Mostly quiet on the northern front

With a little more time to fill in some details, and a few more images following visits both of the last two evenings to make the most of some lovely light as it shines on the north face of the church, here goes.

June 5 BHG 1

Some of you may have noticed that this is not a Peregrine (!), so why post an image of a Black-headed Gull?  In recent years, there have been a few occasions when the adults have chased off Lesser Black-backed Gulls, the female even towing one backwards mid-air a couple of years ago (reproduced below).

Peregrine LBBG 2 June 2013

Since then, every time a gull passes the tower there’s a hint of excitement at the prospect of another pursuit, presumably as the gulls pose a threat to the eggs or young chicks.  So, when the above adult Black-headed Gull passed over at tower height I wondered if there might be some fireworks.  However, I was totally unprepared for what happened as the gull continued to call loudly and headed back towards the church tower, which it circled.  It decided to mob the Peregrines perched on the tower (all 5 at the time) and passed within a metre of two of the juveniles and then the female.

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This seemed to be asking for trouble, but none of them made any attempt to pursue it.  Without doubt, one of the more bizarre occurrences of recent days!

June 5 1

The female has continued seemingly to encourage the juveniles to fly by tempting them with prey items that are withdrawn as the young birds approach.  This strategy doesn’t seem to be working too well, as this evening two of the young remained steadfastly around the nestbox, and eventually the female fed them there, watched from above by the third.

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This third juvenile continues to show good flying skills, and set off after the male when it brought in some food and then took off again, the young bird coming round to make a good landing near the top of one of the turrets.  The combination of peachy tinge to the underparts, streaking down (not across) the breast and pale blue eye ring and base to bill (yellow in the adults) can all be seen in the first image below, and will remain good ways to tell the young from the adults over the coming months.

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The other two show little sign of flight, and continue to exercise their wings vigorously on and around the nestbox, often under the watch of the female.

June 6 2

Another interesting piece of behaviour observed both last night and tonight was the birds cleaning their beaks after feeding, using metal on the frames of the webcam or nestbox to do so.  In the image below, it’s the male that is doing this, using the struts of the panoramic webcam to novel effect, but one of the young did the same tonight.

June 5 3

Finally, a couple of images that try to capture the thrill of seeing these wonderful birds overhead as they come and go from St George’s.  It’s been great to talk to so many people there over the last few days and share the enjoyment they bring to so many in our community.  One thing that emerged in conversation is a bit of an urban myth about the rings used on the young birds.  Some have worked out that the rings are on different legs and have come to the conclusion that this has been used to tell the sex of the young birds.  If it does, then it’s a pure coincidence!  When we ringed them we couldn’t be sure how many males or females there were, though we suspected two females.  In the first photo below is the male (with ring just visible on his right leg – perhaps part of the source of the urban myth), and then the unringed female.

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Weekend update

A quick post to report that all is well after a turbulent weekend.  Following the maiden ‘flight’ on Friday 3rd, and the subsequent rescue of the juvenile, a visit on Saturday morning found another of the young birds on the ground in the churchyard.  This time, members of the University’s Estates and Security teams had responded and had captured it by the time I arrived.  Great job guys!

June 4 bagged

Safe in its sack, I helped Lee return it to the top of the church, where we released it inside the wall without venturing out onto the roof, so as not to disturb the young bird that was resting on top of the nestbox, although the female again went bananas.  By the time we got back down, two juveniles could be seen from below, with the third suspected still to be out of sight behind the wall around the top of the church tower where we’d left it – at least that’s what the female’s line of sight seemed to suggest.

A second visit in the evening confirmed that all three juveniles were indeed on the church, and signs that the female was trying to coax them into flight using food.  She brought in a feral pigeon and landed on the webcam housing, where she plucked it before flying off without feeding the young birds in the nestbox, producing much noisy complaint!

June 4 fem takeoff

However, one of the juveniles seems quite an accomplished flier already and had landed on top of one of the turrets with minimal fuss.

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As the female flew off with the prey, it followed and chased her around near the church before she headed off to a nearby University building, where she was joined by the more confident of the juveniles.  After allowing the prey to be taken, the female stood by as the juvenile enjoyed a good feed.

