Hi there Peregrine watchers! Happy Monday to you all.
Let’s start off the week with a nice photo of TRF showing a rare glimpse of his leg ring. It’s much harder to catch sight of it on the webcams this year compared to last. Regular watchers will have noticed how his appearance has changed subtley since the 2023 breeding season and his winter moult has shed any last vestiges of his juvenile plumage. It would appear that his latest set of feathers cover his legs much more than was the case previously and the colour ring stays out of sight much of the time. Fortunately, this year’s plumage also seems to have provided us with a handy white spot on his crown which helps us to continue to be able to identify him quickly on camera.
Anyway on to the main event: Tucked away underneath the warming body of an adult bird the four eggs are nearing the end of their incubation. Inside each should hopefully be and almost fully formed chick. Our Peregrine eggs generally take around 31 or 32 days to hatch, when measuring from the date the clutch was completed. This would make the likely hatch date to be Wednesday or Thursday of this week. Exciting!
However, this is not set in stone. We’ve had years in recent times where eggs have taken 33 days and even 36 days before the 1st hatching, these were years where there was either some disturbance around the site or a bit of cold snap. Hopefully not significant coinsiderations this year.*
Occasionally UK Peregrine eggs elsewhere have been recorded to hatch after a shorter incubation of 29/30 days, if we take this into account and add in the observations mentioned in our previous blog [this clutch has been well incubated since Egg 2 was laid] it’s probably worth watching the webcams very closely from now onwards. One way or another we should see some activity this week.
Lookout for the adult birds shuffling about when the eggs are underneath them or watch for them staring at, or listening to, the clutch, particularly on a changeover. Once the birds appear a bit more interested in the eggs rather than nibbling at gravel (!) it’s worth assuming that they sense something may be about to happen.
With typical bad luck, I myself will be out of town and away from a computer on Wednesday and Thursday when the first egg is anticpated to hatch so more than ever we need you all to keep watching the webcams! Please share any notable sightings with the Sheffield peregrines Twitter account or the SBSG Facebook page.
*Disclaimer: While the excitement surrounding the hatching is palpable, it’s essential to remember that the natural process may not adhere precisely to our predicted schedule!
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.
Falcon on eggs 19/4/24 (all screenshots by Jill Greenwood)
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.
Four eggs in sight, just!
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….
Changeover time
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.
Carefully covering 4 eggs
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.
Male incubating. Note the little white dot of feather on his crown – helps to identify him!
**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 