer stopovers, but travelled faster than in autumn, suggesting a time-selected spring migration and the importance of wind assistance in major barrier crossing. The swifts in this study were highly mobile during the wintering period. All individuals used multiple major stationary sites in sub-Saharan Africa, as revealed by a kernel density based method to identify winter space use. The Congo Basin, the coastal areas of north-eastern Mozambique and the areas around Lake Malawi were identified as important hubs for the wintering swifts. We further investigated the timing of their winter movement, combining the positioning data and the 16-day Enhanced Vegetation Index (EVI). We found that the swifts largely tracked the local phenology and the greenness landscape, while they did seem to have an innate schedule and regular wintering sites. (Less)
Popular Abstract
Swift’s journey away from home

The common swift (Apus apus) is an iconic species and visitor of our summer months. Not long ago, their life away from their summer home had remained largely unknown. Thanks to the development of tracking technology, we have now started to reveal some exciting aspects of their migration and winter lifestyle. Geolocators are miniature tracking devices that can be mounted on small birds. They record the light intensity and can give us the sunrise and sunset time. Day length and midday/midnight time can then be used for calculating the positions of birds. In this study, we have applied a traditional threshold method and a more sophisticated curve-fitting method to analyze tracking data from 15 individual... (More)
Swift’s journey away from home

The common swift (Apus apus) is an iconic species and visitor of our summer months. Not long ago, their life away from their summer home had remained largely unknown. Thanks to the development of tracking technology, we have now started to reveal some exciting aspects of their migration and winter lifestyle. Geolocators are miniature tracking devices that can be mounted on small birds. They record the light intensity and can give us the sunrise and sunset time. Day length and midday/midnight time can then be used for calculating the positions of birds. In this study, we have applied a traditional threshold method and a more sophisticated curve-fitting method to analyze tracking data from 15 individual swifts breeding in the Netherlands. We aim to compare the two methods for geolocation, and investigate their winter activities as well as their migration strategy.

We found that the two methods gave relatively consistent results on the broad picture of the swifts’ journey, but it has also opened up some new possibilities for the later-developed evaluation method in future studies. Our swifts were found to travel faster in spring than in autumn. This can be a sign that they are in more of a haste in this time of the year, aiming at being the early one to arrive at the summer home. The faster speed also came with longer stopovers on the way, where the birds had to fuel up their energy deposit, while waiting for favorable wind conditions for crossing the Sahara Desert.

Fascinating winter movements
Unlike the Swedish counterparts, the Dutch swifts typically used several staging sites during the winter period. Roaming from the Congo Basin to the coastal areas of north-eastern Mozambique, the swifts were shown to be highly mobile. We further mapped their positions with the shift of the greenness landscape. Their fascinating movements seemed to closely track the green wave across sub-Saharan Africa, while at the same time the swifts appeared to have their own destination and schedule in their mind. Their movements can thus be an adaptation to exploit the resources that change spatially and temporally, or to reduce competition, while relying somehow on an innate migration program. It will be most interesting to explore further the ongoing technological development, to reveal more of the swifts’ winter activities, which very recently used to be poorly known.

Master’s Degree Project in Biology 45 credits 2020
Department of Biology, Lund University
Advisor: Susanne Åkesson
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Chen, Xier
supervisor
organization
course
BION02 20192
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
9022090
date added to LUP
2020-06-25 14:43:27
date last changed
2020-06-25 14:43:27
@misc{9022090,
  abstract     = {Migration is an adaptation for birds to exploit the resources that change temporally and spatially. The recent development of miniature light level geolocators has revealed this previously poorly known aspect of birds. From light intensity data together with time recorded by geolocators, we can infer the positions of the birds, i.e. latitudes and longitudes, using a threshold method or a curve-fitting method. The focal species of this study, the common swift (Apus apus), is a long-distance migrant in Palearctic-Africa. Previous studies by geolocation has revealed the annual cycle of swifts from Sweden, Germany and the Netherlands, using the threshold method alone. In this study, we analyzed geolocator data of 15 individuals of common swifts from two colonies breeding in the Netherlands. We reconstructed the annual cycle of their migration and nonbreeding activities using a threshold method, GeoLight, and a curve-fitting method, FlightR. We found that the two methods gave consistent results on the migration route and schedule, as well as major stationary sites during the wintering period. Swifts in spring migration were found to make longer stopovers, but travelled faster than in autumn, suggesting a time-selected spring migration and the importance of wind assistance in major barrier crossing. The swifts in this study were highly mobile during the wintering period. All individuals used multiple major stationary sites in sub-Saharan Africa, as revealed by a kernel density based method to identify winter space use. The Congo Basin, the coastal areas of north-eastern Mozambique and the areas around Lake Malawi were identified as important hubs for the wintering swifts. We further investigated the timing of their winter movement, combining the positioning data and the 16-day Enhanced Vegetation Index (EVI). We found that the swifts largely tracked the local phenology and the greenness landscape, while they did seem to have an innate schedule and regular wintering sites.},
  author       = {Chen, Xier},
  language     = {eng},
  note         = {Student Paper},
  title        = {Migration strategy and winter area use of common swift (Apus apus) breeding in the Netherlands – using combined GeoLight and FlightR approach},
  year         = {2020},
}