House Martin spectacular at Sizergh Castle

Flights of house martin about the tower at Sizergh Castle

A house martin spectacular is a highlight this week-end at Sizergh Castle.  The air is filled with their calls as they swoop toward the tower, and away again in a rush.  Such an abundance comes out of the blue. I always follow their progress through the breeding season, studying their behaviour. The south-facing windows of the tower have neatly sculpted nests tucked into upper corners,  affording shade in summer heat-waves. I'd seen only a small number of birds so far this year but suddenly there are hundreds.  Interpreting the scene is a challenge  I'll consult my friend Jeff Holmes, a life-time birder and naturalist. He's keen-eyed and expert. This summer he's appearing on Get Birding with Sean Bean, on the Avalon marshes.
'I could stay here and listen to them all day,' says someone watching house martins at Sizergh. 'Just to listen.'
House martin are small and agile birds and the greatest number go for the highest window. For the first time this summer I'm in the aura of house martins  and it's sensational. Later, there's the forensics involved in interpreting images with detail caught in a moment of flight and teased out  of shadows and reflections.
I came for the butterflies and there's another humming bird hawk moth amongst painted ladies, small tortoiseshell and whites, but all the while  house martins are calling in flight about the tower and I'm drawn back again and again. 

Birds are flying to their nests, 'a second brood' someone suggests, and it seems probable.  Glass below the nests is splashed with droppings, with a thick impasto on window sills.  Some birds fly to the nests but others cling to the masonry of the solar.  My images show birds adorning the head of the window tracery  and they must have fledged and be trying out their flight skills  because (through an image sequence) there are no birds, then they appear.  Others  show as tiny black and white bodies crammed into a crevice below the lead drip-mould above the window. So birds are from different broods, some still being fed by adults flying in with insects. 
They'll be mustering, soon to depart on migration. And house martins from other sites will arrive,  speculating on possible breeding sites for next year. So Jeff tells me.  This heat-wave summer has been good for insects. The colony is a complex and growing gathering. 
Friends who volunteer here tell me they see no birds on 25th August, so has migration begun?  
Photographing house martin about the highest window of the tower gives me a crick in the neck, so an interlude with butterflies along the terrace is a diversion. This is a great summer for painted ladies and I've taken so many photographs I know the composition I'd like- a butterfly on verbena against the sharp green of vine leaves on the terrace wall. 

In the kitchen garden, the hungry caterpillars of small whites and large whites are devouring cabbage leaves. Whites are the most abundant butterflies.  A female brimstone appears on flowers of the nearby herbaceous border, her  wings, leaf-shaped and veined,  are perfect camouflage.  Sometimes they're translucent,  shot through with light and leaf-green. I've seen few brimstone or comma this year. Perhaps, when sedum flowers, comma will appear late in the summer.

One morning, there's a silence and the swifts are gone.  I wonder if the house martins about Sizergh Castle are gone too. Editing images,  I discover unusual perspectives on birds in flight with others crouching about the masonry. A fascinating week-end studying the colony and trying to interpret what we saw.  
My blog of 2nd September 2023 is  witness to a muster of house martins about the tower.  The weather that summer had been very different and the birds were gathering, not visiting their nests.  Swallows had nested high within an archway of the castle facade,  an old nest with no sign of swallows.
18 September 2026
House martin were feeding high, over Maud's Meadow and above Queen's Road, on a drizzly September day. I wonder if they're still seen at Sizergh.