Research: Impacts of climate change on the northern wheatear
Climate change has major consequences for ecosystems and populations. The uneveness of climate change across the planet presents particular challenges for long-distance migrant birds because they have to time their migrations to coincide with food availability at locations hundreds or thousands of kilometres apart.
In my PhD research, I am investigating how climate-linked changes in food availability affect the breeding success, migration strategies and survival of the northern wheatear Oenanthe oenanthe (or wheatear for short). The wheatear undergoes the longest known migration of any passerine (songbird) in the world, with those breeding in Alaska travelling all the way to sub-Saharan Africa to spend the winter. The wheatear has a very large breeding distribution, from northwest Europe, through Siberia and Alaska in one direction, with another race (The Greenland wheatear, Oenanthe oenanthe leucorhoa) breeding in Iceland, Greenland and eastern Canada.
I am carrying out field-based feeding experiments, setting up feeding stations consisting of
bowls with mealworms placed on top of an electronic balance and monitored remotely by video camera.
I have been doing this on (1) Fair Isle, Shetland, where there is a high density of breeding wheatears,
as well as many stopping over on migration, (2) Senegal, where many wheatears of both Greenland and
nominate races overwinter, and (3) Disko Island, Greenland, where many Greenland wheatears breed.
Migration
The wheatears breeding in Greenland have one of the most arduous migratory journeys of any passerine (songbird) in the world. Twice a year, they must cross the Atlantic on the way to and from their wintering grounds in west Africa. Before leaving on migration, birds are triggered into a feeding frenzy by a hormonal change, and spend all hours of daylight eating food to build up their flight muscle mass and fat stores.
Climate change is predicted to affect the abundance and timing of emergence of the invertebrates
that wheatears and others like them eat. I am carrying out feeding experiments to better understand
how the migration strategy (e.g. how much fuel to accumulate, when to leave) is affected by changes
in food availability. I am also using geolocators on Greenland wheatears in collaboration with
Prof Susanne Åkesson (Lund
University) and Dr Ulf Ottosson (AP Leventis
Ornithological Research Institute).
Breeding Success
How will climate-linked changes in food availability affect the reproductive success of migratory birds? I am monitoring variables including laying date, clutch size, hatching success, brood provisioning rate, chick growth rates and fledgling success. I have been recording brood provisioning rates using a combination of video recording and custom-made automatic nest loggers.
Survival
Do differences in food availability affect the survival of migratory birds? What life history stages are most affected? I use colour ringing to identify individual wheatears. As well as being necessary to monitor individuals for the questions surrounding migration and reproductive success, this enables survival of individual birds to be estimated by resighting birds returning in subsequent years. Fair Isle is a small island, and wheatears are very site faithful.
My PhD is jointly based at Cardiff University and the James Hutton Institute (formerly the Macaulay Institute), supervised by Dr Rob Thomas (Cardiff), Dr Colin Beale (formerly Macaulay/James Hutton), Dr Lucy Gilbert (James Hutton) and Dr Hefin Jones (Cardiff).
