30 July 2020

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.

18 July 2020

Kittiwakes fail AGAIN

With slightly higher hopes than last time, we paddled out to the Kittiwakes sites at Trewavas Head to check up on the c140 pairs nesting at the three sites. The first stop was Trequean Cove where there were encouragingly still good numbers of birds, but a closer look revealed just 11 nests still with chicks which was a poor return from the 40 sitting birds we found in May. There were plenty of our colour-ringed birds and so far this season we've seen 13 birds at Trequean that have previously been seen at the main colony or at the engine houses colony. This might suggest that birds are slowly moving along the coast, but why they might be doing this is unclear.

The reason for this became apparent as we paddled along to the engine shouses, where the 28 pairs we'd seen in May were down to just half a dozen forlorn birds sat on empty ledges. The main colony at Trewavas Head wasn't much better either, as despite there being plenty of birds still present (including 17 of our own colour-ringed birds and a French bird), there were just three nests with chicks, down from the 65 sitting birds in May. Why these birds have failed again so disastrously is a a mystery, but it's interesting that the nests dominated by younger pairs seem to be doing better than the established sites, so maybe change really is for the better.

To back up this move away from the main colony, we received an email from fellow Kittiwake workers in France (Professor Emmanuelle Cam from the University of West Brittany) with a report of two of our birds seen in their colonies in Brittany in recent weeks. Both of these birds are regulars at Trewavas Head:

  • EC was actually a chick ringed (metal ring only) on the Isles of Scilly in 1996, but we recaught it in 2015 and added a colour ring. It's been seen every year since as a breeding bird, last seen here on 2nd June 2020.
  • EN was ringed as an adult at Trewavas Head in May 2015 and was seen 2015-2018 but not seen in 2019. It was however seen back in the colony on 19th May 2020.

These are the first of our birds seen in your colonies, and it's great to have the coverage that produces these sightings. It'll be interesting to see what happens in the coming years and whether the colonies can recover.

26 June 2020

Mullion gull numbers

With the last of the (supposedly) calm seas for a while, we took the chance to get over to Mullion Island to ring any surviving Great Black-backed Gull chicks. At the start of the month we counted at least 59 nests with 146 eggs/chicks, but we know that survival is incredibly low to fledging, so we never know what to expect.

Worryingly the first chick we found on the island was tiny, perhaps only a week old and far too small to ring. With most chicks on Looe Island a good size now (we visited two days ago to ring them there) we wondered if Mullion birds were nesting far later and we'd struggle to find any chicks big enough to ring. The remainder of the island was a mixed bag though, with some nests still with eggs, one just in the process of hatching.

However, we did also find enough larger chicks to keep us occupied and in the end we colour-ringed 14 birds. This is still only 10% of the eggs/chicks we counted three weeks ago. but seems typical of recent years. We'll make a return trip in a couple of weeks time to see if the remaining chicks have survived, so the number may yet improve.

2013 2014 2015 2016 2017 2018 2019 2020
GBB Gull nests - 62 37 83 70 60 71 (59)
GBB Gull eggs/chicks 98 174 90 204 166 - 195 (146)
GBB Gull chicks ringed 4 17 12 13 5 3 16 14

For the first time we also saw not one but two of our own ringed birds on the island, of an age now where they're probably breeding. It was good to see the rings on these birds were still looking good, as in some cases they can wear quite rapidly, making them hard to read. See below examples from Looe Island (taken two days ago) of worn rings from 2010 and 2011.

LDA2 was ringed as a chick in 2015 and has been seen several times at Southerly Point, Lizard
and once at Coverack. It was last reported in November 2018.

With a remarkably similar history, LBH7 was ringed as a chick in 2014 and is also a frequent visitor to
Southerly Point, has also visited Coverack once and was last reported in September 2018.

Not all ring wear is even though, as the photos above and below are actually different sides of the same ring (L:AL8)

Strangely there were still also one or two Cormorant chicks in the nest which is very late, but most were long gone, leaving just their mallow-stick nests as evidence.

