Friday 30th May
Four more newly fledged birds today – 3 Robins and 1 Dunnock plus two adult Jackdaws and new for the year, a male Turtle Dove.
TURTLE DOVE is one of the latest of the summer visitors to arrive and everyone is now aware of how scarce they have become, even in Kent, Essex and Suffolk, where densities have always been highest. The breeding distribution is restricted to the eastern half of England as far north as Yorkshire and west to the River Severn. The new BTO Atlas maps show one of the most striking changes in both range and population of any British breeding species, with a progressive loss of range in the north, west and south west of the breeding area. This now seems to be happening in the south east as well.
A large population decline was taking place in England between 1967-2010 and these losses tie in with a 73% decline across Europe between 1980-2010. Despite this information Turtle Dove remains a legaltarget species for French ‘hunters’ during migration. This fact plus changes to habitats on the wintering grounds and agricultural intensification in the breeding range are possible explanations for the species’ dramatic decline. Turtle Doves particularly enjoy feeding on the seeds of short-lived agricultural weeds such as Fumitorys, which are easily controlled by herbicidesand large-scale hedgerow removal will have affected breeding success. (The photograph shows a bird onits flimsy nest in a tall hedgerow Blackthorn.) Jim Flegg also notes in his book ‘Time To Fly’ published by the BTO that not only droughts but the removal of Acacia woodland in Africa for fodder and fuel will have had a major effect on roosting success.
A sad result of hunting during the Turtle Dove’s migration through Europe has led to much ring-recovery information, revealing their route from Britain in August and September through France, crossing the western end of the Pyrenees, through Spain and Portugal to Morocco. They start their moult once breeding has finished but suspend this until they arrive on their wintering grounds in Senegal and The Gambia, where they arrive in late September.
Wednesday 28th May
After a ‘washout’ yesterday a few birds were ringed today. Only three new birds – a Wren, a juvenile Blue Tit and a juvenile Robin.
Four birds were re-trapped but the most interesting was a Jackdaw that was first ringed here as an adult on 16th March 2008 and not controlled again until today making it at least 8 years old. The BTO haverecords showing that the typical lifespan of a Jackdaw is 5 years with a maximum recorded age of 17 years, so our bird is doing well and nearly half way to the record. Even more fascinating and important information obtained through bird ringing.
CHIFFCHAFFS are still singing although they are one of the first summer visitors to arrive from wintering areas in North and West Africa. Some already have young fledged from nests built less than 18 inches off the ground in thick cover (mostly brambles) situated under mature trees in woodland and copses. 5-6 eggs are laid into dome-shaped nests of grass, dead leaves and moss and they are incubated for 12-14 days before hatching and young fledge in 12-17 days.
Sunday 25th May
A busier day today with a lot of newly fledged young processed.
Birds ringed were Chiffchaff, Whitethroat, Blackcap, Chaffinch, Jackdaw, Rook, Jay and juvenile Robins, House Sparrows, Great Tits and Blue Tits.
COMMON WHITETHROAT There are lots of Whitethroats around at the moment having arrived as summer visitors from their wintering grounds in the dry scrubland of the Sahel which extends along the southern fringe of the Sahara Desert in West Africa. It is worth remembering, as you watch a male singing its jaunty, scratchy song from the top of some bramble or gorse and then launching into a crazy song-flight, that the bird is a trans-Saharan migrant which has just crossed the desert on its way to reach its breeding territory here at Sandwich Bay.
Whitethroats build a fairly bulky nest of dry grass about 18 inches off the ground in bramble and other dense cover. They lay 4-5 eggs and incubate for 11-12 days before the eggs hatch and the young fledge very quickly in 10-12 days. We will be seeing adults carrying food to their young and making their ‘burring’ alarm calls any time now. Whitethroats breed in their first year and will raise 1-2 broods.
