Up and Away

Over the course of the last week the two juveniles have been becoming increasingly confident in their flights, ranging away from St George’s with regularity.  They have often been accompanied by one of the adults, part of their ongoing learning.

Landing on the towers at the church is more and more accomplished (as above) and they are able to move around from one pinnacle or ledge to another quite comfortably.  A couple of evening ago one of the juvs landed on a ledge above the nest box and squawked repeatedly at the male, apparently wanting a feed, for which they’ll rely on the parent for a little while yet.

The male was unmoved and the juv hopped/ flew across to get closer

before continuing to call loudly, again with no result.  The female had already left the church after being pursued by the noisy juv and had been lost to view.  On changing my angle below the church I noticed a shadow projected on a distant wall that looked like a giant Peregrine.  A check with the bins confirmed that the female was indeed there.

So even when the parents (or juvs) aren’t in view on the webcams they are typically within a couple of hundred metres of the church and there are still opportunities for good views as they come and go.

As the juveniles continue to grow in confidence and hone their abilities they too will offer good viewing, as the photo below of one of them arriving shows.  Even in flight the buff-coloured underparts and vertical barring are quite obvious.

I’d expect the young birds to remain in the vicinity of the church for another week or two, often accompanied by one or other of the parents as they perfect their flying techniques and begin to learn how to hunt.  They may continue to be seen from time to time on the webcams, but they’re also likely to be perched on other parts of the church.  Over the next few weeks they’ll gradually move further afield, but will probably stay around Sheffield into the autumn and perhaps beyond, before eventually seeking out their own territory when they are ready to breed.  The two juvs have made a secure start to life, unlike the two unhatched eggs, but the statistics suggest that they still have a less than 50% chance of surviving their first year, so fingers crossed for them.  For some further details of the Peregrine life cycle don’t forget to have a look at the material available on the ‘Peregrine FAQ’ tab at the top of the page.

And finally for now, I’ll leave you with this picture of one of the juvs on the church, captioned ‘The watcher watched’

The Failed Eggs Explained

Since we removed the unhatched eggs from the nest when the chicks were ringed, I’ve been curious to know what we might be able to learn as to the reasons behind their failure.  We’ve been very fortunate to be able to enlist the help of Dr Nicola Hemmings of the Department of Animal and Plant Sciences here at the University of Sheffield, and she has now had time to analyse the eggs.  Below is a report she’s written especially for the blog that expands on the brief notes posted to Twitter: great work Nicola!

Causes of hatching failure in Sheffield’s urban Peregrines

Dr Nicola Hemmings

On 03 June 2015, I examined two failed eggs from the 2015 Sheffield Peregrines clutch in an attempt to understand why the eggs had not hatched. The eggs were collected for analysis under license on 15 May, when Sorby Breck Ringing Group went to ring the chicks that had hatched from the other two eggs. They were then stored in a refrigerator for just over two weeks before analysis at the Department of Animal & Plant Sciences, University of Sheffield.

Hatching failure is a common problem for birds and something that I have studied for a number of years. In general, a small proportion of eggs (i.e. 1-2%) remain unhatched, but occasionally entire clutches fail. The extent of hatching failure varies markedly across birds and tends to be higher in endangered species. This year, the Sheffield Peregrines experienced a fairly high level of loss: 50% hatching failure.

Hatching failure results from two main causes: (1) the egg fails to be fertilised (infertility) or (2) the fertilised egg fails to hatch (embryo death). These two causes of hatching failure are driven by different underlying factors, so it is useful to distinguish between them. In addition, the developmental stage at which embryo death occurs can provide insight into what went wrong. Distinguishing between these different causes of hatching failure requires specialised techniques: I’ve provided some links to additional reading (see at the end of this report) in case you would like to learn more.

The first Peregrine egg felt light, indicating that it was degraded and may have even dried out slightly. This often happens if there is a slight crack or hole in the shell. The egg opened with a ‘pop’ and the unpleasant aroma of rotten egg filled the air! Inside the egg’s soupy contents was an obvious but badly deteriorated embryo. It was incredibly difficult to determine an exact developmental stage because most of the embryo’s distinctive features had turned to mush. However, the embryo was approximately 2-3 cm long and one fairly large limb was recognisable, suggesting that the embryo must have been developing for at least a week before it died. There were no late-stage features such as feathers and claws, so it is unlikely the embryo was older than approximately two weeks.

