If one swallow does not make a summer ...

... what does an absence of swallows mean?

I always took the old saying to mean, don't get excited just because you've seen the first swallow arrive, because it's not summer yet. 'Ne'er cast a clout 'til May is out' is also reasonable advice, although I've never quite been sure whether it means don't take your vest/shawl/whatever off until the May blossom is out, or until the end of May.

Back on the farm, the swallows used arrive quite reliably in the first or second week of April, twittering with excitement while they picked off flies and gnats which had come out to enjoy the spring sunshine. The swallows would feed up a bit and quickly settle to making or repairing nests, with mud from around the farm yard and the edge of the farm pond.

Late spring weather would always be a bit uncertain, but there was generally a period of high pressure with sunny days and frosty nights. We would generally have a last frost around the end of May.

Now 25 miles away and closer to sea level, I've not been able to establish when, exactly, the swallows and the last frost might arrive, because in the four years since I've moved, the weather seems different each year.

Every time I was out in April and then May, I listened and scanned the sky, eager for my first sighting of swallows. I caught blog and Facebook posts from people saying they'd seen swallows elsewhere in the county, but still there were none here.

Their absence worried me. What had happened? Where were they?

In the end, I saw my first swallows in Pembroke Dock on 10 May, but it was over a week before I saw and heard some here, while I was out in the garden. I heard and then saw swifts the same day. My heart lifted with joy.

The RSPB listings show the swallows' conservation status as green, although swifts and house martins are listed as amber. Migration can be hazardous; storms can take a great toll, and there were worrying reports of mist nets used to catch birds for food in Egypt. Anything which adversely affects numbers of flying invertebrates, on which swallows, swifts and martins feed, will also cause problems for them. Then they need places to nest; swifts like dark cavities, high up in a building. Martins also like to be high, building their mud cups under eaves. I used to see a lot of tattered plastic hanging from the eaves of buildings to dissuade house martins from building nests 'because of the mess they make', which is so sad. I'd love some house martins, although the local sparrows could be a problem. Swallows prefer to make their mud cups on ledges and beams in sheds and outhouses, sometimes only a couple of meters above ground level, requiring only a clear flight path in and out. I'd like some swallows too; perhaps something could be done when I come to sorting out the shed.

What if, one year, they simply don't arrive? A summer without swallows is unthinkable.