the weak hweet part two

In this post I described how a bird that ticked most of the plumage boxes for a siberian chiffchaff threw us a curve ball by making some rather untristis noises - and I finished by suggesting that it would be great to get some more recordings. It's far from being the first time that tristis looking birds have made unusual calls - there is plenty to read about it here and here, for example

Well, fortunately for me, an excellent opportunity came along.

There have been several chiffchaffs on my local patch this winter (perhaps 7 all together - a remarkable number of wintering birds for a scottish site) and a local ringer expressed an interest in doing a study to see how long they lingered on their wintering grounds and ultimately, whether any remained to hold territory. I knew that some of these birds looked like tristis and some of them sounded like tristis, so this presented me with an opportunity to have a look at some of these birds in the hand, record any noises they made, and ultimately to be able to link calls with plumage types.

After an excellent first session during which 5 different birds were caught, we were delighted to get an unringed bird in the nets almost immediately on our second session.

Plumage wise it was a bit of a puzzler, appearing quite dark and olive but with nice whitish underparts, dark bare parts, decent super and reduced impact eye-ring. I suspect that in better light it would have looked paler - this picture was taken pretty much at first light, and I reckon that a certain coldness can still be detected in the mantle - still, it's a confusingly green looking bird! While we admired it and puzzled over it's origins it began to call...

While it could basically be described as sounding like 'hweet', there are obvious differences between it and the standard collybita call. The differences can be seen on the sonogram in the prior post linked at the top of this one, but there are audible differences too. You can hear the call here:

http://www.xeno-canto.org/356004

To me this sounds subtly, but clearly higher pitched, thinner, and weaker. It's also damn near identical to the calls recorded on that first encounter - quite probably near enough to say that it's the same bird - and definitely near enough to say it's the same call type.



This call was the only one given while the bird was in the hand, and I was cautious that it might not be doing its 'normal' call under the duress of being handled. We had the initial (awful) recordings of course, but it was nice to get more confirmation that this was a call that was regularly being used. Below is a recording made in the field of a chiffchaff that despite being seen briefly, looked pretty good for a tristis. Unfortunately I didn't get to see whether it was ringed or not.



Below, some of the calls above can be seen in comparison with the in-hand calls and those from the initial encounter, and the field recording can be heard here:

http://www.xeno-canto.org/356005



Unfortunately on this occasion the bird did not shed any feathers. Luckily though it did on a later date so hopefully we will be able to get a genetic confirmation of what this bird is. Personally I have no idea but I guess I'd be a little surprised if it didn't come back from the lab as a tristis. Whatever it comes back as, it'll hopefully go some way towards answering the general confusion over what these variant calling birds are.

I'd welcome any feedback on this birds appearance or any other encounters with chiffs that call like this.

The weak 'hweet'

On 3rd January 2017, Ryan Irvine and I found a couple of chiffchaffs in Nigg Bay, Aberdeen. This has become a regular wintering site for chiffs over the last few years (possibly the only one in NE Scotland) and has hosted the odd Siberian chiffchaff too.

When we got the first few glimpses of the first bird, we assumed that we had stumbled into another 'tristis' bird, based on plumage features. Rather confusingly though, while we watched it, this bird called several times and consistently gave calls that to our ears sounded like a weak version of the standard collybita 'hweet'. At this point a proper Siberian chiffchaff call started up and we abandoned the original chiff to get views and recordings of the bona fide Sibe. The original bird is shown in the photos below.

It wasn't until a week later that I decided to listen back through all of the recordings I made while trying to record the Sibe. I was surprised and quite pleased to find that I'd accidentally managed to record the original bird calling twice. Running it through Audacity, it quickly became clear that what sounded to our ears like a weak version of a standard 'hweet' bore very little resemblance to the sonogram of the standard call. Both call types are compared in the sonogram below.

