the changing status of balearic shearwater in northwest

392 © British Birds 100 • July 2007 • 392–406

The Balearic Shearwater Puffinus maure-tanicus is one of the world’s most endan-gered seabirds (Oro et al. 2004; IUCN

2006). It is a regular visitor in varying numbersto west European (Atlantic) inshore watersduring the summer and autumn, most com-monly seen off Iberia, France and the south-western coasts of Britain & Ireland during itspost-breeding dispersal. The species is gregar-ious and found predominantly in inshorewaters, the main food source being smallshoaling fish, such as Sardines Sardinapilchardus and Anchovies Engraulis encrasi-cholus, obtained largely through plunge-diving(Le Mao & Yésou 1993; Arcos et al. 2000;Mayol-Serra et al. 2000). Trawler discards arealso an important food source (Arcos & Oro

2002; Yésou 2003).Although the species has attracted the

interest of taxonomists and conservationists inrecent years, there are, as yet, no comprehensivestudies documenting the numbers reachingnorthwest European waters (note that, for thepurposes of this study, ‘northwest Europe’ isdefined as the area north of 48°N, roughly coin-ciding with the northern margin of the Bay ofBiscay; fig. 1). An assessment of temporal andspatial trends away from the breeding groundsis crucial when considering whether ‘at sea’factors, e.g. increasing sea-surface temperaturesand changing fishing practices, are contributingto the species’ apparent population decline (seebelow). Consequently, in this study we haveattempted to assimilate the available data on the

The changing status of Balearic Shearwater in northwest European

watersRussell B.Wynn and Pierre Yésou

ABSTRACT Sightings data collated from the European Atlantic coastline reveal arecent change in the post-breeding distribution of the Balearic Shearwater

Puffinus mauretanicus, and provide evidence for a progressive northwards shift indispersal patterns. Numbers recorded in the traditional post-breeding quarters,centred on the French Biscay coast, have declined since the mid 1990s and now

show marked inter-annual variability. In contrast, numbers recorded fromnorthwest European coastlines have increased since the mid 1990s, the

majority being seen along the coasts of northern France and southwest Britain,with smaller numbers north to southern Scandinavia.Although variability in

observer effort may have contributed to the observed increase in northwestEurope, the spatial and temporal consistency of the data suggests that the trend

is real. Large numbers of this Critically Endangered seabird are now spendingpart of the year in British and Irish waters; this paper highlights the need forfuture effort-based surveys across the species’ non-breeding range, and will

provide a baseline for conservation measures in northwest European coastalregions, where large concentrations now occur regularly.

393British Birds 100 • July 2007 • 392–406

species’ status in northwest European waters, toassess whether there has been any change in dis-persal pattern and the number of birdsinvolved. These data are compared with thosefrom elsewhere in the species’ non-breedingrange and are intended to provide a baseline forfuture conservation-based surveys and studies.

Taxonomic statusThe taxonomic history of the species iscomplex. In Britain, the first major step was asplit from Manx Shearwater P. puffinus in 1991when, following a proposal by Bourne et al.(1988), it became known as the western race ofMediterranean Shearwater P. yelkouan. Then, adecade later, a further split led to recognition ofBalearic Shearwater P. mauretanicus and Yel-kouan Shearwater P. yelkouan as separatespecies (Sangster et al. 2002). Although BalearicShearwater is presently listed at species level inmost national and international avifaunas,uncertainties over its true taxonomic statusremain. For example, recent studies have shownthat some birds breeding inMenorca resemble yelkouan inplumage pattern but are interme-diate between mauretanicus andyelkouan in terms of both bio-metrics (Ruiz & Martí 2004) andgenetics (Genovart et al. 2005,2007). The field identification ofManx, Balearic and YelkouanShearwaters has been coveredpreviously in detail and will notbe discussed here (see, forexample, Yésou et al. 1990,Hobbs 2003, Gutiérrez 2004,Holmström 2005).

Breeding and population trendsBalearic Shearwaters breed exclu-sively on the Balearic Islands, inthe western Mediterranean, thebreeding season being betweenFebruary and June. Post-breeding dispersal into Atlanticwaters occurs from late Mayonwards (fig. 1), with a return to the Mediterranean (to wintering grounds off the coastof northeast Spain) between Sep-tember and November (Mayol-Serra et al. 2000; Ruiz & Martí2004). This post-breeding dis-

persal involves mostly non-breeding immaturesand newly fledged juveniles; birds do not breeduntil at least their third year (Aguilar 1999; Oroet al. 2004). Most Balearic Shearwaters undergoa full post-breeding moult between April andOctober, occasionally November (Yésou 1986;Mouriño et al. 2003; Sandoval 2005), approxi-mately coinciding with their presence inAtlantic waters.

Recent estimates of the breeding populationhave varied: 1,300–2,800 pairs in 1984 (J. Mayolper J. Muntaner in litt.); c. 2,100–4,500 pairsbetween 1991 and 1999 (Ruiz & Martí 2004);1,750–2,125 pairs in 2001 (Ruiz & Martí 2004)and 2,000–2,400 pairs in 2005 (Rodriguez-Molina & McMinn-Grivé 2005). Although theestimates show no obvious trend over the lasttwo decades, the breeding range has contractedand numbers at long-term monitoring sites haveclearly declined (Rodriguez-Molina & McMinn-Grivé 2005). A sharp drop in the numbers win-tering off northeast Spain has also been noted inrecent years, with 10,000–11,000 birds recorded

The status of Balearic Shearwater in nor thwest Europe

20° 10° 0° 10° 20°

Fig. 1. Map showing post-breeding dispersal range of BalearicShearwaters Puffinus mauretanicus. Bold lines delimit the core range

(Mayol-Serra et al. 2000); dashed lines show extended range in northwest European waters (Yésou 2003; this study).

