Early Courting Dunnocks

We have been asked by the BTO not to ring outside of the boundaries of our property whilst lockdown is in force, as they are concerned that it might reflect badly on them if we are seen out ringing. Personally, I rarely ever mention the BTO when on a ringing session. They provide the licence that allows me to do it, but it is the landowner who decides whether or not I can carry out the work on their property. The DVLA provide me with my driving licence, but if I get caught speeding I don’t think the DVLA need worry about damage to their reputation.

Indeed, if anybody ask, I tell them I am doing a volunteer survey on behalf of the landowner, so they know what is happening on their land, which is genuinely how I see it and how I work. It is why I end up writing so many reports (session reports, annual reports, trend analysis, love it!). I briefly opened my nets in the garden this morning. Briefly because it quickly became too windy and I closed them again about 40 minutes later. Should have done it yesterday, when it was calm all day, but I was busy on other things!

Anyway, despite that, and only catching six birds in the short time the nets were open (Blue Tit 1(1); Dunnock 2; Robin 1; Goldfinch 1), the Dunnock catch was interesting.

Back on the 5th December my wife asked me if it was likely that Dunnock would have newly-fledged young this late in the year. What she witnessed was a food begging and wing fluttering display. That is something newly fledged young will do, but it is also part of a courtship display, with a female begging to an attentive male. It has been very mild, so are they gearing up for an early start to the breeding season? I have noticed that there has been a lot of Dunnock activity in the garden and a lot of calling from tops of bushes and small trees. Anyway I thought nothing more about it until this morning.

The two Dunnock that I caught this morning were very definitely male. Being sexually monomorphic you can, generally, only tell them apart in the breeding season. With the average laying date for first clutches being the 27th April, with the earliest first clutch being recorded on the 1st April (thanks to the BTO Bird Facts and data in the Nest Record Scheme), it does seem awfully early for the male to have developed the distinctively enlarged cloaca (known as a cloacal protuberance) this early in the year. It seems like a lot of energy to expend to produce the extra bodily fluids needed to engorge that part of the body.

Trust me: of all the sexually monomorphic passerine species, the male Dunnock is the easiest to positively identify as male.

Being intrigued by this I thought I would have a look in the online database at our group records, going back through all of the records (even to pre-IPMR days, which is probably only meaningful to other ringers), even into records from the 1990’s. In that time the group has processed over 9,000 records of Dunnock. They have identified just under 1,900 of those records as being male. Amongst them there have only been two other January records of identifiably male birds: on the 23rd January 2005 and the 24th January 2009 (the latter being just a couple of weeks after I started my ringing career).

That makes these two birds the earliest we have ever recorded as male by just under 2 weeks! Is this likely to become a trend, with our ever milder winters? It will be interesting to see.

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