A sorry reminder of the times we're now living in

15 June 2020

More Barn Owl visitors from up-country

Following the recent arrival in one of our boxes of a Barn Owl from Manchester (details here), yesterday saw another visitor from up-country. Whilst visiting a regular nest site at Tregarne (St Keverne), a male bird flew out of the barn as we approached, but we managed to catch the female in the box, where she was sat with four downy chicks. Noticing she was ringed, we presumed it was the female we ringed there in 2017, but it was actually a female that had been ringed as a chick in 2017 at a site near Gweek (8km away). Oddly, this bird had bred elsewhere in 2018 and 2019 (near Crosslanes), 9km from where she was now nesting, so must have been a new arrival here.

As if this wasn't interesting enough, we then removed the bulk of an old Jackdaw nest in the box in the adjacent barn, finding the body of a long dead Barn Owl built into the nest. This bird was also ringed and remarkably was a chick from Devon ringed in 2019. When this bird arrived at Tregarne we won't know, but it must have been late winter or spring to be built into the Jackdaw nest, but there must have been some fight with two new females arriving at the same site to take it over!

3 June 2020

Visitors from up-country

We recently received details from the BTO of a nesting Barn Owl we recaught in on of our boxes at the end of May. We mostly catch our own birds, ringed as adults or chicks, but just occasionally we welcome a visitor to Cornwall. GR53474 is now breeding in a box near Fraddam, but had been ringed in 2017 as a chick at Irlam in Greater Manchester, over 420km to the north!

Since we've been monitoring Barn Owls in the county, the only other long-distance visitor we've recaugt was a bird ringed as a chick in Suffolk in 2017 that was breeding in Newbridge the next year (see here). Apart from that, a bird ringed as a chick in Cumbria in 1990 was found dead near Golant in its first winter and incredibly we have also had birds ringed in Germany an The Netherlands found here.

The same day the Irlam Barn Owl was caught we were also able to catch up with another visitor from the north (the second line on the map above). Red AXF was ringed as an adult on Puffin Island off Anglesey in summer 2016 but since then has found Cornwall to its liking, breeding ever since at Western Cove, Portreath.

1 June 2020

2020 seabird update

It's been a while now since we've updated the blog, but to be honest lockdown has meant that we've not really been up to much anyway! We've been out reading gull rings locally and that's about it. But now lockdown has eased slightly we've been able to get out and start to look at Barn Owls and some of our seabirds. More on the owls later, but it was great to get out to Trewavas Head and Mullion Island recently and see how our birds are getting on.

A quick kayak out past Trewavas Head last week found very healthy numbers of Kittiwakes back on the ledges, including lots of 'new' birds at Trequean which has only recently been used. This new site appears to have been taken on by younger birds, with several birds we've ringed as chicks now sat on the ledges there. A quick paddle found 23 of our colour-ringed birds and four French birds which is a great start.

We then had our first trip over to Mullion Island today to check on the numbers of Great Black-backed Gulls nesting there. We weren't able to get over to ring any Cormorants this year due to lockdown, which was unfortunate as they were in a very accessible part of the island! But we were able to photograph and count nests earlier in the year and the count of at least 53 (and probably 57) is the highest we've seen in recent years.

Some of this year's fledged Cormorants enjoying the sun

Back to the gulls, there was one section of the island we couldn't cover due to nesting Shags and Cormorants, but we covered a majority of the island and counted 59 nests, mostly still with eggs. This is slightly down on previous years, as was the 146 eggs/chicks counted.

Great Black-backed Gull nest with a view

2013 2014 2015 2016 2017 2018 2019 2020
GBB Gull nests - 62 37 83 70 60 71 (59)
GBB Gull eggs/chicks 98 174 90 204 166 - 195 (146)
GBB Gull chicks ringed 4 17 12 13 5 3 16 ?
Cormorant nests 24 52 50 39 47 38 47 53-57
Cormorant chicks ringed 11 19 7 16 0 0 14 0

We'll be back over in a few weeks to see how those 146 have got on, so more on that later.