70°

60°

50°

40°

30°

6,000 m

4,000 m

2,000 m

0 m

-2,000 m

-4,000 m

-6,000 m

each winter in the early 1990s (Gutiérrez &Figuerola 1995) halving to a peak count of c.5,000 during the winter of 2002/03 (Gutiérrez2003). A similar decline has been observed intraditional post-breeding concentrations in thecoastal waters of the Bay of Biscay, the8,000–10,000 recorded annually off southwestFrance in the 1980s (Yésou 1986, 2003) havingdropped to no more than half this numberduring census work in 1999/2000 (Yésou 2003).The total world population is currently believedto be in the region of just 10,000 individuals(Rodriguez-Molina & McMinn-Grivé 2005) andit has even been suggested that the species couldbecome virtually extinct by 2040 (Oro et al.2004). However, there are clearly still manyuncertainties surrounding existing populationestimates. As with all nocturnal, cave-nestingspecies, breeding numbers are difficult to assessaccurately. In addition, the species is apparentlyprone to changing its favoured non-breedingquarters over relatively short periods of time,probably in response to fluctuating prey densi-ties (Mayol-Serra et al. 2000).

The species’ apparent decline is thought tobe due to the low adult survival rate, which is inturn related to disturbance by humans and pre-dation by introduced mammals on the breedinggrounds, together with a lack of food resourcesand accidental bycatch in long-lines at sea(Aguilar 1999; Oro et al. 2004). Unsurprisingly,given the above statistics, the Balearic Shear-

water has recently been categorised as ‘CriticallyEndangered’ on the IUCN Red List (IUCN2006).

Data collectionLand-based sightings of Balearic Shearwater,covering the period 1980–2003, were obtainedfrom nine countries along the northwest Euro-pean coastline (north of 48°N). Records wereobtained mostly via the relevant national orlocal ornithological records committee and inmany cases these records have been peer-reviewed before acceptance. Records which hadnot been through an assessment procedure werescreened and any for which the identificationwas in doubt were removed. In addition, anattempt was made to reduce the effects ofobvious duplication between sites, particularlywhere records were received from closely spacedlocations on the same date.

There has never been any effort-basedsurvey of Balearic Shearwaters in northeastAtlantic waters. As a consequence, the datautilised in this study are likely to be affected bysome degree of observer bias. Factors whichmay introduce such bias include: variation inobserver effort and identification skills; agreater awareness of or interest in the speciesfollowing its elevation to species status; and theimprovement of optical equipment. Suchfactors are obviously difficult to quantify.However, after initial screening and analysis of

394 British Birds 100 • July 2007 • 392–406


161. Balearic Shearwater Puffinus mauretanicus, Lyme Bay, Dorset, July 2006.

Tom

Bre

reto

n

the data, it becameclear that the spatialand temporal consis-tency of the resultswas high. Data fromsites where experi-enced seawatchershave been recordingseabirds for manyyears are especiallyvaluable, and recordsfrom three such sites,the bird observa-tories at Dungeness(Kent), Portland(Dorset) and CapeClear (Co. Cork), arepresented in fig. 2.Data from Portlandand Dungeness are broadly comparable withthe overall British and Irish trend, althoughCape Clear shows a peak in the early 1990s andsubsequent decline.

Status in Britain & Ireland: pre-1980Although records prior to 1980 are generallypatchy and incomplete, useful insights may begained from sites such as Portland Bill and CapeClear, where Balearic Shearwaters have beenidentified and recorded for several decades. Atboth locations, numbers generally remained at alow level prior to 1980 (average annual totals of<150 at Portland and <30 at Cape Clear) withno overall trend, although there have been peri-odic influxes. For example, between 1958 and1961 several hundred birds per year wererecorded at Portland (exact numbers are hardto quantify as most birds were apparentlyundertaking local feeding movements and werecounted repeatedly on successive days). Thelargest numbers were seen between August andOctober in 1960, with a peak day-count of 229on 3rd October. This influx was not noted else-where, although records for this period aresparse. A further influx, between 1977 and1980, was also noted at Portland, and to a lesserextent in west Cornwall and at Cape Clear. AtPortland, numbers peaked in 1978, betweenJune and October, peak day-counts being 450on 5th August and 618 on 9th August. Again, itis not possible to calculate an accurate annualtotal because of birds lingering offshore forseveral days. These short-lived influxes mayhave been related to unusual climatic events.

For example, the 1978 influx coincided withunusually low sea-surface temperaturesthroughout western Europe that year, tempera-tures in the western Mediterranean Sea duringsummer 1978 being more than 1°C below the1949–2001 summer average.

Status in Britain & Ireland: 1980–2003Data for the Balearic Shearwater are availablefrom across Britain & Ireland for much of thisperiod, allowing a detailed analysis of trends inabundance and distribution. Although Irish andWelsh data for 1980–89 are incomplete, it isunlikely that, even when combined, they wouldcontribute more than a further 20% (c. 60birds) per year on average to the annual totalduring this period. This assumption is basedupon data from 1990 onwards and is supportedby long-term data from Cape Clear Bird Obser-vatory.

Between 1980 and 1989, numbers of BalearicShearwaters recorded in British and Irish watersremained consistently low (fig. 3), with anaverage of 318 birds reported per year. Since1990, however, the species has shown a clearand dramatic increase, especially since the mid1990s (fig. 3). During 1990–94 an average of820 per year was recorded; numbers thendoubled again to an average of 1,827 per yearbetween 1995 and 1999 and 1,961 per yearbetween 2000 and 2003. The peak year was2001, when no fewer than 3,474 were recorded.The overall upward trend is characterised bymarked inter-annual variability. For example,the peak year of 2001 is set against relatively



80 82 84 86 88 90 92 94 96 98 00 02

Fig. 2. Numbers of Balearic Shearwaters Puffinus mauretanicus recorded atDungeness (Kent), Portland (Dorset) and Cape Clear (Co. Cork) Bird

Observatories during 1980–2003. Note that a logarithmic scale has been used on this plot to enable the time-series data for the three observatories to

be plotted together and the trends at each site to be compared.

1,000

100

10

1

no.b

irds

rep

orte

d (lo

g)

Dungeness Portland Cape Clear

poor years in both 2000 and 2002, with annualtotals of 846 and 1,187 respectively (fig. 3).

The distribution of Balearic Shearwaterrecords in Britain & Ireland is heavily biasedtowards the southwest (fig. 4), as might beexpected for a southern European species. Thefollowing accounts outline the species’ temporaland spatial distribution in more detail.

