TRACKING WHITE STORKS WITH GPS LOGGERS
An exciting
collaboration between the University of East Anglia, UK, and local researchers
in Portugal to attach experimental GPS data loggers to White Storks.
Kris (39+) takes flight with a logger on his back |
One important habitat
change of particular interest to me is the imminent closure across Portugal of
the landfill sites that storks rely on heavily for food supply, especially in
winter. Open landfill is gradually being replaced by hi-tec facilities where
food waste is handled under cover to prevent smell. This means food will no
longer be available to foraging birds, including White Storks, Gulls, Kites and
Egrets.
Why Study the White
Stork?
Changes
in Migratory Strategy: Many species breed in Europe but migrate to
Africa as a strategy to overcome the lack of food resources in winter. However,
in the past few decades climatic and habitat changes have allowed several
previously wholly migratory species to form partial migrant populations where
some individuals remain resident all year round in Europe. I find this a fascinating research
topic!
The White
Stork population of Portugal is one of these species that has undergone recent,
significant and fascinating changes. It used to be a wholly migratory bird but
since
approximately 1984, increasing numbers of White Stork are choosing to stay in
Iberia continuously all year rather than migrate to Africa. The numbers of
overwintering birds in Portugal has increased significantly from approximately
1,180 individuals in 1995 to over 10,000 in 2008. Being a highly opportunistic and adaptable species this
trend this widely considered to be the result of i) guaranteed, abundant food
supply from landfill sites and ii) milder European winter temperatures.
Iberian Distribution
Changes: The white stork distribution in Portugal is
also changing. This species is colonizing new areas in the North of the
country, possibly because they have recently become more climatically suitable
but also because of the availability of food from rubbish dumps. However, the
majority of the white stork population still occurs in the south.
One of a series of colonised pylons near Coimbra |
Impact of Landfill: Access
to landfill ‘junk food’ has influenced White Stork nesting decisions across
Iberia. Large colonies, some containing over 100 nests, have been established
close to landfill sites. This has likely affected chick dispersal and
population expansion patterns, as well as migratory decisions of both adults
and chicks. However the open landfills of Portugal are almost full to capacity
and reaching the end of their working lives. They are already being superseded
by modern facilities where waste is handled inside huge covered hangars and is
not accessible to scavenging birds. White
Storks will likely return to foraging in agricultural fields to find an
alternative winter food supply and I predict this will likely impact on their
distribution, breeding location, chick fledging success and migratory
decisions.
My
research will investigate the link between climatic warming and habitat use to
predict the white stork’s future distribution. These data are highly relevant
for other species impacted by climatic change and also by the landfill
closures.
A big colony near the landfill site at Ermidas do Sado, Portugal. |
Both pictured colonies are ones I am monitoring.
A logger, partially packed ready for attachment to a stork. |
Every day each logger
collects 5 GPS locations; 1 by night at 5am, 4 by day at 8am, 11am, 2pm and
5pm. Each location consists of a number of GPS fixes in rapid succession that
tells us the direction of movement. The logger also collects accelerometer data
that allows us to determine whether the bird is in a head up (standing) or head
down (foraging) position, as well as the speed. Every 2 days the data is
transmitted via GSM. This will hopefully allow us to track the same individuals
between their wintering and breeding habitats and record how
many chicks they rear successfully.
The British Trust for Ornithology Website: 2 location fixes per day (1 at night, the other at 11am) will be uploaded to the BTOs website for you to track their progress. We are expecting lots of exciting movement and behavioural data from the storks carrying our loggers so log on and see what they are up to!
Website: http://www.bto.org/science/migration/tracking-studies/stork-tracking
The Main Objectives:
- Winter: To understand the White Storks winter movement patterns in response to temperature and precipitation, and also understand their preferred foraging habitats, reliance on food from rubbish dumps and how they use nests and communal roosts. Amongst other things, I am interested to know how far do the storks travel? Do they feed on rubbish dumps more in bad weather? Do storks defending nests in winter keep those nests, or will they be forced off them by returning migrants?
- Summer: Once the birds are nesting I am keen to know what habitats the adults visit to find food for their young. Do birds that feed heavily on rubbish dumps in winter also nest near rubbish dumps? Do they fly a long way just to visit rubbish dumps, or do they only forage close to the nest?
- Predictions. All this data will help us understand responses to climatic and habitat variables and the mechanisms influencing the decision over whether on not to migrate. It will also allow us to predict future distributions and population changes based on i)global climate model scenarios for different time scales and ii)after the closure of the landfill sites.
- Electricity Pylons. The GPS data will also give fascinating insight into how the birds use their nests during both the breeding and non-breeding season. Nest defending is starting earlier and earlier, with resident birds occupying nests all year round. Storks are increasingly choosing to nest on pylons which can lead to collisions with high tension electricity cables. Several of our logged storks are using nests close to and on pylons and Phil had a recent lucky escape (see photo). Our data will allow us to investigate how the logged birds are using the nests and the frequency they go through power lines. As the stork population is changing its distribution in Portugal, this will be valuable information on where and how pylons are likely to be used by storks in the future. The logger data shows that Phil seems to be behaving normally and is none the worse for his lucky escape.
'Phil' (34+) -suspected collision with a power line. |
Keep checking my blog and the BTOs web page and find out what the logged storks are up to!
Catching Storks. Although storks are a familiar site nesting on roof tops across their
breeding range, they are actually very shy of being approached, particularly in
open fields. For this reason we captured them on various rubbish dumps across
Portugal. Here during the winter they congregate in their hundreds and, in some
sites, thousands, increasing our chances of successful captures.
Short video of 'Goncalo' (30+) being released after being fitted with a logger.
A BIG THANK YOU To all the rubbish dumps for their interest in our project and for kindly permitting us to catch storks on their premises:
Aterro Sanitário Intermunicipal de Evora (GESAMB)
Aterro Sanitario de Vila Ruiva (AMCAL)
Aterro Sanitário de Ermidas do Sado (Ambilital)
Aterro Sanitário da Herdade do Montinho, Beja (Resialentejo)
Special thanks also to Kris and Luc van Uffelen at Fleetronic for adapting their loggers to suit our needs, and for all their subsequent support.
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