The second egg required more careful examination. On opening, it wasn’t as ‘soupy’ as the first egg and didn’t smell quite as bad. There was no obvious sign of development but the yolk had collapsed so it was impossible to locate the germinal disc (where embryo development begins). Looking for further clues, I fished out from the mixture a crucial component of the egg – the perivitelline layer (PVL). The PVL is a thin layer surrounding the egg yolk, almost like a clingfilm bag. It is made up of glycoproteins and actually consists of two layers stuck together: the ‘inner’ and ‘outer’ PVL. The inner PVL binds the yolk from the start, and as part of the process of fertilisation, sperm must dissolve a hole through the inner PVL, using enzymes stored in their head. Once inside, one sperm fuses with the female pronucleus – located in the germinal disc – after which development begins, fuelled by the nutritious yolk. Just minutes after fertilisation has occurred, the outer layer of the PVL forms around the yolk, trapping all the other sperm surrounding the egg at the time. The sperm are firmly stuck in this layer and the whole thing is very resilient to degradation. Therefore, if I take the PVL from an unhatched egg and look at it under the microscope, I can see if any sperm managed to get to the egg. This allows me to decide whether or not the egg was fertilised.

(Microscope image of sperm from the Peregrine egg.  The fluorescent DNA dye is visible in the sperm’s head, which measures about 5 microns, or 0.005 mm. The tail is visible to the ‘south-west’)

I found numerous sperm on the PVL of the second unhatched Peregrine egg– a total of 42 sperm were found in a single 1cm² sample. There were also lots of large clumps of ‘normal’ cells on the PVL, which were probably traces of embryonic tissue. There was no sign of an observable embryo, nor any trace of blood vessels, so in contrast to the first embryo, this embryo died very early on, probably in the first day or two of incubation when it was little more than a tiny disc of rapidly dividing cells.

So why did these two Peregrine embryos die? It is very difficult to identify the exact cause of embryo death in wild birds such as the Sheffield Peregrines, since so many different factors can influence embryo development and survival. However, the fact that they died at such different developmental stages suggests that there was a different cause for each embryo. Early-stage embryos tend to be fairly resilient to changes in environmental conditions, such as cold temperatures or delayed incubation, so it is more likely that the early stage embryo had an inherent developmental problem. In the early stages of development, cells are dividing rapidly and rates of gene expression are at their highest. This means that there is much more scope for genetic mutations to arise, which change the DNA sequences that make up genes and therefore alter their expression. If this happens to genes that are essential for development, normal cell division and differentiation will be disrupted and the embryo will die. I cannot be certain this is what happened to the early-stage Peregrine embryo, but it is a common cause of early embryo death in birds.

The other embryo, which developed for at least one week, is much more likely to have fallen foul of the prevailing environmental conditions. As embryos grow larger and their organs begin to form, they become much more dependent on stable incubation conditions, including consistent temperature and humidity. If the egg was left exposed for too long, or was allowed to become too damp and dirty, the embryo may have died due to chilling or infection.

Finally, any damage – however minor – to either egg would have disrupted gas exchange and accelerated water loss and infection. These would almost certainly lead to embryo death, at any stage. Therefore it is possible that both embryos may have simply been victims of a small crack or hole in the eggshell.

Happily, there is no evidence that mum or dad have any significant fertility problems: plenty of sperm reached all eggs and they had a fertilization rate of 100%. Let’s hope that next year, conditions during the egg laying and incubation periods are more favourable, and they enjoy 100% hatching success too.

