photographic counts of Ortac and Les Etacs, Channel Islands in The Alderney Ornithological Group, P.O, Box 24, Alderney GY9 3AP, Channel

75 PhotogaphiccountsAlderney gannetries 75

The Alderney

Northern Gannetries

—

photographic

counts

of Ortac and

Les

_Etacs,

Channel

Islands

in 2005

Jeremy+G.

Sanders

1 &

Michael+P. Harris2

Sanders J.G. & Harris M.P. 2005. The Alderney Northern Gannetries —

photographiccountsof Ortac andLes _Etacs, Channel Islands in2005. Atlantic

Seabirds 7(2): 75-82. .Aerialsurveys ofNorthern Gannet Morus bassanuscolonies on

Ortacand Les Etacs, Channel Islands,in July 2005,found2547 and 4862Apparently OccupiedSitesrespectively. The totalpopulationincreasedatanaverage rateof3.3%_per

annum overthe last55 years. There_maynowonlybe limitedroomfor expansiononOrtac

where therateofincreasehasdeclinedsubstantiallyin recent years.

INTRODUCTION

1

TheAlderney Ornithological Group,P.O, Box24,AlderneyGY93AP, Channel

Islands;

2

Centre for

_Ecology

and

_Hydrology,

Hill of Brathens, Banchory, AB31

4BW, Scotland,UK.E-mail;jerry.sanders@cwgsy.net

The Channel Islands’ Northern Gannet Morus bassanus colonies are on the

islets of Ortac and LesEtacs, closeto

_Alderney.

In June

1940,

the entire human

population

of

_{Alderney, including}

a small

_{military garrison,}

was evacuated to

the UK. Prior to the

_evacuation,

_Major

J.A.A. Wallace

_MC,

who was

commanding

the

_garrison,

and _someof his

_{junior officers,}

visited Ortac to look

at a

Black-legged

Kittiwake Rissa

_tridactyla

_colony.

One of his subalterns

reported

in_greatexcitement of “a

_big

white bird likeanalbatross”. On

climbing

tothe _topof the rock he discoveredaNorthern Gannet

incubating

anegg. Local

people

assured him that itwas the first

_(Lockley

_{1948), i.e.,}

the first _{year the}

species

had bred. He also landedonLes Etacs severaltimes, but therewereno

Northern Gannets. The

_people

of

_Alderney

did not return until the warwas

over, five years

later,

hence the

origin

of Les Etacs

colony,

and the initial

growth

of the Ortac and Les Etacs colonieswerenot documented. However,in 1945 E.

_Quinain,

_an

_Alderney

fisherman

_returning

home after his enforced

absence,

reported

that the eastern side of Ortac was covered with Northern

Gannets and discovered another

_colony

onLes Etacs,

just

off thewesternend of

Alderney (Dobson

&

_Lockley

_1946).

_Here,

wereportoncountsderived froman

76 J.G. Sanders &.M.P,Harris Atlantic Seabirds₇₍₂₎

Les Etacs in 1979 (top) and 2005 (bottom). Les Etacs in 1979 _(boven) en in 2005

77 PhotogaphiccountsAlderney gannetries 77

METHODS

Both colonies_were

photographed

between 1800 and 1900 hrs BST on 12

_July

2005

_using

100 ASA colour film and 35 mm cameras fitted with 28-90 mm

lenses.

_Photographs

_were taken

_through

the windows of_a

_{single-engine,}

high-wing

aircraft

_flying

atabout 200 _m altitude. The weather_was fine and the

gannetries

were in sunshine. Additional

photographs

of Les Etacswere taken

from the

_adjacent

mainland of

_Alderney

on20

July 2005,

and of Ortac and Les

Etacs from _a boat_on 6

_August

2005. Counts for Ortac were made from the

aerial

_photographs

but 17% of the final total for Les Etacscame from the later

photographs.

Northern Gannetson Les Etacs are usedto

aircraft,

since 20-50 small

aircraft

_{using Alderney’s}

_{airfield pass} over

daily,

and

_non-breeding

or ‘club’

birds did not take off when the aerial

_photographs

were

being

taken. Fewer

aircraft pass over Ortac andsome, but not

all,

club birds took off. The

_August

boat

_trip

allowed the

_breeding

_areastobe delimited.

Three

_complete

counts weremade from 30x20cm colour

_prints

overlaid

with

_tracing

paper

(first count)

oracetatesheet

(second

and third

counts).