Southwest EnglandBetween 1990 and 2003, an average of 70% ofthe Balearic Shearwaters recorded annually inBritain & Ireland came from this region (fig. 4).The majority were seen off Cornwall (about35% of the total), followed by Dorset (18%) andDevon (16%). Between 1980 and 1989, the

numbers reportedfrom southwestEngland averagedabout 250 per year,but showed no cleartrend (fig. 5).Between 1990 and2003, however,numbers increaseddramatically, particu-larly from 1996onwards, peaking at2,661 in 2001. Thisoverall pattern ofincreasing numbers isconsistently reflected

at a county level, as is themarked inter-annual variability(fig. 5), and also by the datafrom Portland Bill (see above).

The key sites in the regionare all well-known headlandsfavoured by seawatchers. Theseinclude Porthgwarra, Pendeenand St Ives (Cornwall), Hope’sNose, Berry Head and PrawlePoint (Devon), as well as Port-land. Birds have been recordedin all months, but the vastmajority occur between Julyand October. For example,records from Cornwall for1971 to 2003 reveal that 92%were noted in these fourmonths, most in August (32%)and September (29%). Only3% of records fell betweenDecember and May, coinciding

with the birds’ gradual return to the breedinggrounds. Peak counts include 150+ lingering offBerry Head on 31st July 2001, and 78 there on7th September 1998; 123 at Porthgwarra on10th August 1996 and 85 there on 21st July2001; and 85 off Portland Bill on 29th July 1998and up to 90 lingering offshore there in late July2001.

Relatively few are seen from the Isles ofScilly, where the peak annual total of 66 wasrecorded in 1999. However, it is notable thatsmall numbers are recorded sporadically in Julyand August associating with the Manx Shear-water colony on Annet. Very few seem to pene-trate far up the Bristol Channel, just 11 beingrecorded from Somerset up to 2003.



80 82 84 86 88 90 92 94 96 98 00 02

Fig. 3. Numbers of Balearic Shearwaters Puffinus mauretanicus reported in Britain & Ireland, 1980–2003.

4,000

3,500

3,000

2,500

2,000

1,500

1,000

500

0

90 92 94 96 98 00 02

Fig. 4. Distribution of Balearic Shearwaters Puffinus mauretanicus by regionin Britain & Ireland, 1990–2003.

100%

80%

60%

40%

20%

0%

SW England Wales Ireland SE England E England Scotland

WalesThe Welsh coast isthe second mostimportant region forBalearic Shearwatersin Britain & Ireland,accounting for anaverage of 13% (butup to 35%, in 1990)of the annual totalbetween 1990 and2003 (fig. 4). Thenumbers recordedbetween 1988 and2002 show a slightincrease (fig. 6), withsuccessive five-yearmeans of 107(1988–92), 150(1993–97) and 224(1998–2002) and arecord influx (of 773)in 2003.

The key site hastraditionally beenStrumble Head, inPembrokeshire (andPembrokeshire tendsto account foraround 80% of theWelsh annual total),but significantcounts have also beenmade farther north, from Bardsey (Caernarfon-shire) and Point Lynas (Anglesey). MostBalearic Shearwaters at Strumble Head occurbetween mid July and early November andusually involve birds associating with feedingmovements of Manx Shearwaters. There is ascattering of winter records, apparently relatedto displacement during strong southwest gales.

Prior to the major influx in 2003, the peakday-count was 36 off Strumble Head, on 2ndOctober 1999. During 2003, unprecedentednumbers lingered off the Glamorgan coastbetween Port Eynon Point and Rhossili, mainlybetween 18th August and 20th September,peaking at 250 on 3rd September. Significantcounts were also reported from Anglesey laterin the autumn, where there was a peak of 32 offPoint Lynas on 3rd October.

IrelandOn average, 7% of Balearic Shearwaters

recorded from 1990 to 2003 were in Irish waters(fig. 4), though Ireland’s share of the totalpeaked at 19% in 1990 (cf. Wales). Although theoverall Irish totals do not extend back beyond1990, there is no obvious trend in numbersthrough the period 1990–2003 (fig. 6), in con-trast to the situation in Wales and England.

The majority are seen between July andOctober, and small numbers occur betweenNovember and February. The pattern observedduring the peak year of 1990 was typical, therebeing a total of 149 recorded between 16th Juneand 28th September, of which 118 were seenfrom Cape Clear. Away from Cape Clear,Balearic Shearwaters are recorded regularlyfrom other headlands in southern Ireland,including Carnsore Point (Co. Wexford), GalleyHead (Co. Cork), Brandon Point (Co. Kerry)and Bridges of Ross (Co. Clare). Small numbersare also seen off Northern Ireland, particularlyin the North Channel.



80 82 84 86 88 90 92 94 96 98 00 02

Fig. 5. Numbers of Balearic Shearwaters Puffinus mauretanicus reported in southwest England, 1980–2003.

3,000

2,500

2,000

1,500

1,000

500

0

SW England Scilly Cornwall Devon Dorset

88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03

Fig. 6. Numbers of Balearic Shearwaters Puffinus mauretanicus reported in Wales and Ireland, 1988–2003.

800

700

600

500

400

300

200

100

0

Wales Ireland

Southeast EnglandOn average, around 3% of the annual totalbetween 1990 and 2003 was seen from the well-watched coastline of southeast England (fig. 4),the figures varying between a peak of 12% in2001 and <1% in several other years. Althoughthe numbers recorded are small, they haveclearly increased since the mid 1990s, both inthe region as a whole, and at Dungeness, whichis an important site in terms of consistency ofeffort (figs. 2 and 7). An average of nine peryear in 1980–89 increased to 32 per year in1990–99. In 2001, up to 418 were recorded;these are unprecedented numbers, illustrated bythe fact that, in Hampshire, Sussex and the Isleof Wight, more were recorded in 2001 than inall previous years combined. Records are spreadfairly evenly across the region, and show noobvious geographical pattern.

East EnglandThe long stretch of coast between Essex and

Northumberland wasresponsible for 6%on average of theannual British andIrish total between1990 and 2003 (fig.4), but made up 14%of that total in 1995.An average of 34 peryear in 1980–89doubled to 69 peryear in 1990–99 (fig.8). From 2000 to2003, the averagerose again to 91 peryear, and there was amoderate influx of101 in 2001 (cf.southeast England).In Suffolk, Norfolk,Cleveland andNo r t h u m b e r l a n d(four of the six coun-ties from which datawere received), thepeak years wereeither 2002 or 2003.

