Friday, 22 June 2018

Keeping in touch with the male Goshawk

Adult male Goshawk, 3.vi.2018, N Apennines.
Bulky body, broad hips, narrowed long hand, rounded tail end,
and bulky white undertail coverts (partly flared)
After the incredible Goshawk encounter back on the 3rd June, as outlined in the previous post, it seems increasingly unlikely to have any competition as Goshawk 'highlight of the year'.  I've been revisiting the half dozen best images quite often since!  But If later sightings have been brief and of more distant Goshawks, I am not complaining because I did not expect to see any at all in the valley this year after the apparent (but not absolutely certain) failure of breeding after its initial stages last year and the absence of any signs of breeding at the usual nest site this spring.

In my previous experience, the calls and flight behaviour associated with breeding seemed to provide the only realistic opportunity to contact Goshawk (here, either the provisioning male or the newly fledged juveniles in flight), even if such contact is irregular and unreliable.  However, I have now seen what I think is the local male Goshawk several times, but I don't know if he is breeding or not.

I have been back to the 'white scar' watchpoint several times since the 3rd but observation time has been severely limited by adverse weather at the start: frequent total cloud cover with rain falling or  thunderstorms imminent.  The past several days (writing on 22 June) have seen a return to more typical conditions with extended sunny and warm conditions (and still risk of afternoon thunderstorms).

The 'white scar' is an old landslip area in the chaotically faulted and unstable limestone and shale bedrock of the valley, steep and stony, with tumbled blocks the size of a car fragmenting into flakes the size of a 5 euro coin.  It is still relatively open but is reverting to woodland.  High up on one of the wooded slopes bordering the Goshawk valley, it gives a good view across the valley where the nest tree is located (the site itself  is not visible, hidden in the deepest part of the valley) and of the airspace above the next valley beyond.

An adult male around the old nest site

Adult male Goshawk, 3.vi.2018.
Further sightings after the 3rd began to show that there was a male Goshawk resident in the area, and it frequents both the zone in the immediate vicinity of the nest site of past seasons and the wider hill and valley landscape beyond, where the breeding male has been seen in flight in the past.

About 08.40 on the 7th I just glimpsed the flash of a pale underwing against the green background of the far slopes of the nest valley, with a momentary second wing flash ahead of it.  The first bird was a Goshawk: not much to see at distance other than the size and brilliance of white undertail coverts and it was soon lost as it flew up the nest valley and so behind a descending spur of the nearer hillside.  Less than an hour later a Goshawk appeared over the edge of woodland encircling the upper rim of the scar area, doubtless the same bird, it circled as it moved along the wood edge, uttering one quiet k-k-k,  and then went out of sight over the immediate skyline.  Previously a Sparrowhawk came into view along the same wood edge and flew rapidly over the skyline: perhaps this could have made the brief wing flash that earlier drew my attention to the distant Goshawk.

Does food-carrying definitely mean breeding?

At about 09.30 on the 9th a bird suddenly came into view about 150 metres away, above the more distant downhill part of the wood along the higher edge of the scar.  I don't know if it had just come up from the wood floor nearby or had arrived from the higher slopes out of direct sight.  On size and wing length I immediately thought it was the Goshawk, although with more persistent wing-flapping than usual as if labouring very slightly to make height.  He headed away high across the upper part of his usual nesting valley but in the poor visibility I lost sight of him against the distant background trees, so got no significant clue to the possible whereabouts of an alternative nest site.

A quick look at the poor images of the distant bird (left) show it was carrying prey, probably the cause of slightly different flight action, but the apparently square-cornered tail made me wonder about the identification.  Had I got the ID wrong?  Well, I've since found several Gos images where the tail can look very square-cornered, especially in oblique or foreshortened views, so I'm sticking with my first impression (though to be honest that's a 'probable' identification rather than certain).  The ID in this case is important because I assume that if the bird is carrying prey, he must have a nest to supply?  Other possibilities are: 1) I misidentified the bird, 2) the bird was a Goshawk but a second bird, not the local male, 3) it was the local male and he was taking food for himself to some site away from his usual haunts.

