Field Observation 4: Social Behavior and Phenology

This field observation took place on Tuesday, March 24th, in Basel, Switzerland. These observations were made between 3pm and 5pm. The temperature was approximately 50° Fahrenheit and the sky was clear and sunny. The majority of these birds were observed along the banks of the Rhine river which flows through the middle of the city. The river is quite wide, deep, cold and has a strong current. The banks of the river are man-made stone and have lots of walkways, parks, and benches for pedestrians, however there were less people than usual out today because of the quarantine.

While walking along the river I saw several groups of ducks and swans swimming along the edge. I believe that many of these birds prefer to swim near the banks of the river because there is more food, and the current is less strong where it is shallower. For example, I saw many Mute Swans near the banks of the river; often swimming in groups of two. I did some research on this and learned that this is because swans are monogamous birds which mate for life. One pair of swans were vocalizing to each other using a series of grunting and snorting sounds. This could have been a way of communicating the location of food or perhaps a way of alerting each other to my presence. Further down the river, I noticed another group of three swans feeding in the shallow water. In this group one of the swans had his feathers had his feathers fluffed up and his wings raised slightly in a defensive position. I think this could be because one of the swans was not a part of the other pair, which may mean that he was encroaching upon their territory. The puffed up feathers and wings were most likely an effort to make himself seem larger in order to make himself seem more intimidating and communicate to the other swans that he would be willing to fight to defend his territory. Luckily, the dispute quieted down quickly as the swans drifted apart.

As I walked along the river I saw two different species of ducks. I spotted a pair of Common Mergansers sleeping in the sunshine on a log. I was impressed by the striking difference in plumage between the male and the female. The male had a sleek, iridescent green head and stark black and white markings on his body. In contrast the female had more muted tones. She had a brown, crested head and a white/grey body. I think that the more striking male plumage most likely evolved as a way of attracting mates and showing fitness. Meanwhile the female plumage is more muted so that she can blend in to her surroundings better and avoid the attention of predators. After some research, I learned that juvenile males have plumage similar to the females, which supports the theory that this color pattern is better when avoiding predation. I also saw several pairs of Mallards, which have a similar difference in plumages between males and females. The males have iridescent green and blue markings while the females have brown feathers designed for camouflage.

While on my walk I saw several other birds hunting for food along the river. For example, I saw two White Wagtails flitting out over the surface of the water to catch small insects. I also saw a Great Cormorant out in the middle of the river where the current is strongest. It dove under the water and didn't come back up for quite awhile, until it appeared much further down the river. Because I saw so many birds looking for food, I wondered if the afternoon/early evening was a particularly good time to find food. It is no longer as hot and sunny as noon and there might be more insects out later in the day. However, I also wonder how city life might affect the circadian rhythms of these birds. For example, there are more people out in the evenings and I noticed a few people feeding the ducks and swans. Meanwhile, more reclusive birds might be inclined to hide during the busier hours of the day. In addition, there are many streetlights and noises in the city which may disrupt circadian rhythms. These factors might encourage birds to diverge from their natural rhythms.

Lastly, in addition to the birds mentioned above, I noticed two trees with large groups of Carrion Crows in them along with several nests. The crows were loudly cawing and flying around the trees. While walking through a more residential neighborhood I came across a bush full of loud House Sparrows as well as two small birds with yellow breasts and black caps, which I later identified to be either Great Tits or Eurasian Blue Tits.

I wanted to add to this journal that the day before I went on this excursion, I visited a public park near my house in the afternoon and found two White Storks walking around. They seemed very unbothered by all the people around them. Apparently, Storks are fairly common in this region and the nearby region of Alsace in France. In Alsace storks feature in a lot of old folklore. They often nest on top of chimneys and are a symbol of the region.

Publicado el 24 de marzo de 2020 a las 11:11 PM por abreyo