Swifts and tree sparrows

Swift diary

A quick swift colony update in a busy week. The pair that first entered box 2 together on 9th May had just started incubating two eggs. Yesterday during poor weather both swifts were absent when a tree sparrow entered their nest box and removed and destroyed both eggs. I hold no grudge, this is nature, it’s happening under eaves all over the country as species compete for nest holes. It always has and always will, but only recently have we had the technology to see what goes on in the dark recesses of our eaves. Swift eggs are very vulnerable when left, particularly in the time between laying eggs (every 48-72 hours) before incubation where they sit exposed while the adults are away feeding.

So we now have one pair that has lost its clutch and two single birds. Time is ticking and while there is still time to make up last year’s numbers we quickly need more swifts as mates for the singles and to present substantial colony activity that can stand up to increasing competition from tree sparrows.

I should add there are plenty of boxes for swifts, tree sparrows and house martins but conflict still occurs. I block some nest boxes up until early May but this doesn’t stop sparrows starting their first brood late or sparrows moving to these boxes for a second and third brood.

Seeing the video of the unpaired tree sparrow removing the swift eggs was not a surprise. They certainly appear frustrated and casually wander into occupied and unoccupied nest boxes alike. In my experience this behaviour changes quickly once a mate is found and they settle on one nest box. But our only pair of swifts has expended lots of energy making these eggs and now they have to start all over again.

Thank you to those who have written to tell me about the state of your own swift colonies. Anecdotally many are still well down in number. It will still be a few days before we can fully assess the return of last year’s breeders. There is certainly huge variation between numbers at colonies in different areas which is hard to understand. 

House martin diary

House martins, like last year, are doing much better than swifts here. We seem to be up to five pairs with some new prospecting birds this morning. I am optimistic that numbers have recovered somewhat after the very poor years of 2021/22. Some birds are roosting in very tall lime trees near the village. These are almost certainly newly arrived first time breeding birds that haven’t yet claimed or built nests. The recent rain is well timed for house martins in providing fresh mud for the nest building frenzy which takes place in the second half of May. Every cloud has a silver lining!

So another swift season starts with drama. I am still thrilled to see an increase in nesting tree sparrows here but long for more swifts to arrive to bolster our only pair. Let’s see what the next few days bring…

All text and images copyright Jonathan Pomroy 2024

Swift incubating- watercolour

Tree sparrow removing swift eggs- recording from camera box 3.