Bird migration through Suffolk

34

Suffolk Natural History, Vol. 35

BIRD M I G R A T I O N T H R O U G H S U F F O L K STEVE PIOTROWSKI From thc many aspccts of ornilhology, thc movcmcnts of birds is to my mind Ihc most intcrcsting. Our knowledgc of migration has incrcased iremendously ovcr thc ycars aidcd by almost a Century of ringing. Field observations have also played an importanl pari and we can now prediel with some accuracy when and whcrc wc arc likely to see migrant birds.

For cxample, coastal wctlands arc ideal localitics for viewing waders stocking up on passagc from tundra breeding grounds to the African coasl and early May and August arc thc best months. The timing of their migration wasn't lost on early hunters who harvested the waders as a food source.

Thc Eurasian Dottercl formerly passed through Suffolk in good numbers with groups rccordcd annually on both spring and autumn passage. 'Trips' were not uncommon on Thetford Warren, sometimes involving a dozen birds and occasionally as many as 20. King James I was reported to have taken dottcrcls with a Sparrowhawk whilst at his Spotting retreat at Thetford on 8 May 1610. Dottcrcls returned to traditional ftelds, heaths or warrens each spring, spending a few days there beforc moving to more northern breeding grounds and, during the early 1800s, their arrival was cagerly awaited by netters who took them for food. However, such pcrsecution dcpleted their numbers and a decrease was noted in thc Breck as early as the 1830s. By the end of that Century, it had become rare with only eleven records between 1890 and 1930. The Golden Plover was caught using similar methods.

Breydon fowlcrs labelled May 8th as 'Godwit day' as this was peak passage for Bar-tailcd Godwits. Many waders are long-distance travellers, some flying from aretie breeding grounds to winter in the tropics or further south. Thc patterns of migration arc complex and ringing has shown that different populations have discrctc wintering areas, with some races travelling much further than others. For examplc, Dunlin wintering in Suffolk are mostly of the race arctica which breeds in north-eastern Greenland. Those breeding in northern Britain and Iceland arc of the race schinzii which winters largely in Morocco and Mauritania. This race occurs in Suffolk as a passage migrant.

Colour-ringcd Turnstones wintering in Suffolk originate in Canada and movcmcnts of Avocets from northern Europe to North Africa are quite common. Two Purple Sandpipers wintering at Landguard werc ringed in Sweden.

Lapwings passing south at thc end of May arc usually the first retuming migrants of the year in Suffolk. By the middlc of June, returning Curlcw, Spotted Redshank and Green Sandpipers also appear. Some wader spccics use Suffolk purely as a Staging post on their long journeys and neither winter nor summer herc. Coastal lagoons form the main attraction for thesc transients and in May, July and August good numbers of Common, Wood and Curlew Sandpipers, Littlc Stints, Grccnshanks, Bar-tailcd Godwits and Whimbrcls appear. The tundra race of the Ringed Plover is purely a passagc migrant rarcly occurring beforc thc last weck of May. Onshorc gales often force migrating flocks closc inshorc and large movcmcnts arc occasionally noted at migration watch-points.

Trans. Suffolk Nat. Soc. 35 (1999)

35

BIRD MIGRATION

Man's fascinalion with ihc migralions of birds gocs back ccniuries. Early philosophers failed to undcrstand why some species disappcarcd during thc winicr months only to rcappear thc following spring and, in conscqucncc, forwarded cxplanations which relied on logic rather than fact. Thcrc were wild theories concerning thc disappearance of thc Swallow. 1t was widcly bclicvcd that these birds hibernated during wintcr by burying thcmsclvcs in mud on thc bed of lakes. Othcrs belicved that therc was an annual migration to and from the moon. Kites were thought to have hidden in a torpid State in crcviccs amongsl rocks during winter.

