Written by Kushiro City Zoo contact manager Fumio Matsumoto
A short summer came to Eastern Hokkaido this year.
The weather has been less than ideal: May brought warm weather, after which, temperatures did not rise and July saw lots of rain and clouds with few hours of sunshine.
However, as there was no heavy rain in early spring, Red-crowned cranes appear to have had no trouble breeding this season. Around Akan village in the Kushiro City region, a dozen or so pairs of red-crowned cranes are raising their chicks. Wetlands are the main habitat of red-crowned cranes.
In Eastern Hokkaido, there are many large marshlands such as Kushiro Wetland, Bekanbeushi Wetland, Kiritappu Wetland and the swamplands around Lake Furen and these have become the principal habitat of red-crowned cranes.
It is thought that the existence of such expansive wetlands is a major factor in the survival of red-crowned cranes in Eastern Hokkaido.
However, with increasing numbers of cranes in these regions, it is becoming evident that there are insufficient wetlands suitable for breeding.
Gradually, red-crowned cranes have expanded their nesting grounds from within the wetlands themselves to upstream of the rivers that feed the wetlands.
The Akan village region is somewhat far from Kushiro Wetlands and there is no large wetland area there.
Both the Akan River, which flows into the Pacific Ocean, and the waterway known as the Ninishibetsu River, which joins the Kushiro at its furthest downstream reaches, flow through this region.
Around 20 years ago, the number of nesting pairs did not exceed 3 to 4 in each of the Ninishibetsu River basin and in the Akan River and its tributary, the Shitakara River basin.
However, at present, it is believed that there are around 6 to 7 pairs nesting in the Ninishibetsu River basin and more than 10 pairs in the Akan River basin.
There are some wetlands scattered around the Ninishibetsu River basin, but many Japanese cranes seem to be nesting in the remaining narrow spaces along these rivers or their tributaries.
There are farms and houses nearby, and the places where they spend their lives is close to human habitation.
Such a place as this, an environment subject to change while also being vulnerable to encroachment by predators, can hardly be said to safe.
Especially after chicks have hatched and leave the wetlands for areas used as pastureland, they are vulnerable to attack by foxes and many chicks have unfortunately been taken.
In the past, it was quite rare for chicks to grow up fully, but in recent years, the number of chicks growing up safely has increased.
It could be that the adult red-crowned cranes may be raising their chicks more shrewdly and with greater care.
However, it is not only foxes that are dangerous.
Because the birds are venturing close to human habitation, traffic accidents are also on the rise.
In June, 3 dead chicks were admitted to the zoo.
While only one of these cases was clearly attributed to a traffic accident, there is the possibility that the others are due to accidents as well.
We want to exercise care so that we can watch over the thriving of red-crowned cranes.