THE MACHAIR OF THE OUTER HEBRIDES
by Rob Fuller and Nigel Buxton
Recently there has been increasing awareness that the Outer Hebrides of Scotland support really outstanding populations of breeding waders. The great majority of the birds breed along the western seaboard of the southern isles: North Uist, Benbecula and South gist. We thought that brief descriptions of the habitats of this coastal strip would be useful to those readers who are unfamiliar with the islands, particularly as the Wader Study Group has recently carried out a survey of these breeding populations (see the accompanying article$•.
The most characteristic feature of the area is the "machair" which forms a flat sandy plain running virtually the entire length of the west coast of the three islands. Machair is effectively a type of sand dune system in which the area of flat plain is relatively large compared with the area of undulating dunes. The sand itself is calcareous shell sand. Figure 1 shc•s clearly hc• the machair and dunes in the southern isles are confined to the western fringe. These islands support by far the most extensive machair formations in Britain.
SoundHarrisof WEST EAST stable machair blackland grass marshes mobile cultivated machair moor- dunes machair loch land
S• • I I I I I I I I I i I I I ,
Figure 2 A diagran•natic cross-section of a typical sequence of machair and associated habitats in the Southern Isles of the OuterYHebrides (Reproduced from BTO News; artwork by Elizabeth Murray).
I Machairsand dunesand
I•,1Land150m over
0 10 I I km
Figure 1 The approximate distribution of machair and sand dunes *in the Uists and Benbecula (Reproduced from BTO News.; artwork by El. izabeth Murray). Sound of Eriskay
Associated with the dune machair are several other distinctive habitats. A simplified cross-section of a typical sequenceof these west coast land types is presented in Figure 2. Along muchof the •oast a strip of mobile dunes fringes the machair plain. In manyplaces these dunes are .extremely narrc• or even absent; elsewhere they form substantial systemsextending up to one kilometre from the Atlantic-facing beach. Sometimesthe dunes give way to the machair plain through an intermediate zone of semi-mobile dunes or gently undulating dune grassland. The machairplain itself is widely cultivated, sometimeson a strip rotation resulting in a patchworkof cultivation stages. The crops include oats, rye and barley. The land is often left fallc• for several years. Wherethe cultivation is not of the traditional strip type, the land is farmed in larger more uniform blocks, sometimesincluding silage. The mach&irplain frequently carries dampslacks, someof which stand under water in the winter. Particularly on the inland edge of the machairthere maybe areas of dampgrassland and rich fen which are labelled as "machair marshes"in Figure 2. Highly productiveshallc• lakes - machairlochs - occur on the inland marginof the machair, especially in South gist. Mostof the landin the gistsand Benbecula is unproductive moorland and blanket bog overlying gneiss. Between the machair and these extensive peatlands there is a transition zone termed "blackland". This land was once peatland but has been greatly modified by humanactivity, especially by peat removal and the application of middenrefuse. This, together with some"sweetening" of the land by calcareous sandhas created rocky grasslandsoften with permanentand seasonalmarshes. Some of the blackland is managedas in-bye land for wintering stock. Frequently at the transition from machair to blackland there are traditional hay meadows.
Different communities of breeding waders are associated with each of the land types described above. Oystercatcher Haematopusostralequs, Lapwing Vanellus vanellus, Redshank Trin•a totanus,Ringed Plover Charadrius hiaticula, Dunlin Calidris alpina and Snipe Gallinago gallinago are the characteristic species. The data collected by the Wader Study Group and the Nature ConservancyCouncil will be used to assess the population sizes, densities and patterns of habitat distribution.
Rob Fuller, BTO, Beech Grove, Tring, Herts HP23 5NR, gK. Nigel Buxton,4 SandStreet, Coulreõrein, Stornoway,Isle of Lewis, Outer Hebrides, U.K. lO
Plate 1. Loch tiallan, As•ernish Coast, South Uist. Vie• loo•ing eastwards sho•ing dry. •achair (•ith rabbit burrows) in the œoreõround• •et •achair and t:en adjacent to a eutrophœc •achair loch½ and cattle õra•inõ on blackland beyond the loch. •he bac•õround hills are •oorland.