The majority havebeen seen fromNorfolk and York-shire, and surpris-ingly few off Essex

(nine up to 2003) and Suffolk (27 up to 2003).Nearly all records fall between June andOctober, peaking in August and September,together with a small number of winter records.The main site is Flamborough Head (East York-shire); a total of 722 Balearic Shearwaters wasrecorded there between 1976 and 2000,numbers peaking annually in August (44%) andSeptember (33%), but falling to <5% in theperiod from November to June.

Northwest EnglandOnly eleven were recorded in Cumbria andLancashire up to 2003, the majority betweenJuly and September.

ScotlandBalearic Shearwater is still a rare bird in Scot-land, which accounted for just 2% on average ofthe British & Irish annual total between 1990and 2002 (fig. 4). Although the numbersinvolved are small, they have increased since the



Fig. 7. Numbers of Balearic Shearwaters Puffinus mauretanicus reported in southeast England, 1980–2003.

450

400

350

300

250

200

150

100

50

0

Fig. 8. Numbers of Balearic Shearwaters Puffinus mauretanicus reported in east England, 1980–2003.

150

120

90

60

30

0

80 82 84 86 88 90 92 94 96 98 00 02

80 82 84 86 88 90 92 94 96 98 00 02

mid 1990s (fig. 9). Anaverage of aboutseven per year in1980–89 increased to25 per year in1990–99, and rose toa peak of 58 in 2003.Most are seenbetween August andOctober, with a fewsummer and winterrecords.

The majority areseen off southwestScotland, particularlyAyrshire and Argyll,but small numbersare reported regularlyoff the OuterHebrides and alsoFife Ness, on the eastcoast. The speciesseems reluctant towander far beyondthe northern tip ofmainland Scotlandand there are cur-rently no acceptedrecords from Shet-land.

Status elsewhere innorthwest Europe (north of 48ºN)Northwest FranceBalearic Shearwaters have been recorded regu-larly along the coast of northwest France sincethe beginning of seawatch surveys in the1960s. Along the northern coast of Brittany, inthe western part of the English Channel, birdsare recorded frequently between the end ofJune and early October, followed by a fewsightings of single birds or small partiesthrough to January. Large groups can beencountered feeding on shoaling fish in theGolfe de Saint Malo, between Baie de Saint-Brieuc and Baie du Mont-Saint-Michel andthe Chausey Islands. Fewer than 100 were seenat any one time during the 1970s, andnumbers rarely exceeded 300 in the 1980s.However, counts then increased rapidly to apeak of 2,150 in 1996 and 2,250 in 1997,before declining to a few hundred in the late1990s and early 2000s (e.g. only 130 counted

in 2001). Variation in numbers is partlyexplained by the fact that birds are movingover a large area and sometimes remain off-shore beyond sight of land; however, localobservers are confident that the increase in themid 1990s was genuine, as was the post-1997decrease (Yésou 2003).

The species is much scarcer in the easternhalf of the English Channel, where it is a scarcesummer and autumn migrant, there being, atbest, a few tens of individuals seen each year atany single locality. At Le Clipon, nearDunkerque, increased autumn seawatchingeffort has revealed no significant trend over theperiod 1987–2003, but has recorded an average0.14 to 0.25 birds per hour for the period July toOctober. The exception was in 2001, when thefrequency of sightings doubled to 0.42 birds perhour, after a total of 81 was recorded between19th July and 13th September (cf. southernEngland).



Fig. 9. Numbers of Balearic Shearwaters Puffinus mauretanicus reported in Scotland, 1980–2003.

60

50

40

30

20

10

080 82 84 86 88 90 92 94 96 98 00 02

Fig. 10. Numbers of Balearic Shearwaters Puffinus mauretanicus reported in The Netherlands, 1980–2003.

30

25

20

15

10

5

0

80 82 84 86 88 90 92 94 96 98 00 02

The NetherlandsIn The Netherlands, Balearic Shearwater hastraditionally been regarded as a scarce summerand autumn migrant. Prior to 1980 there werejust nine records and during 1980–89 anaverage of just over two per year. This rose to 16per year in 1990–99 and to 20 per year in2000–03. The peak annual total of 27 wasreported in both 1996 and 2001 (fig. 10). Thevast majority of records occur in July (33%),August (35%) and September (20%), smallernumbers in June and October and just one hasbeen seen outside these months, in December.

DenmarkBalearic Shearwater is a scarce summer andautumn migrant in Denmark; all but two recordsfall between July and October (and c. 70% in August and September) and the vastmajority come from the North Sea coast. Therewere just three records before 1988, nine between1988 and 1991, and then a more obvious increasein sightings from the mid 1990s (fig. 11).

SwedenAll records are from the southwest coast, andmost were seen during strong west or southwestwinds. Up to 2004, a total of 25 were recorded(fig. 11), the first as recently as 1977, but since1997, there has been a marked increase: a totalof 18 between 1997 and 2004, and peaks of fivein 1997 and six in 2003 (cf. Scotland, Denmarkand Norway). All birds were recorded between20th June and 7th October.

NorwayThe 17 Norwegian records fall between lateJune and early October, with the exception of

one on 9th May 1991; most are of single birdsfrom the southwest of the country. Seven werereported before 1991, and ten between 1997and 2004, including four in 2003 (fig. 11).

The southwest European perspective (south of 48ºN)Southwest France and the Bay of BiscayAccording to Mayaud (1936), Balearic Shear-water has long been known as a regular andcommon migrant along the French coastbetween Arcachon in southern Biscay andsouthern Brittany. It was apparently regular andfairly abundant in the late nineteenth century,most birds being recorded between June andSeptember–October, then becoming rare inwinter. The first organised census, whichincluded birds recorded at sea and from thecoast, took place in the early 1980s, and thisfound an estimated 8,000–10,000 individuals in1982–84 spending the summer months close tothe French coast of Biscay. The main concentra-tions occurred in two areas: Mor-Braz insouthern Brittany, and along the coast ofVendée (Hémery et al. 1986; Le Mao & Yésou1993).