The two calls on the right are the bird in the photos above - totally different to a collybita 'hweet', and reassuringly similar to one another. I can't find any similar looking calls in Xeno-Canto (although I can't say I've checked all of the chiffchaff calls as there are hundreds...) and there's nothing similar looking (or transcribed) on Alan Deans website, so I'm none the wiser as to where this bird and its unusual call might be from. One possible explanation is that this is not the whole call - sometimes birds give truncated versions of their usual call (I've heard yellow-browed warblers do this, for example) - and perhaps we're hearing the first part of a 'sweeoo'. It was a dull day, and when I've heard YBW truncating their calls it's generally been cold, dull or early.

It's worth noting that the photos over emphasize the coldness and paleness of the bird very slightly - in the field, there was a touch more olive/green in the mantle, too much yellow in the underparts, and even signs of streaking on the chest. Many people have suggested that it could still be tristis - with the calls being within known variations for this taxa. Particularly, it has been suggested that the calls of this bird look very similar to a variation in the Sound Approaches brilliant 'Catching the Bug'. 

While the shapes of this birds calls look very similar to those on page 164 of CtB, there are a few differences that are worth noting. The horrendous sonogram below compares the CtB variants with the bird above, and shows that these variant tristis calls cover a much wider frequency range, and are stronger at the top end of the frequency range rather than the bottom.

However, I guess if Siberian chiffchaffs can make one variant call then they're capable of making a few, and could easily do something similar to the calls above. The thing that could dissuade me from considering this to be a variant call was that we heard this bird doing this call upwards of ten times, and each call sounded like this (rather than throwing in variations here and there among more normal calls). In other visits to the site this winter I've only ever heard tristis calls (although the birds are largely silent, infuriatingly!) rather than a mixture of 'peeping' and 'hweeting' birds.

Whatever it is it's an interesting one, and I'd love to get a few more recordings of it!

Comparison of some chiffchaff calls

Chiffchaffs. Where do you start?

Well, very often, you start with the call, as it's frequently the first hint you get that there is a chiffchaff nearby.

We're used to chiffchaffs saying 'huit' in the UK, and when we're lucky, we get to hear Siberian chiffchaffs making their 'peep' calls (other phonetic renderings are available - such as 'eehp'). To complicate things, we sometimes encounter chiffchaffs that say what can loosely be described as 'sweeoo', and it's a bit of a mystery where these birds or their calls are coming from. For a while, they were ascribed to the various subspecies, with collybita saying 'huit' and the now near-mythical abietinus responsible for 'sweeoo'. We now understand this not to be the case, so there are two positions to start from.

a) these birds are from a distinct population.

b) these birds are the offspring of late breeders, so we hear juvenile, or less crystalised calls at a time when we're not expecting it.

I don't know what the answer is - but what makes the whole thing more interesting is that the 'sweeoo' calls are highly variable, and that the birds that make them seem to be 'irruptive'. I don't necessarily want that to mean the same as it would mean with, for example, waxwings - it's just a way of describing that they can be very numerous in some years, and very uncommon indeed in others. 2016 was definitely a 'sweeoo' year.

Before we get too deep into the nitty gritty of sweeoos, huits, and peeps, lets just have a look at the structures of the different calls. Lining the recordings up on top of one another allows a rough comparison, but putting the calls side by side (and zooming in a bit more, as this will allow) gives a much better opportunity to look at the differences between all of the calls.

The composite is easy to make. I opened a new track in Audacity (tracks menu -> add new -> mono track), and then simply copied (highlight relevent section -> edit menu -> copy) and pasted (click in new track -> edit menu -> paste) into the new track. These ones have had some of the time between calls cut out (scissors tool) so they all fit nicely onto the same page. The real beauty of this is that it lines everything up at the same time/frequency ratio, which allows you to make a valid comparison of frequencies and shapes of motifs. The rapidly upward rising 'huit' is obviously different from the flat topped call of the tristis type bird. The two 'sweeoo' calls are different too. The presumed collybita juv has two parts to the call, the upward inflection at the beginning followed by the downsweep. The winter 2016 birds sounded very different, with some calls showing a clear third component to the call, ending on a smaller, shorter upsweep. This could be heard in the field on occasion, with some calls sounding clearly tri-syllabic.