When you've got to scratch an itch: composite from a flight sequence, 10.vi.2018.
At a similar time the next day, 09.20 on the 10th June, a Goshawk appeared low over the woods running along the upper edge of the scar area.  With a few leisurely wing beats and a couple of soaring turns it moved fast along the wood edge toward the uppermost part of the scar, which from my position forms the skyline, then disappeared over the treetops.  Before he appeared I'd heard a couple of kek-kek-kek call sequences, apparently from points within his usual base area surrounding the nest site; these were not at the typical alarm intensity but I do not know what their context was.  When he first appeared, he seemed to pause and almost dive inelegantly into the wood edge, but distant images show he had an itchy 'chin' that had to be scratched (below)!

The male's core area? 

In the past couple of nesting seasons I have often heard evidence of Goshawk from woodland around the lower end of the scar area.  I strongly suspect the recent male has tended to base himself in that area when breeding, and probably brings prey there before calling the female; this, however, is only an inference from the pattern of male and female calling when breeding - I have never seen such interaction nor found evidence of a plucking site there.  This area is 150-200 metres from the recent watchpoint at the top of the scar, and the nest tree is hidden a further 150-200 metres downslope.

All sightings so far in 2018 have been in the same locations that I have seen the male in flight in past seasons, not just the same general area but particular routes and particular landscape features (eg. the wood edge along the upper and lower margin of the landslip scar.  That is essentially why I assume the same male individual is involved.  A counter argument might be that these are sites conveniently seen from my watchpoint; although I believe it is the same male I cannot prove it.

I saw him again on June 16th and 17th, but not (so far) after the latter date.  There was also a gap in sightings between the 10th and 16th.  On most days when I've seen him in flight I have also heard a subdued call or two, but I did hear a quiet k-k-k call immediately followed by a quiet wee-oo on a day that I never saw him.  I strongly suspect that he tends to shift his centre of activity and may well be a few kilometres away on most days when I've neither heard nor seen him.

Moult starting.  L: 10th June, R: 16th June, 2018.
The latest images (16th June ) I have show the bird is now actively moulting the inner primaries of the left wing.  The composite (right)  shows an image from this date with one from about a week earlier (10th); the arrows indicate the broken-off tip of primary 8 on the right wing, just to confirm these show the same bird.



Monday, 4 June 2018

It's just a bird, why the ecstasy?

Adult male Goshawk, N Apennines, 3.vi.18.
Long wings, distinct and narrow hand, 
faint primary barring, shortish tail
with well-rounded end.
As rather forlornly recounted in the previous post, during a short visit to the valley in the northern Apennines in mid-March this year I found no evidence of the presence of Goshawks around their usual nest site.  I arrived for a longer stay on 23 May.  Until yesterday (3 June) there had been no new evidence and I was trying to get accustomed to the absence of a nesting pair and apparently of any Goshawks at all.

Yesterday - a blissful day - I got really impossibly lucky.  I was in the right place at the right time for a close encounter with an adult male Goshawk.  On my way up to the high landslip scar watchpoint, past the nesting woods, I heard a short call that had a certain Goshawk flavour but which I dismissed as perhaps a Jay mimic or conceivably a Sparrowhawk or even a misheard alarming blackbird.  I didn't dare hope there was a Gos in the area!  About mid-morning, after just a couple of hours scanning the sky and ridgelines,  I looked up from putting something away in my pack and there was a large hawk climbing straight towards me from the woods below and already close.  Big.  Beautiful close-barred grey breast.  Glaring white undertail coverts like jet trails.  Moving fast with little effort.  Surely a Goshawk?  The bird circled over my position, apparently without seeing me directly below, then circled close around the open rocks of the upper scar area, then over the woods along the higher edge, and, quite distant now, after several more soaring circles it vanished behind trees and rocks at my back.

A stunning and ecstatic encounter, perhaps even more dramatic than the meeting related in the post on 27 April last year.   For sure an adult male Goshawk, and possibly the very male that has nested here in recent seasons.  About half an hour later a Goshawk floated low and close overhead from somewhere behind me, crossed the top of the open landslip area, and after a couple of slow deep wingbeats glided toward the trees that run along the highest edge of the scar.  Closer rocks and trees again hid my view of exactly where it went but I was waiting patiently for a possible further flight view when I half turned to my left and saw a Goshawk sitting on a high bare branch!  The movement I made to raise my binoculars must have alarmed him because when I looked through them toward the branch he was gone.