A number of experiments and observations carried out in thc carly 1800s discounted thc hibernation theory and supported that of migration and, by thc 1820s, East Anglian naturalists were firmly entrcnchcd in thc lattcr ideals. One of the earliest works on East Anglian ornithology were papers read to thc Linnean Society in 1824 and 1825 by Rev. Revett Sheppard and Rcv. William Whitear when they said "the proximity of the counties of Norfolk and Suffolk to the northern pari of the Continent, affords an opportunity to many migrative species of birds to visit these parts of the kingdom, in their passage to and from their breeding haunts".

Nicholas Fenwick Hele studied migration from his Aldeburgh home in thc middle of the 19th Century and regularly logged the "Royston crows, rooks, jackdaw, owls, woodcocks, starlings, larks or the enormous 'mobs' or 'rushes' of small birds that reach our shore." As an examplc. he cited movements, between 11.00 a.m. and 1.00 p.m., on 21 October 1877 involving Roystons (Hooded Crows), Starlings, Bramblings, a Single Woodcock, larks and other small birds.

Migration is most obvious on or near the coast. but some species that require specialised habitats may concentrate at inland localities. For example, the vast watery fens that formerly encompassed north-west Suffolk, much of Cambridgeshire, south-west Norfolk and south Lincolnshire were onee a haven for breeding and wintering wildfowl. This proved to be an important food source to local communities and a variety of catching techniques were employed to gather in the harvest. Flightless adults and unfledged young were rounded up and driven into netted traps, but, as the fens shrunk in size, this practice reduced the breeding stock to such an extent that legislation was introduced to limit the trapping. The banning of thc taking of wildfowl during the moulting season in England in 1710 (Kear, 1990) was an early conservation measure.

The fens were drained by Dutch engineers in 1606, but the Dutch brought with them fresh ideas on duck catching by use of decoy ponds with largediameter, tapering funnels. Instcad of breeding birds being capturcd, passage and wintering duck were taken with no obvious effect on thc local breeding population. In the latc 18th Century 200 decoys were sited in Britain, but by 1886, only 47 were operational reducing to 28 by 1918. Early fowlers soon realis'ed that a dramatic increase in duck numbers occurred during thc autumn and winter and decoy ponds situated in regions with a good migratory passage proved to be more produetive. Most of Suffolk's decoys were in the vicinity of the coast and estuarics and, in consequence, were in primc positions to attract

Trans. Suffolk Nat. Soc. 35

(1999)

Suffolk Natural History,

36

Vol. 35

70N

60N

50N

40N

10W

0

10E

20E

30 E

40E

50E

60E

70E

80E

Figure 1. Rccoveries of Pintail ringed at Nacton Decoy

passing migrants. For example, decoys were built at Fritton, Flixton, Herringfleet, Benacre, Worlingham, Friston, Iken, Campsea Ash, Chillesford, Purdis Hall Farm (two ponds sometimes listed as Bixley or Nacton), Nacton Wood/Orwell Park and Brantham. There were only two decoys in West Suffolk at Euston Park and Lakenheath.

Fritton and Orwell Park, Nacton, were still being managed commercially during the 1920s and Nacton tili its closure in 1966, the last fully-operational decoy in Britain. This decoy was built in 1835 and catches have been well documented. From 1919 to 1968, no less than 195,000 ducks were caught although, during the last two years, the birds were ringed rather than killed. The site reached its peak in the 1920s, when catches betwecn 7,800 and, 9,300 were logged. The Wildfowl and Wetlands Trust took over Nacton Decoy and commenced migration studies there using traditional trapping techniques to catch ducks forringing. In the pcriod 1967-1981, a total of 15,569 ducks was ringed from which there were over 2,500 recoveries, averaging one in six. The creation of Abbcrton and Alton Water Reservoirs proved more attractive than the small ponds at Nacton and, faced with dwindling numbers, the WWT ceased its Operations in 1982.

There has always been much scepticism about the origins of Nearctic ducks appearing in British waters, but a Blue-winged Teal shot on the Dcben and bcaring a Canadian ring proved conclusively that Atlantic crossings arc more than a possibility.

