On July 6, 2019 at 4:45hrs UTC, adult Lesser Black-backed Gull Green YASV left the gull colony of IJmuiden Forteiland, the Netherlands. On July 9 at 20:30hrs she would return after having flown to Lille in France, having covered some 600 kilometers in total.
We know this because YASV is one of the 10 adult Lesser Black-backed Gulls of our project that is fitted with a GPS logger. At an interval of 5 minutes, the logger records the date, time, altitude, speed, and more.
First stop: Tilburg
After first following the coast line in a southerly direction and spending some time over the North Sea, YASV headed south-east at 7:10hrs and flew straight to a landfill in Tilburg near the Dutch-Belgian border. It is a place where gulls from the IJmuiden colony are seen on occasion but we did not know that YASV also did this.
Next stop: France
YASV spent the night in Tilburg and left at 6:30hrs on July 7. She flew towards the south-west over Antwerp, Belgium, straight and without stopping to Douai, France (south of Lille).
She arrived there at 17:30hrs after having flown some 190 kilometers at an average speed of 40 km/h and at an average height of 300 meters.
She spent the night at a warehouse located to the north-west at Dourges.
On July 8 at around 3:30hrs, she headed north towards Lille where she visited various sites, mainly of an industrial/enviromental nature.
She stayed in the area the whole day and spent the night on the roof of a building just west of Lille.
Back to IJmuiden
On July 9, at around 9:00hrs, she left Lille and flew back to IJmuiden. At 12:30hrs she took a short break at the Quarleshaven gull colony at Vlissingen, the Netherlands, passed close to my house in Leiden at 18:00hrs, and arrived back in the colony at 20:30hrs.
Why this trip?
It is not unheard of that Lesser Black-backed Gulls make fouraging trips that take up a few days and cover a few hundred kilometers, and the trip to Tilburg is in itself nothing special. As far as food sources go though, similar locations are available much closer to the colony.
However, gulls are very much creatures of habit and it seems that flying long distances to locations where they know they can find food are considered to be more economical than just flying around in every direction with the chance of not finding anything.
As far as time management goes, YASV lost her 2 chicks a few weeks ago and can therefore afford to spend time away from the colony.
A reason why she returned to the colony instead of staying in France could be that she wanted to prevent her territory from being taken over because she needs to breed in that exact location again next year.
Flying to her wintering location in Malaga, Spain, might be a bit too early as well because the conditions might not yet be suitable there.
It has been fascinating to get this insight into her life and hopefully it is the first of many more stories to come.
Many thanks to Judy from the University of Amsterdam for providing the data. Follow our GPS-tagged gulls online at uva-bits.nl.