Wednesday 31 July 2019

Sedge Warblers - Teifi Marsh autumn migration

As we head into autumn migration we have had a look back at data for Sedge Warbler catches just in our Mallard nets on the Teifi Marsh.

Adult Sedge Warbler
In July we catch relatively small numbers of locally bred juveniles and adults then in August the main passage of migrants start, mostly juveniles.

Juvenile Sedge Warbler
This graph shows the total number of new Sedge Warblers caught with similar effort with nets around Mallard pond each year since 2010.

The main conclusion is that we need to open the nets every day that weather permits during August otherwise a peak could be missed. The peak has been different each year but the bulk of the Sedge Warblers pass through around the middle of the month. The largest and most memorable day that can be seen in blue on the graph on the 18th Aug 2010 when we caught an Aquatic Warbler along with 67 Sedge Warblers. (the 5th Aquatic for the Teifi Marshes)

Controls and recoveries of Sedge Warblers last year, shown on this map, were fairly typical of most years particularly the sites along the West coast of France.

Thursday 4 July 2019

A week on Skokholm !

This past week, several of us visited Skokholm Island Bird Observatory. It was my first time and, waiting at the jetty for the Dale Princess, I wasn’t quite sure what to expect. The dramatic scenery which greeted us as we drew nearer held promise for an exciting week ahead. 

From day one, there was much to do. Skokholm is home to a voracious top predator: the Great Black-backed Gull. These have become increasingly rare nationally so it is essential to keep a pulse on their breeding and survival rates.

To this end, many of this year’s young have already been metal and colour-ringed. Our challenge was to ring those left, before they fledge. This, as with a startling number of things in life, is easier said than done! First, one must sight the chicks from a distance. Typically, they stand, quite fearlessly in the open, on rocky peaks. To get nearer, a swift approach is required followed by a thorough comb through of the surrounding bracken, into which they dive like unerring needles into expanding haystacks!
As a trainee used to ~10g Sedge Warblers on the Teifi Marshes, the whole experience, from catching to ringing, was new and exciting for me. Each day, we typically ringed at least 4 new chicks.

 As night falls, the island, never truly asleep, wakes again with the eerie calls of Manx Shearwaters dashing in off the sea. With Wendy’s night-vision camera, we could put faces to the voices of this staggering spectacle; seeing dozens and dozens swirling over our heads (see clip below). And with a torch and net, we ringed 142 in our week there. It’s an immersive experience and incredible to think that each individual will, in a matter of months, begin a journey of over 5000 miles to their wintering grounds.

A Manx Shearwater as seen in the daytime,
 with its chick, likely just a few days old.

Of course, I cannot pass mention of the island’s most well-known residents.

Skokholm has a study plot of ~200 Puffins to observe population changes essential to their protection. Each year, for one day, this population is ‘topped up’ by metal and colour ringing around 30 new individuals. Teamwork is key: three to extract, one to carry extracted birds to the ringing area, one to read out the metal and colour ring combinations, one to metal ring, one to colour ring, one to check and the visitors to release. This was like nothing I had ever done before, and it was amazing to learn so much in a matter of just hours.

Watching puffins in the sunset at the day's end.
In the midst of all this, the long-term volunteers were assessing Storm Petrel productivity using audio-playback to check whether an adult was ‘at home,’ Ian Beggs was observing the Wheatears for a highly detailed insight into their mating and territorial behaviour, and Michael was creating a soundscape of the island.

One of the male colour-ringed Wheatears hopping
around his territory.
As Richard said when we left; every year, visiting at a given time, many things stay the same. The Razorbills, Guillemots and Puffins still return to their cliffs. The Gulls still hunt them from the air. But the people you meet, each passion-driven and fascinating, will change. Likewise of course, new birding ticks (of which I left with an alarming number!) can always fly in; such as the Laughing Gull pictured below. Moreover, plastic pollution and climate change is, and will even more so, threaten this unique and beautiful island, as everywhere of course.

Strong winds on Thursday swept up stronger currents and
The Laughing Gull, native to America, but likely storm-swept
over to Skokholm.
So to wrap up, a wonderful week for me and warm heartfelt thanks to all who made it possible. I will surely return!

Monday 1 July 2019

Unexpected 3J Chaffinch moult 1/7/19

We are all used to partial post juv. moult and complete moult in adult Chaffinch but the shot below shows something that I have not experienced before although I have heard of others finding complete moult in first year birds. I always wondered how one could tell unless a re-trapped bird was referenced by ring number. Catching the bird in the process of moult makes it easier; in moult sequence, P1-5 are in various stages of growth, S1 is growing. The flight feather moult was symmetrical. In all other respects the bird was only just begining post juvenile moult with the lateral/ventral feather tracts showing through. So, A 3J, moult code M, new for me!