Trans. Suffolk Nat. Soc. 35

(1999)

37

BIRD MIGRATION

A variety of marking techniques to delcrminc owncrship rather tiian movements was employed as carly as 1708-1709. The first proven inler-county movement featuring Suffolk dates back to 1850, when one of Archdeaeon Berners' keepers shot a Grey Heron on the Orwell wilh a brass plate on lts leg, giving Information that it had come from Lincolnshire. The owner of the heronry said that he "was not surprised that one of his herons should be shot on the Orwell, for not long previously one had been shot on the Danube notfar from Vienna." There were 18 recoveries in Suffolk of Grey Herons from abroad up to the end of 1995, the bulk of which originated in Holland (11) with others from Denmark (4), Germany, Norway and Swedcn.

Knowledge of migration grew considerably through the 19th Century and was greatly enhanced by a national ringing schcme which commenced in 1909.

Proposais for a network of coastal observatories around Britain, to monitor the movements of seabirds, were forwarded as early as 1834. National schemes did get underway, elsewhere in Europe, and reports from Belgium, Sweden, Russia and Germany were published in 1880.

There was much excitcment during the early years of the nnging schcme with numerous letters regarding recoveries being published in national journals. Rings were originally inscribed with the ringer's name and address, with the ring number on the reverse and there were also appeals for rings together with the birds' legs to be retumed to the nnger. Claud Ticehurst featured highly amongst these early pioneers and his rings were inscribed "Ticehurst, Tenterden," (he was then still living in Kent). Suffolk's first foreign recovery involving a Little Tern ringed at Siz.ewell Thorpe on June 27th 1912 and recovered in France exactly two months later. Ticehurst enthused about the potential of Lowestoft as a migration watch-point. It had many of the ingredients of other well-known migration sites in Britain, including a lighthouse attraction and lots of cover holding an abundance of food for tired and hungry migrants. It is also the most easterly point of the British mainland.

Between 1910 and 1927, Ticehurst and his friend Fred Cook monitored migration in the area, keeping a detailed log of weather conditions including wind speed and direction, numbers and species involved and direction of travel. Their enthusiasm is aptly depicted in Ticehurst's account of the Rook (Ticehurst, 1932) which included detailed diagrams of their incoming approach. Records from light-vessels were also valuable indicators of passagc movements of that time.

The Transactions of the Suffolk Naturalists' Society detailed an amazing war-time account of immigralion witnessed at a Searchlight Station at Lowestoft towards the end of October 1944 (Cook, 1945). It describcd how a horde of Starlings gathered around a searchlight Station at Lowestoft dunng the night of 21 October in such vast numbers that many branchcs were lorn from adjacent oaks by the birds' combined weight. As Starlings are diurnal migrants, it is likcly that birds were disturbed from an overnight roost, although other searchlight stations in the district were also "swamped" by Starlings that night.

Cook visited the Station a few days later and was fascinated by what he saw "in the slowly revolving and almost vertical beam there wavered in bewilderment and panic migrating birds, that it was almost impossible to identify by sight, as

Trans. Suffolk Nat. Soc. 35

(1999)

38

Suffolk Natural History, Vol. 35

all were rendered intensely silvery by the brilliant light." Hc recognised thc calls of Ficldfares, Rcdwings, Blackbirds, thrushes and Skylarks and noled the occasional bird that "came fluttering down the beam on to the lantern, apparently with complete immunity." A few nights later "when the moon shone serenely out of the sky" no birds (or moths) could be localcd in the beam. Previously, there are a few records of bird being drawn to Suffolk lighl-houses and light-ships, but this account must surely have been thc first evidence of birds being attracted to lights in mass.

Ticehurst (1932) also predicted that the coastal towns of Southwold and Aldeburgh as well as Orfordness, Shingle Street and Landguard Point, would be well favoured by passage migrants, although he stated that the sites needed to bc "worked regularly" for this to be proved.

