I've written before about the joy of listening to blackbirds singing at this time of year and was slightly concerned when, in the course of doing some major clearing work last year, we damaged a nest which we identified as belonging to blackbirds from remnants of the readily identifiable green-blue eggs with brown freckles. But apparently they tend to build new nests each time so I wasn't surprised to see a female hopping around me when I was gardening this year. And a couple of weeks ago Mrs H yelped when she was buzzed by two young male blackbirds which flew out of our hedge at great speed, one in pursuit of the other, as young males of any species, including humans, are wont to do. So picking up what I took to be the mother was depressing.
But later in the day, tending the garden around the front where I'd seen the adult female previously, one fluttered down and hopped around me with a worm in her beak, which cheered me up. No, I can't identify individual birds, though individual blackbirds can be recognised by their singing, but like Mrs H is prone to do I've made up a happy story and decided "my" blackbird family wasn't disrupted by the cat.
So now I'm looking forward to seeing the swallows which should be arriving any time now and swooping low over the golf course in north Wales I used to play before the great lockdown. I realised a couple of years ago that I wasn't sure I could tell swallows and swifts apart by their appearance. The birds swooping around me at knee height clearly had a blue patch on their backs but were flying too fast for me to see their more deeply forked tails. But they were making a softer call than the swifts I was used to hearing when we lived in rural Oxfordshire, whose piercing screeches were clearly heard once it went quiet in the evening as they swooped around high above my head. So I'd never seen a swift from above as they don't land, only being able to see their black silhouettes against the sky. But then they are actually pretty much all black. The blue flashes were a sure giveaway of swallows, as you can see from the photo below which shows a swallow swooping down to take on water.
But the blue colour isn't the only difference between them and their other doppelgangers, the swift and the house martin, though they all look quite similar in flight, especially when you can't see any white flashes against the bright sky. Swallow to the right, with the deepest forked tail:
Swift to the left here, nearly all black, and house martin to the right, least forked tail and white rump:
Swifts generally nest under the eaves of old buildings, although sometimes in tall trees. Swallows like to nest in open fronted buildings such as barns and cowsheds, close to large domestic animals like cattle. It is likely that swallows were much rarer before humans practised animal husbandry. The decline in dairy farming in Britain in favour of arable farming has not suited them. Though a few European swallows over winter in southern Spain, most winter south of the Sahara. Curiously the British swallows go further than their continental neighbours, preferring Botswana and South Africa. I don't remember seeing swallows in Oxfordshire, even though our village was quite horsey, being on the edge of the Lambourn downs. Which doesn't mean they weren't there of course, I might well not have noticed being more preoccupied in those days with profit and loss accounts.
House martins are similar in appearance to swallows and swifts but have a white rump and a much less forked tail. We would also see them in Oxfordshire, but only when we moved from the village into the town as they prefer to nest in urban areas. They can be a bit of a pain if they nest in the eaves of your house, as they did on a neighbour's house, making quite a mess. A pair stays together for the season but, while nests get reused (provided sparrows haven't taken them over) it is rare for two to pair again the following year, even if both survive. So they are serial monogamists. They feed at higher altitude to the swallow and so don't compete for food. House martins were just called martins until a couple of centuries ago. While some house martins stay in southern Spain and Portugal for the winter most migrate further south. It's not known exactly where - because martins don't share communal roosts it's harder for many of them to be ringed. The most prevalent theory is that martins go to the Congo basin rainforests, though I've read a theory that they may "aerial roost", in other words spend the night on the wing. They have been seen flying high at dusk and descending at dawn. And when ringed birds are caught early in the morning they appear chilled. Which may be why they have evolved with feathery legs like long johns:
Swifts roost in the air so why not martins?
Despite the fact that it's the swallow and swift that look the more similar, it is swallows and martins that are related, both from the hirundinidae family. Neither are even remotely related to swifts, whose closest genetic relations are humming birds. Also migratory, swifts spend only 3 months here a year, the shortest of any bird that reproduces here apart from the cuckoo. I remember stepping outside in Oxfordshire in August at dusk and feeling sad when I realised the screams had gone and the swifts had flown south as it was a signal for the coming end of summer. They feed at a higher elevation than either swallows or house martins, which is why it was often easier for me to hear them than see them.
Swifts also spend their winters south of the Sahara, with ringed birds from Britain having been found in the Congo Basin, Malawi, Tanzania, Zimbabwe, Mozambique and South Africa. But the routes they use to get there still aren't known.
Swifts are evolved to be able to spend almost their entire life on the wing. They have tiny feet and almost no legs though, contrary to rumour, adults can take off from the ground, though they rarely need to and can require help. Juveniles would struggle though. So swifts pretty much never touch the ground once they have learned to fly. It's thought that once a swift flies the nest it remains airborne for two years until it is first ready to breed and so stops flying to nest.
So of course they sleep on the wing. As is now well known the way swifts - and quite a few other birds and animals - can do this is to enter a state known as unihemipheric slow wave sleep. Swifts can do this in soaring or flapping flight. So they literally have half a brain asleep and one eye open.
As you can tell I'm very fond of these birds, especially the swifts and swallows. I've discovered a smashing bite sized series of facts on them on a site called Tweetapedia....
And, while I can tell the difference between swifts, swallows and martins, chatting on our walk today I told Mrs H that I'd realised what the difference was between me and a swift. While the swift can shut down half its brain to sleep, I appear to usually only have half my brain working when I'm awake......
https://www.livingwithbirds.com/tweetapedia/21-facts-on-swallow
https://www.livingwithbirds.com/tweetapedia/21-facts-on-house-martin
https://www.livingwithbirds.com/tweetapedia/21-facts-on-swift
http://blogs.bu.edu/bioaerial2012/2012/10/14/the-common-swift-anything-but-ordinary/
https://www.audubon.org/news/scientists-finally-have-evidence-frigatebirds-sleep-while-flying
https://www.irishexaminer.com/lifestyle/outdoors/richard-collins/richard-collins-house-martins-take-their-time-230404.html
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