23 August 2012

Curtailed colonies

Roger Peart has been studying House Martins at Canford School, Wimborne, Dorset since 1994 as a RAS project, but has found 2012 to be a very unusual season:

“There has been a House Martin colony on various school buildings for at least 50 years and in the 1960s there were at least 65 active nests. This halved suddenly in 2002 and since then, 30-40 has been the norm. I aim to catch as many adult birds as possible each year and from 1994 to 2011, 555 adults were ringed, and a further 116 juveniles. A good number of birds have been retrapped in subsequent years, most within three years of first ringing, eight up to four years later and just two hardy individuals after five years.

Canford School

Catching sessions have to be confined to July and August when the school is on holiday; being a boarding school even the early mornings are not suitable during term time! The birds usually return at the end of April or during the first week in May and they have always been active feeding young at nests well into September, a few remaining into the first half of October. So it was a surprise this year to find that there were no birds at all on August 21st, either roosting in the nests or flying around.

House Martin nests

Where have the birds gone – and more concerning, why have they left the nests over a month earlier than usual? Although the weather in June/July was pretty poor recent weeks, in this part of England at least have been much warmer and less wet. What has caused this sudden exodus? Having seemingly gone en masse have some of them left unhatched eggs or even unfledged young? Only an inspection of the nests will provide an answer, so use of an endoscope will be required!”

House Martin

We have subsequently heard from another ringer, Jill Warwick, studying House Martins in Ripon, 370km to the north.

“It sounds like Roger’s birds departed about the same time as mine. I inspected the 12 nests on 31 July (all are artificial and slide out for easy checking) and there were five second clutches, some incomplete. Having left things for a week, I returned to catch some adults and the realisation dawned that there was a distinct lack of action around the martin cote. I checked the boxes again last week and the situation hadn’t changed since 31 July, with eggs apparently abandoned. There are House Martins present around the village, but ours had obviously had enough – usually the odd pair will stay into early September, but not this year!”

Thanks to Jill Warwick and Roger Peart for letting us know and to Roger for the photos.


  1. Yes, ours left a few days ago (Hitchin, Herts). Most years they stay until mid-September, so they've departed about a month earlier than normal this year. I have noticed also that the autumn spiders are there already in the bushes, and that the back-to-school chill is in the air, so I wonder if it's a general seasonal shift they are responding to.

  2. Still plenty of House Martins flying around the nests on my house in Aberdeenshire at the moment

  3. Likewise I still have 5 pairs around my house in Northern Ireland