Further reading:

Birkhead, T.R., Hall, J., Schutt, E., & Hemmings, N. (2008). Unhatched eggs; methods for discriminating between infertility and early embryo mortality. Ibis 150: 508-517.  Available here or via <http://onlinelibrary.wiley.com/doi/10.1111/j.1474-919X.2008.00813.x/full&gt;

Hemmings, N., West, M. & Birkhead, T. R. 2012. Causes of hatching failure in endangered birds. Biology Letters doi: 10.1098/rsbl.2012.0655.  Available here or via <http://rsbl.royalsocietypublishing.org/content/roybiolett/8/6/964.full.pdf&gt;

Testing Times

Since we left the adventurous juv in a tree in the churchyard on Thursday evening, a lot has happened.  Below are a few shots from that evening, taken again by Andy J (you can tell he’s a professional), first of the female taking a Feral Pigeon to the juv on the roof across the road.

Unfortunately, when the adult released it for the juv to feed itself, the young bird failed to grab it and the pigeon rolled down the roof without begin retrieved.  Perhaps driven by hunger the juv hopped up onto the plastic ventilation pipe

and launched into flight back across the road

landing in a sycamore in the church yard back at St George’s.

However, my suggestion that she’d spend the night there proved optimistic and late in the evening she fell out of the tree and spent the night on the floor in the churchyard.  Incredibly, one of the local residents, who saw her fall, spent Thursday night sitting in the churchyard with the juv to make sure she came to no harm.  That really is hugely impressive, and she (and we) owe a massive debt of gratitude to Steve Beer for his dedication: he’s done us all proud.  And if that wasn’t enough, he then managed to track the juv down when she made a failed attempt to fly back up to the church tower, instead turning and flying back across the road.  After an hour or so of searching, Steve found her on a patch of gravel between some railings and a house, being mobbed by Magpies.  With assistance from someone on their way to work at the University, they called the Estates team and the juv was rescued, being carried back up the tower.  By this time, I’d arrived en route to the train station and saw the juv being released at the top of the tower, only to fly straight off again and be lost to view!

By the time I got back to Sheffield on Friday evening she’d been located and was on the roof of the University’s north campus, where she seemed quite settled.

Meanwhile, the second juv had taken its first flight from the ledge by the nestbox and landed on the narrow ledge at the base of the louvred window halfway down the tower.  So June 5th had proved to be the date of the first flight for one of the juvs, an uncanny repetition of timings from the previous two years.  As if this wasn’t enough action for one day, some lucky observers on Friday also saw a Red Kite over St George’s, which caused some agitation for the adults.

Saturday 6th was a lovely bright morning, so I headed down to St George’s hoping to catch up with the birds and have a chance for some photos in good light.  On arrival, the adults and juv in the louvred window were immediately apparent, and as I walked round the church looking for the roaming juv I came across her on the lower level of castellations towards the E end of the church, where I enjoyed some fantastic views and had some time to attempt some creative shots.

After an hour or so, she began to hop/ fly from one ‘outcrop’ to the next, making her way back towards the tower.

On reaching the W end of the run of castellations, instead of trying to fly up, as I’d imagined she might, she dropped down onto the roof of the church, out of sight.  This prompted the adult female to drop down to check on the juv, which again gave some superb views and photo opps.

A second visit on Saturday, in the afternoon, coincided with the juv from the roof popping back up into view.

Shortly afterwards, she hopped back down out of sight

only to reappear flying out across the road and disappearing down the hill behind the flats.  A couple of us went off to try to locate her, without any joy, but 20 minutes later she flew back in and landed on one of the higher ledges on the tower.  It seems this one is now increasingly confident and capable in its flights, having come and gone several times.  I’m not sure if the local Woodpigeons are so clever that they know the juv is not yet a threat to them, or so daft that they don’t realise the risk, but a close encounter passed without incident.

By the end of yesterday (Saturday 6th) all four Peregrines were on the church tower – one juv on the ledge on the E face and one back in the nestbox – and Steve Beer could enjoy a night’s sleep!

After spending several hours there on Saturday, a visit mid-morning today (Sunday) found all four still on the tower and the occasional flurry of action, although things were pretty chilled on the whole.

The juv on the lower ledge fed on some remains left by the female the day before, but seemed a bit listless, even failng to show any interest when the adult came down to present it with the remains of some prey.

She then took it back up to the other juv and handed over the remains

before leaving the juv to its own devices, part of gradually encouraging the juvs to feed themselves.

