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| Siskins http://www.lbcarchive.co.uk/forum/viewtopic.php?f=4&t=24010 |
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| Author: | Alan Ball [ Mon Apr 04, 2016 9:11 am ] |
| Post subject: | Siskins |
There have been huge numbers of Siskins around this Winter/Spring, though they were later than normal switching to artificial food (sunflower hearts and niger) presumably because there was plenty of natural food (larch and alder) this year. Numbers caught at Bourne Wood and Bob Sheppard's garden have been lower than recent previous peak/irruption years with nearly 300 birds ringed. Just before they move, on some individuals can put on huge amounts of weight in terms of fat to sustain them for a long journey. Base weight of Siskins is around 11 – 12 gm, but some can weigh over 17 gm before they leave, which is a staggering 40% increase of their body weight! It is possible that these individuals are heading off to Scandinavia, as I would have thought there would be no need for a long single migration movement if they were heading up to Scotland (where most of our wintering Siskins breed). This last week-end, most have left and mainly females remained (80%), suggesting that males may leave earlier in order to claim breeding territories. Past experience suggest that all will have gone by mid April. Alan |
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| Author: | Stuart Britton [ Mon Apr 04, 2016 4:45 pm ] |
| Post subject: | Re: Siskins |
My Siskin site near Osgodby mirrors Alan's results at Bourne - we have ringed 270 and the weight gains are impressive. The only difference is we have caught our best numbers in the last couple of days so they are obviously moving north. I don't know for certain whether we have a breeding population but a female ringed on January 6th weighing 11.6g was re-trapped today weighing 12.2g - obviously not ready to move to Scandinavia just yet! I have looked at previous Mid-Lincs RG data and it is surprising that only 7 Siskins were ringed by the Group between 1974 and 1989! |
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