Lining them up together also allows a comparison of the frequencies the birds call at, such as the sonogram below.

Here it's clear to see how the tristis type call utilises a much narrower range of frequencies than all of the others - which explains why the call is uncomplicated, and sounds flat. I always took this familiar tristis description to mean flat as in the musical sense - but now when I hear it, I 'hear' a flat motif on a sonogram - or at least a 'flattened' one. 

It's also clear that the 2016 'sweeoo' birds reach some really high frequencies. They sound high in the field, but here it can be seen that they reach over 5.5 khz, over 1 khz higher than their 'huit' calling cousins. 

None of this helps with the conundrum of where the variable 'sweeoo' calls come from of course. But the more we recognise them in the field, or even get good, useable recordings of them, the better equipped we will be to come up with a reasonable answer.

When yellow-brows sound wrong

Sometimes Hume's warblers can be relatively easy to identify, but there are plenty of them that look pretty similar to good old fashioned yellow-browed warblers. Usually the really tricky ones can be done on plumage given good, prolonged views, but in the end with these birds, it's usually the call that finally nails the ID one way or the other, as with this bird described by Martin Garner, and this bird on Scilly, which to my eye looks very similar to a bog standard yellow-browed.

Much is made of the variation in the calls of Hume's warblers and the reliability of yellow-brows to say 'tsooweet', and I think that as a general rule, that's totally fine, However, when confronted with a tricky striped phyllosc in late autumn, it's worth remembering that not everything is set in stone. Yellow-brows frequently drop a syllable here and there among sequences of their standard calls, but how often do they give sustained bouts of consistent variant calls?

One morning in mid November 2014, Will Miles and I were birding the Nigg bay sewage works, enjoying a late fall of goldcrests and the odd chiffchaff. Andrew Whitehouse had reported a yellow-browed warbler at the site a few days previously, and it didn't take too long sifting through the crests to pick this bird up. While watching it, we were shocked to hear it give what consistently sounded like thin, high pitched monosyllabic calls. We agreed that these sounded much more like Hume's, and were audibly a decent match to a Hume's call I had on my phone. I managed to get some recordings of these while watching a bird that I considered to look like a yellow-browed warbler, with the understanding that I definitely hadn't seen it well enough to rule out something like the Scilly Hume's example above. We cautiously put the news out that the Nigg Bay YBW might be a Hume's, and sent the recording off to the Sound Approach, who also cautiously suggested that the bird might be more likely to be a Hume's warbler too.

I went back to the site at lunchtime, by now fine, sunny and warm, and picked up the same flock of crests at just about exactly the same spot. Almost instantaneously, a classic YBW call started to ring out from the flock. I was pretty sure that it was the same bird. The chances that a crest flock would host a single YBW, then a single anomolous bird, and then a single YBW again were much too slim for me, and also, based on what I'd seen, I was happy that the bird looked much better for a YBW.

Many features consistent with YBW can be seen in the photos above, including:

plenty of yellow in the supercilium
well marked dark eyestripe, particularly in front of the eye
mottled ear-coverts
no real paleness or greyish cast to the upperpart tone
dark centred greater coverts
dark bar at the base of the secondaries contrasting with strong, white greater covert bar
dark tertials with neat, narrow white fringes
The legs and feet especially were pretty pale

Along with the appearance of the bird, the calls heard at lunchtime confirmed (to me at least!) that this was a YBW. The sonogram below shows this birds calls alongside a YBW recorded on Sanday (Orkney) in September 2015. Despite the Sanday bird having a slightly wider frequency range, the calls are clearly very similar, 'V' shapes with the bottom halves 'pinched in'.

So what about the calls that fooled us so much first thing the same morning?

