0:47:49 > 0:47:56.
0:48:27 > 0:48:31We've just had a spectacular aerial display from lots of swifts.
0:48:31 > 0:48:35There are the odd ones still in the sky here.
0:48:35 > 0:48:38But we're really here to see bats.
0:48:38 > 0:48:41And this estate has eight species on it.
0:48:41 > 0:48:43That's all of what's available in Northern Ireland.
0:48:43 > 0:48:46And I have to say, why are we going to catch one here?
0:48:46 > 0:48:50Emma Boston is the expert. We'll she if she can.
0:48:50 > 0:48:52All of the swifts are going to bed
0:48:52 > 0:48:54and we're waiting for the bats to come out.
0:48:54 > 0:48:57Looks like Emma needs the patience of a heron standing there
0:48:57 > 0:48:58fishing for them.
0:49:00 > 0:49:03We got one!
0:49:07 > 0:49:10- Wow!- OK, it's pretty tiny.
0:49:10 > 0:49:14Well, going by its size, I'd say this is a pipistrelle bat.
0:49:14 > 0:49:19You can see here that the tragus in the ear is an identifying feature.
0:49:19 > 0:49:23- OK.- Also, you can tell... It has a very pale face.
0:49:23 > 0:49:27I'd say this is a soprano pipistrelle rather than a common pipistrelle.
0:49:27 > 0:49:30One just flew directly over our heads.
0:49:30 > 0:49:31And another one!
0:49:33 > 0:49:36If you're watching this at home and you have a two pence piece
0:49:36 > 0:49:39in your pocket, take it out, put it in your hand and look.
0:49:39 > 0:49:42That is the weight of that bat.
0:49:42 > 0:49:46You're licensed and trained to touch these,
0:49:46 > 0:49:48so I can not put my hands on this creature at all.
0:49:48 > 0:49:50Yeah, that's true, they're a protected species.
0:49:50 > 0:49:53But I think, Emma, we really should let this one go,
0:49:53 > 0:49:56- let it feed up with the rest of its friends.- Yeah, definitely.
0:49:56 > 0:49:58Here we go. Oh, look at that. Yeah!
0:50:00 > 0:50:02And another one going past us, as well.
0:50:02 > 0:50:04SCRATCHING
0:50:04 > 0:50:07You can actually hear them up underneath the roof there.
0:50:07 > 0:50:10Yeah, you can. They're actually quite noisy.
0:50:10 > 0:50:13- There's still quite a few to come out.- Where are they going?
0:50:13 > 0:50:15Well, I'd say... We have such a great habitat here in Crom,
0:50:15 > 0:50:18these bats probably aren't going too far.
0:50:18 > 0:50:22I'd say, probably at the far edge, within a kilometre of the roost site.
0:50:22 > 0:50:26So, their habitat is really rich in insects
0:50:26 > 0:50:29and they eat an enormous quantity every night.
0:50:29 > 0:50:33They do. The average pipistrelle is thought to consume over 3,000 midges.
0:50:33 > 0:50:36It's a soprano pipistrelle, so it actually specialises
0:50:36 > 0:50:39- in aquatic and small insects. - They're out, they're on the wing.
0:50:39 > 0:50:42But we're actually going to do something really exciting.
0:50:42 > 0:50:44We're coming back here at first light.
0:50:59 > 0:51:03What's happening here is you get small flocks of birds
0:51:03 > 0:51:06coming from north, south, east and west.
0:51:06 > 0:51:12They build as dusk approaches until what you have is hundreds,
0:51:12 > 0:51:16if not thousands and thousands, of birds swirling like smoke,
0:51:16 > 0:51:19like intelligent soot along the skyline here.
0:51:19 > 0:51:23And it is one of the most fabulous spectacles you're ever likely
0:51:23 > 0:51:28to see. Look, there's a sparrowhawk underneath.
0:51:28 > 0:51:31Look at the birds twisting and moving, look at that!
0:51:33 > 0:51:37The sparrowhawk is trying to position himself
0:51:37 > 0:51:41so he can get in a striking position, but the birds
0:51:41 > 0:51:47are moving and circling, a bit like a shark going after a shoal of fish.
0:51:47 > 0:51:51There he's going up to meet them. Look at that! Oh, wow!
0:51:54 > 0:51:58And that is a perfect demonstration of why these birds
0:51:58 > 0:52:00flock together like that.
0:52:00 > 0:52:04That was an unsuccessful attempt by the sparrowhawk.
0:52:04 > 0:52:07Oh, sparrowhawk, look!