...... "• '?';"½:'":•:""*'}'! ""•'"'•' ...... :::"" : " ?? :•::-*:i• •.•.•:•?.•:•:.:.•:•s::•:•/•,;.•,*.•`:•::`5•:•:•?<*`•:,.a.<•:•.`.•`,•`:•-.-.:•.,..-,:':.:t...,-': ?::'•.- ...... •;.;.;'"'•:'•:•.-::•....•c•..•-.•:-x•.•, .. . :; • "-•.....*x-,",:-:'-:-'.'.'?'---':•__•-'.-...•'•.... -•--:.: ...... ,,•.•. • .f/!:?.i.:•-':• . .,::....•'."..... :.. •':; ...... -.:... ' '...... ':%•:--;;::':, "•"----;?-'"•?•L..' ' -.•4.,....•.• .:,'x"" :..-?-• ...... *'"•.•'-:•..... ' --•.•.-.- ; ..,,...... -.,•,•:..•....,..:,. • .•.•"*,•.-•,. • --•;'•"•::•,..,.•:•...... ,...... -:...-'•:./•.•.•. ,.,,•!,•}$<,,?.,•-•%•..**•:-:• ..'•:•½. ,"• ..:..* .,.:-,-:-:•. •: . --' '.•"'; .:•...... •."-'.':.!;'..•:..::, **..-..,,r.• •.,•'"'"' ..-..:?S<,.•:.. •...... • :,,,...:-:--":•.•.'•'•-.•.•'. .:.:...•....,:::.e.-•.:.....-..;..o:.: c;: - r:.•,*:.,•:--.... .-'.....•'..r•..:;:- • ..::o,•--'.':..;--..,:•.•..•..•.;s?::•..s..-• : ."•'-...... •:•,.: •.,.,:: •.•;• ..f.•.•'..:•,..-:' :,:....:...•...... ?. .:,..,"-•' •,:•o:•• ...... z:•,,...* .-• ....•-; •..' .• .:a.';..z;..z.::.:...-.•:.::: .{'•:-..:.½.* .'.• II•t•":""•'•-....;?'•:•'---.•..:• ' ....-'•'•'•*.:;.:;,• '•- k.. .:.'-:;;•.• 'e;'•,-½-"•-::..**.•;? ...... x-:.,•,--•:;,.,.;:.!!*.: "..½'.''-.'5• ' .a:-'x'.•c.:',':.•'½a½-•..•,;..•}.-- .....::-:.!:---'-.-•* '•'?.:.•;--;:S•'•.!.-•;-':• .... "•,.,::-.' ,/,•, :.'½;•'.• .. '=':F; a• -:•:¾ ...
,, • ,,,,., •. ,,,,•:,*'"-,•.,,,•,, ..... •a, .'x.-•.--,.:...:..:..::...... :
.<. •.:.•.'•h .• ß....,... ,,,. "• ß< ,• .• • * •, ,, ,f•,,,'• .. • Plate 2. Fencing on dry machair, North Uist. Much of the level land visible in this photograph is cultivated at least periodically. ll
..
;;;•:•.•::•.-,4.::- ' ...... -...... -.'•, ,l•. .... ::::.,ß'•e. ;.'.:.•.••*.;, .'. :•-•::.-.-.,•%'4½* ,,.'•7-...... • .•:..,...:.:•;•...--...... -..:'"•,$:•":'-:::'""•' .:... ß...... •"'"'" •:>•'-.,•,•' '.... ,.',---::' .:•...:;•-- •..:-,,,½.S,•-:;.-'•.(t•'•' •:'•,F"-";"•:.'.'..':...... ::... •:'.• ,.. ,'.::,. .... "'•"x'..:. ß .... . -**._ß' '-'-' •::".• :,•-' **'::-".-:*::.:...... ----•-..,E.,• ',/•.• ".• -,•--.. -.;-.-:...... ,r/:-v:':•., '.... '•.•- . .,,-'":..- -- :'•,,,'... *"'" -•.-':,:•[.-..,•.• '• '"'t:.-*-;;:.-•,.::\• -"-:-. :-:'.." _•.- 'r. ,'"-' ..; .....,-. :•...... '/.,'•.'.'""' "' :":',:.•": '"'...... * '•-'•- .,; ' -," :'.; ': '-'•-" ' :" '- ...... -"•.. •;.•'*.":" '" -.... '•.;..,..'"' '-::.' ' '.,•ii•.' ' ' •:..:.... ._.'•½•½::"'--. .... -''* '•: •"•. -•'- ' '"':" --. •-.."-*...... :-. '•..'"' ,....•:,;.... .;.!%:.'-...... ß...... ;;.;.,;:"7:•;-"":..•...... '..'.. '.:...-' './r,•-' .... .:':..:. '. ß I½' :•. '.. ß .... .*..•;•--•-:-..;'...•:•-.½."•, ...... •;.-.'-•, ..;•- -;.• ",...,•½; .'L::.-•' --.