Monday 19th, Tuesday 20th & Wednesday 21st May
Few birds are being caught at the moment but some interesting species are being ringed nonetheless. Over the three days new birds have been 2 Chiffchaffs, 2 Reed Warblers, 2 Long-tailed Tits, 3 Dunnocks and single House Sparrow, Jackdaw and Rook. Among these and some of the re-trapped birds, we are seeing good numbers of fledged young, with particularly good success from Great Tits using nest boxes around the estate.
BTO NEST RECORD SCHEME This quiet time for birds caught in the nests is used helping Jane ring ‘pulli’ (nestlings) in our many nestboxes. Nest record cards are completed for each box and valuable data is sent to the BTO Nest Record Scheme which monitors the breeding success of British species. It looks as though it may be a successful year for the Observatory’s nestboxes with much valuable information continuing to be fed to the BTO by Sandwich Bay ringers.
The photograph of the nestling Jackdaws shows two particularly interesting points. One is the shape of the fairly typical passerine tongue with backward pointing barbs which transport food from the mandibles back into the oesophagus and because of the lack of feathering at this stage, the ear opening (behind the eye) is obvious on the right hand bird.
Saturday 17th May
A much busier day for a change with 35 birds processed. New birds ringed were:
3 Chaffinches, 1 Chiffchaff, 1 House Sparrow, 11 Long-tailed Tits, 2 Robins, 2 Stock Doves, 4 Whitethroats and 1 Yellowhammer.
Of special note:
A re-trapped Blackcap has returned to breed having been first ringed here last autumn on 26th August probably on its way to S. Spain or N. Africa.
A re-trapped Great Tit is now 7 years old.
Four new Whitethroats indicates a fairly late influx of this species.
The Yellowhammer is one of an increasing number moving into our area.
And continuing on the previous theme of young birds, 2 adult Long-tailed Tits, ringed here last year now have a family of young with them.
Tuesday 13th May
A Willow Warbler ringed today reflected sightings of a fairly late movement of this species through the Bay. Other new birds ringed were 3 juvenile (recently fledged) Chaffinches. There are more and more young birds to be seen as first broods are fledging during what looks like a successful start to the breeding season for some species. The weather is staying relatively mild and after the wet winter weather huge amounts of vegetation growth has come on very early, providing welcome food for insects and cover for nesting birds. Even ‘seed-eating’ finches and sparrows feed their young on insects during a critical stage of their development.
NEST BOXES – Jane has monitored all the nest boxes around the Observatory and on the Estate covering species including Blue and Great Tit, House Sparrow, Starling, Stock Dove and Jackdaw. Great Tits seem to be doing really well after a poor season last year, some already fledged and others with broods of up to nine young. Last year was disastrous locally for Blue Tits and although not great at the moment there are a few good size clutches of eggs and broods of young.
INCUBATING EGGS – During the spring we are able to identify the sex of species, even those showing little sexual dimorphism (obvious plumage differences between sexes) whilst in the hand, as female birds particularly moult off a definite bare area of feathers on the underside called the brood patch. Blood flow increases around this area of skin and blood vessels become engorged. The brood patch is placed directly onto the eggs to transfer body heat allowing the embryo to develop under a steady temperature. The average egg temperature for birds is about 34˚C while the average body temperature is 43˚C. The brood patch remains throughout incubation and into the early stages of brooding the young.
The photograph shows detail of a female Great Tit with a brood patch at ‘stage 4’ where the patch is less engorged, paler and with wrinkled skin once eggs have hatched and the young are growing in the nest.
Wednesday 7th May
A young Moorhen hatched this year in the Observatory pond and a Mallard caught in the Heligoland trap were ringed today. Higher water levels in The Haven stream have attracted more non-passerine wetland species into the Heliogoland trap this year.
Monday 5th May
Another new species for the year today was a Swallow and other birds ringed were 2 Common Whitethroats, Woodpigeon, Great Tit and Rook. Re-traps were Reed Bunting, Woodpigeon and Greenfinch.