Newly-hatched Great Black-backed Gull chick

11 January 2020

French Shag on Looe Island

Recently we've been going back through some records and making sure that all of the French colour-ringed gulls seen on Looe Island (or more correctly St George's Island) over the years have been processed at the BTO end, thanks to the efforts of Claire the Warden's Assistant. There's been a Great Black-backed Gull colour-ringing project on the island since 2010 and Claire's efforts reading the colour rings are key to the success of the project. More details of the project can be found on the Cornwall Birds website.

But in amongst the gull records was a sighting of a colour-ringed Shag which is pretty unusual in the southwest. Claire photographed the bird by the jetty in December and it turns out it belonged to a French project, perhaps not surprising considering the closest UK projects are in west Wales and southern Ireland. K26 had been ringed as a chick in 2015 on Chausey, a small group of islands off the Normandy coast, geographically part of the Channel Islands group and managed as a bird reserve by the Groupe Ornithologique Normand.

It turns out that this is just the seventh record of a French-ringed Shag to be found in the UK. Of the previous six, three have been in Cornwall, sadly all young birds found dead in fishing nets (in 1982, 1984 and 1985). Of the other three, two were also in the southwest, found dead on the Isles of Scilly in 1981 and in Devon in 1989 (actually ringed 11 years earlier).

The only other record was also from the same French colour-ringing project, of a bird ringed as a chick in 2017 and seen later that year in Sheringham, Norfolk. The project on Chausey has ringed 1550 Shag chicks and remarkably these are the only two birds to have been seen in the UK, with the only other 'international' movements being two birds seen in The Netherlands. It's quite remarkable that these birds don't wander more widely, but know we all know what to look for we can hopefully find some more!

Thanks to Claire on Looe Island for sorting out all the records (and spending hours reading colour rings) and to Fabrice Gallien in France for the information on the birds and the project.

1 January 2020

New Year, new Chiffs

It's been a long time since we've blogged, but what better time to change that than New Year. Today was a rare calm day and despite not being very cold we decided to have a couple of hours at Gwennap Sewage Works anyway. The vagaries of ringing at sewage works is that we often only use the smallest size rings (AA) and today was no exception. In the two hours (and just three nets) we ringed 28 Chiffchaffs, including this very smart tristis Siberian Chiffchaff. Unfortunately we didn't recatch any ringed birds from last winter (when we ringed 44 Chiffchaff here), but once the colder weather arrives I'm sure we'll be catching more.

There were well over 40 Chiffchaff on site (and two Yellow-browed Warblers), so plenty more to keep us occupied on the next calm day. The bycatch wasn't too bad either: Firecrest, two Long-tailed Tits and the obligatory Wren.

11 October 2019

Another German Med Gull

It's been a long time since we've blogged, but having received this photo we had to share. Yellow AZTN was one of 166 Mediterranean Gull chicks ringed in Saxony, Germany this summer. Of those 36 have been seen since, 25 in the UK, so it was nice to see AZTN at Stithians Reservoir earlier in the week.

In total almost 500 German-ringed Med Gulls have been seen in the UK, with just 20 seen in Cornwall. Thanks to Andreas for the quick reply on the sighting and the photo.

6 August 2019

Month-old French Kittiwake at Portreath

Following the depressing failure of the Trewavas Head Kittiwake colonies (see here), it's vaguely encouraging that the colony in Western Cove, Portreath seems to be thriving. A late evening visit to catch up on some nest recording saw a very busy colony, with some birds already fledged.

It was also good to see a nice variety of ringed birds, with a bird from Puffin Island (Anglesey), three from Pont du Raz (Brittany) and also one of our own Trewavas Head birds (VM, ringed as a chick in 2017). It was surprising to see good numbers of loafing birds away from the main colony as well, which we presumed were local birds, but in amongst them were three French-ringed birds we've not recorded before at Portreath. So we did wonder if these were dispersing birds or failed breeders. But we were then amazed to see a recently-fledged juvenile on the cliff with a nice set of French colour rings!