0:52:07 > 0:52:10Look! He's got a bird! He's got a bird!
0:52:10 > 0:52:15I saw that sparrowhawk take a starling on the wing
0:52:15 > 0:52:17as it was coming in to land
0:52:17 > 0:52:21and it flew out directly onto the span next to us.
0:52:21 > 0:52:26Its talons firmly had that starling in its grip.
0:52:28 > 0:52:30My heart's going like crazy.
0:52:30 > 0:52:34That is unbelievable to see that! That was very clever.
0:52:34 > 0:52:38That bird was hiding in the shrubbery at the far end
0:52:38 > 0:52:40of the river there. There's a bird in here now...
0:52:40 > 0:52:43More, more, more.
0:52:43 > 0:52:47They're being sucked in like confetti down a plug hole.
0:52:47 > 0:52:50And when they all turn sideways and show you their wings,
0:52:50 > 0:52:54all at the one time... Like that! Oh, like that!
0:52:56 > 0:52:58Black magic!
0:52:58 > 0:53:01Now you see them, now you don't.
0:53:02 > 0:53:05Shifting, pulsing, vibrating.
0:53:05 > 0:53:10You know, I'm just going to shut up and let you watch it. It's...
0:53:10 > 0:53:13You don't need me telling you about it. That is just glorious!
0:53:29 > 0:53:33We're witnessing something here that's happening
0:53:33 > 0:53:38by the million right across the UK and Ireland,
0:53:38 > 0:53:41at this time, in the winter, every night.
0:53:44 > 0:53:47That's it! Oh, my...!
0:53:49 > 0:53:52It's like... Ah!
0:53:54 > 0:53:58It looked like a great speech bubble.
0:53:58 > 0:54:00You know, like in a cartoon.
0:54:01 > 0:54:04You hear the rustle and murmur of their wings
0:54:04 > 0:54:08and you gain a sense of why they call it a murmuration.
0:54:12 > 0:54:14It's... Here they go again!
0:54:14 > 0:54:16Look at that.
0:54:16 > 0:54:20Like bats going into a cave to roost.
0:54:22 > 0:54:27And it's as if the relief of getting under there, getting to safety,
0:54:27 > 0:54:30finding a perch for the night, they can suddenly talk, you know?
0:54:30 > 0:54:35And all of this magic in the centre of Belfast.
0:54:48 > 0:54:51FLAPPING WINGS
0:55:09 > 0:55:11Now you see the light.
0:55:11 > 0:55:14Moment by moment almost, the light is coming up
0:55:14 > 0:55:16and there's more frantic activity.
0:55:16 > 0:55:19They're really beginning to go in now.
0:55:19 > 0:55:22Just before they turned the camera on,
0:55:22 > 0:55:26a long-haired owl came swooping in here trying to catch them.
0:55:26 > 0:55:29- So, it's a dangerous time for them, as well.- It is, definitely.
0:55:29 > 0:55:32This is when they're at their most conspicuous.
0:55:32 > 0:55:34They're really taking quite a risk, at this point,
0:55:34 > 0:55:36- to be in such large numbers.- Yeah.
0:55:36 > 0:55:39You can actually see them crawling up the wall,
0:55:39 > 0:55:43disappearing into a crack. This...
0:55:43 > 0:55:46I had no idea that they did this!
0:55:46 > 0:55:50- Yeah, it's pretty spectacular. - A real first for me! Classic.
0:55:50 > 0:55:52- How long will they live? - Well, bats...
0:55:52 > 0:55:56Actually, it's been found some species can live up to 30 years.
0:55:56 > 0:55:58There have been some recorded over 40.
0:55:58 > 0:56:02So, for the size of a bat, it's interesting they can live so long.
0:56:02 > 0:56:05I thought they were short-lived - they're so small.
0:56:05 > 0:56:07Yeah, and they have a high metabolism.
0:56:07 > 0:56:09Generally, that means it's a short-lived species.
0:56:09 > 0:56:11But they can live for quite some time.
0:56:12 > 0:56:14I have to tell you...
0:56:14 > 0:56:18two hours of sleep to come and see this,
0:56:18 > 0:56:20and I'd do it all over again.
0:56:20 > 0:56:24I really do have to say it, I didn't know they did this.
0:56:24 > 0:56:29I've never seen it before. It's a real first. Thanks a million.
0:56:29 > 0:56:30It's absolutely perfect.
0:56:38 > 0:56:41Subtitles by Red Bee Media Ltd
0:56:41 > 0:56:44E-mail subtitling@bbc.co.uk