Month: March 2014

Four and no more?


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Today (Thursday) saw the arrival of a fourth egg, as we’d hoped.  By coincidence, 27th March was a notable date in 2013 too: last year it was the first egg of the season that was laid then, also on a cold sleety day.  So it’s taken a week, almost to the hour, for the clutch to be laid from start to what is expected to be finish, assuming this female follows the typical pattern of laying the same number of eggs as in previous years.  Several people saw the fourth egg being laid a little before 08:30, after which it was left exposed as the female incubated the other three eggs for 15 minutes or so before pulling the new egg under her to form part of the clutch.  Why it would be left out like this is a puzzle, but it’s another fascinating insight into their breeding behaviour (thanks to Andy D for the details).

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So after the first egg was laid early Thursday morning, there have been gaps of around 52-54 hours, 70 hours and 49 hours between eggs.  This conforms to the pattern identified by Ratcliffe in terms of gaps and preferred period of the day for laying, but the longest gap coming between second and third egg (rather than third and fourth) certainly does not.  

Following the initial anxiety of the final egg being left out in the cold, for the rest of the day the male and female have been taking turns to incubate, sitting tight and only briefly leaving the eggs when carrying out a takeover.  The literature states that the female does most of the incubation, but today the male has spent at least half the time on the eggs, apparently unwilling to hand over to the female on more than one occasion.

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In the screengrab above the female arrived with much calling, to which the male responded by calling and sitting tight, with the female departing again to leave him sitting for another two hours.  When they do make the changeover, the difference in size is quite obvious, as in the side-by-side comparison below.

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The male (right) looks barely large enough to incubate the four eggs and takes a while to get settled, shuffling from side to side and pulling the eggs tight in under his body, as below.

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Handovers of incubation duties took place today at 12:48 (female took over), 14:32 (male took over) and 18:29 (female back on).  She’s still sitting now (21:10), with at least one eye open, and seems to do the night-time stints.  I may have missed some changeovers, as I’ve used the calling to alert me to look at the webcam, but don’t think I have during the day, so my reckoning is that between 10:00 and 19:00 the male sat for almost 5 hours and the female a little more than 2.  Given her greater size, might she be better equipped to incubate the eggs at night, when temperatures are lower?  The other snippet of behaviour I’ve noticed is that the female is still busy improving the nest scrape, regularly picking at stones and dropping them close to her body to increase the lip on the nest cup, presumably to reduce the wind getting under her to the eggs. 

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I’ve not seen the male do this today, but could easily have missed it, so one to look out for perhaps.  Is this part of their breeding behaviour we can help to appreciate?  It has been suggested that this could be a remnant of nest repair activities undertaken by species that build a nest of sticks, as raptors other than falcons do.

If four does indeed represent the full clutch, then an incubation period of 29-32 days would give a likely hatching date of 24-27 April.  In the meantime, we’re going to see a lot of scenes of sitting Peregrines!  Anyone looking for a project could keep track of the time the male and female spend sitting, or note changeover times observed (and whether it’s the male or female that takes over), to build up a picture of how this pair shares out the incubation duties.  Ratcliffe suggests that the male may do 30-50% of the incubation in the earlier stages, though in many pairs this has been seen to decrease later in incubation.  So much to learn and so little time to watch!

Three and counting?

Today (Tuesday) saw the appearance of the third egg, visible to some lucky webcam viewers at around 7 this morning.  Given that the second egg was laid between 8 and 11 on Saturday morning it seems that there was a gap of about 70 hours between eggs (assuming it was laid early this morning, with early mornings apparently the preferred laying time), at the upper end of what is quoted as the normal range by experts.

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One study of Peregrines suggests that the longest period between eggs is noted especially between the third and fourth eggs, while incubation is quite widely considered to get under way once the penultimate egg is laid.  This results in all the eggs hatching in fairly close proximity to each other and no significant difference in size between the chicks, so reducing competition and nest aggression.  Could it be that this will mean that we will only have three eggs this year?  Let’s hope not!  Clutches of three or four eggs are the norm, with larger clutches (a maximum recorded of 7!) estimated at around half of one percent.  One cause for optimism that there will be a fourth egg is that individual females tend to lay the same number of eggs in successive years, and we know that this female has had clutches of four in each of the last two years.  Whatever the case, we’ll know in the next day or two, and are likely to see a lot of images like the one below for the next few weeks.

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Once incubation gets under way in earnest, the period to hatching is 29-32 days, but we’ll have to wait to see if a fourth egg appears before making an estimation on hatching dates.  The male will incubate, though the female will typically do the bulk of the sitting.  To tell the male from the female, the smaller size of the male can be obvious, but another means of separating them is the pattern of the black hood: on the female (above) there is a clear white patch on the ‘cheek’ between the moustache and the nape, while the male has an almost entirely dark hood (below), with no obvious white ‘cheek’.

