The bird center outside Kungälv is one of the places that receives lean and exhausted herring pigs every year.
Especially during the autumn when there are often strong winds in the North Atlantic where the herring guillemots nest.
In a normal year, around ten birds are usually rehabilitated.
This year, 30 have already been received.
-They can't find any fish and they are very hungry, so they have to come here and rest up, eat herring and swim, says Elisabeth Sjöström, game rehabilitation at Fågelcentralen.
Warmer water and less food
Why so many herring guinea pigs need help this year is unclear.
According to Jan Uddén, biologist at Bohuslän's museum, it is likely that it is mainly due to higher water temperatures.
The plankton species that benefit from hot water probably do not contain as much fat, or fatty acids.
This means that when small fish eat them, they do not gain weight and when the birds then have to eat the fish, it becomes the same for them.
So they eat emaciated fish, says Jan Uddén.
Hear him tell more and see the herring piglets in the clip above.