Adult male Goshawk, N Apennines, 3.vi.18
Slowly coming down from the high of the morning events, it took me a while to start wondering if my first assumption - that the male is not breeding this season but simply resident in his usual territory - was correct.  This assumption is based largely on the complete absence of any of the usual calling between nesting adults, associated with food provisioning or nest security.  I've heard no such vocalisations from the specific nest woods or from anywhere else in the valley within earshot.  His seemingly 'relaxed' demeanour yesterday, lacking the urgency that often characterises flights during nest-provisioning (and I have never seen a Gos perched high in an exposed treetop before), was consistent with this assumption.  But  the startling semi-flared white undertail coverts made me wonder if he has an alternative nest location somewhere in the valley.  For some reason, and I'm not at all sure if this is well-founded, I had the notion that the male only showed prominent coverts when breeding.  Today, his were not flared out to the maximum extent but were not tucked away either.  Perhaps more clues will emerge if I'm lucky enough to have further close contact.

Sunday, 25 March 2018

Mid-March 2018: no sign of Goshawk at nest valley

The Goshawk nest site in sloping Beech-Aspen woodland, northern Apennines, Piacenza Province, 16.iii.2018.  The nest is prominent against the sky just right of centre (and see image below).
Made a short visit to my usual site in the north Apennine hills between 15 and 19 March, partly to check on the house plumbing after the winter and a recent period of intense cold (temperatures down to minus 15 deg C for several days), and partly to check for signs of Goshawk activity around their traditional nest, or perhaps elsewhere in the valley.  All good for the former, but sadly no evidence of Goshawk presence at all.  No sightings, no calls, nothing encouraging.  Ah, well, that's not quite correct: the woods in which the nest is situated have not been cut, the nest and the nest tree are still in position, and not further exposed by nearby tree fall.  So that much is positive - just no signs of Goshawk!

The Goshawk nest structure, 16.iii.2018,
high in an Aspen Populus tremula.
I'm pretty sure that if an active potential breeding pair was present in this small valley I would at least have heard some early morning calling.  Silence was in complete contrast to the noisy and exciting  early interchanges between the pair last year (see post on 4 April 2017, "Mist, mud, and Goshawks nesting again!").  But bearing in mind that the early promise of last year turned again to silence in early summer, strongly suggesting failure of the breeding attempt (see post of 23 June 2017, "Despondent as breeding fails"), I was already half expecting no pair to be in residence this year.

Trying very hard to be positive, I guess it's possible that resident hawks dispersed during the recent hard weather and have not yet returned.  Perhaps if one half of last year's pair is in the area he or she will find another mate; perhaps they or another pair will settle at the nest; perhaps I'll manage to locate another nest site within the wider valley system.  That's three "perhaps" in one sentence.  We'll see.

Wednesday, 16 August 2017

A more substantial Goshawk

Surprise juvenile Goshawk, 14.viii.17
I wouldn't quite say that the last two posts have been "scraping the barrel" of Goshawk sightings, but yes, they betray a certain desperation now that contact with a Goshawk has become so very very scarce.

Something more substantial a couple of days ago (14 Aug.) when a definite Goshawk was suddenly there, about 100 metres away and at modest height over the steep track ahead.  The bird soared a couple of turns, crossing the track, moved over the woods on the uphill side, then disappeared fast over the treetops, apparently heading along the ridge.

The confusing thing is that the bird had juvenile plumage.  It was in the heart of the local pair's territory and, like the bird mentioned in the previous post, was taking a course that I've previously seen the adult male follow; last year's juveniles also.  So how to explain its presence here if the pair's breeding attempt at the nest just a few hundred metres up the valley had failed, as I thought (post #25, on 23 June)?

