A formerly extinct species of large bird returns: the common raven (Corvus corax)
Thousands of corvids in Europe have been poisoned, shot down or killed, writing a “black history”. The largest native songbird, the common raven (Corvus corax), also suffered massive population declines in Europe and was finally wiped out over a large area.
In the Netherlands, for example, a sharp decline began around 1900, which led to the complete disappearance of the species in 1927. In Belgium it bred for the last time in 1919 and in Luxembourg it disappeared already at the end of the 18th century.
In Germany, ravens once occurred as breeding birds in all major forest areas.
In the middle of the 18th century, a decline in population size was recorded. Around the turn of the century, the raven was already absent as a breeding bird in Baden-Württemberg, Hamburg, the Palatinate, Saxony, Silesia, Thuringia and Westphalia.
Its last refuges were in northern Germany, Poland and remote valleys in the Alpine region. Only after the end of aggressive persecution by humans and initial protection efforts did the Common Raven expand again toward its former and ancestral ranges. The recolonization was nourished by the subpopulations of the retreat areas.
Although the Common Raven has been expanding again for several decades, not all of its former range has been recolonized to date. In some German states (Schleswig-Holstein, Mecklenburg Vorpommern), however, it is again represented as a breeding bird almost everywhere. Today, Common Raven can be observed again in large parts of Central Europe and the once common large bird enriches the native fauna again.
With its fate, the raven is exemplary for several European large animal species such as the black stork, the lynx or the wolf. While many species in Central Europe are endangered in their populations, some formerly extinct species manage to recolonize their former ranges due to conservation efforts. For future species conservation efforts, it is important to document and understand such recolonization processes in order to develop future conservation strategies and ensure the long-term survival of the species.
The exact sequence of the Central European recolonization by the Common Raven – starting from the three refugial areas – has not been conclusively clarified. It is also unclear from which relict populations the ravens in the area of the current recolonization front are descended. To what extent the ravens differ genetically and may have developed so-called “ecotypes” (beech breeders, conifer breeders, rock breeders) is an open question. Within the framework of a research project at the Department of Biology of the Philipps University of Marburg, working group Animal Ecology, funded by the Animal Protection Foundation Wolfgang Bösche, the graduate biologist Sascha Rösner deals in his dissertation, besides the purely descriptive aspects (cartographic representation of the recolonization), among other things with the genetic diversity of the ravens.
- Several ecological questions are in the foreground:
Does a cryptic genetic diversity of Central European ravens exist (cf. studies in North America) ?
What is the origin of the animals that are currently dispersing in Central Europe ?
Is there a genetic “impoverishment” due to local extinctions (historical data from collections, museums, if applicable)?
Did the recolonization initially proceed over large closed forest regions (map material)?
How will the further population situation of Central European Common Raven develop (computer-based modeling)?
What conclusions can be drawn about the recolonization and establishment processes of other species?
The results will illustrate the fascinating process of natural recolonization by a formerly native species of large birds. However, the long-term establishment and survival of common raven populations in Central Europe depend on public acceptance …