For the first time in the course of the Stonechat project, this winter we attempted to gain a clearer picture of both site and territory fidelity by regular coverage of all the territories outside of the breeding season. We wanted to determine a number of things if we could.
How many of our ringed Stonechats remained on the reserve? How many of the existing territories were occupied during the winter and by whom? How many of our existing pairs would remain as they were or would new partnerships form, which would then continue into the spring? Would new pairs take over existing territories or establish new ones?
In other words, how much of a shake-up occurs each winter and does that picture change again by the next breeding season?
Each territory was visited at least once a fortnight, sometimes more often, by one of our volunteers. As the territories are spread fairly evenly throughout the reserve and the whole reserve was walked regularly, we’re pretty confident that most of the Bog was covered throughout the autumn and winter. Such regular coverage through another mostly mild winter has thrown up some interesting sightings and probably raised as many questions as it answered in terms of winter territory fidelity.
Of the 13 active territories during the 2016 season, 8 were occupied consistently throughout the autumn/winter period; 3 more held Stonechat pairs intermittently and 2 territories appeared empty on every visit.
These two territories were both in areas where the conditions can be fairly harsh during winter; one is out on the mire and another suffers from a complete lack of sun in that part of the reserve in the winter. Interestingly, both those empty territories have now been reoccupied, one with exactly the same pair that bred successfully last season and who had been absent from the Bog all winter.
Of those 11 occupied winter territories, 4 were held by the same ringed pairs that bred in 2016; 2 other occupied territories held unringed pairs so we have no way of knowing if they’re the same birds; 5 other territories were held by one of the existing 2016 ringed pairs but with a new partner. This change of partners proved to be a mix of new males and females scattered throughout the reserve.
We’ve speculated previously on how many Stonechat territories can be squeezed onto Dersingham Bog and once again last year, we thought 13 territories must be fairly close to the reserve’s limit. But apparently no one has communicated that to our Stonechats!
During the course of the winter, it became clear that 3 new territories were being established. All were new arrivals and all were colour-ringed pairs from our 2016 broods and they carved out corners of existing larger territories. It will be interesting to see if those new pairs remain into the new breeding season or if it’ll be all change again.
Our two most prolific breeders, a male and female from separate territories and born in 2013, both have new partners from the 2016 broods. They’ve also both stayed throughout the winter on territories which they’ve occupied since 2014. Some of the new colour-ringed birds who arrived on the reserve during the winter have spent time on their natal territories, some with one parent. Some have established new territories in neighbouring areas to where they were born, or have taken over existing territories but again ‘next door’.
Once again all these observations and results have shown the value of colour-ringing. Without it, we’d have been unaware of all these changes and it would have been tempting to make the wrong assumption that any unringed pair staying from last year’s breeding season through the winter would be the same birds, and that they’d be the same territory holders staying into this year’s breeding season.
As it is, some territories have seen 3 separate pairs so far in the course of six months. And judging by observations by volunteers during the past week, it’s all change again. Some of the existing territories now have new colour-ringed pairs entirely, as a wave of new arrivals seems to have taken place, either ousting the winter pairs or mixing up the partners yet again.
As the 2017 season starts, it appears the picture of territory occupation is by no means settled… which deserves a blog entry of its own soon. And if anyone knows of any monitoring of winter territory or site fidelity for Stonechats in other parts of the UK, we’d be interested to hear their findings.