Thc Dinglc Bird Club established a ringing Station at Walberswick in 1953.

The two Dingle hills were in prime position for the study of migration and two Heligoland traps were constructed to increase the number of birds caught.

From 1953 to 1962, 12,000 birds of 110 species were ringed and all bar 600 were passerines. Thc County's first Bonelli's Warbier was trapped by the group in April 1961, and was followed by Suffolk's first Pallas's and Radde's Warbiers within the next three years. Early moming coastal movements of larks, pipits, Starlings, Tree Sparrows, finches and buntings were noted annually between late September and mid November. Northward movements of Linnets were considered to be "a curious feature of Suffolk" (Pearson, 1963), although, as this phenomenon has not been subsequently witnessed at other Observation sites further south, it is likely that these birds were coasting locally. Although work at the Dingles is less intense today than in those early years, there are still valuable studies being carried out on Bearded Tits and the migration periods are still covered.

Ringing took place at Benacre in the 1950s and again in the 1970s and the Sluice Bushes at Minsmere were well worked during the 1960s. Suffolk's first Common Rosefinch was trapped at Benacre Pits on 2 September 1959.

The most significant development of migration studies in Suffolk coincided with the growth of the Port of Felixstowe. The towering floodlights illuminated a huge area of land and sea and the number of migrants present was at times amazing. This effect was soon to be realised at nearby Landguard Point.

Access to the former military area had been restricted for many years and, when the army moved out, the land was divided - the majority going for dock development, some to tourism and a small section as a nature reserve. There was scant reference to Landguard by authors of Suffolk avifaunas and the few ancient records for the Site (e.g. Snowy Owl and Storm Petrel) related to birds attractcd to the old wooden lighthouse which was destroyed by fire in 1925.

Observcrs who visited the site in the 1960s reported little in the way of migrants. However, all was to change in 1975 when public access to the peninsula was rcinstated and a Local Nature Reserve was established.

Incrcased observer coverage contributed to a string of rarities found at the site and interest blossomed to such an extent that in 1982 a bird observatory was established in thc old war-timc bunkers which overlook the reserve. Ringing and migration studies are carried out on a day-to-day basis and much has been leamt about passage birds that migratc through Suffolk.

Trans. Suffolk Nat. Soc. 35

(1999)

39

BIRD MIGRATION

Table 1. Species new to the County List rccordcd at Landguard or Fagbury 1981-1998 Year Landguard (14) Fagbury (3) 1981 Lark Sparrow 1984 Thrush Nightingalc 1986 Subalpine Warbier Southern Grey Shrike 1987 Desert Whcatear Dusky Warblcr 1988 Paddyfield Warbier 1993 Yellow-breasted Bunting Blyth's Reed Warber 1994

1996 1997

Sardinian Warbier Blyth's Pipit Red-flanked Bluetail Crested Lark Lanceolated Warbier Spectacled Warbier

Arctic Warbier Pied Wheatcar

Table 2. Birds ringed at Fagbury Cliff and Landguard 1991-1994 Fagbury Landguard 159 473 Sedge warbler 0 2 Blyth's Reed Warbler 3 5 Marsh Warbler 231 2079 Reed warbler 6 12 Icterine Warbler 0 1 Melodious Warbler 2 1 Subalpine Warbler 1 5 Barred Warbler 277 924 Lesser Whitethroat 455 1942 Whitethroat 277 842 Garden Warbler 949 4350 Blackcap 1 0 Greenish Warbler 0 1 Arctic Warbler 5 9 Pallas's Warbler 0 7 Yellow-browed Warbler 1 0 R a d d e ' s Warbler 14 23 Wood Warbler 707 809 Chiffchaff 1568 . 2229 Willow Warbler (18%) 4656 (63%) 13714 Total Warbiers 25327 21699 Total (all species)

Trans. Suffolk Nat. Soc. 35

(1999)

Suffolk Natural History,

40

Vol. 35

The porl was cxlcndcd further up the Orwcll estuary in the latc 1980s, swallowing up the old oystcr-bcds and mudflals in front of Fagbury Cliff.

