I have been asked by a few people how I do it so thought I'd share a few tips and suggestion.
"WHAT LENS DO YOU USE"
Tricky question really, it helps if you use a fast lens preferably with some sort of image stabilisation however I know of people who have obtained brilliant flight shots using a Sigma 50-500mm lens with no image stabilisation mode. Personally just in case the Swallows stay a bit distant I like to use my 500mm f4 prime lens and if the weather is sunny setting it at f/5.6 however I do find using a teleconverter slows things down too much so don't use one and with Swallows being quick...well you need your equipment to be quick to respond.
If I am at a location where I know the birds will be close I will use my 300mm f/2.8 this will eliminate poor weather too. If you're having a problem with Swallows along the ground like the image below, welcome to the club. But seriously try sky shots first, with a blue sky. It's easier and makes good practice.
Right ideally you want to be photographing in glorious sunny weather with blue skies as it helps massively and the blue on the bird just looks great. Make sure the sun is behind you of course.
I will switch my camera into AV mode as this guarantees that I get the fastest shutter speed regardless where I point my lens. ISO setting varies on location and light condition for example if I am in a field on a good bright day that isn't shaded too much I will go anywhere from 400 to 640 and shoot at f/5.6 and exposure wise anywhere from +2/3 to +1. If it is overcast or slightly late in the evening I will up the exposure settings from anywhere +1 to +1&2/3rd's and change the ISO to values of 640 to 1000. You ideally need a shutter speed of anywhere from 1/1500th to 1/2500 however I have got flight shots with less shutter speed just with wing blur.
However if you are photographing over water remember you have the reflected light off the water surface which helps on slightly cloudy days to get both better exposure and shutter speeds.
Also set the camera to Continuous shooting mode for obvious reasons.
Again welcome to the club. It's what makes photographing Swallows equally frustrating and rewarding face the facts you have to keep the bird both in the viewfinder and in focus whilst a small bird flies at speed low to the ground twisting and turning normally trying to catch and even smaller and more nimble insect...however there are a few tricks I do.
1st Try either early in the morning when the Swallows first start to hunt both the Swallows and the insects aren't quite up to speed/warmed up.
2nd Unless you want sky shots avoid mid afternoon's as I find normally this is when they're mostly high in the sky as are the insects, unless it's sky shots you are after... Plus if the UK weather is hot you will too get hot and sweaty.
3rd Try about 5pm onwards the light is soft, less heat haze, and to me I swear the Swallows feed more but slower.
If you have more than one Swallow zipping around, as often is the case sit back and watch them, learn the flight pattern they do, it may look like a manic feeding frenzy but it ain't if it was there would be collisions and I've not seen Swallows collide EVER. With some it is like a figure of eight pattern other times its up one way and back the other...just watch them you'll figure out what I mean and figure out the way they hunt. Also they will disappear, taking food back to the young, this is your chance to get your breath back and check your images, they will return as long as you haven't done something stupid to scare them away Swallows are quite tolerant to us humans so they shouldn't have been scared off.
I also have seen others frantically point the camera at the nearest bird, curse, then point at the next nearest bird followed by more cursing, don't choose this method you might get lucky but you will also get frustrated equally quick. Pick one bird that's at a fair distance from you and keep tracking it in the viewfinder the bird will do one of two things stay far away, in which case choose the next bird and wait/keep tracking until it gets closer this method is good if you have either a slow lens/camera if you choose the closest bird to you often both you and your camera aren't quick enough. Also try out photographing juveniles for your first time as they're not as quick as the adults. However my TOP tip is practise, more practise, have a drink, more practise and....more practise but on a more serious note take loads of images the hit/success rate is shockingly low, I am lucky if from a full 4 gigabyte card I keep 20% of the images on a good day( I think I heard Adrian faint and hit the floor).
I don't use neither! Even when using my 500mm lens I prefer to handhold the lens but my biceps are big lol. So it's a case of use a tripod if you have one or a monopod if you got one. I would opt for the monopod with a gimbal head, which is what I used to use. However I felt either option was to clumsy and prefer handholding the lens as it gives me better fluidity whilst tracking the bird and with high shutter speed being used "stability" is not really an issue plus if need be I can lay low on my belly for a better point of view plus whilst laying low/kneeling down I find the Swallows come in closer.
"WHERE IS THE BEST PLACE TO PHOTOGRAPH SWALLOWS". That's a tricky one. Most Swallows in my home County tend to nest in barns/stables or outbuildings. So if it's nesting in a stable I will try and photograph them in the field or paddocks that they tend to hunt in near to their nesting sites. However sometimes they build their nests in strange places like the one below, a flock regularly nest in garages belonging to residents of one village who leave their garages open all Summer and the birds then either hunt the nearby fields or as in this image a playing field/football pitches.