2024 Barn Owl update

We thought that 2023 was an odd year for Barn Owls, but 2024 seemed to continue the trend! The very wet spring was perhaps a boom for early grass growth, with a consequent increase in vole numbers. So 2024 saw our highest ever average clutch size (5.4), with three clutches of eight eggs being found.

This didn't necessarily feed through into large broods though, with the average (3.2) very much in line with the last couple of years:

	2015	2016	2017	2018	2019	2020	2021	2022	2023	2024
Sites visited	41	47	64	85	87	106	93	112	127	150
Unoccupied	11	12	23	34	36	43	35	34	29	66
Occupied, no breeding	7	8	5	4	3	4	5	4	10	4
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
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
Chicks ringed	70	47	90	132	119	177	133	189	193	209
Adults ringed/recaught	17/8	14/9	21/14	18/14	16/15	22/17	19/17	20/22	30/24	22/35

The most productive area seemed to be Penwith (average of 4.0 chicks per brood) with the lowest being Roseland (2.4) and East Cornwall (2.9). For only the second year, we also recaught more ringed adults than we ringed new birds, which is very satisfying.

As for movements, the map below shows the origins of birds recaught as breeding birds in nestboxes during the 2024 season. As expected, most of these is short distance dispersal of young birds, on average 8.5km but ranging from 1.7km up to 37.2km.

This only relates to recaptures though, but we unfortunately also hear of many of our birds found dead. In 2024, 11 of our birds were reported dead, including three hit by cars and one that hit wires.

Barn Owl throuple and other odd goings on

Over the long bank holiday weekend we had a chance to make our first visits to Barn Owl nestboxes across part of our patch. It was a long slog, with plenty of sites covered and overall it seems to be an early season with several broods of good-sized chicks and even some not too far off ringing age. But of more interest were some of the 28 adults caught over the weekend (just eight were new, unringed birds), which had some surprising histories.

Overall, there were plenty of short movements, which is what we'd expect from dispersing juveniles, but you can see from the map below that these birds generally don't go too far. The longest movement of the weekend was a bird ringed as a chick in 2023 near Probus and now residing in a new box put up at the National Trust offices on the Roseland!

The strangest happenings were saved for the Lizard though. On the expected end of the spectrum was the new pairing at one site, with both of the pair ringed locally as chicks, in 2022 and 2023. In the middle of the spectrum was a breeding female ringed near the Helford river in 2020, then recaught breeding down near Goonhilly Downs in 2022, was then back up near the Helford to breed in 2023, and now breeding in another box near Goonhilly Downs again this year (below), so four sites in five years!

The far end of the weird spectrum though was at another site near the Helford, where the nestbox camera showed two birds in the box, but we could also hear chicks hissing on a nearby ledge. As we put a ladder up to check the ledge a female flew off, with the ledge home to an impressive seven chicks and an egg, which may well still hatch. We don't see many clutches of eight, but this was our fourth of the weekend. So who was in the box? Well one bird was the regular male that's been breeding there since 2020, but the other was a male ringed as a chick at a site 10km away in 2022. It'll be intriguing how this throuple get on and I must admit it's a first for me.

We couldn't have a Barn Owl post without a photo of a Barn Owl, so here's a few of the various stages we found, including just some of the largest larder we've probably ever seen.

Spanish Black-head and record Cormorant numbers

Mullion Island Cormorants are already well into their breeding season now, with some chicks almost ready to fledge. Our regular count from photos found a reciord 75 nests across the front of the island, beating the 73 nests in 2021 and 72 in 1999.

Annoyingly, photographs also showed an interloper in the colony. This white- (or blue-) ringed bird is likely to be from Wales or Ireland, but without being able to read the ring we'll never know. We're currently investigating the options for remote pan-tilt-zoom cameras, so watch this space.

The highlight from this weekend was a great sighting by Shaun Grose at Hayle. This Black-headed Gull (black ring N016) is actually the first Spanish-ringed bird to be seen in Cornwall, so quite special. In fact only 30 have ever been seen in the UK, so even at a national level this is notable.

It was ringed as an adult on the north coast of Spain in January 2022 and was regular there until 11th March 2022, then seen again in March 2023. It returned in January 2024 and was last seen there on 26th February, before being seen at Hayle. Presumably it's breeding somewhere in the UK, so one to look out for in future years.