June 4 fem and imm

A more detailed post will follow, but this evening (Sunday) the three juveniles were back on St George’s, and hopefully the worst of the nervy few days of first flights is now behind us.

Taking the Plunge – Right on Time

Having seen reports that only two birds were visible mid-morning today (Friday 3rd), I popped along to St George’s at lunchtime to check on the situation.  Two of the young birds were flapping vigorously on the nest platform, exercising those wing muscles.

As ‘branchers’ (a term explained in the previous post), they were also heading out onto the webcam housing and generally half hopping, half flapping about, all under the watchful gaze of the male perched on the top turret.

June 3 DW 5

It didn’t take long to locate the third juvenile, which had made its way round to the W side of the church, facing the Diamond, where it was using one of the lighting structures to do similar exercises.

With all in order, I headed home to mark essays…

When I checked my e-mails later in the afternoon it became clear that I’d missed some serious action.  At 15:29 one of the two juveniles flapping on the perch pole had lost its grip and fallen off.  I must thank Andy J for the detailed account of what happened, and for the amazing series of images below.

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In an attempt to break the fall, it collided with the side of the church as it scrabbled to grab onto something.

On failing to cling to the wall, it took to flight and circled out over Broad Lane.

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Fortunately, it came back towards the church and attempted to land in a tree, but failed and rather crash landed on the ground, where it looked pretty stunned.

The evidence of the collision with the facade of the church is apparent on the left-hand side of its beak, though this doesn’t look too bad and shouldn’t be a cause for concern.  Once it had gathered itself, it made towards the busy road, but quick action by Andy and a few others headed it off and it made instead for the doors of the church.  Perhaps it wanted to get back up!

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Members of the University Estates team (big thanks to Emma) worked with Andy and Mike S to capture the bird and take it back up to the top of the church, where it was released onto the nest platform.  This was effective in securing the plunger, but spooked the other two: the bird I’d seen on the lights on the W side flew onto the roof of the Diamond, while the other flew across Broad Lane onto a block of flats.

June 3 15

In the meantime, the female understandably repeated her agitation of the ringing and flew around the tower calling noisily.

June 3 16

By the time I got down there this evening, the returned bird was sitting quietly on top of the nestbox and the two adults were perched up not too far away.  There was no sign of the other two juveniles, but fingers crossed they’re settled quietly.  So the time from hatching to fledging has again been remarkably consistent, with the prediction of 3rd-4th June coming good.  All seems quiet tonight, with the juvenile having dropped back into the box for the night.

June 3 night

This is always a nerve-wracking time, and we’re in for a fraught weekend I suspect, with further excitement to come no doubt.  If you are about tomorrow or Sunday, it’ll be great to have people around to keep tabs on the young birds, especially if they try to fly back towards the church.  Thanks to all those who sent me an e-mail to let me know what was happening this afternoon.  Do keep them coming if there’s a situation developing.

Five Weeks Old – Almost There

Having been away for a week, I came back yesterday to find the young Peregrines transformed from fluffy white chicks to immatures that look like browner and streakier versions of their parents.  It all seems to have happened so quickly!  This brown plumage on their upperparts and vertical streaking on the breast/ belly will be the easiest way to recognise the immatures from the adults when they leave the nestbox, which will take place in the next few days.

In two of the last three years (when we’ve known the dates for laying, hatching and fledging) it’s been 38 days after hatching that the chicks have left the nestbox.  The exception was 2015, when one of the chicks left the nest 35 days after hatching – though this wasn’t planned, as the young bird was blown off the edge of the box in strong winds when exercising!  My calculations suggest that we should expect the first departure on 3rd or 4th June, and this weekend should see all of the young birds take the plunge.

May 28 AJ 1

Thanks to Andy J for the picture above, taken while I was away, and Andy also captured a great image of one of the young birds peering out onto the world it will soon inhabit.  They’re now regularly visible from below as they exercise or just chill.

