It has been a difficult year for most ringing studies and our Bearded Tit RAS at Leighton Moss RSPB is no exception with poor weather and the resulting high water levels reducing our activities. However with re-traps and sightings of our colour ringed population we have a reasonable insight into the size of the breeding population, the survival through last winter and the productivity this season.
Breeding Population and Survival
This year we have either re-trapped or re-sighted a total of 16 adult females and 15 adult males. Past experience is that we always miss a few and this would suggest a breeding population of ca 18 pairs.
Survival this year has been most interesting. Of 21 adults known to be alive in 2011, 10 were present in the breeding season of 2012. This gives a crude survival rate of 48%. This is about average for adults in years with reasonable winter weather. However of 32 juveniles ringed in the 2011 breeding season no less than 21 survived to the 2012 breeding season, a survival rate of 66% and the best survival rate yet recorded for juveniles and only the second year in the 21 years of the study that juvenile survival has been better than adult survival. Overall this gives a survival rate of 60%, the highest yet recorded.
Productivity was very poor this year with only 17 juveniles ringed. Although at least two un-ringed birds have been seen recently suggesting we have missed a few. If the results from the wigwam nest boxes are anything to go by predation was a feature in the first broods with four of the six occupied boxes predated. Later broods suffered from heavy rain and especially the resulting high water levels and many natural nests were undoubtedly flooded out with July recording record high water levels.
Grit Tray Sightings
With 284 sightings of 37 different birds so far on the grit trays and still probably more to come it is too early to do a comprehensive analysis. But birds seem to fall into two groups-those that visit a lot -( the record so far this year is 20 days) and those that seem to get by with two or three visits. Of the first group female Y151875 is typical. From 27/9 to 12/10 it visited on 13 days . Then was not recorded for 22 days but has been back on five days recently.