At Mor-Braz, Balearic Shearwaters usuallyoccur well offshore and are difficult to survey.Nevertheless, between 1,600 and 4,000 wererecorded on several occasions between the1960s and 1980s. Subsequently, numbers appearto have declined and only a few hundreds havebeen counted since then (Yésou 2003),although there were up to 1,500 in late Sep-tember 2002 and 1,100 in early September 2006.Surveys are more easily carried out in Vendée,where the shearwaters often congregate in raftsclose to the coast at the end of the day. Between

1982 and 1984, over1,000 were countedregularly here fromJune onwards,numbers peaking at6,000–7,500 inJuly–August (fig. 12).Subsequent surveysat sea up to the mid1990s showed littlechange in relativeabundance. Since1999, regular countsof rafting birds haveresumed from thecoast (Yésou 2003),



80 82 84 86 88 90 92 94 96 98 00 02

Fig. 11. Numbers of Balearic Shearwaters Puffinus mauretanicus reported inScandinavia, 1980–2003.

10

8

6

4

2

0

Denmark Sweden Norway

and these reveal amarkedly differentsituation. BalearicShearwater nowtends to occur muchlater in the summer,peaking in lateAugust and Sep-tember, and its abun-dance shows markedinter-annual vari-ability (fig. 12). In2003, numbersreturned to the levelof the early 1980s; atleast 5,000 werecounted on ten dif-ferent eveningsbetween 20th August and 15th September, andestimates of 6,000–7,000 were made on 31stAugust and 1st September. Numbers peaked atapproximately 4,000 in both 1999 and 2005, butat only 1,500 in 2000 and just 450 in 2004.

Ship-based observations covering thewestern English Channel and eastern Bay ofBiscay have been made by the Biscay DolphinResearch Programme during year-roundmonthly ferry crossings from 1995 to 2001(Brereton et al. 2003; Hobbs et al. 2003). Duringthe survey period, only 57 Balearic Shearwaterswere reported along this route, about 95% ofthese being seen between June and Novemberand a peak occurring in October. Records werewell scattered, but there were slight concentra-tions off the Brest Peninsula and over the upperCap Breton Canyon off northern Spain (Hobbset al. 2003). However, few were seen in deepwater over 100 km from land. In contrast, thevast majority of the 3,000 Cory’s Calonectrisdiomedea and 6,000 Great Shearwaters P. gravisrecorded during the survey period were in thedeep waters of the Bay of Biscay, beyond theshelf edge (Brereton et al. 2003; Hobbs et al.2003). It appears that Balearic Shearwater isscarce in deep water.

SpainObservations of birds moving to and from theirmoulting grounds in the Bay of Biscay havebeen made from the Galician coast of northwestSpain since 1976 (Mouriño et al. 2003). Theseobservations reveal a pronounced passage to thenortheast between June and August and areturn movement to the southwest in Sep-

tember and October. The largest recordedmovement was of 2,085 birds heading north offFinisterre on 28th July 1985. The abundance ofsuitable prey in this region, linked to seasonalupwelling, also encourages large flocks (>150birds) to linger, particularly at the mouths ofthe Pontevedra and Vigo rias (Mouriño et al.2003). Few large flocks are seen betweenNovember and May, 84% of records occurringbetween June and September. The highestcounts of ‘non-migrating’ birds at most Gali-cian sites were made prior to the mid 1990s,possibly indicating a recent decline. The peakcount was of 1,395 birds at Pontevedra ria on27th August 1991.

PortugalLarge numbers of Balearic Shearwaters are reg-ularly seen moving along the Portuguese coast,migrating to and from the Bay of Biscay. Thehighest counts are typically in September, thepeak being 11,000 moving south off the Lisboncoast in just two hours on 29th September 1990(Paterson 1997). There is some evidence for adecline in numbers over the last decade; forexample, the peak count in the Lisbon area inrecent years was just 1,591, on 23rd September2000, whereas in the early 1990s counts ofseveral thousand were regular (Paterson 1997;Ruiz & Martí 2004; Poot 2005).

Recent studies have also shown that largenumbers of birds may linger off the Portuguesecoast for several days or longer. In August andSeptember 2002, a boat-based survey wascarried out over the inshore waters along thecoast between Figueira da Foz and Aveiro



Fig. 12. Numbers of Balearic Shearwaters Puffinus mauretanicus reported off thecoast of Vendée, western France, between May and October during 1982–84

and 1999–2005, showing the maximum count within each ten-day period.

8,000

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0

1982–1984 1999 2000 2003 2004 2005

M2 M3 Jn1 Jn2 Jn3 J1 J2 J3 A1 A2 A3 S1 S2 S3 O1

(Petronilho et al. 2004). Two coast-parallel tran-sects, about 1 km and 11 km offshore, were sur-veyed. Balearic Shearwaters were thecommonest species encountered, the averagebeing about 715 per trip during the five surveys.The peak count was 1,258, on 28th September(of which 93% were on the inshore transect).Birds were seen rafting in large flocks (100–200birds) as well as flying in different directionsand feeding, indicating that this may be a signif-icant staging area. Large numbers were also seenalong the Lisbon coast, between Guincho andCascais, in June 2004 (Poot 2005). Successivecounts on 2nd–4th June produced totals of1,294, 953 and 1,177 birds respectively. Ingeneral, about 60% of the shearwaters wererafting, the largest single flock comprising 900birds. Feeding flocks of up to 700 birds werealso seen, in association with large numbers ofNorthern Gannets Morus bassanus and otherseabirds.

DiscussionThe Balearic Shearwater has never been thesubject of a systematic survey in northwestEuropean waters, meaning that any analysis ofnumbers is reliant upon predominantly casualobservations. Taking that into account, and alsobearing in mind the potential biases outlinedearlier, we still believe that the dataset obtainedduring this study is remarkably robust. Forexample, in Britain & Ireland, there has been nosignificant temporal change in the proportionof Balearic Shearwaters reported from differentregions (fig. 4), suggesting that any observed

changes in numbers are not simply due to vari-ations in observer effort at a local or regionallevel. In addition, by normalising values for dif-ferent countries for which comprehensive datawere received, a remarkably consistent trendemerges across northwest Europe, a majority ofcountries showing a marked increase in BalearicShearwater numbers in the mid 1990s (see fig.13). We contend that the spatial and temporalconsistency of the observed increase since themid 1990s supports the hypothesis that thetrend is real and not simply an artefact ofobserver effort.