May 28 AJ 3

At this age the young raptors are called ‘branchers’, as species that nest in trees take to branches around the nest to exercise and flap/ jump from perch to perch.  The adults will soon begin to tempt the immatures out of the nestbox with prey brought to the ledges around the box, and this seemed to be happening yesterday afternoon as the male arrived and the young birds rushed to the corresponding corner of the box.

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There was a report that one of the young birds had jumped out of the box late yesterday, but by lunchtime there was no sign of anything out of the ordinary, and all three were back in view via the webcam.

May 31

It’s always a nervy time as they flap and totter on the edge, though the photo below by Andy J shows how firmly they are clinging on with their talons.

May 28 AJ 2

They look to have a bit too much down at present compared to how they looked in previous years when they fledged, but those young feathers are shaken out as they exercise their wings and can come in handy as they fall.  Not only did Andy get some great pictures of the Peregrines, he also managed to photograph one of the local Swifts making off with one of the shed feathers for its own nest lining.  Impressive!

Swift-feather AJ

The Swifts also find the church to their liking for the flies that are present, some no doubt attracted by the meat of the prey items brought in.

Swift2 AJ

So if anyone wants to share in the excitement over the weekend, do get down to St George’s.  It’s always great to have several pairs of eyes (and hands) in case one of the young birds ends up on the ground after its first ‘flight’.  If anything does happen that requires some action, send me an e-mail (david.wood@sheffield.ac.uk): I’ll be checking in on a regular basis.

Four Weeks Old

It’s been great to see the positive comments about Nicola’s post: delighted others have found it as interesting as I have.  As part of her research, Nicola would be keen to analyse other failed Peregrine eggs, so if anyone with connections to other Peregrine nests where failed eggs have been removed is reading this, do get in touch!

Despite the disappointing weather, a quick post to mark four weeks since the chicks hatched.  They’re increasingly left to their own devices between feeds, and are starting to take a greater interest at feed times.

May 21

Something to look out for in the days ahead is them beginning to look to feed themselves.  They’ll also continue to change their appearance apace as the down is lost and replaced by the emerging feathers that are already visible when they stretch their wings.

As ever, even when the chicks are left (apparently) alone, one or other of the adults is nearby.  The female likes to perch on top of the church’s turrets, from where she can crane her neck and look down into the nestbox.  Behind you!

May 22 4

A visit early in the morning on Sunday (with sun!) allowed for some observation of behaviour and a few photos.  The female flew in with a loose primary feather.

May 22 2

As she preened on the perch, the feather fell out and dropped.  It looked as if it was going to fall to the ground, which would have enabled a direct DNA sample, but it didn’t quite make it over the lower wall and dropped onto the lower roof of the church.

May 22 3

As she left, there was no discernible gap (unlike in the immature bird that visited recently) and it didn’t affect her flight in the slightest, as you’d expect.

May 22 1

The panoramic camera has come into play as a perch too, as occasionally in previous years, and it appears to have left a bit of a smudge on the lens, judging by the atmospheric effect created in the evening drizzle.

May 23 dusk

The Fourth Egg Explained

For today’s blog post I’m handing over to Dr. Nicola Hemmings, from the Department of Animal and Plant Sciences here at the University of Sheffield.  Nicola, to whom I give a really big vote of thanks for her work here, is an expert on the causes behind hatching failures and has had a look at the fourth egg removed (under licence) during the ringing…   Over to Nicola:

Those of you who followed the Sheffield Peregrines last year (2015) will remember that two out of four eggs didn’t hatch. These eggs were collected during chick ringing, and I was able to examine them in my lab at the Department of Animal & Plant Sciences, University of Sheffield, to determine the causes of hatching failure. To learn more about my findings last year, you can look at the archived post here

This year, things went a little better for the peregrine eggs – three out of four hatched, leaving only one egg left behind.

Nicola Hemmings 1

When the chicks were ringed (Monday 16th May), the egg was collected so that we could once again try to identify why it failed to hatch.

I received the egg in rather amusing protective packaging –this was one egg you certainly wouldn’t want to bite into!

