Photoperiodic response of body mass gain in migratory juvenile European pied flycatchers (Ficedula hypoleuca)

Abstract

Climate change forces organisms to adapt to new habitats with migratory birds facing unique challenges, especially when they initiate the migratory behaviour to gain mass for migration. Many bird species adapt to their ancestral latitudes by changing their behaviour and physiology to the photic environment. Current predictions indicate that climate change can also limit range shift capacity due to a photic mismatch. The pied flycatcher (Ficedula hypoleuca) is a migratory bird that migrates from northern Europe to western Africa therefore depending on specific cues to initiate migratory body mass gain. This experiment examined whether photoperiod triggers the migratory phenotype, specifically body mass growth of the pied flycatcher, a long-distance migrant. In Stensoffa, Southern Sweden, 24 juvenile pied flycatchers experienced three different photoperiods: 24 hours of continuous light, onset of autumn light, and local light to Stensoffa. Results indicate that the day length significantly influenced body mass, demonstrating that as the 24 h experiment progressed, the birds body masses diverged between treatments. This result indicated that the birds perceived themselves to be in their potential breeding grounds. The onset of Autumn experiment showed a significant difference in mass, however not as initially expected. This was due to the limited change in the manipulated photoperiod demonstrating a favourable photic environment conducive to their potential breeding grounds. During the third experiment, local light at Stensoffa, there was a slight disparity in mass therefore depicting an increase in body mass triggered by a change in photoperiod to their local environment. In summary, this study showed that the effects of photoperiod are evident on the bird’s migratory behaviour.

Popular Abstract

Pied flycatcher’s response to a changing daylength


Climate change is affecting many species around the world, and as a result, some are predicted to change their existing ranges. Birds, in particular, are having a tough time responding to these conditions. In fact, migratory birds must adapt to changes in their breeding habitat as well as in their wintering habitat. The birds respond to environmental cues to help trigger their preparation for migration, one of the most important being day length. As the days get shorter, the birds understand that they must increase their body mass to migrate from their breeding grounds to wintering grounds. However, due to range shifts caused by climate change, the birds are exposed to an altered day length, which they are not necessarily adapted to.

A long-distance migratory bird, the pied flycatcher relies on specific signals to begin preparing for migration as it travels from northern Europe to western Africa. In this study, I wanted to understand if this species relies on the change in day length as a critical cue for migration. I exposed juvenile pied flycatchers to different day lengths, using artificially manipulated light, to see if they changed their body mass according to where they believed they were located. The individuals were split into two groups: control and experimental. I carried out three experiments at Stensoffa ecological field station in southern Sweden: Firstly, they were exposed to a 24-hour continuous day length, then to an onset of autumn, replicating the day length at the beginning of autumn, and lastly to the local day length found at Stensoffa. The results show that for the duration of the 24-hour continuous light experiment, the experimental birds did not increase their body mass. However, the control birds did. This strongly indicates that the experimental birds thought they were still in their potential breeding grounds. This result was also supported by the findings in the onset of autumn experiment. Furthermore, the birds drastically increased their body mass when exposed to a significant shortening of the day, the local light at Stensoffa.

The findings throughout these three experiments support the prediction that birds rely on photoperiod as a critical cue for migratory preparation. Therefore, as the birds shift their ranges and move further north, they will be exposed to longer day lengths. This is likely to cause the birds to migrate later or even change their migratory patterns completely, from long-distance to short-distance, or even stop migrating altogether. This response seen in this relatively adapted species, the pied flycatcher, causes us to think about the birds that have recently moved their distribution further north. How will these species adapt to exposure to altered day lengths? How will they respond?





Master’s Thesis project in Conservation Biology 60 credits 2024 Department of Biology, Lund University

Supervisors: Susanne Åkesson, Nicholas Per Huffeldt Department of Biology

• author: Floyd, Jessica Marie Victoria
• supervisor: Susanne Åkesson; Nicholas Per Huffeldt
• organization: Degree Projects in Biology
• course: BION03 20221
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9149193
• date added to LUP: 2024-02-28 13:27:10
• date last changed: 2024-02-28 13:27:10