Finally, a look at the webcam this evening found the first juv to leave the nest back on the edge of the nestbox exercising its wings before hopping onto the ledge and enjoying the evening sun.

Over the course of the weekend it’s struck me just how many people are keeping an eye out for the Peregrines and are committed to their well-being.  In addition to Steve and the other local residents who watch out for them, many people came to see them while I was there, some popping in on a regular basis, others from further afield (as far as Wakefield) to see them for themselves.  And when the juv flew off on Saturday afternoon and couldn’t be relocated, Tessa from the University’s Information Commons came down to St George’s to report that a student had rung in to say that one of the young birds had landed near their flat and they were concerned for it.  It really is fantastic to see so many people enjoying the Peregrines and looking out for them.  I continue to be delighted at the pleasure they are bringing to such a wide range of locals and not-so-locals, young and not-so-young alike, and would like to finish by giving a very big thank you to everyone who has contributed to the project’s success, both over this weekend and well beyond.

Update/ downdate

A quick visit before work this morning (4th June) showed no change since yesterday evening, with one juv on the ledge and the other on the camera housing and not a great deal of action according to someone who’d been there since early doors.  I was busy all day, but the juv on the ledge became the juv on the roof at about 2 p.m.  Speaking later to some local residents who’d been watching the action most of the day the juv slipped off the ledge while feeding on the remains of a pigeon brought in and flew across the main road that runs by the church, landing in a reasonably controlled manner on a roof about 50 metres away.  Once there she seemed to enjoy the ability to stretch her wings and flapped from the pitch of the roof with some short practice flights.  Andy J was on hand and sent me a series of fantastic images – jealous much!

The stuff of dreams, and many thanks to Andy for sharing these.  She’d settled down by the time I got there, but her increasing confidence in her wings may mean she doesn’t stay there for long.

The mystery of the first chick’s maiden voyage has also been partially cleared up by Rachael T, who sent a comment to the blog to say she was watching the webcam just before 10 a.m. on Tuesday when one of the chicks toppled off the edge of the nestbox!  It seems she was preening and lost her balance, though there’s a good chance the wind played a part in this.  So it was not a planned departure and how she managed to land on the narrow ledge below will remain a mystery, but it’s an impressive feat given that she wasn’t quite ready to leave.

By this evening the second juv has left the nextbox, though in rather less dramatic fashion, hopping onto the ledge, where she’s spent the evening shuffling to and fro, scavenging remains from the larder the adults keep up there.

At times, she’s less obvious and still looks to be quite attached to the box, lying next to it tonight, where I guess she’ll sleep.  In the screengrab below you can just about make out a tail sticking out below the line of the box on the far side.   And by nightfall the adult male had taken up station on the perch pole, keeping watch.

They’re not likely to spend much time in the box from now on, though they may return to it at night once they become more confident flyers.  At least the second camera will allow us to see a bit more of what’s going on and further blog posts will follow to update on developments, whether these mean travel in an upward direction or down.

Stop press!  A flat tyre meant I couldn’t get down this evening (grrr) but Andy J has told me the juv on the roof has flown back towards the church and is in one of the trees in the churchyard.  It’s likely she’ll stay there overnight and then try to get back to the church tower tomorrow at some point.

Still Downy, One Down…

Having suggested that the end of the week might see the first flight of the chicks, the recent gale-like conditions seem to have brought things forward.  After posting last night’s blog post a quick check of the webcam showed the female on the perch pole, being battered by the heavy rain and very strong winds.  Shortly afterwards, she moved into the nestbox in search of some shelter, and stayed there for some time with the two juvs out of sight.

By Tuesday morning  (June 2nd) the rain had cleared, but the wind was still verging on gale force.  At some point around 10 a.m. one of the juvs left the nestbox, though whether this was intentional or not remains in doubt!  My suspicion is that it was caught by a gust and blown off the edge of the box as they seemed a couple of days away from leaving the nestbox on the basis of recent years’ experience.

Somehow or other it ended up on the ledge above the clock face, halfway down the tower and on the same face of the church.  It spent the day there, mostly settled but also running to and fro and occasionally flapping vigorously, though without any apparent desire to take off – much more like the exercising on the edge of the nestbox seen in recent days.  A visit in the evening coincided with parallel feeding as the female brought a Feral Pigeon in to the chick on the ledge, which hadn’t fed all day.