Nicola Hemmings 2

As I opened the container, I could smell that familiar stench. Remember, this egg had been sat in a warm, humid nest for about seven weeks. It had undergone a full incubation period, followed by several weeks of being sat (and excreted) on by the chicks and their parents. It was covered in faeces, feathers, and other debris. There was no doubt its contents would be severely degraded.

Nicola Hemmings 3

Despite this, I wasn’t quite ready for extreme level of deterioration I encountered on opening the egg – even I have rarely seen such putrid egg contents! As the rich green soup poured out, my eyes began to water. My research colleagues were repulsed by the foul fumes that filled the lab.

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I must admit I was concerned this egg was beyond examination. However, with characteristic determination, I began steadily to sift my way through the gunk, pouring subsample after subsample of the soup into a new dish and diluting it with saline solution to help clear the fluid.

I wasn’t simply filled with blind hope; I had good reason to think I might find something interesting or useful in among this smelly concoction. I’ve examined many unhatched eggs – probably several thousand – over the years, as part of my research into the causes of hatching failure in birds, so I am used to finding golden bits of information among a rotten mess! I also conducted an experiment a few years ago (using turkey eggs) to see how long non-developing eggs could be incubated before I was no longer able to get useful information from them. Even after several weeks of intensive incubation, I was still able to find degraded embryonic tissue, as well as sperm cells embedded in the layer surrounding the egg yolk. It’s amazing how much you can learn from a rotten egg!

Unhatched egg examinations are an important tool for bird conservation. Across species, around 10% of all eggs fail to hatch, but in some critically endangered species the failure rate is over 70% – that’s almost three-quarters of all potential chicks never hatching! By looking at unhatched egg contents, we can diagnose fertility problems (i.e. insufficient sperm), detect egg infections, and identify abnormalities in developing embryos that may be linked to genetic problems or environmental factors. Understanding these causes of hatching failure allows rapid and effective measures to be put in place to improve success in the next breeding season.

Back to the peregrine egg. Despite the extreme degradation, my long-practiced egg examination skills didn’t fail me. In one diluted subsample, I suddenly noticed a tiny lump, surrounded by what looked like a thin membranous sack.

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On closer inspection, the “lump” was very obviously a tiny peregrine embryo that had begun developing, but then died at a relatively early stage. The photo below shows the embryo, separated from its “sack”, next to a 1 cm square grid for scale (each of the smallest squares on the grid = 1mm). The “sack” is in fact a glycoprotein layer that surrounds the yolk, called the perivitelline layer. When you dunk a bread soldier into your fried egg, it’s the perivitelline layer that ruptures to allow the yolk to ooze out. The perivitelline layer attaches the yolk to the embryo, which is important because the yolk is the embryo’s only source of nutrition throughout the entire developmental period. Remains of the other extra-embryonic membranes may also be present: the amnion, which surrounds the embryo and secretes amniotic fluid to prevent the embryo from drying out; the allantois, which provides a gas-exchange surface so the embryo can breathe, and also removes waste; and the chorion, which serves as a protective membrane for all the embryonic structures.

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It is possible to roughly estimate the “age” at which an embryo died (i.e. how long it had been incubated for before death) based on its developmental stage. The developmental stages of the domestic chicken embryo are well-established, having been described by Hamburger & Hamilton (1951) using morphological landmarks. You can see the full developmental series  here, and read the original paper if you are interested. These stages have also been described for a few other bird species – in general, early development proceeds at a very similar rate across species. I therefore used Hamburger & Hamilton’s staging series as a guide when examining the peregrine embryo.

If you look closely at the embryo, you can clearly see that the eye is pigmented and the limb buds are slightly elongated. This corresponds with stages 20-23 of Hamburger & Hamilton’s series i.e. approximately 3-4 days development. It is difficult to give a more precise estimate of the developmental stage, because some of the fine morphological structure of the embryo had degraded.

