Having built up a fairly clear picture during the winter of which pairs were occupying which territories, including any new colour-ringed Stonechats arrivals, there were still some surprises as we moved into the start of the 2017 breeding season.
We’ve been lucky with another mostly mild winter this year and while the numbers of Stonechats on the reserve have fluctuated, there have been regular sightings throughout the autumn and winter periods on most of the territories. Our only spell of bad weather was in February, when there was a brief spell of around a fortnight where Dersingham Bog appeared virtually devoid of any Stonechats.
When birds started to return to the site during March, that’s when the main changes took place and the situation is still fluid as we move into April, with several new colour-ringed arrivals only this week.
Several territories which had been occupied during the winter by the same pair that bred successfully in 2016 now have completely new pairs, colour-ringed birds which hadn’t been reported elsewhere or on Dersingham Bog since they fledged last year.
Other territories have given a convincing rendition of musical chairs. Two females have moved to other territories on the reserve, ousting the existing pair or becoming the new partner to an existing territory holder. One female (from Ugly Dale) has taken over another territory, right at the other end of the Bog, far from where she nested last year. And the female from that territory (Tranquil Valley) can now be found just around the corner in her neighbouring territory (Piezos), which was previously held by our most prolific female. Confused yet?!
As mentioned in our most recent blog, 2 other territories which were empty throughout the winter are suddenly re-occupied, one being again held by the 2016 breeding pair. Where had they been through the winter? Had they wintered together somewhere or were now returning separately to the site?
Either way, it’s interesting that they returned to exactly the same territory. As that has been empty throughout the winter, maybe they didn’t have the territory battles when they arrived that might have occurring in other parts of the reserve?
Interestingly, a new colour-ringed pair which occupied a new territory on Phil’s Heath through the winter have remained into this breeding season, and on the same spot so far. Another of the new territories established during the winter, which had a new 2016 colour-ringed male present, now has another new, previously unreported colour-ringed male, also from last year’s crop.
As we’ve said many times before, without colour-ringing, we wouldn’t have noticed these changes at all. So far, all 3 new territories established through the winter are still occupied, though not necessarily with the same ringed pair that set them up in the first place.
Our oldest male has remained on his territory all winter and is now preparing for a new breeding season with a new female, also from the 2016 crop. He has a particularly large territory, spanning an area up on plateau and extending down onto the mire, although corners are being nibbled away by new pairs. Last year, the northern boundary of his territory on the mire was occupied by a successful pair (the male of which has just returned to the same territory again after being absent all winter).
The other large corner of our oldest male’s territory now has at least one, possibly two pairs, carving out a chunk of ground for themselves. One pair established a territory on the periphery during the winter and seem to be still there, and another is a new colour-ringed male.
Unfortunately, our oldest female may have disappeared, as there is a new female from the neighbouring territory now occupying her territory, and with a new ringed male. If she isn’t re-found, it’ll be a sad loss but she has contributed significantly to subsequent generations since she started breeding in 2014. Her progeny have been scattered through the reserve over the last few years forming new successful pairs and establishing new territories.
One of the most interesting aspects of this shuffling of the pack has been how late it occurred. We hadn’t exactly become complacent by the end of the winter but we were confident we had a handle on who was where as we entered the new breeding season. So in the space of a few weeks, after our only spell of bad weather cleared the site, finding that many of the territories had changed was a bit of a surprise for the volunteers as yet another new colour-ringed Stonechat popped up somewhere new!
Is this typical? A late winter shuffle around occupying pairs? Or was it governed by the weather and the empty site, allowing early new arrivals to take over empty territories? So if we’d had the bad weather earlier in the winter, would the shake-up also have occurred earlier, but with another potential late winter / early spring change as birds wintering offsite returned to the Bog? As always, lots of fascinating and unanswerable questions keep arising with these charismatic birds.
It remains to be seen how many more new territories can be squeezed onto the reserve, or if the current state of play remains the same, or whether further changes will happen before they begin nesting. We’ve already had nest building taking place and given how synched many of our Stonechat pairs have been over the past few years, it won’t be long before most of our females are incubating their first broods, weather permitting.