Distribution change in northwest EuropeanwatersData analysed during this study confirm that asignificant proportion of the Balearic Shear-water population disperses northwards beyondthe Bay of Biscay into northwest Europeancoastal waters in late summer and autumn, andthat the largest numbers are recorded betweenJune and October. The majority are seen alongthe coasts of northern France and southwestBritain, with decreasing numbers north tosouthern Scandinavia. Relatively few arerecorded throughout Atlantic waters during thewinter and spring, which indicates that bothbreeding and non-breeding birds return to theMediterranean at this time.

Although short-lived influxes of BalearicShearwaters into northwest European watershave been seen before during the past 50 years(see page 395), the data presented here suggestthat the species is now undergoing a more sus-

tained northwardshift in its post-breeding distribu-tion. Data fromalmost all the north-west European coun-tries investigatedshow a markedincrease in numbersfrom the mid 1990sonwards (fig. 13).Furthermore, thisincrease may beongoing, as 2003 (thelast year for whichcomprehensive datawere available) wasthe first year when allof the northwest



Fig. 13. This figure shows the increasing numbers of Balearic Shearwaters Puffinusmauretanicus being reported in northwest Europe between 1980 and 2003.

The numbers of birds have been normalised by dividing individual annual totals for each country by the average annual total of that country for this period.

Totals >1 are higher than the long-term average. Data for Denmark (De), Sweden (Sw) and Norway (No) have been summed to provide a figure for Scandinavia.

6

5

4

3

2

1

0

England Wales Scotland Netherlands De/Sw/No

80 82 84 86 88 90 92 94 96 98 00 02

no.b

irds

rep

orte

d (n

orm

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European countries represented on fig. 13 hadannual totals of more than 1.5 times the long-term average.

This overall upward trend is overlain bymarked inter-annual variability (e.g. fig. 3),while there is also distinct spatial variabilityduring influx years. For example, in 2001 recordnumbers were seen all along the south coast ofEngland eastwards to northern France and TheNetherlands, whereas in 2003 countries farthernorth (e.g. Wales, Scotland, Denmark, Swedenand Norway) experienced record numbers. Thispattern may represent progressive northwardsrange expansion.

Controls on distribution changesThe increase of Balearic Shearwaters in north-west European waters since the mid 1990s hascoincided with a decline in numbers recordedfurther south. For example, the main post-breeding concentrations off the French Biscaycoast have decreased dramatically over thisperiod, and there is some evidence that birdsare occurring later in the autumn and withgreater inter-annual variability (fig. 12).Numbers recorded from Atlantic Spain andPortugal also appear to have declined since themid 1990s, while population estimates in thebreeding and wintering ranges in the Mediter-ranean suggest that the species is in overall

long-term decline. The larger numbersobserved in northwest Europe may thus repre-sent greater dispersal within a declining popula-tion, and this raises the question of whether ‘atsea’ survival is a factor in the species’ apparentpopulation decline. Previous studies havetended to concentrate on factors affecting thespecies at, or adjacent to, the breeding coloniesto explain this decline (e.g. Aguilar 1999, Oro etal. 2004, Ruiz & Martí 2004). A detailed analysisof controls on the recent distribution change inAtlantic waters is currently in preparation, andwill focus on the importance of increased sea-surface temperatures and changing distributionof prey fish, and the resulting impact onBalearic Shearwater distribution.

Summary and conservation implicationsThe most recent estimates of population size forthe Balearic Shearwater are in the region of2,000–2,400 pairs, or 10,000 individuals whennon-breeding birds are taken into account(Rodriguez-Molina & McMinn-Grivé 2005).Although the data presented in this study arenot derived from systematic surveys, they nev-ertheless reveal that an increasingly significantproportion of the world population now regu-larly inhabits northwest European watersduring the late summer and autumn. In 2001,3,500 birds were reported from Britain &



162. Balearic Shearwater Puffinus mauretanicus, off Scilly, July 2005.

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Ireland alone, although this figure doubtlessinvolves significant duplication as birds are (i)often highly mobile and move between sites,and (ii) show an overall northward dispersalthroughout the autumn. For example, peakcounts in southern England during 2001 and2003 generally occurred in late July and earlyAugust, whereas farther north, e.g. in Wales,peak counts were typically from late August toearly October. Although duplication is clearlyan issue, it is also likely that many will havegone unrecorded at locations with littleobserver coverage.

Individual day-counts of 100–250 birdsfrom key sites in southwest Britain in the lastdecade confirm that an absolute minimum of1–2% of the global population of BalearicShearwaters is present during ‘influx’ years inthis region, and there is a possibility thatactual numbers may be an order of magnitudehigher. More recently, a count of 110 BalearicShearwaters moving west off Porthgwarra on29th–30th July 2006 indicates that significantnumbers (>1% of the world population) arecontinuing to penetrate into northeastAtlantic waters and this has obvious implica-tions for the species’ conservation status in theregion. Although numbers reported fromcountries north of 55°N are less significant(fig. 11), the trend in these areas is alsoupward, perhaps suggesting that they may also

hold important concentrations at some timein the future.

Farther south, large numbers still concen-trate sporadically in the traditional post-breeding quarters along the French Biscaycoast, a recent estimated peak of 6,500 birds in2003 (fig. 12) representing a staggering 65% ofthe estimated world population. In some waysit is unfortunate that Balearic Shearwaters aresuch highly gregarious birds, as their habit ofcongregating in relatively small areas makesthem potentially susceptible to threats such asoil spills and displacement by offshore devel-opment, e.g. windfarms. Improved under-standing of their current post-breedingdistribution is crucial if suitable ‘at sea’ conser-vation measures for the species are to be put inplace. International co-operation shouldimprove the acquisition of information aboutthis species but also the study of the param-eters which control its distr ibution andnumbers (Yésou 2006). Indeed, co-operationat international level is called for by the Con-vention on Migratory Species; since November2005 the Balearic Shearwater has been listedunder Annex I of this convention (UNEP/CMS/Resolution 8.29), which compels signa-tory parties to facilitate concerted actions forthe conservation of species listed under AnnexI. Consequently, it is essential that a Europe-wide monitoring scheme is implemented as



163. Balearic Shearwater Puffinus mauretanicus, off Scilly, May 2004.

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soon as possible to identify key sites and toinvestigate whether the observed distributionchanges are ongoing.