Embryo mortality in birds is most common very early (first three days) or very late (just before hatching) in incubation. This peregrine embryo died at the tail-end of the critical early development period. In these early stages, death mainly results from problems with the formation of organs and the respiratory system, which may result from interference during incubation (e.g. eggs being exposed to abnormal temperatures for prolonged periods). It would be interesting to look back at the nest camera footage (and weather conditions) 3-4 days after incubation started, to see if there are any clues about what went wrong [ed – the temperature dropped to 1.5ºC on the early morning of 28th March and the night of March 30th, with the clutch haivng been completed on March 26th ; the cold tempratures do coincide with this 3-4 day timeframe, but it’s not possible at present to look back to see if there was a period when an egg was left uncovered for any length of time].

It is worth noting that prior to the onset of incubation eggs remain in a state of suspended animation. The embryo undergoes some development (rapid cell division) inside the mother’s body before the egg is laid, but assuming ambient temperatures are below ~24ºC, development pauses after egg-laying until incubation begins. In birds, 24ºC is considered to be to “physiological zero” – below this threshold no development occurs. For UK breeding birds, this makes timing of incubation and chick hatching fairly straightforward. For example, blue tits (Cyanistes caeruleus) can lay up to 16 eggs (usually 8-12) at a rate of one egg per day. However, the female only begins incubating after the ultimate or penultimate egg is laid (as do the Peregrines), ensuring that all the chicks hatch over the course of just one or two days. The pre-incubation period poses a bigger problem for birds in hotter climates, where ambient temperatures frequently exceed physiological zero. If the egg temperatures rise above 24ºC, but do not reach full incubation temperature (36-38ºC), developmental abnormalities will occur and the embryo is likely to die. As a result, birds that breed in hot environments often have smaller clutches and begin incubating as soon as the first egg is laid, leading to asynchronous chick hatching.

I have now stored the embryo, along with some other samples from the egg, in 100% ethanol for DNA analysis. The molecular lab here in Sheffield are hoping to find funds to pay for this work, which may reveal whether or not we have a new peregrine female this year.

For now, I will leave you with a stark reminder about why you should always store your eggs somewhere cool and dry, and avoid leaving them too long before eating them. This is what was left of the once-nutritious yolk, after seven weeks of being sat on by a peregrine falcon. Delicious.

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Ringed (II)

A few days on from the successful ringing on Monday, a chance to respond to a few questions people have posted.  One thing we’ll certainly consider next year is to use coloured darvic (plastic) rings in addition to the metal rings from the British Trust for Ornithology (BTO).  Both types of rings used are very lightweight and have no impact on the birds’ ability to fly or live their normal lives, but coloured plastic rings would make it easier to identify the birds away from the nest once they fledge and disperse.  The current arrangement of the metal rings allowed us to identify the young male that was taken into care a couple of summers ago, and was sadly picked up dead subsequently.  To find out more about the BTO’s ringing programme, look here .  There are some amazing stories that have resulted from all of this, and the good work of the Sorby Breck Ringing Group always results in some fantastic data for the Sheffield Bird Study Group annual report.

May 15 imm Jeff Allesbrook

Above, for example, is a picture taken by Jeff at St George’s last Sunday (thanks Jeff!).  The damage to the primaries on the right wing (how would that have come about??) reveals it’s clearly a different bird to the resident pair.  And the streaking that runs down the breast – rather than across it – tells us that it’s an immature bird, one that hatched last spring.  It could well be that this is one of the birds that fledged from St George’s last year, though it could also be a wanderer from another nest in the Midlands or Yorkshire.  Even at the distance in Jeff’s photo a coloured ring would probably be visible, allowing us to know for sure and mapping the movements of the Sheffield birds.

While I was up St George’s during the ringing, Andy D was on the ground and took a series of great photos, showing Simon removing the chicks from the nest (one by one) and then returning them all together from the bag in the top right image.  Simon’s an experienced climber, but even so it gets the adrenalin pumping: rather him than me!

May 16 ringing AD 4

Andy also got some terrific images of the female as she circled the tower, including the one above in dive mode and a couple more below.

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May 16 ringing AD 3

Dr Nicola Hemmings of the University’s Department of Animal and Plant Sciences has been examining the unhatched egg and is preparing a report to explain why it didn’t hatch.  That will follow soon: her piece in a similar vein last year was fascinating, so don’t miss it!