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Visits to St George’s continue to produce good views of the birds, with copulation again noted on Sunday morning.  The Peregrines are not the only birds breeding around the church, with Blue Tit, Mistle Thrush, Blackbird and Crow all preparing for the breeding season.  The Mistle Thrush even flew up to perch on one of the church’s turrets to scold the male Peregrine, while he flew off at one point to attack a Crow.

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The Crow could be considered an egg thief, but it is thought that other potential prey species may in fact benefit from nesting near to the Peregrines.  While smaller birds may enjoy protection from potential predators (such as the Crow) the Peregrines in turn may benefit from the early warning of potential predators provided by the many pairs of eyes of other breeding birds.  Things are likely to settle down to a pattern of one bird sitting and the other perched nearby, but there will still be much to enjoy, either via webcam or in person if you can get down to St George’s.

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 And with the clocks set to change next weekend, light evening are on the way!  In any case, we can enjoy watching them by night, something experts like Derek Ratcliffe, who wrote the definitive study of the species, simply couldn’t do in all his hours of watching Peregrines.  This is great stuff and real insights into aspects unknown until very recently.  In the picture below, the female has just stood up and turned at least one of the eggs, showing that incubation is active, day and night.

25 March night 2

 

Two down

After the appearance of the first egg on Thursday, yesterday was full of anticipation, but the second egg failed to arrive.  The female spent extended periods on the nest, adopting postures that suggested she might be about to lay (as below), but it wasn’t to be.

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Both the tiercel (male) and the female incubated over the course of the day, mostly in rather half-hearted fashion, often standing over the egg rather than snuggling down onto it.

When I checked the webcam early this morning I fully expected a second egg to be visible, but there was still just the one.  Could there have been a complication?  I’d planned to go down to St George’s in any case, and when I got there both adults were around the nest platform, all looking fine.  By the time I got home at 11 after running some errands a second egg had appeared, at least 48 hours (probably some 54 hours) after the first.

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Another visit to St George’s in the afternoon revealed some surprises that would be impossible to appreciate via the webcam.  On arrival the male was on the ledge to the E (the platform is on the N-facing ledge) and I assumed the female was on the eggs.  After a few minutes, however, a Peregrine came into view from the E, fairly high up and carried on towards the N.  I presumed this was the female on a hunting trip, but a little later the resident female popped up out of the nest platform – clearly a third Peregrine is in town.  She hopped onto the perch and became very agitated, calling repeatedly.

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Whatever was causing the agitation wasn’t going away and she set off towards the city centre, where another Peregrine could be seen circling – apparently a fourth!  Having defended the territory she returned and landed on the ledge, from where she called to the male, who had not moved during the whole episode.  He flew round and they mated, which was interesting to see as the eggs are well on their way.  In his seminal study of the Peregrine, Derek Ratcliffe states that ‘copulation continues in most pairs until the third egg is laid, and occasionally occurs after the clutch is complete.’  Whether this is a biological necessity at this stage or ongoing pair bonding isn’t clear to me (or to Radcliffe), but it seems that it could well be both, with the latter the more likely option.

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The female eventually returned to the nest and the male took to the air, giving a good fly-past, even allowing the ring to be seen.

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During the afternoon the weather in Sheffield took a turn for the worse, with a drop in temperature and steady rain turning to sleet.  The pair seemed to respond to the conditions, and took to incubating the eggs, the male also doing a stint, as below.

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So no complications after all and things progressing nicely.  Apparently the typical interval between eggs is around 48 hours, with  52-62 hours in captive Peregrines, so another egg may come tomorrow or may not: watch this space and the webcam to find out!  

 

 

The first egg of the season!

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The first egg has been laid at the St George’s nest platform, a week ahead of last year’s date and earlier than I’d suggested as a prediction.  It may well be that the milder weather has triggered an earlier start to laying, and it would be interesting to plot dates from across sites to compare with last year.  We should see another 2-3 laid in the coming days, with one egg typically laid per day, so it’s definitely worth keeping a keen eye on the webcam.

The egg seems to have laid either overnight or very early this morning.  The first image to show it is below, from shortly after 05:30 this morning, when the female left the platform.

20 March 0530

The single egg has been left unincubated and apparently unattended for much of the day.  Some people have expressed concern in the comments to see the egg left unattended, but it is quite normal behaviour for incubation not to get fully under way until the clutch is (almost) complete and is no cause for alarm.  And they are far from unattended: views from the windows of my building nearby showed that at least one adult was on the perch or corner of the church whenever I looked, and on my way to a meeting the other side of St George’s this afternoon both adults were on station, though neither was visible on the webcam.  Both the male and female did spend time on the platform from time to time, with the female in particular present for extended periods, doing further rearrangement of individual stones.

20 March female with eggShe seems occasionally interested by the camera, and eyeballs it from time to time, though there have been no attacks on it, as there have been elsewhere!

20 March eyeballing

She also kept her eye on the egg and you can rest assured that it is being well looked after.

