April

House martin

The iridescent aerial acrobatics which are a welcome sing of spring!

It is that wonderful time of year, when the weather is getting warmer, the days get longer and there is a sense of optimism in the air as spring brings fresh and new life all around us – although the farmers could do with a bit of rain, dare I say it!

We welcome our migrant species back to our shores and there is nothing quite like seeing the ‘firsts’ to arrive. On my way home from work last week, after an all-staff fond farewell gathering at HQ, to wish Teresa Dent, our long-standing chief executive, well on her next chapter of retirement, I had to pull over quickly in a layby to marvel at hundreds of house martins (and a few swallows) flying over the fields and skimming across the nearby lake, proclaiming spring is here! It could be thought that this was a sign of new beginnings for us too at the GWCT, as we warmly welcome our new chief executive, Nick von Westenholz, into the fold.

Within seconds my family WhatsApp group was opened and I sent the gleeful voice note – “I win, I have seen the first house martin and swallow this year!”

The house martin (Delichon urbicum) is a small hirundine (the family of passerine birds that includes swallows, sand and house martins), which is familiar to most of us by the habit of nesting in small colonies in cup-shaped mud nests under the eaves of our houses. Sadly, this isn’t as common a sight as it used to be. They arrive in early April, returning to the UK and Ireland from their winter non-breeding range in Africa, although the exact range is still unknown.

Identification

It can be hard to identify house martins from swallows as they whizz around at great speeds, collecting insects and aphids above crops and through our village streets, so it can be hard to get a good look at them, but for reference they are smaller than swallows (and swifts), some people say ‘dumpier’ at only 13cm in length and a 28cm wingspan. They have glossy, iridescent, blue-black upper parts; pure white under parts; and a shallow, small, forked tail to assist in their aerial acrobatics, but I find it handy to look for the flash of white as they have a distinctive white rump.

As I mentioned earlier, house martins build their mud nests under the eaves of our homes and buildings – hence their name. But unlike a swallow’s open cup nest, house martins only leave a small opening at the top of their nest, which the pair make together, collecting over a thousand pellets of mud. They lay 4-5 eggs and generally have two broods during the summer, and as the chicks grow they can often be seen peeking out from the hole, impatiently awaiting their next meal, which is a good way to keep an eye on how the chicks are doing from afar. House martins are very sociable and tend to nest in colonies, sometimes with several nests built side by side, and they typically live two years and will return to their nest sites – so please don’t knock them down when they have finished nesting as it will save them about 10 days next season to repatch rather than rebuild!

Population

It is a sad fact that there has been a 44% decline of house martin numbers since 1995, which has led to this species being added to the UK Red List in 2020. These declines have been most severe in the south and east of Britain. The reasons underpinning this decline are not well understood, although birds that build nests on PVC as opposed to brick, concrete or wood have much lower breeding success, with nests more likely to collapse on the PVC substrate.

What can we do?

Whilst research has not yet confirmed what factors are likely to be driving the decline, warmer, drier conditions as a result of climate change have also been suggested as a possible cause. There are actions that individuals and organisations can take to address some of the potential factors whilst research is ongoing, however. Artificial nest cups are a successful means alongside or to replace nesting opportunities, particularly in cases where soffits and/or wall surfaces are replaced with PVC materials. Another action that could be considered by site managers, planners and housing developers is the creation of ‘house martin towers’ to provide potential nesting sites for house martins on protected areas away from buildings. Such towers have been built for both house martins and swifts in several locations here in Hampshire, and have been very successful.

But we have tried something else on the Allenford and Martin Down Farmer Clusters, which I am involved with. We have created ponds, muddy puddles and let yard taps run a little during times of drought to create wet, muddy areas so the house martins can feed and gather mud, which has been seen to have a positive impact.

When nesting is over, they feed up on insects and leave us again in October, to head to their mystery range in Africa. It was once thought that house martins and swallows hibernated during the winter in the mud at the bottom of ponds!

Fun facts

• The collective noun for a group of house martins is a ‘gulp’ or a ‘flight’.
• The oldest known house martin fossil dates back to the Pleistocene epoch, around 2.5 million years ago.
• In some cultures, house martins are considered to be a symbol of good luck and protection, especially if they nest on your house.
• If you dab a bit of white paint on the opening of a new artificial cup, it looks like it has been used and is more likely to be accepted and used – according to the GWCT legend Dr Mike Swan.

The house martin is a small and fascinating species that continues to inspire wonder and curiosity among us all, with their distinctive plumage, impressive aerial displays, and their appearance being a welcome sign of spring. Whether you are a seasoned birdwatcher or simply appreciate the natural world, why not take a moment to appreciate the beauty of these amazing birds, and perhaps even create a pond or a wet muddy area out in the open, put up an artificial cup, or leave the barn or stable door open if you can to give this species a helping hand when they return to us this season.