When

counting,

natural rock featureswere usedasreference divisions toavoid double

counting

on different

photographs.

The count unit used was the

Apparently

Occupied

Site

_(AOS)

definedasone or twoNorthern Gannets

_occupying

a

site,

irrespective

of whether

anynest materialwasvisible. Counts weremade

by

the

senior author

_using

a x8

magnifying glass,

each AOS

_{being spotted}

outasit was

counted.

Some

previous

counts have

_reported

on the numbers of club-birds

present. We didnot do this since itwas unclear how many had left duetothe

aircraft and because there_were

manybirds on the sea and on the

Renonquet

reef,

situated 1.5 km north-east of Ortac and 3.5 km north-west of Les Etacs.

Northern Gannets started

roosting

on

Renonquet

in 1999. The reef is

_low-lying,

and there hassofar beennoevidenceofNorthernGannets

_attempting

toneston

it.

RESULTS

Ortac Ortac is an isolated

_rock,

_{approximately}

100x70 m

rising

to 22 m in

height,

situated 4.5 km west of

_Alderney;

_{it has very}steepsides. In2005,there

were 1865 AOS

(range

of three counts

1754-1944)

ontheeastside and_top, and

682

_(567-784)

onthewest side,

giving

atotal of 2547

_(2321-2728)

AOS.

Les Etacs ThenameLes Etacs isno

longer

in

_everyday

use,

although

still used

on mapsand

documents, having

been

replaced by

thenamethe Garden Rocks.

78 J.G. Sanders &.M.P. Harris Atlantic Seabirds7(2)

andnames of the various rocks are

essentially

those of Hill

_(1993).

The

_largest

unit,

the Main Rockatthewesternend of the Main

_Group,

is

_{approximately}

120

m

long

x 70 m

wide,

and rises

steeply

from thesea to a

height

of 37m. The

north face of the Main Rock shelves atan

angle

sufficienttoenable Northern

Gannetsto nest onthegreater part of

_it,

and has the

_major

_part of the

_colony.

The south face of the Main Rock is

_sheer,

and birds nest

only

on outcrops.

Adjacent

to the northeastern end of the Main Rock are two rocks called here

North Rock 1

_(closest

to the Main

_Rock),

and North Rock 2

(which

liesto the

north of North Rock

_1).

All three unitsare

joined

atvery low tide. The East

Stacks

_comprise

_a unit which is about_onethird _as

_big

_as the Main

_Group,

and

consist oftwo

_stacks,

the

_highest

of which is 32m

high.

In2005,the Main Rock had 3479 AOS

(range 3327-3660),

North Rock I

had 423 AOS

_(including

an estimate of 100nests in hiddenareas; range

417-429),

North Rock 2 had 266 AOS

_(254-277),

and the East Stacks had 694 ASO

(646-739).

This

_gives

a total of 4862 AOS

_(4644-5105).

Previouscounts It was not until June 1938 that

_(two)

Northern Gannetswere

recorded

_flying

_past the

_Casquets

groupof rocks in summer

(Dobson

1952).

The

_single

nest with an egg on Ortac in 1940 was almost

_certainly

the first

breeding

attempt

(Dobson

1952),

at least in historic times.

_By

the time of the

next

checks,

in 1946, therewere c. 250

pairs

on Ortac and c. 200

pairs

atthe Table1. Counts

_of

NorthernGannets onOrtac, 1940-2005.

Tabel 1._TellingenvanJan-van-gentenopOrtac, 1940-2005.

Year Count

_Range

Source

1940 1 nest Dobson(1952)

1946 250

_pairs

Dobson(1952)

1948 >234nests Fisher & Vevers(1951)

1949 225

_pairs

200-250 Fisher& Vevers(1951)

1950 570

_pairs

Fisher& Vevers(1951)

1951 225

_pairs

K.LeCocq (inHill ₁₉₈₉₎

1952 450

_pairs

400-500 K. LeCocq (in Hill 1989)

1960 925 nests Crampetal.(1974); Anonymous (1961)

1969 1000 AON 800-1200 Crampetal.(1974)

Operation

Seafarer records

1979 1787 AOS 1719-1871 Hill ₍₁₉₈₉₎

1984 2062 AOS 1964-2142 Hill(1989)

1987 2211 AOS 2138-2284 Hill₍₁₉₈₉₎

1989 2106 AOS 1967-2194 Hill₍₁₉₈₉₎

1994 2098 AOS M.G.Hill_{(pers. comm.)}

1999 2500 AOS J.Hooper (inWanlessetal. 2005)

PhologaphiccountsAlderney gannetries 79 79

new

colony

onLes Etacs

_(Fisher

& Vevers

_1951).