20 March egg watching

Tonight she has been incubating the egg, and perhaps will lay another before daybreak.  What will the morning hold?

20 March night

I’m sure everyone, like me, is looking forward to watching the events unfold on another breeding season!

Mid-March Moments

Over the last week the birds have been increasingly conspicuous around St George’s, with at least one in evidence most of the time, often on the very top of the points or on one of the corners.  The regularity with which they are now visiting the nest platform has led to the Twitter trigger being turned off as it was starting to generate a (very!) considerable number of activity alerts.

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The birds are quite vocal now, which is another encouraging sign as the species is largely silent away from nest sites.  The image above shows the male in full screech, and his call is notably higher in pitch than the female’s.

The female has been spending extended periods on the nest platform and was there for a good deal of the morning today, feeling secure enough in her surroundings to have a snooze.

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Later on she undertook some rudimentary nest building, which is taking the form of moving the pea gravel around the nest platform.  Often this is done by scraping, as shown is previous postings, but she also carried out some more delicate preparations, picking up and moving individual stones with her bill.

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A flurry of calling at lunchtime led me to look at what was happening and both birds landed on the platform, apparently engaged in some courtship which saw them face to face with heads bowed and tails raised, a position they held motionless for several minutes.

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The female then shuffled gradually towards the male, who was backed against the far wall of the box, eventually ending up almost vertical against it as he looked to keep a bit of distance between them.

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After another couple of minutes, he suddenly hopped to the edge of the box and flew off.  With her advances apparently having scared him off – and she was most certainly taking the lead – she settled down for another snooze and took up a pose that allowed me to see that she was half asleep, one eye open and one eye closed (see below).

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According to Tim Birkhead’s excellent book Bird Sense this ability to sleep with one eye open is something birds share with aquatic mammals.   It’s a way of resting one half of the brain while the other remains ‘switched on’, with the half on the other side to the closed eye taking a nap.  This isn’t something recorded in all birds, however, and is known from ducks, gulls and songbirds as well as falcons.  For ducks and gulls it provides an obvious benefit in watching for predators, while in species such as swifts it enables them to sleep on the wing without crashing.  The benefit for falcons is less clear (to me at least!), as neither of these would seem a likely explanation, but she was definitely moving her head around while the left eye was closed, scanning the surrounding area with her right eye.  Perhaps the benefit of being able to remain alert – especially at the nest site – while having a nap is all the explanation we need.

So the webcam proves its worth yet again.  Several comments are showing some disappointment that the camera angle cannot be tweaked to the left to capture the perching post, which isn’t possible for reasons previously explained, but the camera continues to allow us to watch more fascinating behaviour, all to be enjoyed from wherever you are.

This time last year copulation was observed around St George’s, with the first egg laid at the end of the month.  We’ve probably got 10 days or so before the first egg might be expected, if indeed they are to breed.  The signs are looking very good, but let’s not count any chick(en)s just yet.

Feeling like spring

The improvement in the weather, with some sunny days (finally!) has made viewing a bit easier, at least in the flesh.  Over the last week one or both of the pair has been present on St George’s as often as not, typically perched on one of the round cornerstone ornaments below the ledge.  Fortunately they’re often visible as I arrive or leave work, and even as I move around the office building, so it’s not too onerous to keep tabs on their presence.  On Tuesday this week, for example, the male spent the entire morning perched on the same spot, even with the cranes in full activity, and was occasionally seen indulging in a bit of wing-stretching.  The webcam, however, showed only an empty nest…  I guess seeing isn’t always believing, or at least not seeing doesn’t mean not believing.

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As the Twitter grabs show, there have been plenty of visits by one or other of the birds, with both present together on occasion, and on Wednesday 5th the morning saw a lot of activity.

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Having left the webcam on as a background tab I could hear a lot of calling mid-morning and couldn’t resist having a peep!  The male (spot the ring) was on the nest platform, which was interesting in itself as last year it was the female that was more visible on the platform in the earlier stages while the regular appearance of the male seemed to be an indication of more serious intent.

5 March male scraping

 

 

 

 

 

 

 

 

The male’s vigorous scraping, as above, certainly suggests a commitment to the nest.

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Shortly after the male left the nest, following an extended stay, the female (above) arrived, with more calling, another feature of a breeding pair on territory, as birds are typically silent otherwise.  She too stayed for quite some time, and continued the scraping of the gravel in preparation of the site.

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More interesting behaviour followed, as she started pecking the back wall of the box.  Last year this led to the removal of a considerable amount of the paint used to treat and colour the wood, creating what was generally reckoned to be a map of Iceland.

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This year there’s no paint – one of several design improvements implemented by Jim’s team – but she gave the wood some determined attention, nibbling at it for several minutes.  Could this be a testing of the surroundings and checking the durability of the nest site?  Whatever the reason, it’s another insight into the breeding activity and behaviours of these wonderful birds in the heart of the city.  The sun is due to shine this weekend, and things certainly look to be hotting up at St George’s!