CEZ Skawina chimney nest – season 2020 recap

Jaszczurka czy nornik? Młody ma już 9 dni, nie musi się dzielić pokarmem z rodzeństwem.On October 16, 2019, a special nest box for peregrine falcons was mounted on the chimney of the CEZ combined heat and power plant in Skawina. The initiative was led by Krzysztof Haja from the Małopolska Ornithological Society, with expert assistance from the "Sokół" Association and financial support from TADMAR and CEZ Skawina S.A.

The nest box was inhabited by:

  • Common Kestrels (Falco tinnunculus) - pair #1 from March to June 2, 2020 – male and female without rings, origin unknown.
  • Common Kestrels (Falco tinnunculus) - pair #2 from June 2 until the end of the breeding season – male and female, without rings, origin unknown.

The nest box was lined with coarse gravel. The initial avian guests included Common Kestrels, Pigeons, Eurasian Magpies, and a male Eurasian Sparrowhawk. Common Kestrels have been living on the CEZ premises for some time, and as expected, they showed interest in the nest from the autumn. Observations began in January when both males and females visited the nest, primarily on the ledge. None of them had rings. At the end of February, two pairs and one young male visited the nest alternately, with visits becoming longer, even inside the nest. Interactions often led to fights and intense competition over the nest. Female-female aggression was particularly evident. Pair #1 eventually won the battle for the nest.

Starting in March, the entire courtship ritual was observed: displaying, "nest scraping," the male bringing food to the female, and mating. The female consumed rodents and lizards immediately, stashing any leftovers in the nest's pantry (corners within the nest). Sometimes the female would fly away with her gift from the nest. The male was an excellent hunter, ensuring a steady supply of food, allowing the female to prepare for egg laying. She spent increasingly more time in the nest. Ten days before laying the first egg (April 12), she spent an entire night in the nest, falling asleep on the ledge.

The dates of egg laying were as follows:

  • First egg: April 24th at 15:25.
  • Second egg: April 27th at 5:23 (after 62 hours).
  • Third egg: April 29th at 4:20 (after 47 hours).
  • Fourth egg: April 30th at 21:25 (after 41 hours).
  • Fifth egg: May 2nd at 19:20 (after 46 hours).

At the beginning, the eggs were only incubated during the day, alternating mainly between the male and the female. After the female laid the fourth egg on April 30, the birds began continuous incubation, with the female incubating the eggs throughout the night from April 30 to May 1. The initial period of incubation proceeded as expected. The male provided food for the female. When the female left the eggs for a few to several minutes, the male took over incubation. After her meal, the female returned to the nest and literally chased away the male with sharp vocalizations. During the night, only the female incubated the eggs. Food was abundant, except for a few rainy days when it was slightly less. Towards the end of the third week, changes were observed, with the male visiting less frequently, and the female leaving the nest for longer periods in the fourth week. In the fourth week, the situation got worse. There was significant agitation and unease displayed by the female, frequent extended absences from the nest, and upon her return, she didn't always sit on the eggs. She even fell asleep next to the eggs at night. The pair engaged in territorial conflict. On the live stream, only the female's actions were observed. She watched the surroundings from the platform, was visibly agitated, vocalized loudly, and chased away intruding males. Male number 1 guarded the nest from the outside, away from the cameras. On May 24, he returned to the platform with a clear leg injury. On May 28, he was seen for the last time. The female fully took over the responsibility of defending the nest from intruders. On June 2, in the 33rd day of incubation, female number 1 left the nest after a fierce fight with a new female. The further fate of pair number 1 is unknown.

The nest with the five abandoned eggs was taken over by the new pair no. 2, which energetically prepared for breeding. The male provided so many rodents that there were caches of them in every corner of the nest. Occasionally, the female sat on the old eggs. On June 8, the first egg of the new pair appeared. The next day, the old eggs were removed from the nest by us. The kestrels slowly accepted the change, incubating the single egg, and four days later, the female laid the second egg.

The dates of egg laying were as follows:

  • 8th June at 12:25 - the first egg
  • 12th June at 8:51 - the second egg (after 92 hours)
  • 14th June at 8:50 - the third egg (after 48 hours)
  • 16.06 godz. 13:10 – czwarte jajo (po 52 godzinach).

The incubation of the eggs proceeded without disruptions. Other kestrels continued to be interested in the nest, male and female often flew to the platform, even looking into the nest. When our male or female made a decisive move towards them, they quickly flew away. We didn't observe any fights between them. There was an abundance of food: rodents, lizards, and a few small birds. The male alternated with the female on the eggs when she left the nest for a meal. On July 11, after 33 days from the laying of the first egg, the first and unfortunately the only chick hatched. It was kept warm for as long as it needed and intensively fed. We couldn't carry out the planned ringing of the young one due to an elevator malfunction in the chimney.

The path to independence involved exploring the entire nest, going out onto the doorstep, then to the platform. On the 33rd day of life, the young one flew out of the nest for the first time, landing on the signaling lamp. The next morning, it appeared in the nest once again.

The young falcon visited the nest only during the day, every day. The male continued to bring rodents to the nest. When the young one wasn't there, he sometimes left the prey in a corner, and at other times, he took it back. He gradually reduced the food deliveries. Meanwhile, the young one ate the two remaining unhatched eggs in the nest (the third egg was consumed by jackdaws). Around late August and September, the young one spent several nights in the nest again, possibly due to strong winds and stormy nights. He slowly became the host of the nest, driving away intruders, and sometimes even defending the nest against the parents.

Visits by pair no. 2 and the young kestrel became less frequent towards the end of September. The last observed visit by the male and female of pair np. 2 was on October 24th, and the young one was last seen on October 25th.

The pictures presented below are snapshots from the 24/7 live stream of the nest.

Prepared by Urszula Srzednicka FalcoFanka


Prepared by Urszula Srzednicka FalcoFanka



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