Monthly Archives: May 2019

May Breeding Report

At the end of April, four of the five chough nests had eggs. Nest 4 was a ramshackle affair, but a good attempt for a new pair. Of the other four nests, only one pair laid fertile eggs – our “go to” pair in nest 1. The totals are as follows:

Nest 1 – three eggs, all fertile. Three chicks hatched
Nest 2 – two eggs, laid in partially finished nest. Both eggs broken.
Nest 3 – four eggs, all infertile. Female incubated but eggs thrown out by parent.
Nest 4 – no eggs.
Nest 5 – Three eggs, all infertile. Female incubated, then removed eggs.

Our hopes for this year are all on nest 1, and the three chicks are now two weeks old. However, the nest is already starting to fall apart – something which normally happens after four weeks, due to the movements of the “teenage” chicks inside.

Three chough chicks being fed by parents
Three chough chicks being fed by parents

The nest box now contains more rocks than before. This is due to some quick rebuilding by myself, as the young birds were seen to be scrabbling about on the floor of the box. This is not good for younger birds, as their feet may not develop properly.

We decided to intervene, and made the nest space smaller by adding four small rocks to the front of the box. This was done during one of the daily weighing sessions – where Alison goes into the aviary to feed and distract the birds, while I sneak the chicks out of the inspection hatch. The parent birds then return, and continue to feed the youngsters. I think the female was slighty suspicious after the rocks had been installed, but the drive to feed overcame any fears.

We also added small twigs in a lattice pattern, to allow the chicks to grip onto something. This is easier to do, and the parent birds accept this much more readily.

We have repeated this, with rocks being added to the sides. So far, so good…

Chough chicks daily weigh-in
Chough chicks daily weigh-in

The chicks are weighed daily, and the weights can be compared with results we have built up over the years. During the first week a daily percentage increase of 20% to 30% is not uncommon, which gives an indication of the remarkable rate of growth.

In the second week, the rate slows to between 10% and 15% per day. As can be seen in the image above, the chicks now have their eyes open, and are beginning to “feather up”.

The two chicks hatched a day before number three, will always be at an advantage. They will always be heavier, and their eyes opened first – a huge advantage at feeding times.

As an example, the weights today (May 22nd) are: 179g, 146g and 123g. Our strategy to overcome this, is to give the smaller birds supplementary feeds when being weighed. This gives them every chance to catch up with the heavier bird.

The third week now moves into monitoring for potential infections and gapeworms…

Female incubating eggs in nest number one.

April Breeding Report

The first chough eggs of the year have been laid. After a staggered start all five pairs have built nests. The new pair (nest four), were slow to start, but have now caught up.

Female chough about to lay egg number two - note the male in attendance.
Female chough about to lay egg number two – note the male in attendance.

The first eggs were laid in nest number three on April 13th and 15th, followed by more on the 17th and 18th. Nest number one was filled with three eggs on April 15th, 17th and 19th. Nest number five was last with three on 21st, 23rd and 27th. Unfortunately, two eggs were laid in nest number two, but were broken – the nest had not been completed, and the eggs broke against the nestbox floor.

Nest number three, with a clutch of four chough eggs.
Nest number three, with a clutch of four chough eggs.


We were approaching the point where we would “candle” the eggs to see how many were fertile. Unfortunately, the female in nest number three had other ideas…

Female chough removing an egg.
Female chough removing an egg.

Yesterday Morning – April 30th – we came in to find only two eggs in nest number three! The female had gently removed two of the eggs early in the morning. At 11 o’clock she removed another, and we went into the aviary to investigate.

We found the two eggs. Both were infertile. Both were also very pungent. Obviously, the female had realised the eggs were not going to hatch, and took them out. She removed the final egg overnight, and this too was infertile.

So, our current tally is six eggs. We are still hoping that the birds in nests four and two will lay. The birds in nest number two may go through another cycle, as can be the case when the initial cycle of egg laying is not quite right.