Monday 19 October 2020

House Sparrows - colour ringing commences

Since writing the last item, I have pursued my interest in House Sparrows that come into the garden.

The BTO approved my application to fit colour rings associated with the creation of a RAS (re-trap adult for survival). In addition to a standard BTO metal ring, an engraved orange darvic ring is now being fitted to the left tarsus of each bird. Three characters appear on each ring and the format is letter/number/number. The purpose behind the colour ringing is to assist the RAS and allow behavioural studies of individuals. 

The total number of individuals handled during the year has now gone beyond 460. Winter survival will dictate how many birds survive until the next breeding season; if survival is good then the village breeding sites may well be at a premium in 2021 unless birds decide to disperse.

It is very possible that dispersal will lead to sightings of colour ringed birds. My last RAS for this species in rural north Oxfordshire showed that individuals would not infrequently travel 2km. A distance of over 5km was recorded for a single bird and, rather strangely, a leg with the colour ring ring still attached was found over 25km away!

Coming back to my rural Welsh birds, the last week of September started to see encounters with birds that I could not give a specific age to. This year some of the sparrows produced three broods. Yesterday (the 18th of October) saw some individuals that were fully moulted and others that were still to drop the outermost primaries meaning that several un-moulted secondaries were also available for scrutiny. I didn't get as much sparrow colour ringing done as I would have liked due mainly to the number of blue tits.

Male house sparrows are generally not too difficult to age using un-moulted secondaries however the females can be a little more ambiguous.  

The two shots below (from late September) hopefully show the differences between adult female and first year female un-moulted secondaries.

This shot is of an adult female. The secondaries are fretted along the leading edge.

This photo below is of an age 3. The leading edge of the secondaries show little wear. Only when looking at the photographs between the two birds have I noticed that the end shape of the un-moulted juvenile feathers seems to be more rounded compared to the blunt edged adult type feather.,,something for me to look at in more detail next year.     

Just before leaving the subject of moult, I had a quick look at the moult score data that I have recorded for all of the birds during the summer and was quite surprised to see such a variation in the rate at which the moult progresses. By looking at the change in moult score over time I could see that some birds were slower at moulting than others. Unfortunately, for all of the birds I looked at, I only had two reference points of moult score data so I looked at some older data that I collected while living in Oxfordshire. I looked at 11 different individuals for which I had three moult scores and found that in all cases the moult score changed at a higher rate during the early stages of primary moult with the rate decreasing over time. This raised a number of questions in my head to which answers remain outside the scope of mark/recapture projects.

Today (the 19th) was a leisurely start for me. I fed the birds and for 30 minutes I sat with my telescope and a mug of tea. N02 (f) and N07 (m) put in numerous appearances. N05 (f) turned up at least twice. The colour rings are relatively easy to read. I am also wondering how so many house sparrows have avoided my efforts over the summer to fit at least a metal ring!!  

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