Fledglings and Caterpillars

Some “fledglings” are just too big for the word.

Okay, it’s recently out of its nest and yes it’s doing the wing-flappy thing and calling for its parents to feed it, but it’s just too big and dangerous-looking. For me a fledgling is a small vulnerable thing. Not a harbinger of doom with great big talons.

So I’m going to call it a young Raven.

For the time being anyway. Without hearing their call, I find it tricky differentiating with certainty between Crows and Ravens – particularly when they’re at a distance, which they usually are. There were no distinctive “honk-honk” calls from the adult birds I saw up on the plain a couple of days ago.

I managed to get one or two pictures of the them in flight and although they had longish wings – a Raven characteristic – the tail was not particularly wedge-shaped, which is also a main identifier for Ravens.

I tried to get an idea of the length of the young bird by using the 4 inch fence posts as a scale/guide. By my calculations (treat with caution) the young bird was a bit more than 21 inches long. So if the upper limit for crows is twenty inches, and the lower limit for Ravens is 21½ inches (RSPB guide), that does suggest the young bird was a Raven.

And when you compare the adult bird on the right of the above picture with the young hungry one on the left, the adult is a bit bigger still – more like twenty two inches (using the same method). But then I think the adult was a little closer in this photo so maybe that distorted things. I’m almost a hundred percent but not quite.

[CORRECTION: (posted a few weeks after this post) Glad I didn’t say I was a hundred per cent on the ID. I had assumed the fence posts were 4 inches in diameter as are the barbed wire fence posts alongside our garden, but it turned out they were more like 3.5 inches. Which of course throws out my calculations and makes it look far more likely that they were crows after all. Yet another schoolboy error in my ever lengthening dodgy record of species identification.]

Ravens have been spreading across the country from the West in recent years. I know of one or two other nests not far away (their distinctive “honk-honk” was heard) which have produced young so it looks like another good year for the species. Not all birds have done so well. I learned the other day that a lot of Great Tit and Blue Tit nests have failed this year due to a lack of caterpillars following the record-breaking cold May.

Apparently those parents that did raise young successfully often did so with the help of suet pellets from garden feeding stations. Which ties in with what I saw a few times with the fledgling Blue Tits that I photographed a couple of weeks back.

The bright pink blob turned out to be one of the suet pellets that Chantal had put out on the bird feeder. Apparently they’re made with berry juice which gives them the strong pink tinge.

The nesting season continues. With more insect life about now, current nesters will probably have a better chance of success. I’ve noticed a bullfinch standing guard in an Elder bush on the other side of the field.

He occasional drops down and goes into the brambles where I suspect the female is on their nest. I saw the male goldfinch of the pair nesting in the ivy tree doing a similar standing sentry thing for a while a month or so back. I wonder if it’s a finch thing. They seem so vulnerable to me out on display like that – no shortage of Sparrow Hawks here – but then our Goldfinches survived and raised a brood so it can’t be that bad a tactic.

An upside down Goldfinch Fledgeling feeding on aphids on the willow tree.

I’ve now also spotted a female Whitethroat, and a delicate wee thing she is. I’m guessing she’s partnered up with the male that’s been around for a while now.  She’s even more secretive and cautious than him.

Rare appearance of the shy female Whitethroat, keeping her distance

The male did come close enough the other day for me to get a couple of better photos, but he was still flitting about in amongst the undergrowth, making auto-focusing difficult. Photographically challenging, but beautiful little birds.

Other species seen during the Raven walk included a Yellowhammer and a Stonechat, both singing their hearts out. I’m guessing they were proclaiming their territory or maybe trying to attract females. Whatever, they should have a better chance of success now.

Yellowhammer in full flow
Stonechat contributing to the background twitter of all the other downland birds.

So the unusually cold weather in spring this year had a devastating effect on caterpillars and the bird life that depended on them. But not all caterpillars have had a tough time of it. A couple of weeks ago I noticed an infestation of caterpillars on an Aaron’s Rod plant which had appeared in the gravel by our back door.

I initially thought they might be caterpillars of the Large White Butterfly – they had a similar yellowy green colouring – but it seemed strange that they were on an Aaron’s Rod plant, their normal food plants being of the cabbage family. But as the caterpillars grew bigger and I looked closer it became apparent they were something different. A little research revealed them to be caterpillars of the The Mullein Moth (the Aarons Rod is also know as Great Mullein). Their black and yellow colouring suggests they might be toxic which, I’m guessing, is why no hungry birds picked them off.

Apparently once the Mullein caterpillars have had their fill, they wander off and find a suitable spot to bury themselves and pupate, only reappearing as moths two or three – sometimes as many as five – years later.