(1)  The very simplest explanation is that I was wrong to conclude the pair had failed, and they had in fact produced at least one offspring.  But I find that hard to accept for several reasons: the decline and then cessation over late May and early June of all the usual calling between male and female associated with food delivery; the decline and then cessation of visible flights by the male, presumed to be food deliveries; the lack of any typical juvenile food begging calls; the lack of first flight events by juveniles; and the lack of any signs of a juvenile's presence in the area when I visited the nest site after accepting that breeding had failed.  The only evidence in favour is that I had thought a few weak 'weeoo'  calls back in early June sounded a little like juvenile calls and not robust like the typical adult female versions.  Perhaps only a single chick survived to fledge and it takes at least two to generate all the usual excited shrieking over food and their first flights above the canopy?  But having fledgling food calls in early June and fully independent flying now would have required eggs to have been laid by late March, almost three weeks earlier than I calculate is the usual date.

The juvenile Goshawk, colour and pattern are
diagnostic (in Europe); note prominent beak.
N Apennines, 14.viii.2017
(2)  The next possible explanation is that it is a juvenile from another pair's nest somewhere in the area, perhaps several kilometres distant.  But assuming that at least one of the local pair is still in the area, one might expect a strange juvenile to be challenged and excluded.  Perhaps territoriality is at its lowest ebb in August or might both adults have moved away?

(3)  A third and more elaborate possibility is that this bird is a 2nd calendar year bird still in its first plumage.  Perhaps it is one of last year's brood, perhaps it was even one half of the pair whose breeding attempt failed, possibly because of inexperience.  But while the images are not adequate to show accurate rendition of fine detail they do not show obvious feather wear or fading, which is consistent with this bird being a fresh juvenile rather than a 2cy.







Goshawk from 7 Aug. now seen to be
juvenile (note buff body colour
and darker blotches).
PS: I have looked again at the very poor images from the Gos sighting on 7 August (see previous post).  I did wonder briefly about the slightly buff body colour but thought it was just some artefactual blurring of an adult's fine barring. I should have looked more closely; I now see some dark spots or streaks, so that bird was a juvenile Goshawk.  In fact there's every chance it was the same individual seen on the 14th!  Its presence in the valley perhaps gives some credence to the idea that the pair did produce a juvenile?  That would be great but I still find it hard to believe!

Friday, 11 August 2017

Looking in the right direction for once

Goshawk, probably the local male.
Distant, but note long wings, depth of beak,
deep belly, undertail coverts not visible.
7.viii.2017
As the last post demonstrated, I was not quite correct when I thought, pessimistically, that after the failure of their breeding attempt back in June the likelihood of seeing a Goshawk in flight during the rest of the summer was about the same as "a snowball's chance in hell".  But that single distant glimpse while waiting for Honey-buzzards to appear, recorded in the last post, does not amount to much considering the amount of time spent in the field.  Now the recent record has improved by a massive 100%: in other words, I've had one more Goshawk sighting, making two in all after the breeding failure.  This one lasted perhaps three or four seconds and the bird was a bit closer than before, around 100 metres at first and over 200 when it disappeared.

It was 10.30 on a hot morning (7 August), I'd just been straining eyes and neck trying (without success) to locate the Honey-buzzard that had just called, apparently from very high behind me, and turned back around to see a raptor not very high over the steep meadow in front.  It was positioned as if it had just emerged from the woods at the far side of the meadow.  With a few deep flexible wingbeats it was up the slope and disappearing behind the treetops on the ridge crest ahead.  Unusually both my camera and I were quick enough to record a few images of the distant bird.

Note long-winged appearance. The bird is not soaring in the right-hand image,
these are from a sequence of shots while the hawk was in active
flight away over the ridge crest. 

So why was it a Goshawk?

A couple of features stood out when looking at the bird: the long-winged appearance relative to Sparrowhawk, and the distinctly slower pace of wingbeats compared with Sparrowhawk (but comparable, possibly greater, flight speed).  It did not give the impression of rather stiff wings that Sparrowhawks often show in active flight.  It was also clearly larger than a Sparrowhawk would have been, assessed in relation to familiar trees and bushes at this site, but I'd suspect it was the local male rather than a larger female.  One of the images shows well the rather deep body and prominent beak, also the barring apparently restricted to the outer primaries.  The absence of visible white undertail coverts is notable; these seem to be more or less permanently flared out in the actively breeding male.  A couple of white patches are just visible dorsally at the root of the tail.

