Warbler Miscellany

With decent weather we caught 333 birds in three visits to our reed  bed sites at Leighton Moss RSPB Reserve. Bearded Tits our main study species started to feature again as the first brood complete their moult. Bearded Tits are one of those species where the juveniles moult their flight feathers and they become almost flightless during the moult but all 5 that we caught had all but completed their moult.  Two had been ringed as first brood nestlings  giving us precise data as to their age in relation to completion of the moult.

Warblers  though proved the most interesting. Our catches of Sedge Warbler have been low this year, on Saturday it looked as though they were picking up with a catch of 25 compared to 39 Reed Warblers, but Sundays catch produced only 2 compared with 35 Reed Warblers. One feature of Saturdays catch was the low weights with many under 10 grams suggesting they had migrated over night, probably from  Scotland.

Reed Warblers appear to be having a bumper season, we are just short  of the 1000 mark for the year. Despite ringing 450 juvs in July all but one of the 28 retraps we had this weekend were from August ringing, the exception was a bird ringed as a short  tailed IJ  on 21/7. this strongly suggests that all the first brood Reed Warblers along with most of the  adults have moved out. We have caught only  14 adults in August.

But the star of the show was Willow Warbler. If our catches are any thing to go by they also have had a bumper season. In the whole of the 2013 season we caught only 183 but to date this year we have already caught 307. Many of this weekends catch were  long winged birds suggesting a northern origin

John.
                                                                                                                   

A tail of two Knot

On a recent trip to the Wash as part of the Wash Wader Ringing Group's summer fieldwork activity a catch of Knot was made in Lincolnshire.  While the number of Knot retraps is always low due to the large numbers around and relatively small numbers ringed each year we did have around 1% of the catch as previously ringed on the Wash.  We also retrapped a bird originally ringed on the 14th February 1998 at Heysham, Lancashire. 

This kind of movement is exactly what we would expect from a wintering Knot at Heysham.  In autumn flocks of many 10s of thousand or even 100,000 form on the Wash where many moult before dispersing to estuaries around the UK and Northern Europe.

While looking at the excellent BTO online recoveries page to see how many have been recorded making this movement before (90), I noticed a rather surprising movement to the Canary Islands.  On further investigation I found this blog which even has photographic evidence of this unusual movement.  Interestingly this bird to the Canary Islands was caught in the same catch at Heysham back in 1998.

The Canary Islands, although a long way away, is not a surprising location for Knot to winter.  What is surprising is that all knot in Morecambe Bay in winter are of the Islandica race which breed in Greenland and Canada then winter in Northern Europe with a few reaching as far south as Portugal. Normally I would have expected a Knot on the Canary Islands to be from the nominate Canutus race however mid August is awfully early for them to arrive on their wintering grounds, particularly as this was still in summer plumage.  How this bird reached the Canaries is a mystery however as they are long distance migrants that do cross large expanses of ocean it is possible a storm picked it up somewhere further north, alternatively it became horribly lost.

Sedge Warblers Remain Scarce

I blogged before about the small numbers of Sedge Warbles we are catching this year. August is usually the best month for both Sedge and Reed Warblers but this August the weather has done us no favors. However on the six mornings of suitable weather this month we have only caught  33 Sedge Warblers  compared to 160 Reed Warblers. Usually we would expect to catch  in a ratio of 2 to 1 in favour of Reed Warblers.

In our cath on Augut 15h at Leighton Moss RSPB we  caught a female and a juvenile from a small party of Bearded Tits- the others went past the end of the nets. The Juvenile had a dark  iris suggesting that it was recently fledged and was still in juvenile plumage with no sign of moult. The adult female had just started to moult with 8 old feathers suggesting that it had  a brood  that had fledged  probably in early August. Bearded Tits can have three broods per season and on occasions we have caught birds still in juvenile plumage as late as Oct 6th.
John

Pied Flycatchers Have a Succesful Season

We run a RAS scheme on  Pied Flycatchers in 15 woods in the upper  Lune valley and its  tributaries. Yesterday we had  a group get together to  talk over our study. This year we have had 83 occupied nest boxes well up  on the 59 in 2013 and a return to the levels of previous years. We also monitor  another population in Bowland of 8 pairs this year.They have all bred very successfully and we ringed 536  nestlings in total and caught or retrapped 111 adults.

In recent years there has been a marked change in distribution with a decline in the lower altitude woods with three woods losing their birds completely but there has been a corresponding  increase  in the higher woods  with the medium altitude woods retaining their populations.

                           
                         
There is the possibility that the provision of more nest boxes in the upper woods that  they have drawn birds away from the lower woods, but there is no support for  this view from our ringing retraps. Another possibility   we considered was an increase in competition from other hole nesting species such as tits but all our woods have plenty  of unoccupied boxes. So the main conclusion was that the distribution changes related to ecological and possibly  climatic change in the woods and we hope to set up a sampling program to compare   occupied and un-occupied woods.

Our ringing over the years has shown that just 3.9% of the nestlings are recorded again. Of those that return to breed 34 % return to their natal wood-50% move to other woods within the Lune Valley and 16%  move  further afield  Most of these are found in  Northern England with smaller numbers from Wales and South West Scotland. Some though are more adventuress. Nestling ringed in our boxes have been found breeding in  Germany and Denmark. It all helps to spread the gene pool.

By contrast adults mainly return in successive years to their native wood with  just 15% moving woods within the Lune valley. A  few do move further afield. One female ringed while nesting in Galloway moved to our area to breed next year, then north again to  Cumbria the following year.

John