Details ofcounts known to us are

given

in Tables 1 and 2. Most of thesecounts are documented

by

Hill

(1989).

The units used in these counts varied - _nests,

pairs,

Apparently

Occupied

Nests

_(AON)

and

_Apparently

_Occupied

Sites AOS - so for

conveniencewefollowthe

normally accepted

convention of

_assuming

that these

areall

equivalent

when

comparing

counts

(Wanless

etal.

_2005).

There issome

uncertainty regarding

the very

high

count from Les Etacs in 1969 since this is

approximately

double the counts of 1960 and 1973.

_{Long (1981) reported}

that

numbers atboth colonies showed “a

_steady

increase until about 1960 when

they

reached about 1000atboth

_sites,

since when the totals seemtohave remained

fairly

constant”. Wanless

₍₁₉₈₇₎

assigned

a count of 1120

site-holding

individuals and 71 club birds in the Main

_Colony

in 1969to W.A.

_Burridge,

and

Hill

₍₁₉₈₉₎

_presented

a map

showing

that the extent of the

_colony

increased

relatively

little between 1960 and 1974.

_Therefore,

it

appears

likely

that the

countof 2000nests in 1969 is erroneousand for

plotting population

trends

_(see

Figure

1)

a

figure

of 1000

_pairs

is used

_(Wanless

_1987).

Table2. Counts_ofNorthern GannetsonLes Etacs, 1940-2005. n.c. =notcounted. Tabel2. _TellingenvanJan-van-gentenopLesEtacs, 1940-2005. n.c.=niet_geteld.

Year

Total Main East

Source

colony

colony

stack

1940 0 0 0 Dobson ₍₁₉₅₂₎

1946 200nests 190 10 Dobson (1952)

1948 >200nests Fisher& Vevers(1951)

1949 418

_pairs

400 18 Fisher& Vevers(1951)

1950 615

pairs

600 15 Fisher& Vevers₍₁₉₅₁₎

1960 1010

pairs

1000 10 Crampet

al.(1974);

Unpublished

J. Fisher_papers,British Museum

1960 1062nests 1000 62 Anonymous (1961);

Unpublished

J.Fisherpapers, BritishMuseum

1969

_{[2000 nests]}

Crampetal.(1974)

1973 > 1003 AOS 1003 _n.c Hill ₍₁₉₈₉₎ 1974 1269 AOS 1019 c.50 Wanless₍₁₉₈₇₎ 1975 1627 AOS 1525 102 Wanless(1987) 1979 1978 AOS 1891 87 Hill (1989) 1984 2325 AOS 2207 118 Hill(1989) 1987 2536 AOS 2412 124 Hill ₍₁₉₈₉₎ 1989 2810 AOS 2655 155 Hill (1989)

1992 2746 AOS 2535 211 M.G.Hill

_(pers.

_comm.)

1994 3380 AOS 3008 372 M.G. Hill(pers. comm.)

1999 3450 AOS J._{Hooper (in}Wanlessetal.2005)

80 J.G. Sanders &.M.P.Harris Atlantic Seabirds7(2)

DISCUSSION

Theremusthave been massive

_immigration

into these two colonies

_during

and

immediately

after thewaryearstoallow the increase from 1 toc. 450nests over a

five-year period

andto 1185nests

by

1950. The increase has

_continued,

albeit

at a

slightly

reduced rate

(Figure

1).

Between 1950 and 2005, the rate of

increase of thetwo colonies combined has been

_remarkably

constantat_{3.3% per}

annum

(9

counts,r 2

=

_97%,

_P<

_0.001).

_However,the_rate of increase

onOrtac

between 1979 and 2005was

only

1.2% p.a.,

compared

with 3.3% onLes Etacs.

The literature

_comprises

many accounts of seabird colonies that

appeared

to

have been

_full,

but which have

_subsequently

increased. Dobson &

_Lockley

(1946) speculated

that the maximum

_capacities

of Ortac and Les Etacs _were500 and

_perhaps

1000

_{pairs respectively.}

In2005, therewere about five times as

many

pairs

asthese

predictions.