Acknowledgments

This study would not have been possible without the useof data collected by dedicated seabird observers acrossEurope, and also the network of local and nationalrecorders responsible for collating and publishing thesedata. We are grateful to them all, as they really are theunsung heroes of this study. Data from the network ofornithological societies in England were received fromNigel Hudson (Scilly), Ian Wilson (Cornwall), Michael Tyler(Devon), James Lidster (Dorset), Graham Sparshott, DavidHunnybun and Kris Gillam (Isle of Wight), Tim Hodge(Kent), Howard Vaughan (Essex), Moss Taylor (Norfolk),David Fairhurst (Suffolk), Geoff Dobbs, Russell Slack andAndrew Lassey (Yorkshire), Rob Little (Cleveland), IanFisher (Northumberland), Brian Gibbs (Somerset), SteveWhite (Lancashire) and Colin Raven (Cumbria). Specialthanks go to Martin Cade, David Walker and Steve Wingfor providing data from Portland Bill, Dungeness and CapeClear Bird Observatories, respectively. Data for othercountries in Britain & Ireland were received from StephenNewton (Ireland), Mike Betts (Scotland) and JonathanGreen (Wales). Counts from France were supplied byBenoit Paepegaey (Association ‘Le Clipon’), André Barzic,Gérard Besseau, Fabien Dortel and Alain Gentric (LPO-BirdLife France), Vincent Liéron and Justine Vidal (Réservenaturelle de la Baie de Saint-Brieuc), Gérard Debout andMatthieu Beaufils (Groupe Ornithologique Normand) andJean-Luc Dourin. Data from Denmark were derived fromhttp://www.netfugl.dk, those from The Netherlands byWillem Jan Hooijmans, Pieter Thomas and Jan Wierda,from Norway by Vegard Bunes and from Sweden byNiklas Holmström and Uno Unger. We apologise for anyinadvertent errors or omissions.

We would also like to thank George Bennett, HelenBooker, Ricard Gutiérrez, Niklas Holmström, Stan Howe,Simon Josey, Adrian Martin, Marc Moody, Martin Poot,Norman Ratcliffe and Ian Whitcomb for assisting with datacollection, analysis and discussion.

References

Aguilar, J. S. 1999. Species Action Plan for the BalearicShearwater Puffinus mauretanicus in Europe. BirdLifeInternational, European Commission, http://ec.europa.eu/environment/nature/directive/birdactionplan/16_actions_plan/10puffinus_mauretanicus.pdf

Arcos, J. M., & Oro, D. 2002. Significance of fisheriesdiscards for a threatened Mediterranean seabird, theBalearic Shearwater Puffinus mauretanicus. Mar. Ecol.Prog. Ser. 139: 209–220.

—, Massutí, E., Abelló, P., & Oro, D. 2000. Fish associatedwith floating drifting objects as a feeding resource forBalearic Shearwaters Puffinus mauretanicus during thebreeding season. Ornis Fennica 77: 177–182.

Bourne,W. R. P., Mackrill, E. J., Paterson,A. M., & Yésou, P.1988.The Yelkouan Shearwater Puffinus (puffinus?)yelkouan. Brit. Birds 81: 306–319.

Brereton,T. M.,Weir, C., Hobbs, M., & Williams,A. D. 2003.A low-cost, year-round seabird monitoring programmein the English Channel and Bay of Biscay: preliminaryresults 1995–2001. Ornis Hungarica 12–13; 105–113.

Genovart, M., Juste, J., & Oro, D. 2005.Two sibling speciessympatrically breeding: a new conservation concern forthe critically endangered Balearic Shearwater.Conservation Genetics 6: 601–606.

—, Oro, D., Juste, J., & Bertorelle, G. 2007.What geneticstell us about the conservation of the criticallyendangered Balearic Shearwater. Biol. Conserv. 137:283–293.

Gutiérrez, R. 2003.The Balearic Shearwater : apparentlyheading for extinction. Birding World 16: 260–263.

— 2004. Identification of Yelkouan, Balearic and ManxShearwaters. Birding World 17: 111–122.

— & Figuerola, J. 1995.Wintering distribution of theBalearic Shearwater off the northeastern coast of Spain.Ardeola 42: 161–166.

Hémery, G., Pasquet, É., & Yésou, P. 1986. Data banks andpopulation monitoring in France. In: Medmaravis &Monbailliu, X. (eds.), Mediterranean Marine Avifauna:population studies and conservation. NATO ASI seriesG12, Springer Verlag, Berlin, pp. 163–177.

Hobbs, M. 2003. Searching souls. Birdwatch 134: 27–30.—, Brereton,T.,Weir, C., & Williams,A. 2003. Baseline

monitoring data on Procellariformes (Shearwaters) inthe Bay of Biscay. Ornis Hungarica 12–13: 115–125.

Holmström, N. 2005. Smaller shearwaters – a truechallenge for every sea-watcher. Roadrunner 1/2005:30–35.

IUCN. 2006. IUCN Red List of Threatened Species.www.iucnredlist.org

Le Mao, P., & Yésou, P. 1993 The annual cycle of BalearicShearwaters and west Mediterranean Yellow-leggedGulls: some ecological considerations. In:Aguilar, J. S.,Monbailliu, X., & Paterson,A. M. (eds.), Status andConservation of Seabirds: 135–145. Soc. Esp. Orn.,Madrid.

Mayaud, N. 1936. Inventaire des Oiseaux de France. Blot,Paris.

Mayol-Serra, J., Aguilar, J. S., & Yésou, P. 2000.The BalearicShearwater Puffinus mauretanicus: status and threats. In:Yésou, P., & Sultana, J. (eds.), Monitoring and Conservationof Birds, Mammals and Sea Turtles in the Mediterraneanand Black Seas: 24–37. Envir. Prot. Dept, Malta.

Mouriño, J., Arcos, F., Salvadores, R., Sandoval, A., & Vidal, C.2003. Status of the Balearic Shearwater Puffinusmauretanicus on the Galician coast (NW IberianPeninsula). Scientia Marina 67 (Suppl. 2): 135–142.