Well, I guess the first lesson is that a sonogram can tell you much more about a call than your ears can! Will and I were both convinced that the call we'd heard repeatedly that morning was monosyllabic, but the sonogram tells a different story, showing a very short, quick call with a similar 'V' shape to a YBW

In comparison with other calls though, these morning calls are consistently different. They only cover roughly half the frequency range of the standard YBW calls (the higher half), lack the 'pinched in' look, and they are shorter in their duration, lasting for approximately 0.2 seconds rather than the 0.3 seconds of the standard call.



The two bird theory has been suggested several times in this instance, and while it would make sense, I'm convinced there was only one stripy phyllosc present. So - was this a Hume's and we dropped the ball, or was it a weird variant YBW call?

Spotted crake - daytime calls

The nocturnal 'dripping tap' call of the spotted crake is well known but no less exciting for it, and evokes images of wild, remote fenlands. Last year on my travels, I was lucky enough to spend time at a site where a pair of spotted crakes were present, and as well as being treated the rather bizarre spectacle of the pair chasing each other in flight over the marsh, I got to hear some variety in their vocalisations that I hadn't previously been aware of.

There are a few assumptions that I certainly had made about spotted crakes, mainly that they only vocalised at night, and that it was only the males that vocalised. I've found that both of these, while broadly reflecting reality, are not strictly true.

Both birds vocalise

While unfortunately I don't have any recordings to verify this, both birds were heard to 'sing' at the same time at least once, and there were numerous occasions when the locations of calls from within the site hinted very strongly towards two birds vocalising, albeit not simultaneously. The idea that both males and females can vocalise is not particularly new, but I suspect that when confronted by a singing crake, most would assume that the bird was a male. RBBP records of this species are almost exclusively attributed to 'singing males' - can this really be stated confidently? Perhaps females only vocalise when paired up? Or perhaps all those recording 'singing males' have eliminated the apparently slightly softer vocalisations of females? Whatever is going on, at sites where more than one territory is suspected, there is potential for confusion caused by singing female birds.

Day time vocalisations

One thing I really wasn't expecting was to hear the birds during the day, but in fact it wasn't particularly unusual at all. I never heard full song during the daytime (this was mostly heard in the dead of night, or around dawn and dusk), but I did hear several variations on that theme in broad daylight. These can be broken down into three broad categories, as defined below. Another aspect of these vocalisations that really surprised me was that they were not always given from within the depths of the abundant cover - birds quite frequently vocalised in the open on the edge of banks of sedge or marigold,  in full view. This gave the opportunity to watch the physical effort the birds made with each sound, standing steady and compact, heads jerking downwards with each note. In fact, the birds were surprisingly confiding during the day, and allowed themselves to be filmed through a scope (under agreement from the relevant authorities of course) if you waited quietly enough.

The three categories of daytime vocalisation are:

Hesitant song

This was usually heard before dusk, and could feasibly just be birds warming up, or genuinely being hesitant about advertising their position while it would still be light enough for them to worry about diurnal predators. Hesitant song basically sounds just like the standard song, but is delivered for short bursts.

Hear the 'hesitant song' here

Here, the bird threatens to get going a few times but without ever really managing it. Note how it never really finds it's rhythm too, with the pauses between notes being slightly extended from time to time. In this recording it's also clear that the singing bird doesn't enter immediately into full song, but starts off gently and ramps things up over the course of a few notes. This recording was made at around 10 pm, so late, but still fully light. The sonogram below is taken from this recording, showing the portion between 1:13 and 1:27. The 'ramping up' is visible here, with the notes noticeably reaching higher frequencies and getting louder (= darker on the sonogram) as the song progresses.

Sporadic song notes

The most frequently heard daytime vocalisation away from early mornings or late afternoons was of single or double song notes, uttered quite loud, but without ever developing into song. Perhaps these calls are used as contact calls or alarm calls? Perhaps it's exactly the same as hesitant song but with the birds being even more cautious due to the time?