After the driest and sunniest spring on record in 2020, and the coldest May on record this year, who knows what kind of a spring will await them.

Strange Flutter

On the rare occasions over the past couple of weeks that I’ve been out into the garden – we’ve had pretty relentless cold winds and rain – I haven’t seen a huge amount of nest site activity. I suspect they’re either sitting on their nests keeping eggs warm, or the chicks have fledged and the families moved on.

There is one site though, where there have been plenty of comings and goings: the Long Tailed Tits’ nest in the brambles. And it’s a slightly weird kind of activity that I’ve not seen before.

Both parents seem to be visiting the nest regularly with beaks full of mushed up insect life – they clearly have a hungry brood – but they don’t go straight into the nest. They usually land nearby and then fly a few feet into the air above, and do a sort of fluttering hover for a few seconds, before dropping down into the tangle of brambles and the nest below. But they don’t always go down into the nest first time. Sometimes they land on the brambles and fly up and do the hover-flutter thing again, occasionally several times before finally dropping down to the nest.

(If you visit the website, rather than viewing on email or the WordPress Reader, you’ll be able to see the below slideshows rather than the individual pictures.)

It’s a strange and delicate display, almost a dance. And it’s conspicuous too. I’ve been wondering what the purpose of it is.

Log Tailed Tit Ballet

Pretty much all the other species of birds do everything they can not to be noticed entering their nest, or otherwise do it very quickly. Which is understandable with all the potential nest raiders around.

But not the Long Tailed Tit.

If they wanted to alert a partner of their arrival, a partner perhaps sitting on the chicks to keep them warm in cold weather, why not just make a gentle tweet, or call out in some way like other species do, while staying safely hidden and not giving away the location of the nest to any watching eyes. 

I can understand why they would need to enter the nest from above: The Long Tailed Tit nest has a roof to it, and the entrance is on the side near the top, so from above would be the easiest way to access it in a bramble thicket with sharp, potentially wing-shredding thorns on every side. And I can also understand why they might want to alert their partner to get out of the nest to allow easy access for feeding the chicks. But why be so conspicuous?

I wondered whether fluttering above the nest was some kind of evolutionary trade off: the security of a thorny bramble protection weighed against a necessarily conspicuous entering-the-nest-from-above behaviour. Maybe. But it seems odd that no other birds seem to do it.

Apparently Long Tailed Tits have a nesting success rate of less than twenty per cent and I’m tempted to think their conspicuous behaviour may be part of the reason. But then again their population is currently stable or increasing so they must doing something right.

And then I saw two of them fluttering above the nest at the same time. What was that about? If both the long tailed tits were off the nest either one could have entered straight away. Why still hover?

Second hovering long tailed tit, low to the right

A little while later, I noticed three Long Tailed Tits together, foraging in the large willow tree near by, and it occurred to me that the third adult might be a related bird perhaps from a failed nest that was there to help the original couple (Long Tailed tits are apparently well known for this behaviour). So maybe there were now three Long Tailed Tits – or more – raising the brood. After the very blowy, potentially nest-wrecking weather we’ve had lately (gusting to 45 mph today and all tomorrow), a few casualties would have been inevitable. So perhaps when there are two birds hovering over the nest at the same time, they’re waiting for a third to make way.

Thinking about it some more, I can’t remember ever seeing magpies or Jays trying to get at a nest in a bramble thicket, so maybe the Long Tailed Tits’ behaviour isn’t that reckless. Even if they know where the nest is, the corvids may not want to risk damage on the thorns trying to get at it. I’ve seen sparrow hawks going after birds from blue tits to pigeons, but their prey is usually taken when perched on a branch or in mid air by the pursuing raptor. I’m wondering if, when Long Tailed Tits are hovering up and down they would be difficult, unpredictable targets. And I suppose if a Sparrow Hawk mistimed its strike, it could easily end up tangled in the thorns, which would be a bit off-putting as well.

Whatever, their hovering dance behaviour seems to work, though a Whitethroat who was watching from another bramble patch near by looked sceptical.

I first noticed him about a week ago. He seems to keep his head down most of the time. I haven’t seen a female yet, but I have noticed him returning now and again to another bramble patch not far away, so he may be another bramble-patch-nester. Or it may just be coincidence. We’ll have a better chance of knowing when the chicks – if he has any – start demanding food. It’ll be interesting to see, if he does have chicks, what the Whitethroats’ nest-approaching behaviour is. I can’t see it being as much of a delicate dance as the Long Tailed Tits.