Over the years there has been a steady decline in both species, nationally and locally.
I’m no expert on these matters and I do not know what happens in their wintering areas in Africa but in the UK there seems to me to be 2 main causes in the UK.
Lack of insect food and lack of nesting sites.
Our constant and over use of pesticides (kill insects) and herbicides (kill insect food plants) are a major factor in the decline of insects. You only have to look at your car wind screen to see there are none or very few impacts with insects these days.
Flying insects are the staple diet of Swifts and House Martins as they are exclusively aerial feeders.
Nest sites for the 2 species in question have also disappeared. I remember back in the 60’s when I lived in Cross roads we had 2 pairs of Swift nesting every year in the eaves and there were several pairs of House Martin on houses on the road.
More recently we had 2-3 pairs of House Martin breeding along Church road. This year none have arrived!
As for Swifts there are a few areas around the village where they still breed. Cholsey Meadows, Papist Way and Station road and maybe the odd pair elsewhere. However this year numbers are well down on previous years.
What can we do: maybe not a lot but what we can do is highlight the plight of these species?
Educate! I won’t go into full details but:
Stop using pesticides and herbicides! The chemical companies that produce the aforementioned products are huge corporates and Farmers are on board with using these products (as are a lot of gardeners) and in my view it is completely unnecessary! I for one have never used chemicals in gardening.
Put up specially designed nest boxes for Swifts and House Martins and encourage developers, Housing associations, Councils and individuals to consider creating nest sites and putting up nest boxes on properties and new builds.
Be tolerant of them nesting on your homes, they are only there for a couple of months to raise their young and then they are off!
This will be a huge task and I have not got all the answers but the more we get on board the more we can progress. We cannot allow these species to disappear from our avifauna.