Howevcr, the trccs on the cliff itself were preserved and thousands more were planted as part of the compensation measures. It was soon realised that the illuminated plantations were attracling many passagc migrants and the sitc then bccamc the focus of attention for birdwatchers. For a Short period Fagbury rivalled Landguard as the County's premicr migration ringing sitc. Ringing covcragc was maintained throughout passage periods and yieldcd some amazing results. The annual total ranged bclwecn 5,000-8,000 dunng the period 1991-1994 and no less than 63% of these were warblers (see Table 2).

Howcvcr, all was to changc in 1995. In spring of that year, the brilliant white lamps on onc of the floodlight towers were replaccd by less intensc, peaehy orange ones and gradually throughout the summer and autumn all the lights were changcd. This had an immediate effect on the birds that were groundcd at the site with numbers plummeting alarmingly. The most dramatic dcclincs involved Sylvia and Acrocephalus warblers.

Onc of the most amazing ornithological events of recent times was the 'Great Fall' of Sept. 3rd-5th 1965. A low pressure system to the southeast of Britain produeed an overnight, light, north-northeasterly wind and an approaching depression brought an early-morning thunderstorm. Freshcning southeastcrly winds were soon followed by continuous heavy rain and as the depression tracked northwards. the onshore winds brought an "avalanche" of passcrincs; estimated numbers are given in Table 2. The migrants were considered to have been of Scandinavian origin and during that week, some 3,000 passerines were ringed. Of these four were recovered in Iberia.

Table 3. Great Fall of September 3rd-5th 1965 (from Axell & Pearson,

Whcatcar Redstart Whinchat Garden Warbier Willow Warblcr Picd Flycatchcr Trec Pipit Othcr highlights: Wryncck Whitcthroat Rcd-backcd Shrikc Blucthroat

Minsmere 4,000 7,000 750 2,000 500 1,500 150

Walberswick 700 2,000 400 600 200 400 500

150 350 13 160

Lowestoft 2,000 5,000 1,500 300 500 3,000 25

Spotted Flycatchcr Ortolan Bunting Ictcrine Warblcr Tawny Pipit

1966)

Estimated County Total 100,000 250,000 3,000 3,000 1,200 10,000+ 2,000 500 8 6 5

Weather systems similar to those of the 1965 'Great Fall' resultcd in disorientated migrants on the Suffolk coast in 1955. Similar species were involved, although few counts were made. The remnants of Hurricane Horlense which hit the Suffolk coast from Octobcr 5th-7th 1984 resultcd in

Trans. Suffolk Nat. Soc. 35

(1999)

B1RD MIGRATION

41

Suffolk's largcst concentralions of Song Thrushcs and Blackcaps. Many readcrs will rcmcmbcr thc ferocious storm of 16 Octobcr 1987 which causcd widespread damage on thc Suffolk coast. Vast arcas of woodland wcrc destroyed and thousands of parkland and hedgcrow trccs uprootcd. Thcrc was much activity at migration watch points as disorientatcd birds tricd to rclocaic their migration paths. A few Sabine's Gulls werc forced closc inshorc and a Little Bunting and Dcsert Wheatcar wcrc locatcd at Landguard, but otherwise few passerines were grounded. Thc following Octobcr was much calmcr, although an easterly airflow during mid-month along with low cloud and light rain, grounded passing migrants and around 10,000 Robins wcrc noted in thc Felixstowe area alone. Another large fall occurred in Octobcr 1998. Again Robins predominated with early data showing at least 6,000 birds cffcctcd.

This figure is likely to rise as further records are collated. Ring Ouzels occurrcd in numbers never seen in Suffolk before with flocks of 134 at Minsmcrc and 98 on Orfordness.