Another reason I'm happy to call this a Goshawk, although not an identification feature in itself, is that I have often seen the male from the local site (only a few hundred metres from the meadow) take a very similar course when leaving the nest area on a new foraging trip.  Typically he will leave fast at treetop height down the valley centre then turn to his left (sometimes right) and move directly up the slope before flying along the ridge crest toward higher woods.

Surprise encounter

However, the recent record probably stands at three encounters. Back on 21 July, about 9am, I was labouring up the ridge track toward the local mountain and had reached a particularly attractive section where the wooded slopes fall away steeply on one side and rise steeply on the other, and the trees overhang the stony trackway to form a high tunnel-like corridor.  I'm pretty sure the Goshawk favour this area for hunting; one evening a couple of years back I saw (from the back) what must have been a Goshawk perched on a bough overlooking the path, and I've several times heard kek-kek calls in the area.  This section is just a couple of hundred metres further up the ridge from where the bird this morning was headed.  This morning the first conscious information I had that a bird was approaching was when there was a sudden flash of pale whitish underwings about 25 metres ahead, low to the ground and just on the cusp of a bend.  The flash came as a hawk, having seen me in his path before I saw him, braked and turned an instant right angle and shot away between tree trunks into the shadows up the rising slope to my right.  No specific identification marks registered, but it was a hawk and I judged significantly larger than any Sparrowhawk: "probably" a Goshawk.

Curiously, I once had a very similar experience walking along a hedged drove at home in Cambridgeshire when a male Sparrowhawk appeared and did a cartoon-like crash stop almost in my face, barred tail and pale striped wings all outspread, before streaking away through the hedge.

Tuesday, 4 July 2017

Tiny and far away, but it is a Goshawk!

Distant and out of focus but it's the male Goshawk out foraging, 2.vii.2017.
At my usual watchpoint again (2nd July), up at the top of the high landslip scar where the elevation and lack of woodland cover allow relatively good views across a wide sector of the side valley where the Goshawk nest is located, and, turning the corner made by a buttress of shattered rock,  part of the southern slopes of the main valley.

Now that this year's breeding attempt by the local Goshawks has failed (see previous post), the woods feel impoverished, as if an entire dimension of the experience of being out in the Apennine hills has vanished.  It has been a shock to realise quite how much I'd come to count on their wild cries around the side valley, and the occasional sight of the male rushing away over the woods on another hunt.  I guessed they would still be around their territory, but pretty much impossible to see, with no calls and no nest to focus their activity.  Happily, in compensation the Honey-buzzards have begun to show a little more often, and around mid-morning I'd been fortunate to catch a short encounter between three of the local birds high over 'my' side valley.  Although they were inconveniently high, I managed to get images of each that were just about adequate to see which of the local birds they were.

Then I turned the corner of the rock exposure in order to scan the main valley airspace for more Honey activity, feeling unreasonably greedy to expect more sightings.  Not long after, I was electrified by a distant but unmistakeable 'kek-kek-kek' call from somewhere in the side valley, out of sight to my left and lower down.  Goshawk!!  I rushed back around the rock corner just in time to see a grey-brown streak burst out of the patch of woods down beyond the bottom of the landslip scar and 100 metres or so upstream of the nest site, rocket low down the valley between the treetops, and disappear behind a hill spur below.  Got to be the male Goshawk, that patch of woods is where he used to call from to initiate a food delivery.

Today's call was quite strident, with an edge of excitement to it, unlike the often quite gentle and discreet k-k-k call preceding a food delivery.  I recall the same tone of call being heard earlier in the season, apparently when he just takes off after the area has been quiet for some time.  Today I also remembered a couple of sightings in past years: while standing in the meadows below the woods I'd seen him come fast down the side valley, turn across and over the bottom of the woods to his right, then making a wide hairpin turn, power away uphill again, back toward the crest of the southern slopes and theoretically within sight of where I'd just been looking for Honey-buzzards.  Well, nothing to lose by rushing back around the rock to look down the main valley, just in case - and there he was, distant already, in active flight toward the ridge crest as if heading for the woods on the far side!!  No physical identification features, but his behaviour means I'm sure it was the male Goshawk.  So what? Well, just that it is not impossible to see him post-nesting!