A quick email (and equally quick reply) to Jean Yves Monnat in France and he confirmed that this was Green/Yellow/metal - White/Black/Orange. It was ringed on 28th May at Pointe du Van and took it's first flight on 6th July, then being seen daily until 15th July. It was one of the first juveniles to leave the colony and made a pretty quick movement over to Cornwall, and just goes to show how closely linked these colonies are across the Channel.

So it's always worth casting a glance over Kittiwake flocks at this time of year as you never know what you might find.

15 July 2019

Trewavas Kittiwake failure

A flat calm sea and a day off is the perfect opportunity for a paddle out along the coast, so might as well combine it with dropping in on the Trewavas Head Kittiwakes. It started well, with a new sub-colony (at Trequeen Zawn) holding nine nests, some with good-sized chicks. The first ever resighting of one of our birds ringed as a chick was here in the early days of the colony, as young birds prospect new areas. This held true, with the zawn holding four birds we'd ringed as chicks in 2015 and 2016, one now at a nest with chicks.

PP (ringed as a chick in 2015) with two chicks

There was also a new French bird in the colony, so it'll be interesting to see if this too is a young bird recruiting into a new area.


But as we paddled round to the main part of the colony it was eerily quiet with a dozen or so birds on the cliffs, but these soon left. Early on in the season we were worried that the return rate of ringed adults was low, then we were unable to ring any adults as they hadn't laid, but we weren't expecting a complete failure. So not a single egg or chick at a site that should be holding over 70 pairs!

Thimgs were no better 'around the corner' as well, with the site by the engine houses also deserted, with not a single bird to be seen. This site should hold over 65 pairs.

So with the recent complete failure of the colony at Newquay, that leaves just two Cornish sites holding any number of birds this summer! The site at Western Cove, Portreath is thankfully thriving (250+ pairs) and there are good numbers at Porthmissen, but other than that we have nine at Trewavas and two at Rinsey!

The rare sight of a brood of three Kittiwake chicks (far left), at Western Cove, Portreath

8 July 2019

Final Mullion totals

At the end of last week, a small team of four paddled over to Mullion Island for our last visit of the year, aiming to ring Great Black-backed Gull chicks. Productivity on the island is always poor so it's with trepidation that we land, not knowing how many chicks we'll find.

After a slow start, we finally started to find chicks, although most were single birds. But as we covered the top of the island we found groups of two and three chicks and we ended the evening ringing 16 birds, which is the second highest total since we started marking chicks in 2013.

2013 2014 2015 2016 2017 2018 2019
GBB Gull nests - 62 37 83 70 60 71
GBB Gull eggs/chicks 98 174 90 204 166 - 195
GBB Gull chicks ringed 4 17 12 13 5 3 16
Cormorant nests 24 52 50 39 47 38 47
Cormorant chicks ringed 11 19 7 16 0 0 14

 Having said that, finding just 18 chicks (16 ringed and two which were too big to approach safely) from 195 eggs/chicks earlier in the season is still pretty poor. We did also find four large dead chicks, but it wasn't clear how they'd died. It was also depressing to find a dead adult on top of the island with fishing line and presumably a hook in its throat, anothe victim of our polluted seas.

3 July 2019

23-hour ringing day!

You know it's summer when you're up before 5am to be out ringing gull chicks and then back home at 4am having been ringing Storm Petrels all night!

This last week has seen various small teams out on rooftops around Falmouth ringing gull chicks, all part of the ever-growing project looking at the behaviour and movements of urban Herring Gulls. So far we've ringed 25 birds on St Mary's School, 20 on Tregnoniggie Industrial Estate, 65 on the university campus roofs in Penryn and various other smaller groups.

Ringing chicks on the roof of Wilko in Falmouth

It's was also full moon last night and perfect weather for some Storm Petrel ringing, so a small team headed down to Gwennap Head, Porthgwarra. As the wind dropped the birds started arriving at the nets and we were set for a busy night!