Table 4. Othcr recent notable falls Oct. 5th-7th 1984 Black Redstart 60 Robin 9 Ring Ouzel 500 Blackbird 10,000 Song Thrush 15,000 Redwing 25 Garden Warbier 500 Blackcap

Oct. 12th-21st 1988 30 10,000 40 700 700 2,650 2 15

Oct. 6th-7th 1998 (provisional) 4

6.000 350 200 1,000 200 10 100

The number of birds from the Far East has increased significantly in recent years and since 1980 there have been a number of birds new to the County from that region. Yellow-browed and Pallas's Warbiers are now annual visitors and the pattern of occurrences are very similar. Both spccies did not occur regularly until the 1980s and both are late migrants occurring in Octobcr and November.

i

i

I l l i f l n I, ,, ,, • • • • ,. B , • , i M ^ ^ CO <•) OD e i ® « " S S S " ' " ' Year "" Figure 2. Occurrences of Pallas's Warbier from 1948-1997

Trans. Suffolk Nat. Soc. 35

(1999)

Suffolk Natural History, Vol. 35

42

Pallas's Warbier oflcn arrives in Suffolk on easterly winds, but wind d n f t is nol cntirely responsiblc for thc occurrences. The species brecds in thc Siberian taiga and thc ncarcst breeding pairs occur 7,000 km from thc Suffolk coasl. Ii would probably take over a month for this tiny warbler to rcach Suffolk during which time it would have encountercd several cyclones and comc against many periods of westerly winds. So why didn't the species Visit Suffolk prior to the 1980s? Could it have been overlooked or misidentified or is it that wc are now more aware of thc timing of its arrival and whcrc we would bc likcly to see it? There have been suggestions that global warming is playing a pari and that as thc spccies is breeding further north, it is morc likcly to makc a mistakc and choose the wrong migration path.

Since 1983, Landguard Bird Observatory has carried out intensive studics on the mixed Herring and Lesser Black-backed Gull colony on Orfordness. Thc colony currently holds around 15,000 pairs and there arc at least two pairs of mixed Lesser Black-backcd/Yellow-legged Gull. In 1996, this study was enhanced by the use of colour rings. Early returns arc encouraging, with the recovery rate incrcased from around 7% to 20% in thc first three years.

Up to the mid-1970s, the vast majority of seabird records related to birds being recovercd on fishing boats or lightships, tideline corpses or birds found wrecked in harbours or at inland localities. However, in recent years there has been an increasc in the number of observers Willing to face biting onshore winds to record seabird movements. Improvements to optical aids and a better understanding of the migration patterns and the conditions when movements are likely to occur have made 'sea-watching' a more rewarding expenence.

Idcntification skills are largely based on shape, 'jizz' and habits, rather than plumage characteristics. Now mere dots on the horizon can bc identified with certainty by a trained eye. A small band of observers has spent countless hours gazing out to sea and their results have greatly improved our knowledge of movements off Suffolk. For example, up to 1975 there were only eight records of Sooty Shearwater, but it is now known that thc species is a regulär passage migrant recorded from latc August to October. Similarly, the Long-tailed Skua was once an extreme rarity, although it has now been found to occur annually in small numbers.

References Axell, H. E. & Pearson, D. J. (1966). The great fall of migrants - a special report. Trans. Suffolk Nat. Soc., 13: 250-266.

Cook. F. C. (1945). Somc birds of the Suffolk coast. Trans. Suffolk Nat. Soc., 5: 135-136.

Kcar, J. (1990). Man and wildfowl. Poyscr, Calton.

Pearson, D. J. (1963). Thc Dingle Bird Club - Walberswick. Trans. Suffolk Nat. Soc. , 7: 293-301.

Ticchurst, C. B. (1932). A history of the birds of Suffolk.

Steve Piotrowski 18 Cobham Road Ipswich Suffolk IP3 9JD

Trans. Suffolk Nat. Soc. 35

(1999)