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It is that time of the year again

Spring is approaching and birds are becoming more and more active. Some early breeders can already be heard producing their territorial or reproductive calls. Last week we were at Mindelsee, during a quick excursion at our scientific retreat, and we heard Black woodpeckers (Dryocopus martius) drumming and telling the other conspecifics which territory it chooses.

But there is still long time ahead before we can hear the calls of other species, like Common swift (Apus apus) in the city, swallows (Hirundo rustica) in the fields, or the Redstart (Phoenicurus phoenicurus) in the forest. These species are still in their wintering grounds but something is changing in their body. The levels of their hormones are changing. We could refer to this special mood as migratory anxiety, or the anxiety that make birds focus on one and only one thing during spring: migration.

As scientist, we prefer to use another word to describe this, which is the german word Zugunruhe, a composite word of Zug (move, migration) and unruhe (anxiety/restlessness).

But what does it mean for our forests? An insight at our bird data show that in March and in May the bird species inventory included 43 and 57 species, respectively. The added species are all migratory species, coming mostly from lands south of Germany, some of them even south of the Sahara desert, and arriving usually after mid-April.

Thanks Zugunruhe for bringing more colours and songs in our forests.

Figure caption: Eurasian robin (Erithacus rubecula) a short-distance migratory bird, common in our forests.

by Marco Basile (B6)