After a good feed, at the end of which the chick’s crop was visibly full, the female left, as above.  Within a few minutes of this, the male took food to the chick in the nestbox, so both ended the day well fed.  Keeping tabs on what’s going on hasn’t always been straightforward as the adults have been using the camera box as a perch, occasionally blocking the view with their tail.

This morning (Weds 3rd June) saw the same scenario, with one chick in the nestbox and the other on the ledge while both parents remained nearby.  One image taken as the female came into land caught me by surprise when I looked at it on the back of the camera, as the female Peregrine’s feet seemed tiny.

It soon dawned on me that these were the feet of a pigeon being carried by the female!  She plucked the catch on the ledge and appeared to be looking to coax the remaining chick out of the nestbox, but though it was clearly keen for a feed it stayed on top on the camera housing.

Eventually she flew round and landed alongside it, though there wasn’t enough room for the two Peregrines and the remains of the pigeon, and the chick ended up being fed while perched on the metal strut that supports the camera before hopping back into the box.

So we have some anxious days ahead still as the second chick will no doubt leave the nest soon, and has taken to moving to and fro from the camera housing and also onto the roof of the nestbox, where it can be hard to see.  Perhaps next year we’ll be able to change the panoramic camera  angle to capture this, but it’s far harder to do than you might think!  The remaining chick is following the pattern of the last couple of years in terms of building up to its first flight, which is likely to be tomorrow or Friday.  Perhaps June 5th will be the day again after all!

Five Weeks Old

The chicks have continued to grow well, despite the chilly weather and unseasonally heavy showers, and are starting to look as if they’re almost ready to leave the nest.  As suggested in the last post, they have been exercising their wings ever more regularly in readiness for their first flight.

This will no doubt result in plenty of scares over the next few days as they appear to be on the brink of losing their balance and toppling off the lip of the platform.  What the picture above also reveals is the amount of down that is still present in the rump and wings, which will continue to be lost as they preen and flap, gradually acquiring full adult plumage.

In the image above, taken today by Andy J, you can clearly see the down flying as this juv exercised on the edge of the platform, and it’s also easy to appreciate the classic plumage differences between adults and young birds, which have that buffy tone to the underparts, vertical (not horizontal) barring on the breast and pale blue around the eye and at the base of the bill (both bright yellow on an adult bird).

In recent days it seems to have been mostly the female that has been bringing food to the chicks, and there have been a few occasions when they have competed for the same morsel, as above.  Over the weekend there was also a moment when one of the chicks tussled with the female for control of a prey item.

It may well be that this is why it’s the female that’s doing the majority of the feeding, as the male may now be at risk of having prey taken from him by the chicks that are now about his size, if not bigger, suggesting that they are indeed both females as we suspected at the time of ringing.  The other thing to notice between the two picture above is just how much they’ve changed in appearance between Friday and Sunday!  And to remember just how they’ve changed over the last month, and especially the last 10 days, below is a montage of screengrabs from 1st, 7th, 19th and 31st of May.

In addition to capturing the development of the chicks, it’s been a good chance over the last week to get some decent photos of the birds as they come and go.  Something that was interesting, and not one I’d noticed before, was that the female flew onto a nearby building after feeding and cleaned her beak on the copper of a lightning conductor, the smooth metal presumably making a preferable surface to the concrete.

As the birds come towards the end of their stay in the nest, I’ll take the opportunity to share some shots for their aesthetic qualities rather than showing any particular behaviour.

In my mind, this is captioned ‘Caught on camera’, with thanks again to Andy J for the image.  A couple of days ago I couldn’t resist the moon behind the turrets on a rare sunny evening.

And similarly, the combination of sun and showers provided an attractive screengrab on Sunday evening.

With the weather set to improve towards the end of the week, this may provide the ideal conditions for the juveniles to make their first sorties.  It’s always a nervous time, but fingers crossed for successful maiden flights: we’ll be keeping a close eye on things just in case there are any problems.  Will June 5th prove to be the day once again?