*::.:.'..•'• .•.¾':;•; ; -..•.-, . .. '.• *• .p..... * ß ..... ,-.-:...... •"; •':....•.'--" ...:...... •...... ;...*". "::•'.-',•'-"•:<'",.•,,.,S•!;;.;'•--*...... '..•-:"•. . . .. - ...... :'•:.•-'-•..,S:::.,i•'"•"•.•--•-"•'• ... ß , ...... ;:.$'-,.':;'--.,,'. -'-.,.--:-. ,"-.:;* :.<.":.." . ..."• ... ..•.....:..• ...... ** ...... •,* •,,.,,, •.•- .•..;, .... •,, ,,.-•••:..-•-*-•.•••-.--- ...•½..-••••.•_•?,, .•• •;:: ..... ,•..:•:-:.- -:•--.•,••••• :.---•,:•.; ....,..'<':"*'•-:.::•:...:.:.,.::.-:,:::.::....::•;•,...;, .,:..-..?:•,,.,....-,• -,,•;.,.:::;;-:.•,..-:,;•-::,•:•,.:.:•.:-.•:.,•: .....,.•--,•::.-.•....,•,•....:. :;..•:•....•..-•• -,•,,...:•:.•...- ,...,,•...,, ..-, ?•...-; ;-:-;-..*'•-::'"'--; .•-•;... ß ;. ;.-,:'" '"••*'x,-'• '* ---'"••*'••••:•'-•':•- ' •..-::;..":',i..:'...?: '.•i•,•.;• ..... "-,;;•----*':'-"•; i•'"""'*•'•*•,-:. "::• '••-", ,..:•.*...*•'"':••.?.•"-..'i;---,•;: ?;';...:..:,:•:".,:-:--:-""•:•... '•'•,::• • '., .:i;•..-'--*--•;-•::••••-•.-'•:•:;..--. "•'•,,- <•':;:-•*•i--•:';;•'-'••:'•.,'::,.•"-'••,::•;•-":--'<.c:;:v"-:-** ...'•.'""•-'"'-..:-...!....;.'.":..--*•.•"------'-"-•-•.,•:-:-.;.?•'i.'• ; -:'...•. .' .-...•'•...... ?%:::;...... -- ":"----"'"•. .:.:--.:...-.--'-"-'"•-•..•':...... • '•'"'-?..' .. :'-'....•__•...... *..--?-'-'.• L•.'..::c.._-. •:-"'"'•""'"•'"•" .; •.•'•"'•,•---••'• -•...... "-•-' --:-½-'* ...'•:x'•":.:':.' ...... •;'•...... •,.-•":'•--•-:.:.-:;..*.-o,•:.• .....•.i.. •:;.:... '.•..•...... ^-.?.• •., ,.,,2'"•---•-.•..• •.:•.*:-'•..• ::: :%'.:.;'::...... ß. .•-. '- ..•.:-:•. ..-.:... . --:::: - .. •. .: .-•-.s,•.•..•---•-,,.-..--•:--:•*:.-.-•._-....•.-•- '•.'"•-•:i:,•- ' .-...... :.,::-•- .... ---.*;.-;---..•.:":::;--.;'-'?':•: .4 • ...... '•-{-'-•.•.---• ...... ,,, •--'•:'•"•%:?'"•'•'•'••'•••'•'••":o'::•..•;...:• ..•-...:.:-•'• :.;•:::-:'. -•- '-,½..•;•-*:-•--:- -... ,,,...... -c.-::.:%•.:...,'--...... •.-:./,•-:-:..:'•? ,• ...... •.:. •½.'..-'•-:*'-:. ....•.----.-:-•-•%...;-•:•:•:-•-•- ..:...:.---:•-:•-.,•_ - :----:½.-...-•:.:•::¾.....-.-•- -•?.:•.- ;,.-•. --.*:'--.----:-.;...•:.--•.- --•-%:;-•..•..,i,.•.•: '-• •i:.:-'/'-'•s•....,<--/•.-.::---o..:.:.:'--•-/•%.-•...... -:.;---•-•---- • % .....:.... . •...-..:½:'S%..:::,.:, ' •.:*-•...:...... •.•...•--•-•o•--...,;½,!•:;-.?:%:?.•'%.•-'•,.-..:...... •..c*•i•.•.:•--•-•-•: .... :,•.•::.:.-/ :'-•" ' ..." .•:•.•:-;•-C.•'•..:.,•.*.o..*-.:' '.2'•-..s...•...:';.f .....'" ;•.•.*'•:•-• ..-.-':•:;.?- '•?.-:.::.**:'...,. ' -'.-'; ' .. •..½..:.,;.•l•.•--•'",...gi•.:' ' '.'• ::''.';• ::.?•ß -:•..:-".•:?•'••:'.'> 'ø->".'*' :-:•-:•.:::o..•.' '" ':.... T.:•*..: '"-;--.. :•v..'':.' ....ß , ß ":•"'.:•:•...... :-'•:-½.. ß-:-x ,.- ...... • ...,½'*--½;:•...•....,. •.