1st – 22nd August – a ringing update.   Leave a comment

August can be one of the best times of the year for bird ringing, the weather is still mild, although a bit windy this year, autumn migration is in full swing and the variety of trans-Saharan migrants is at its peak.

I have spent as much time as possible ringing this month at Lytchett Bay and Durlston Country Park although the remnants of hurricane Bertha and getting up at 0430 everyday have proven to be obstacles.

Early in the month there were phenomenal numbers of migrants, especially Sedge Warblers on the move. A couple of visits to Lytchett Bay resulted in nearly 500 birds being ringed, most of them Sedges. Mid-month the weather changed to an unending run of westerlies and the numbers of birds present has been much lower.

Sedge Warblers are usually encountered in wetland habitats but can be seen on migration in scub and low vegetation.

Very common in the reed beds at Lytchett Bay with over 750 ringed this autumn, we have also trapped about 20 in the scrub at Durlston. Sedge Warblers winter in the Sahel, the arid region that lies to the south of the Sahara.

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The heathland at Lytchett Bay has recently been purchased by Dorset Wildlife Trust. We applied to renew our ringing permission with the new owners and they asked us to do a public ringing demonstration. We have only caught a few birds on the heathland but a ‘dress rehearsal’ at the adjacent reed bed has produced a large number of Reed and Sedge Warblers and required us to call in reinforcements to help. Unfortunately the remnants of  hurricane Bertha prevented the actual demonstration from going ahead.

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Whilst taking down nets at dusk we trapped this Brown Long-eared Bat. It might look undignified but this is the correct way to hold a bat, as it does not involve touching the delicate wing membranes.

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Kingfishers appear in the early autumn every year at Lytchett Bay. We presume they migrate down the local rivers to winter in Poole Harbour. In 2014 we have ringed 8 new birds and retrapped one from last year, showing that the single kingfisher seen on each visit is not necessarily the same bird. We have retrapped several in subsequent years, showing year on year site fidelity, but have also retrapped a Lytchett Bay bird in a subsequent winter at Fleets Lane in Poole indicating that this is not an inviolate rule. In this picture a pristine first year (L) contrasts with the ragged adult (R) which is the process of moult. Accurate aging is essential for an understanding of population dynamics which is one of the main investigations conducted these days on ringed birds.

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Grasshopper Warblers, with their graduated tails and long speckled undertail coverts are always a delight to ring. So far this autumn we have ringed 17 at Lytchett Bay and 7 at Durlston. Because of its secretive habits this species has one of the lowest recovery rates of all ringed birds and much is still unknown about its movements and life history.

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Lytchett Bay is the only site where we regularly ring Cetti’s Warblers. An inhabitant of scrub adjacent to wetlands this species is not a true migrant but young birds do disperse as shown by a recovery of one of our birds from Norfolk. The mouse grey-brown plumage, short wren-like wings, broken white eye-ring and just ten rather than the usual twelve tail feathers are all identification features, but most birders will know it by it’s incredibly loud staccato voice.

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We have ringed over 60 Garden Warblers this autumn, mainly at Durlston. It might look like the archetypal ‘little brown job’ to the uninitiated but the stubby bill, narrow grey shawl and plain upper parts with pale tipped remiges give a very characteristic appearance.

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Unlike almost all other members of the genus Sylvia, adult Garden Warblers moult in the winter in Africa rather than before migration. Thus an adult on migration will be more abraded than a young bird. This can be quite subtle, the faded tips to these primary feathers are caused by bleaching by the sun over time and thus belong to an adult bird. It has recently been shown that Sylvia warblers are not warblers at all but representatives of the  mainly Asian babblers.

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However caution is required when aging birds, the tail of this Garden Warbler might look abraded but this can happen in the nest. The presence of a growth bar shows that it is a first year bird. Changes in the availability of food whilst the tail is growing is reflected in the colour of the feathers. The fact that the growth bar occurs across all feathers means that all feathers grew simultaneously and therefore must be from a first year bird.

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Common Whitethroats (the full name is needed to distinguish it from the next species) is a common breeder at Durlston but migrants also move through the Park in some numbers. The dark eye and lack of pure white in the outer tail show that this is a young bird.

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Lesser Whitethroats are (as the name would suggest) smaller than the last species and also are much paler with white underparts, have a pale grey head and lack rufous in the wing. Small numbers breed at Durlston – we have ringed 12 so far this year.

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Breeding mainly in the west of Britain – Devon, Wales and SE Scotland, Pied Flycatchers are pretty scarce on migration where we ring, however the trapping area comprises mainly of low scrub and is not ideal for these arboreal birds.

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In common  with the last species, we have only ringed a single Spotted Flycatcher so far this year, although their migration extends well into September, so there may be more.

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Tree Pipits are regular overhead migrants in late August – early September, usually just after dawn. The fine flank streaking, face pattern and (when you can see it) shorter claw length separate them from the similar Meadow Pipit. In the field the call is diagnostic. So far seven have been ringed at Durlston this August.

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Juvenile Blackcaps have a dark brown crown. This changes during the post juvenile moult to the familiar black of a male or tawny-brown of a female. Note the crown of this bird: this not a mixture of black first year and brown juvenile feathers but rather first winter feathers with brown tips. These will presumably abrade to give the pristine black crown by the spring.

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Most birds fly off immediately on release but some pause to ‘gather their bearings’. This Willow Warbler had a little rest on Margaret’s woolly hat before flying off into the nearby scrub.

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