Home in a half-cup

I popped into my mum's in Worcestershire last week, and was delighted to have my sleep accompanied by the quiet frothy twittering of the nesting House Martins outside the bedroom window.

On her house, they nest under both the east facing eaves at the back and the west facing eaves at the front, some in artificial nestcups, others in 'self-builds'. This one is poking out of an artifical nestcup, a wise choice as a self-build requires a thousand globs of mud and saliva, painstakingly assembled into a hollow cup leaving just a small entrance hole.

My mum has between two to four nesting pairs each year, which is very typical of House Martins. They are what is called semi-colonial, with up to about five pairs nesting in close proximity being the norm in the UK, although some larger colonies can occur.

It is probably credit to my mum and dad that they use the house at all - there are only another handful of houses in the village where they nest, and they almost certainly chose my parents' house because of the artifical cups that my dad put up in the 1970s. There have been breeding pairs ever since, so it is coming up to 50 years of unbroken occupation.

Unbroken, that is, apart from the six months each winter - from October to April - when they are somewhere in Africa!

Quite where, we don't know, because even though a moderate number of House Martins are caught in the UK and fitted with a metal ring on their little legs, they don't roost close to the ground and so are rarely re-caught either on migration or in their winter quarters.

There is some evidence emerging that western European House Martins winter over western Africa, high in the skies over countries like Nigeria, but there is plenty more to be discovered.

But, what we do know is that after a magical mystery tour south of the Sahara, they return, a source of great delight when we were kids, knowing they had maybe not touched ground in between.

Back to a little half-cup under the eaves.

Although leaving that nest cup can be something of a squeeeeeeze!

And then it's a freefall drop for the first microsecond before they can open their wings and take to the skies.

See the white wrap-around rump, a key feature to tell them from Swallows when they are swirling together over lakes. Swallows also have longer tail-streamers and a brick-red throat, and tend to nest inside outbuildings and barns near livestock, building an open cup rather than the full dome.

A 2015 BTO survey estimated about 750,000 pairs of House Martin in the UK, but numbers have been falling since the mid 1980s - yes, sadly another species in decline.

Is it the lack of insects in our skies for them to feed on? Or the same in their winter quarters? Or inclement weather on migration? Well, it's probably a combination of factors.

But together we can do something about it. And it is not only about putting up an artificial nestcup. The following are all House Martin-friendly actions:

• boost the number of insects in your gardens, including avoiding pesticides
• support policies - local and national - that call for the reduction in pesticide use. Many villages, towns and cities have already gone pesticide free, which is fantastic.
• play your part in combatting climate change, the effects of which are likely to be damaging to wildlife.

It's not wonder that this week we're calling on the UK's government's to Revive our World - so, if you haven't signed the petition, please do here, for the sake of House Martins and the rest of the natural world.