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.

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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