2020 Barn Owl update

With the first Barn Owl broods now all ringed and boxes monitored, it's a good time to take stock and see how the season has gone. Averaging out the numbers in the table below, we can see that the project continues to grow and for the first time we have data from over 100 boxes which is a greeat achievement. The occupancy rate contineus to be relatively low, but we hope that previously unoccupied boxes will be taken up by new pairs as the years go by. Of the boxes monitored, clutch sizes appeared to be slightly down on previous years, but the subsequent brood sizes didn't necessarily reflect this. The figure of 3.2 hides a much more complicated story though.

	2011	2012	2013	2014	2015	2016	2017	2018	2019	2020
Sites visited	32	34	32	44	41	47	64	85	87	106
Unoccupied	2	7	12	11	11	12	23	34	36	43
Occupied but no breeding	13	2	7	7	7	8	5	4	3	4
Average clutch size (where observed)	4.8	4.1	3.6	4.6	4.6	4.6	5.3	5.2	4.7	4.6
Average brood size (where observed)	3.1	3.1	2.4	3.5	3.5	2.8	3.0	3.3	3.0	3.2
Number of chicks ringed	33	46	19	63	70	47	90	126	119	170

It was apparent as the season progressed that brood sizes (and numbers of chicks ringed) was decreasing, but this is always hard to measure. But if we simply look at the number of chicks present at ringing through the season then a trend does seem to appear. The sample sizes are rather low, but we do think there's something in the data.

The much lower brood sizes later in the season we presume was due to the period of very unsettled weather, with plenty of rain. This makes feeding very difficult for adults which obviosuly has knock-on effects for chicks. We hope to be able to place cameras in numerous boxes over the winter (watch this space on that), which will give us much better data over the coming years.