Forest ranger Frans Kapteijns shares his knowledge of nature every week. Anyone can submit questions via [email protected]. This time Frans pays attention to large groups and small groups of jackdaws, a beach find, a hybrid blackbird or a blackbird with a pigment deficiency and a spider. Part one of this Stuifmail was already published on Saturday.
Is this a hybrid blackbird or one that has too little pigment?
Peter van Melis saw a beautiful blackbird in his garden. He wondered whether this blackbird is a hybrid species or whether the blackbird has little pigment. The blackbird in Peter’s photo is certainly not a hybrid species, it certainly has pigment problems. The blackbird in the photo has a partly beautiful black suit, but there are also several feathers that are white. This blackbird has leucism. The eyes, beaks and legs of this type of blackbird are normal in color. Leucism is a pigment disorder. This abnormality occurs in all animals. In birds, the coloring of the feathers is caused by the substance melanin, a natural pigment in the body. In birds with leucism, the substance melanin is produced, but it is not expressed in the feathers. The cause of this is a lack of certain proteins. As a result, some feathers – such as the blackbird in Peter’s photo – remain colorless. This protein deficiency is often caused by a diet that is too one-sided or a shortage of food, which causes the bird to be in poor condition.
Flip de Nijs has one video made from a blackbird with Leucism in his garden.
What is the reason that a large group of jackdaws splits into a small group?
Jeanne Meijer currently sees that jackdaws gather around noon, but that they disperse into smaller groups in the evening. During winter periods, jackdaws indeed gather in large groups to go to their roosts. We call this the sleep trait. Jackdaws do this because they protect themselves from the cold, close to each other, but also from predators such as owls and hawks. More eyes see the predators faster than a single pair of eyes. In addition to safety, being in a group also offers warmth. A ranking is determined, information is shared and it offers the opportunity to play in the evening air.
Now that winter is almost over, the jackdaws from the north are returning to Scandinavia and Eastern Europe. So the evening groups will be smaller anyway. The fact that groups gather briefly in the afternoon and then disperse again may have to do with the scattered search for food. Soon, around mid-March, the groups of jackdaws will separate completely, because then the breeding season will begin. By the way, not every jackdaw goes his or her way, but they continue as pairs. Jackdaws stay with the same partner for life. Together they then look for a suitable territory within which a suitable nest location is sought.
Which starfish is this?
Dirk Eijk received a photo from his niece who had photographed starfish on the beach near Ouddorp. He would like to know which starfish these are. Since I can now often be found in Zeeland because of my grandchildren, I also visit the beach more often. I have also identified some things there, such as the starfish in the photo of Dirk’s niece. The name of those starfish is common brittle star.
The common brittle star, also called the large brittle star, is quite common in the North Sea. They live there on sand and mud bottoms, often up to two hundred meters deep. The common brittle star’s menu mainly consists of bait. Research shows that this is a fairly common species, found in densities of twenty to fifty individuals per square meter. In the summer, but also during the winter, they often wash up on the beach. This specific starfish can be recognized by a three to five centimeter central disk with five thin, snake-like arms attached to it that they can shed when threatened. The arms have hard plates and spines, which can be as much as fourteen centimeters long.
Is this a false wolf spider?
Kristel de Bruijn was asked by her colleague whether she is afraid of spiders. She responded: “It depends on which spider.” She thought the spider she encountered looked quite big. She caught the spider in a glass and put it outside. Her question to me is if this is a false wolf spider. The answer is a resounding yes. The photo clearly shows that the spider is a beautiful light brown color and has dark brown spots. In addition, the cephalothorax has a beautiful drawing.
Females of the false wolf spider can grow up to two centimeters, males only thirteen millimeters. False wolf spiders do not originate here, but from the area around the Mediterranean Sea. They look very similar to the wolf spiders we know, hence the name false – not real – wolf spider. These arachnid animals prey on flies, mosquitoes and other insect species. They have slowly come to our region from Southern Europe. In their familiar habitat, you will mainly find these spiders under stones or tree barks and in forest areas. In the Netherlands you see them almost exclusively in or around houses.
Beautiful photos section
In the beautiful photos section, this time a photo taken by Marianne Wijten. She captured a beautiful natterjack toad. The amphibians have already woken up and are hoping for a beautiful spring. A fantastic photo!
Nature tip
On Saturday, March 7, from ten in the morning to twelve in the afternoon you can participate in an excursion through the Oisterwijk Forests and Fens.
Maintaining this beautiful nature reserve is not easy. During this excursion you will learn more about the work of Natuurmonumenten. For example, what does it take to make the fens surrounded by forests reflect and shine?
The Oisterwijk Forests and Fens were created thousands of years ago. Over the centuries, humans have changed the landscape here in various ways. Natuurmonumenten tries to return the forests and fens to as natural a state as possible and to improve biodiversity. This does not happen automatically. During the excursion, learn more about the work of Natuurmonumenten to make the beautiful fens shine in the forests of Oisterwijk.
More information
• Registration required, see this link.
• Departure point is the Visitor Center Oisterwijkse Bossen en Vennen at Van Tienhovenlaan 4 in Oisterwijk, see this link.
• Participation costs eleven euros, members of Natuurmonumenten pay 7.70 euros.
• This excursion is aimed at adults. Older children are also welcome if accompanied by an adult.
• Wear sturdy walking shoes.
• Wear clothes that suit the weather.
• Always check yourself for ticks afterwards!
• Dogs are not allowed.