Oro, D.,Aguilar, J. S., Igual, J. M., & Louazo, M. 2004.Modelling demography and extinction risk in theendangered Balearic Shearwater. Biol. Cons. 116: 93–102.

Paterson,A. M. 1997. Las Aves Marinas de España yPortugal. Lynx Edicions, Barcelona.

Petronilho, J. M. S.,Vingada, J.V., Ferreira, M., Paulino, N.A. C.,Eira, C., Costa, R.A., & Tenreiro, P. J. Q. 2004. Seabirdcensus along the Figueira da Foz-Aveiro coastline(Portugal) during August/September 2002. Airo 14:94–100.

Poot, M. 2005. Large numbers of staging BalearicShearwaters Puffinus mauretanicus along the Lisboncoast, Portugal, during the post-breeding period, June2004. Airo 15: 43–50.

Rodriguez-Molina,A., & McMinn-Grivé, M. 2005. Populationand Distribution of the Breeding Colonies of the BalearicShearwater Puffinus mauretanicus.Abstracts 2ndInternational Manx Shearwater workshop, Belfast.

Ruiz,A., & Martí, R. 2004. La Pardela Balear. SEO-Birdlifeand Consellaria de Medi Ambient del Gover de les IllesBalears, Madrid, Spain.

Sandoval, A. 2005. La Muda Visible de Rémiges de la PardelaBalear Puffinus mauretanicus en Galicia. Presentation tothe 5th Congress Grupo Ibérico de Aves Marinas(GIAM), Xixón, 4th–6th February 2005.

Sangster, G., Collinson, J. M., Helbig,A. J., Knox,A. G., &Parkin, D.T. 2002.The specific status of Balearic andYelkouan Shearwaters. Brit. Birds 95: 636–639.



Yésou, P. 1986. Balearic Shearwaters summering in westernFrance. In: Medmaravis & Monbailliu, X. (eds.),Mediterranean Marine Avifauna: population studies andconservation: 513–517. NATO ASI series, v.G12,Springer-Verlag, Berlin.

— 2003. Recent changes in the summer distribution of theBalearic Shearwater Puffinus mauretanicus off westernFrance. Scientia Marina 67 (Suppl. 2): 143–148.

–– 2006.The migration of seabirds and coastal bird species

outside the Mediterranean basin: co-operation isneeded. In:Aransay, N. (ed.), Proceedings of the FirstSymposium on the Mediterranean Action Plan for theConservation of Marine and Coastal Birds: 32–35.UNEP-MAP-RAC/SPA,Tunis.

—, Paterson,A. M., Mackrill, E. J., & Bourne,W. R. P. 1990.Plumage variation and identification of the ‘YelkouanShearwater’. Brit. Birds 83: 299–319.



Russell B. Wynn, National Oceanography Centre, European Way, Southampton, Hampshire SO14 3ZH; e-mail [email protected] Yésou, ONCFS, 53 rue Russeil, 44000 Nantes, France

Note: In order to improve the assessment of the numbers of Balearic Shearwaters visiting UK waters, researchers atthe National Oceanography Centre, Southampton, have recently teamed up with several UK-based conservationbodies to set up the SeaWatch SW Project. The aim is to provide a central recording base for the species in UKwaters, and to undertake round-the-clock, effort-based surveys from the southwest tip of the UK mainlandbetween July 15th and October 15th, over a period of several years. Full details on project background, latest results,and how to get involved can be found at http://www.seawatch-sw.org

Looking backOne hundred years ago:

‘ALFRED NEWTON. THE death of Professor Newton,which took place at Cambridge on the 7th of Junelast, creates a void in the ranks of British Ornitholo-gists which it will be impossible to fill.

‘He was one of the small band of enthusiasts whofounded the British Ornithologists’ Union, the estab-lishment of which has had such a sterling influenceon the study of Natural History in the British Islands.Respected and loved by his contemporaries whojoined him in this great achievement, revered andconsulted by the younger generation, he held aunique position among zoologists in this country andthere is no one who can exactly take his place.

‘The foundation of the British Ornithologists’Union was one of the most important events in thehistory of ornithology, and with the publication of itsquarterly journal, the “Ibis”, in 1859, commenced thatlong series of memoirs which have added so much toour knowledge of the Class Aves.

‘…the idea of the “Union” was started in Cam-bridge and Professor Newton was one of the primemovers in its foundation. It had been the custom, sosays the “preface” to Vol. I. of the “Ibis”, for a few gen-tlemen attached to the study of ornithology, most ofthem more or less intimately connected with the Uni-versity of Cambridge, to meet together, once a year, oroftener, to exhibit to one another the various objectsof interest which had occurred to them and to talkover both former and future plans of adding to theirknowledge of this branch of natural history. In 1857the gathering of ornithologists had been greater thanbefore; and it was proposed to publish a magazinedevoted solely to ornithology, and in the following

year the question was again to be considered. InNovember, 1858, when another meeting took place atCambridge, the publication of a quarterly journal wasagreed upon, and the British Ornithologists’ Unionwas founded, the number of members being limitedto twenty. Dr. P. L. Sclater, who was then Secretary tothe Zoological Society of London, was appointed thefirst editor.

‘Professor Newton took a keen interest in thesuccess of the “Ibis”, of which he edited the secondseries (1865–1870), being succeeded by Mr. Salvin.The reviews and criticisms which appeared in thesecond series were fine examples of what criticismshould be, and as a reviewer he stood unsurpassed.

‘In 1864 he wrote the “Aves” portion of the “Zoo-logical Record”, and continued the work till 1869.More scope was allowed in those days for criticalremarks on the various memoirs recorded, and hereagain Professor Newton was able to do muchadmirable work.

‘In 1866 he was appointed Professor of Zoologyand Comparative Anatomy in the University of Cam-bridge, and held the post for forty-one years. All thistime his influence on the study of zoology was verygreat, and numbers of ornithologists were helped andguided by him as to the particular line of study theyshould pursue.

‘He was one of the best type of English gentlemen,dignified in his manner and in his correspondence,but withal possessed of a kind and generous nature,which showed itself to young and old, whenever theopportunity occurred to do any one a good turn… R. BOWDLER SHARPE’ (Brit. Birds 1: 33–39, July 1907)

the changing status of balearic shearwater in northwest

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