However,the much reducedrate of increase_on

Ortac does_{suggestthat space may be}

_becoming

limited.

Figure

1 Number of

Northern Gannetbreedingsites

_{(AON/AOS/nests/pairs)}

onOrtac

andLes Etacs, 1940-2005.

Figuur1.Aantal

_{broedplaatsen (AON/AOS/nest/paar)}

vanJan-van-gentenopOrtacen

PhotogaphiccountsAlderney gannetries

81 81

The Channel Island colonies were not counted

_during

the British and

Irish Northern _{Gannet survey in}

_2003/04,

and Wanlessetal.

₍₂₀₀₅₎

assumed a

figure

of 6500 AOS based on thepastrate of increase. This wouldnowappear

tohave been

slightly

too low but even so, thesetwo

_gannetries

still hold less

than 3% of the total British and Irish

_{population (c. 260,000}

_occupied

_AOS;

Mitchell etal

_2004).

_However, whereas _{the average} rate of increase of the

British and Irish

_population

_{since the last full survey had declined}to 1.2% p.a.,

that in the Channel Islands had remained

_high

at_{2.8% p.a.} Therate of increase

atthe

_large

French

_colony

onRouzic

₍₁₃₅

km from

Alderney)

has alsodeclined

in recent years

(Siorat

& Bentz

₂₀₀₄₎

so it will be

interesting

to see what

happens

tonumberson Ortac and Les Etacs in thenearfuture.

ACKNOWLEDGEMENTS

Weareindebted toRichard Herivel forpilotingthe aircraft for the aerialpart of thecensusand Mike

Hillfor encouragement andhelp.

Jan—van—gentenkolonies opAlderney,

inventarisatie van Ortac en LesEtacs,

Kanaaleilanden,in 2005

Eeninventarisatie vanuitde luchtvankolonies vanJan-van-gentMorus bassanus colonies opOrlac

enLes Etacs(Kanaaleilanden)in_juli2005,resulteerde in_{respectievelijk}2547en4862 schijnbaar

bezette_{plekken (Apparently Occupied}Sites).De totalepopulatienamdeafgelopen55jaartoe met

eenjaarlijks gemiddeldevan 3.3%. Mogelijkisruimtegebrekop Ortacnudebeperkendefactor

voor eenverderetoename.In deze kolonieisdegroeisnelheidde laatste_jarensterk_gedaald.

REFERENCES

Anonymous. 1961. Reportand Transactions for theyear 1960 ofLaSociete Guernesiaise. Vol.

XVII, Part 1, Ornithological Report, Guernsey.

Cramp S.,Bourne W.R.P. & Saunders D. 1974, The seabirds of Britainand Ireland, Collins,

London.

Dobson R. 1952. The birds of the Channel Islands. Staples Press,London.

Dobson R. &Lockley R.M. 1946. Gannetsbreedingin the Channel Islands. Brit. Birds. 39: 309-321.

FisherJ. & VeversH.G. 1951. The_{present population}of the North Atlantic Gannet(Sula bassana).

Proc, Int. Om.Congress 10:463-467.

Hill M.G. 1989. TheAlderneygannetries-photographiccountsof Ortac and LesEtacs,Channel

Islands,1979-1989. Seabird 12:45-52.

Hill M.G. 1993. Seabirds of the Bailiwick ofGuernsey. LaSocieteGuernesiaise,Guernsey.

LockleyR.M. 1948. Firstbreedingof Gannetsin the Channel Islands, Brit. Birds_41:216.

LongR 1981. Review of birds in the Channel Islands,1951-1980. British Birds 74: 327-344. MitchellP.I.,NewtonS., Ratcliffe N. & Dunn T. 2004. Seabirdpopulationsof Britain and Ireland:

82 J.G.Sanders &.M.P.Harris Atlantic Seabirds7(2)

Siorat F. & Bentz G. 2004. Reserve naturelle desSept-Iles, Rapportd’activite2004. Liguepourla ProrectiondesOiseaux,Rochefort.

Wattless S. 1987. A_surveyof the numbers and_breedingdistribution of the North Atlantic Gannet andassessment ofchangessince 1969/70. NatureConservancy Council, Peterborough.

WanlessS., MurrayS. & HarrisM.P. 2005. Thestatusof the Northern Gannet in Britain & Ireland in2003/04.Brit. Birds 98; 280-294.