Friday, 23 June 2017

Despondent as breeding fails

It's taken a while for the penny to drop but I've finally realised that the somewhat atypical behaviour of this pair that I noticed in June was indicative of real problems at the nest, and I'm now sure as I can be that this year's breeding attempt has failed.  "Devastated" is perhaps a little too strong, but in fact it describes very well my feelings when I realised the silence around the nest site is the new normal for this summer.  My wife tells me to shut up and just be grateful for contact up to now.  It's a valid point of view, and one I'll strive to adopt wholeheartedly.  It's true, I've been able to listen to their calls, occasionally see the male in flight, and in previous summers experience the joy of those glorious few days when the wild shrieking young first fly above the woods in their valley.  But I was counting on doing it all again this summer ("don't count your chickens..."), and I've probably got a snowball's chance in hell of catching sight of either adult out of the woods until late in the year.

Not this year: one of last year's juveniles in first week
 of flying above the woods,  29.vii.2016
Still, these things happen.  The pair using this nest have added juveniles to the Goshawk population of the Apennines for at least the last three seasons, and that's the really important fact.  I fervently hope these or other adult Goshawks will get things together next winter.

Adult vocalisations around food delivery decline to silence

The last post (4 June) mentioned the many many hours of observation I had put in for little return.  Few spells of calling as anticipated around food delivery, and even fewer sightings of the provisioning male leaving the nest valley.  On several days I'd be in the area for five or six hours with no evidence for nest provisioning at all.  Not unheard of normally, but not day after day, and not at a time when advanced chicks might be expected in a successful nest.  I originally put this down to the pair simply being naturally quiet, perhaps with a different male showing different flight habits.

In fact the events (of 3 June) outlined in that last post turn out to have been the last calling sequence that seemed largely as expected: since then I have rarely glimpsed the male, there have been no 'normal' exchanges of k-k-k and wee-oo calling by male and female of the pair, and in the last few days (writing this paragraph on 15th June) almost all vocalisations have ceased, apart from some occasional quiet k-k-k calls, mainly from a part of the woods 100 metres or so uphill from the nest tree.  This is normally a patch from where the male first calls when bringing food, but between 10-15 June when I've heard some k-k-k calls from there, there has been little or nothing in response from around the nest tree.

It was all going so well.  The male back on 21 April 2017
The last robust and excited female wee-oo call I have heard was on 5th June.  On a couple of days after that date I thought I heard an occasional thin and weak version of this general wee-oo call, which sounded a little like the early food-begging calls given by advanced fledglings; not only were the calls not typical of the adult female but on occasion they seemed to come from locations around the nest site, not the site itself, as if from branched and active young.  But I cannot believe that this pair could have been so far ahead of the typical schedule here (advanced fledglings calling by late June, flying free by late July) without me hearing definite evidence before now.

Significance of the female "wee-oo" call

I use "k-k-k" and "wee-oo", or similar, as a kind of shorthand.  Penteriani (2001), and Schnell (1958) more thoroughly describe the range of calls, their occurrence over the year, and presumed function. The female "wee-oo" call is particularly significant as an indicator of events at the nest.  Schnell (1958), followed by Penteriani (2001) recognise variants of this call type: 'recognition scream' (when she sees the male return to the vicinity), 'transfer scream' (around transfer of prey, possibly to encourage transfer), and 'dismissal scream' (encouraging the male to leave the nest, presumably to continue hunting).

Sometimes I can fit what I hear with this classification but I have no visual contact with the birds so can only infer a very coarse picture of what may be happening.  Typically a more or less agitated exchange of calls, with the birds apparently coming into proximity from initial more separated positions, the female uttering a few wee-oo calls, sometimes loud and excited, after which the male can sometimes be seen as he leaves the nest site.

The decline in frequency of this female call type during June, and its apparent absence since the 11th, the last definite record in my notebook,  made me seriously concerned about the status of this season's breeding attempt.  Did absence of female calls associated with prey delivery by the male mean absence of the female, or absence of prey deliveries, or both?