The final tally was 114 new birds ringed and six birds retrapped that weer already ringed. Three of these were birds we'd ringed previously, one just a month ago at Lizard. Another was a bird we ringed at Porthgwarra in July 2018 that was recaught in North Wales just a week later. Another has a slightly more interesting history. It was ringed at Porthgwarra in June 2015, then recaught on Skokholm Island in July 2015 and in Ceredigion 10 days later. In an almost identical occurence it was recaught again on Skokholm Island in August 2018 and in North Wales nine days later!

Other ringed birds came from Co Mayo (ringed in 2008, so a good age), Skokholm Island in 2018 and also a Spanish-ringed bird. This is only the seventh Spanish-ringed Storm Petrel to be found in the UK, but the fourth at Gwennap Head (after birds in 2008, 2009 and 2017)! Others have been caught at Pendeen (in 2005), Tyne & Wear (in 1992) and two in Scotland.

8 June 2019

Breeding season hotting up!

It's been a while since we updated on the start of the breeding season, so this is a quick tour of some of what we've been up to recently. Most recently we've had our first session out ringing Storm Petrels and managed to get teams out to Lizard and Porthgwarra on the same night. PG won out, catching 52 birds, including birds originally ringed in France and on Skokholm Island, Wales (as an adult in 2016). The Lizard team caught 22 birds, but also two birds from elsewhere: birds ringed in 2018 at Portland, Dorset and on Bardsey Island in North Wales.

Aside from that, we've mostly been counting and ringing chicks recently, including Chough, Dipper, Cormorant, gulls and Kittiwakes. It's been fun as well monitoring successive Robin nesting attempts at Penventon Garden Centre, nesting in amongst some of the plant displays! The first fledged two chicks, with two dying in the nest (lack of food due to the baked-hard ground perhaps?), and the second attempt (photographed below) currently has five chicks.

We're also well into the first checks of the Barn Owl season and whilst some pairs are only just hatching chicks now, others already have chicks that are 5-6 weeks old!

One of a brood of five chicks ringed last week on the Lizard

A rather unusual barrel nestbox we found removed from an old site near Marazion.
There must be some pirate heritage in birds that nest is such an impressive barrel.
Whilst most of the owls we've been ringing have been in boxes, it's also been busy in the owl hospital at the Screech Owl Sanctuary. We've already made several visits this year to ring birds before release and our last visit saw us ringing three small chicks (including the very rusty bird below), an older chick and an adult.

Away from ringing, we've now managed to count the gull nests on Mullion and the total of 71 is on par with previous years, though the number of eggs and chicks is second highest we've seen.

2013 2014 2015 2016 2017 2018 2019
GBB Gull nests - 62 37 83 70 60 71
GBB Gull eggs/chicks 98 174 90 204 166 - 195
GBB Gull chicks ringed 4 17 12 13 5 3 -
Cormorant nests 24 52 50 39 47 38 47
Cormorant chicks ringed 11 19 7 16 0 0 14

We've also seen the first Kittiwake eggs of the year, at Rinsey. At the same time some of the Shag chicks are already close to fledging!

The main zawn at Rinsey, sadly now pretty much devoid of Kittiwakes
and with drastically-reduced Shag numbers

Next on the agenda is trying to up our numbers if colour-ringed adult Kittiwakes and then we'll be thinking about gulls and more owls! It never ends...

20 April 2019

Cormorant ringing on Mullion Island

With the swell finally dropping off, this morning gave us the opportunity to get over to Mullion Island to ring some Cormorant chicks. With a ragtag fleet of a kayak, a dingy and a paddleboard we made it over and in pretty perfect conditions. We thought we were pushing it with timing, but remarkably a lot of birds on the island were still on eggs!

But there were enough birds to keep us occupied and in less than 45 minutes we colour-ringed 13 chicks, with one smaller bird just metal-ringed. With birds from the island moving as far south as Spain (see a map of Mullion Cormorant movements here) it'll be fascinating to see where this year's birds go.

In previous years, the ringing totals have varied rather depending on where the birds nest and how accessible they are: 2013 (11 chicks ringed), 2014 (19), 2015 (7), 2016 (16) and none in 2017 or 2018 when the nests were all too close to the edge of the island to access them safely.