Hear the 'sporadic song notes' here

Subdued song

Occasionally, during the day, birds would enter into what I have called subdued song. Here, a reasonable succession of notes are delivered, but the individual notes are given much more quietly, and never quite hit the same frequencies, or have the same quality as the full night time song. Note that the subdued song below was made from the same location as the other recordings, and the bird was at a similar distance (it must have been, as it was a very small site!). Perhaps this was the female bird singing? Whatever the reasons, you can barely hear it over the song of the skylark the my mic was pointing nowhere near, and was much further away than the crake

Hear the 'subdued song' here

I'd love to know more about these differences, and whether they're sex related, or merely products of the urge to sing, compromised by the desire not to be eaten! It must be one of the least known British breeding birds, and the opportunity to spend time in their presence was a real privilege. While they are without doubt annual breeders in the UK and probably in underestimated numbers, there are only 7 previous verified breeding attempts, apparently!  Mega!

Corn buntings - songs and calls

When I was a much younger person, corn buntings used to sing in the farmland that was a short walk from the end of my road, and it was a song that I remember being familiar with right back to the very earliest days of my time in birding. A lot has changed since then of course. I've moved away from the pretty, rural edge of Durham city, and of course corn buntings have moved away from pretty much everywhere. Consequently, despite North East Scotland remaining a stronghold for the species, it's a bird I hear very occasionally at best.

In November 2016 I was visiting friends near Auchnagat, in North East Scotland. After a heavy night for most, I got up at dawn and headed out, with the hope of finding and recording some tree sparrows. I hadn't bargained on stumbling into singing corn buntings - I had no idea that they sang in November (despite my earlier claims of familiarity) but here they were, several birds, perched up on fenceposts and singing as boldly as they would in spring.

Here's a recording of one of the singing birds.

http://www.xeno-canto.org/348805

And a sonogram of the song from the same recording.

Having done a little research, I've found that singing in November is not particularly unusual in corn buntings at all - which highlights how little I know about this once common bird. Another thing I couldn't say I was overly familiar with are other corn bunting vocalisations. I don't remember them from my younger years, a time when bird sounds were essentially none existent unless my dad had pointed them out to me. I've heard the distinctive calls of small groups of birds in flight on South Uist, but I encounter them so infrequently, I suspect that I wouldn't have felt too confident about nailing one in flight if I were 'out of range', especially if I were only to hear it call once or twice.

This encounter provided a perfect opportunity to listen to the calls of these birds and cement them in my minds ear. The recording below is a bird that was calling while sat up on a fencepost, and it doesn't sound noticably different to the noises that other birds were making as they flew around with a small flock of linnets. That said, this bird had just been singing and stopped as it became aware of my presence, so despite the fact that I wasn't particularly close to this bird, these calls could feasibly be alarm calls.

The calls can be heard here.

http://www.xeno-canto.org/348811

The corn bunting calls are the short, high pitched and slightly raspy sounds.

While they superficially look like quite simple calls, zooming in shows how they are composed of two distinct notes, an initial one that covers a narrow range of lower frequencies, (very) quickly followed by a second note that covers a wider frequency band, reaching up to about 8 khz. This structure can be seen in the sonogram below (I've cut out much of the sound between each call). Were talking about a gap of about 1/100th of a second between these notes, so it's no wonder that this is not clearly discernable by ear! Having heard these birds so well, and listened to the recordings, I'd now be much happier doing one solely on call if one was ever to fly over girdle ness. I'd be even happier if I got a recording that let me see this rather distinctive call structure!

While tonally, these calls sound like those that lead into the typical 'jangling keys' song, the sonogram shows a few differences (with this bird, at least!). These lead in notes are slightly lower pitched, and although appearing to have a two note structure, it's less audible (essentially due to an even smaller period between the two notes) and each note appears to cover the same range of frequencies. The lead in notes appear on the left of the sonogram below - note how the time scale in these last two sonograms differs, with the one below being even more 'zoomed in' than the one above, meaning that the horizontal axis in the one below covers a much smaller period of time.