The Peregrine pair of Uccle Saint Job
The history of the observation of Peregrine Falcons in Uccle dates back to the autumn of 2013 when several naturalists from the municipality observed one and sometimes two individuals perched on the dome of Saint Job church.
Then, on May 10, 2014, a cyclist found a falcon grounded 2 km away from the church. The bird is in a very bad position, it runs between the rails of the tram which crisscrosses Uccle towards the center of Brussels. The cyclist manages to capture him easily and brings him to the Rehabilitation Center for Birds and Wild Mammals of the Royal League for the Protection of Birds in Anderlecht. The falcon suffers from coccidiosis but is quickly cured thanks to the treatment provided by the veterinarian of the center. The Peregrine, a male, is ringed. The ring allows us to know he was born in April 2012, at the top of the Saint Rombauts Cathedral in Mechelen, 27 km north of Uccle.
The male Peregrine is then released from the top of the building of the Royal Belgian Institute of Natural Sciences, in the center of Brussels, on June 25. He takes off perfectly, rescue successful!
On March 24, 2015, he is back in Uccle! He is perched on Saint Job's church with a partner. These two begin a first nesting period, resulting in 4 fledglings, 3 males and 1 female. What a success for a first nest! So far, the Ucclean pair has raised 23 falcons in total.
This spring: the female laid her first egg on March 3. At 10:20 am to be precise. The second egg was laid on March 5, the third on March 8 and the fourth on March 10. One egg every other day is custom for a Peregrine. To bring an egg forth is a huge expenditure of energy for a bird and Peregrines are no exception. Considering that a falcon egg weighs on average 49 g and a female Peregrine weighs around 1000 g, the calculation is simple: a clutch of 4 eggs represents 20% of the bird's weight!
The incubation started with the laying of the third egg, therefore on March 8. This is also custom within this species. A custom which again responds to biological contingencies. If the brooding started as soon as the first egg was laid and considering that a minimum of 6 days elapse between the laying of the first and the fourth egg, hatching between the first and the fourth falcon would be... 6 days apart. Elementary logic! So what would be the problem with such a time differentiation? Simple: falcon chicks require care and food that varies according to their age. Raising a brood of similarly aged falcons is far more efficient than having to adapt incubation times or prey size to each chick in the clutch. Obviously, any medal on its reverse. In case of prolonged frost, the first eggs may freeze because they are not incubated. Another disadvantage of the system: the eggs "waiting" to hatch are at the mercy of a predator because they are alone in the nest. But in the end, the unwavering principle of natural selection favored the system of delayed brooding.
But when incubation begins, it is diligent! Female and male Peregrine relay each other continuously in order to maintain the eggs at 37.7 ° C for 32 days.
Do the count: March 8 + 32 days = April 9. We are almost there ! The Uccle chicks are expected to appear in a few days. In fact, before we see them, we'll hear them because the chicks chirp in the egg a few hours before they hatch. Listen!
Video 1. March 11, 2021, brooding started 2 days ago, the female raises from the eggs, and leaves it for the male to come
Video 2. March 11, 2021 continued, the male arrives to incubate the eggs.
Video 3. April 6, 2021, the male incubates and carefully turns his eggs to prevent the internal membranes from sticking to each other