2025 Barn Owl update

After the highs of 2024, we were sadly hit by the lows of 2025 as far as Barn Owls go. Whilst the very wet spring of 2024 saw a flush of early grass growth (and presumably an increase in vole numbers), the very dry early spring of 2025 saw the complete opposite, resulting in by far the worst year we've seen since the start of the project.

The average clutch size of 4.3 eggs was the lowest we've seen, which obviously fed through to lower brood sizes. However many sites failed before hatching. We generally only see one or two failures annually, where eggs were laid but later failed, but in 2025 the figure was 16, a staggering 14% failure rate!

For sites where chicks survived to ringing, the average brood size of 2.4 chicks was again the lowest we've ever recorded, which led to just 96 chicks being ringed, the lowest since 2017.

	2015	2016	2017	2018	2019	2020	2021	2022	2023	2024	2025
Sites visited	41	47	64	85	87	106	93	112	127	150	126
Unoccupied	11	12	23	34	36	43	35	34	29	66	47
Occupied, no breeding	7	8	5	4	3	4	5	4	10	4	8
Average clutch size (where observed)	4.6	4.6	5.3	5.2	4.7	4.6	4.5	4.5	4.6	5.4	4.3
Average brood size (where observed)	3.5	2.8	3.0	3.3	3.0	3.2	2.8	3.1	3.2	3.2	2.4
Chicks ringed	70	47	90	132	119	177	133	189	193	209	96
Adults ringed/recaught	17/8	14/9	21/14	18/14	16/15	22/17	19/17	20/22	30/24	22/35	34/25

The most productive area once again appeared to be Penwith (average of 3.3 chicks per brood) with the lowest central Cornwall (2.0) and Lizard (2.1). Although we caught roughly the same number of adults this year (59 vs 57 last year), fewer of these were already ringed (42% vs 61% last year), which perhaps suggests more turnover of breeding birds this year.

As usual, if we look at movements, fewer recaptures will obviously have produced fewer movements. These movements in general seemed to be longer than in 2024 (see the 2024 map below the 2025 map), but the average was similar at 7.6km (8.5km in 2024), with the furthest being 20.2km. This again maybe suggests birds were moving around more in 2025, perhaps searching for better breeding sites.

2025 movements between breeding sites

2024 movements between breeding sites