After the excitment of our earliest ever Egg1 lay date, Egg 2 arrived 59 hours later as previously documented. Fast Forward another 59 hours and Egg 3 arrived on March 22nd and the clutch was completed when Egg 4 arrived at (we think) 16.51 on March 24th. This is our earliest ever clutch complete date by 2 whole days, surpassing the site’s previous early date (26th March in both 2016 and 2021). With egg intervals of 59, 59 and 58 hours this falcon has been almost metronomic in her timing, which in all likelihood indicates a fit, healthy bird who is in good breeding condition and living reasonably stress free, content with her partnership, her food supply and her environment. The minimum interval between Peregrine eggs is generally acknowledged to be 55 hours so this years productivity is not far short of perfect.
It took a while for the 4th egg to be sighted on camera as the clutch was well sheltered behind the “western wall” of the platform….. but confirmed it eventually was and the birds settled down to the long and patient business of a month of incubation.
Just like the laying, incubation has, so far (never count your chicks before they hatch!) gone like clockwork. Exactly the unremarkable, largely uneventful, period we wish it to be. Pray that continues into next week and then the excitement levels will begin to rise! It will be interesting to see whether all 4 eggs hatch (if all continues to go well) – we have only ever had 4 eggs hatch on 2 previous occasions – 2014 & 2022. More often than not an unhatched egg remains. As a rule of thumb Peregrines tend to start full-on, round-the-clock incubation of the eggs once the third one has been laid (in a clutch of 4) – a mechanism which many species employ to ensure the eggs all hatch closely together.**
The risk to this strategy is that, unlike Blue Tits or Treecreepers etc, who’s nest may be tucked away in a tree trunk or nest box and ensconced in a feather-lined or wool-lined nest, an open Peregrine nest high up on a cliff or a roof or a platform can be exposed to the elements. Wind, rain and snow can potentially pose a challenge to eggs one and two if they are not incubated all of the time and in years where one egg fails to hatch, there’s often speculation that this could be the first laid egg. Of course as they all have similar coloration & marking (and get moved and turned for 31/32 days) there is no way of keeping track of which egg is which, so we cannot know if there’s any truth to this theory.
However, this year our birds have been on top form and, from my viewing, it’s hard to argue that this clutch has been very well incubated almost from the word go, and definitely from Egg 2 onwards. Combine this with the speedy, punctual laying and you never know…. maybe 2024 could be a good year for a full house?? The incubating birds have had to put up with a fair bit of rain but up until this week’s biting northwesterly wind arrived, temperatures have not been too bad – we haven’t seen incubating Peregrines covered in snow this year for once! Intriguing propsects….
The other big thing of note this year is the amount of incubating the male has been allowed to share in. He really has fully played his part. Last year the falcon was very reluctant to let the male near the eggs at all and was openly hostile, despite his apparent keen-ness. Given how inexperienced and clumsy he acted around the clutch in 2023 webcam watchers could concur with the falcon’s thinking! This year however, he looks far more assured and confident, this has been a pair working in complete harmony. He’s done a great job keeping the eggs covered although it’s always clear to see on a changeover just how much harder it is for the smaller male to get all of the eggs under his body compared to when the falcon sits back down. Watch the cameras and take a look – the next 5 or 6 days may be your last chance for incubation watching this year.
There has been intruding birds visiting the area a handful of times but they’ve each time been seen off by one or both birds very quickly and, so far, touch wood, there’s been no dramas. Although it’s always a heart-in-the-mouth moment if they both dive after an intruder and the eggs are left uncovered.
I may write a little more about intruders in a later blog…. once the danger period has passed, I don’t wish to jinx anything at the moment! We Peregrine watchers don’t want any sort of drama, conflict or disruption when eggs are close to hatching nor when there’s tiny new chicks around.
There’ll be another post here on Sunday or Monday in anticipation of an interesting week. Watch this space.
**The Sheffield Peregrine clutches have been fairly synchronous in hatching over the years with the viable eggs often all hatching within 24 hours of the first, a far shorter period than the 7 to 10 days which they have been laid over. Not quite on Blue Tit level where they’ll all hatch within a few hours of each other but nonetheless generally synchronous. However, some species, e.g. Barn Owl, will incubate immediately the first egg is laid then keep on laying. Given that each egg requires the same incubation period, providing there are constant temperatures, the eggs in these species then hatch asynchronously and the hatching intervals more closely match the laying intervals – days apart. In this situation, early eggs are not allowed to stay dormant or chill in the way that they might in synchronous hatching birds but the downside is that there can be large size differences between the oldest and youngest chicks and the unequal competition that creates when it comes to each chick getting enough food to survive and grow.
Sheffield Peregrines 