What is going on in Woluwe-Saint-Pierre?

The Peregrine pair in Woluwe-Saint-Pierre has lost its two chicks in only a couple of hours. The male and the female still take turns brooding on the two remaining eggs, but chances are very slim that they will hatch.

This is of course sad news, but the important thing now is to try and understand what happened. Falcons for everyone is the popular part of a scientific observation program for Peregrine falcon populations. And the purpose of the program is to monitor the evolution of that population, to sound the alarm if something would threaten this splendid species. Let’s not forget that they had completely  disappeared from Belgium and most of Europe and North America from the 1960’s until the 1990’s.

We have recordings of everything that has happened between the hatching and the death of the 2 young falcons, so we can try to understand what has caused it. This is the thread, minute by minute:

12/04   07:05, hatching is underway, we see a cracking egg!

            08:15, the hatching is going well, the chick has almost entirely open the shell.

            09:06, the young falcon has come out of the egg, all wet. His mother warms him.

11:20, the first meal! The father brings a songbird, the mother feeds it to the chick.

            12:10, the male returns to see what is going on, but he leaves soon.

14:08, the female leaves the nest for the first time since the hatching of the eggs. The male replaces her immediately.

14:10, the female returns with a piece of pigeon and feeds the newborn.

14:14, the female leaves, the male replaces her and he warms the little falcon and the 3 remaining eggs.

During the rest of the afternoon, male and female take turns 10 times in the nest. The female feeds the young 3 times (2 x pigeon, 1 x Song Thrush).

Everything seems perfectly normal during this first day: fast hatching, frequent and synchronous relays between the female and the male, the female feeds the chick 5 times.

13/04   07:50, first feeding of the day : the male brings a common starling.

09:07, the female stands up carefully, observing the chick. He tumbles, has disorderly movements.

10:15, the female leaves the nest. Same strange behaviour by the chick.

10:15, the male arrives with a Song Thrush, the chick seems to have trouble breathing.

During the rest of the day, the parents relay 12 times and the female feeds the young 5 times (3 x pigeon, 2 x Song Thrush)

Absolutely no strange behaviour from the Peregrine parents and in the way of feeding the chick. But the young behaved strangely on multiple occasions.

14/04   07:40,  a second chick hatches under the female, like usual.

09:11, she leaves the nest, the two chicks behave completely normal.

09:16, the female returns with a pigeon.

11:00, the falcon born in the morning does not really seem fit, he does not sit up as he should, but instead is lying on his back, paws in the air.

11:59, the female, who was relieved by the male moments earlier, returns with a pigeon and feeds it to the chicks.

13:03, the male arrives with a thrush that he gives to the female. She stands up, but the chick born this morning has died. The mother feeds the elder chick. He falls over again multiple times

The parents switch 10 times during the afternoon and feed the first chick 4 times (3 x pigeon, 1 x thrush).

One chick has died just hours after he came out of the egg. The behaviour of the parents appeared perfect. The second one does not seem 100 percent fit but he feeds regularly. The 2 remaining eggs have still not hatched. Something is clearly wrong.

15/04   06:45, the female broods, the male brings her a blackbird, she feeds it to the chick.

06:53, the feeding is over, she leaves the nest and he replaces her immediately.

The rest of the day passes normally. The parents take turns 12 times watching the chick and there are two eggs still to hatch. They feed 4 times (1 Common Starling, 1 male House Sparrow and 2 unidentified small songbird).

Nothing unusual or suspicious from the parents today. The surviving chick from 12/04 on the other hand seems more and more apathetic. The one who died the day before is still in the nest, the female sometimes brings him back under her body. But most of the time, he's next to her.

16/04   06:08, the dawn rises and the little falcon has died. He lies right in front of the female.

             07:19, the female leaves the nest.

07:22, she returns with a small songbird, but there is no more falcon to feed. She leaves again 2 min later.

            07:28, the male brings another small songbird.

07:30 the female leaves the nest, the male does not brood but observes the nest. He seems very attentive. He has not shown such behaviour before.

07:57, the male suddenly leans forward. We see his back and cannot distinguish what he does. And then he turns. He found the remains of the first falcon! He takes it with the tip of his beak, steps over the other dead falcon and leaves the nest! Was he looking for the corpse? For nearly half an hour? To take it out of the nest? Or is it a coincidence?

08:09, the female returns to brood, the corpse of the chick that died in the morning is still clearly visible in the foreground.

The parents take turns on the 2 eggs, 8 times during the next 2 hours. The male brings a sparrow at 09:47.

            10:39, the female leaves the eggs.

10:45, the male returns. He goes straight to the corpse of the first chick, without hesitation. He bends. Stretches out his neck. It is almost incredible, but he touches the falcon with the tip of his beak, a little on the left, a little on the right. It lasts 8 seconds, an eternity. And then he grabs the body with his beak, raises it, turns back and leaves the nest. He clearly decided this morning to remove his two dead young from the nest.

The action itself is surprising and remarkable, the way of doing it is touching. But the timing is simply stunning! Did he wait until both chicks were dead before taking them, leaving nothing but the eggs? That is possible. Did he do it to avoid contamination in the nest? Equally possible. But then how can we explain why he leaves the carcasses of prey in the nest? It is a mystery.

That is the list of events. It was a long post, but facts matter and we have to document exactly what happens. Why it happened is another question, on which we have no answer. An autopsy of the dead chicks could have given us some clarification, but that is not possible anymore.

But we can conclude that the death of the chicks was not caused by bad parenting. They took perfect care of their youngs. Also not by an external intruder, either a predator or a competing Peregrine that came to attack the nest. This happens! The quick death of one of the chick, the behavioural problems of the other, the fact that 2 eggs did not – and most likely will not – hatch, very possibly indicate a structural problem in the 2017 egg laying by the falcon pair in Woluwe-Saint-Pierre. Yet in previous years, they nested with success. Life goes on! The adults are safe and sound, and that is also very important.

Thank you to everyone who sent in their observations through the contact form. It is very useful. If you have any suggestions as to what would have caused their deaths, or if you have observed any behaviour that has escaped us, please let us know.