Male leaving after food delivery, arrow
marks full crop, 7.vii.2017
The last date for which I have direct evidence for prey being brought to the nest area is 7th June, when the male's bulging crop could be seen as he left the area after a late morning delivery; this was preceeded by the usual quiet k-k-k call from his spot uphill from the nest.  Of course I do not know if any part of that prey item was taken by the female, who gave only a few weak wee-oo calls.  Despite the extreme dryness of the year so far, which I began to speculate might have affected hunting success in some way, there is still an abundance of blackbirds and jays which are high on the list of known prey species.

Nest apparently deserted

So on 15 June I decided to take a gamble on perhaps disturbing them by going further uphill on the track through the woods to where it curves around the top of the large concave slope in which the nest tree is located; there is a spot on that track (reconnoitred in winter) where, with a lucky breeze to move intervening foliage, it is sometimes possible to get a partial view of the nest (100 or 120 metres away downslope but not much above eye level) and check if there is an adult or chick near fledgling size visible or not.  There was not, nor were there alarm calls from any hawk that might have been on watch nearby, even though I stayed for some time (and would no doubt have been seen by any adult hawk in the vicinity) trying to sort out whether different patches of light were just light reflecting from leaves or perhaps a downy chick.  I could not exclude the possibility that a young bird might have been laying flat in the nest bowl, but thought it unlikely.  Despite everything apparently going well in May the nest now appeared deserted.  I returned over the next couple of days, just in case an adult had temporarily left the nest area when I viewed it on the 15th, but I neither heard nor saw any sign of occupation and concluded reluctantly that this year's breeding had failed.

It is not clear to me why the breeding attempt should have failed at this point.  The last time I'm aware of it happening was in mid-June 2013 after a sequence of days with torrential rain followed by a  massive and damaging hailstorm.  Is there some kind of milestone around the middle of June, perhaps to do with chicks attaining some critical size and vigour, that has to be passed for the brood to progress and fledge successfully?

I'm not aware of any disturbance around the nest site beyond the very occasional trail bike rider in the vicinity.  There has been no timber extraction in the vicinity over the breeding season.  Typically there will be a few people in the area looking for truffles and other fungi after periods of rain, but there has been virtually no rain.  Perhaps the most likely explanation is that either the male has not been able to keep up an adequate food supply to the nest (perhaps also connected with the extreme dryness), or one of the pair has met with an accident while away from the nest, or been overtaken by disease or old age. Perhaps the female was an inexperienced 2cy bird*.

Penteriani, V. 2001. The annual and diel cycles of Goshawk vocalizations at nest sites. J. Raptor Res. 35(1):24-30.
Schnell, J.H. 1958. Nesting behavior and food habits of goshawks in the Sierra Nevada of California. Condor 60:377-403.  Available online (accessed 16.vi.2017): https://sora.unm.edu/sites/default/files/journals/condor/v060n06/p0377-p0403.pdf
*The feathers later recovered at the foot of the nest tree, see Postscript, suggest the female was an adult, at least 3cy.  This is based on the faded bars on the secondary (thanks to P.Sunesen), see BirdForum post HERE.
_____________________________________________________

Postscript added 21 June 2017. 

The nest (circled): an adjacent Aspen has leaned over
and both have several dead upper branches,
the nest is much more exposed than before.
With a complete lack of calls around the site and no birds seen in flight, on the 18th I cautiously visited the nest tree itself.  No sign of any young at the nest or nearby, no sign of any adult in attendance.  Twigs with leaves had clearly been added around the rim some time ago but no fresh twigs with green leaves were visible; this need not be significant.  Nothing untoward was seen around the nest tree.  I picked up three feathers, presumably moulted by the female, and I believe this can be taken as confirmation that she had been incubating and sitting with young.  The moulted feathers appear to be an outer secondary or inner primary from the right wing and two outer tail feathers from the left side. The nest tree (an Aspen Populus tremula) appears to have deteriorated this year.  Several of the lesser branches around and above the fork supporting the nest look dead, and the leaf canopy over the nest looks less complete than in past seasons.  The year has been exceptionally dry so far and I'm wondering if this might have had some impact on tree health, and could the loss of some leaf cover have had a seriously adverse impact on conditions in the nest?  Still no sign of Goshawk presence in the immediate vicinity of the nest tree on 19th and 20th.

Secondary and tail feathers found under nest
Upper surface, left. 18.vi.2017