Another Summer passes and as we move into September the days have warmed up – hottest days of the year so far. The Summer migratory birds have either moved on back to Africa – birds such as Cuckoos and Swifts – or are moving through our area feeding up and getting ready for the long flight south.

A few days ago in the fields immediately west of the village a large flock of House Martins (well over 200 of them) with a few Swallows in them were busy feeding in a large swarm above the field. A great sight to see after a relatively quiet walk beforehand.

House Martins – they are the ones that nest under the eaves of houses – are an interesting bird. They are in decline. Although it is known the decline is significant – something like a 67% reduction between 1967 and 2013 – the reasons for it are not clear. In addition, it is a bird we know relatively little about. For what is a relatively common widespread bird that is surprising. Some of the reasons for the decline could be:

• Reduced numbers of flying insects (their main diet and what my large flock were feeding on)
• Plastic soffits, more difficult to attach their mud nest to
• Households perceive them as messy nesters and discourage House Martins from nesting on their house – I would love to have House Martins nesting on the house!
• Lack of easily accessible damp mud when they are making their nests – another good reason not to tidy everything up.

A common cause of decline for migratory birds is the migration route and / or where they migrate to. Again, for House Martins relatively little is known about this for them. Over 1 million House Martins have been ringed, but despite that only a few hundred have ever been recaught. The recapture rate for their cousins the Swallow is curiously much higher. Ringed House Martins have been recovered in West Africa and as far south as South Africa. Not much is known of their preferred habitat in their winter quarters. It used to be thought that they preferred mountainous territory, but it is clear their choice of winter quarters is much more diverse than that. They have even been seen swooping over bush fires, picking up the escaping insects – an easy meal for them, I guess. But not often in large groups either on migration or when they arrive in their winter quarters.

When Swallow migrate, they do so in large numbers and will often roost in reed beds overnight. Before they leave the UK large numbers can often be seen flying over reed beds as dusk approaches and then diving in for their nights safety.

This behaviour and the fact they often feed over large bodies of water meant that, for many years it was thought that rather than migrate Swallows hibernated under water. Whoever came up with that obviously did not check those reed beds, next morning – because they would have seen them all leaving.

The famous 18th century Hampshire Naturalist, Gilbert White, believed this was the case and wrote about in his book.

And even more fanciful in 1680 the English educator / scientist Charles Morton concluded that Swallows were living on the Moon. His logic was that everyone knew that Swallows disappeared in the winter, but no one seemed to know where they went to. Morton had looked everywhere. Where else could they be!

And he did his research! He estimated that birds would take 60 days to fly to the moon, so an average of 167mph.

That Swedish priest, Olaus Magnus in 1555 wrote extensively on how swarms of Swallows winter in the soft, unfrozen mud of shallow rivers and lakes. A few naturalists even recorded that fishermen in northern waters sometimes hauled in mixed catches of fish and hibernating swallows. This misinformation lasted all the way into the late 1800s.

I love the fact that almost wherever you travel in the world you will see ‘our’ Swallows – called the Barn Swallow, to distinguish it from many types of Swallows. In the summer Barn Swallows can be seen all across the Northern Hemisphere. And in our winter across much of the Southern Hemisphere. They get two Summers every year – that’s a good plan!!

A bird related to the House Martin, the Sand Martin, was believed to spend the winter buried in sand at one point. They do nest in burrows in sand, but they are migratory birds just as their cousins are. They are one of the first summer migratory birds to arrive back in the UK – often sightings from the south coast are reported from early March each year. Not a bird often seen in Vernham – we have no large water body or sand banks. Occasionally one will fly over in a flock of Swallows / House Martins at migration time.