•...... '...... •.,..:.,, ..:'-GS...: a.:•...... ,:...... •-*•?...... '...... •----'*..:•.•.' .! ,?,.** ',,•.½...:...... :*- .';:::,*•-"'...... ,.;,-...../;•-•--;•..•---..•%,. :?:-; ';•. -- ....-:..-'.::'.:-.... ':::•.•'..•.'-•...... -:.:.•:*.:...... •...... •.-.'.-':• ..--:,....'• ...... ',•...,.• Z:;:•...... -.:*--..- ...... ; ' •.:•...•,,•.•' ."-....•...... -.',, • :.-.-•'.*..,:.•'-,e:, -•?C;.::..?? ...,r-;-.S-'"'..:;..•'-,';:X•;' '•'-"ß..,-? ;'.' .¾.;,':"i'..:..:::::.. '•";-.:?-;:-.':•,:• "•-:'-*":.:•..'.;;::.'"" 2, ' ...... -.-.,.,:-,,4,,•:.•...... -;•.,•.•---.: ...... ;--..?.-.....•,:q... ?..:,;..,:::..•.:-...,,.•,:•..-,..-,.. • ...... ,,, , ' . ...,... .;:...- - ß' ' * .• ...:-:.i'**;.' -•'•1"•,-.'"-••.•.-,.-;"."*' - .-;.-•... :...... •½::-%.:.-•--.- .. ;•;'*' '. ' .' *• **'**'.:';'•:•' ':: •.,.,,• •. -, ,,,.•-•':':;'":<- I•,il•.:....•::. '• •-- -, .:...*.'•' o' '..•."-:t:'.:.:<•."•:. '" .:. '*,... '*'•' •':' ß....• '- ...,• ,.• ...... ----;-L- .-'- --:'•.-..-:. -•'.:: '; --4.: --....•:. :-'.•: .;..-::-:-: '":...... :- ?•:•,;.;-•...... -- : ' • ß ;...... '- ": ...... -,,..:ß ....' , •'.:::.-¾"' ...-:%.::.;-::.--,•...'i:-'<.- '-'• • .• •.:-'•..•:...'.',..':.*.;.-.-:':'.-:-;:";';•,'.',:.::..?;%.?-';.;'::?*' ' ..:' .-'" .•';-;:.;.:-:' • ' .:- . *.-•-'•..-:',..'.;,,*'•' '":*;....z.... '.'-'""• .%• '."'.;•:-'•-"•i•.- •..':,' :: .,ir,•,a•L.. ..•':.L.• ::.'•....•..:..-:-':•':•':;;.: •:'•:-•ß . '?:.:.'.**i • ".• >:o$::i•..•:;•.;,4.. ' ß'ß .• :. -•*,•R. - -'-:"-?':': *: ' •".,,,• ' "•...•,,.;.•..•• ' • '.'•..- ß•ß ...... -,:s---..,..• ...... • .'•..•.::::..: ' ...... •.•.•. ... --...... ,...... - ...... -'.,%....:•...-..-"'• ..,•,% .... -' ...... ' ::. -'-.'. . • .• ½..'ß2•-.-...... -• • ß.. ,..' ..•!'..-...... - :-...... ::-•- -•. •.:.:-•*....:...:-•::•..' • "-:'"'•.,...... - -.','* . e'.,,,,*•.• • . ,•'. "-' :•. - • ...... -.-;. ...• '...... -- -; ...... •<-.... /'-'...... - '%-."..:...... ::':":';.•-•:'•" ...... --'"•;'•,..,,:..."•' ...... :, .;:--;.'"...-.-.•:'•;-::•:.•.,;, : ß .....• ...... '-•-:; ' '•.:.:'•,• :; ,.. • 7.:•:-?.... 'L:.-.::/;'•!"•:--*:'.",, .-. .¾...... :...... "
•...... ,::..•..;•.•$ß*.... *• ,.,.:.:***:•...•*:.,::,% .':::':•..- ',:.•' •..' '-.** ,..' ..... •_.•....:..:...... :• :',;:'"".i'•:;...:•-.-;..,,.... ,.;;•"'•'---•'"•-•••-••-•••••_ ...... '. *'-'._.•/X-•!!.,:-:" .**-',a.*Zi :,-::--:--.-,•"..,*...... -...... =-**-:.:.:...... ,;:.•..'a.• ...... ---.•,.,..... -.'::.' "•,,-:.•",*:::'•.::•:•'• ,..*-•...-:-'•.;• ..•;.?:.-..'?'. ,....•....':,g?d?...... •.'.•.•..•/• ,....,. Plate 3. An extensive area of machair cultivation on •orth Uist.
. .- , •.•.•:• •_• ..•"• .-7.. ;;::..•....::½.. . .;-•- '-•*-"•-..•--•-.:•::-:-'-•:•'e •:•*•'c•'•.:.::,-::,...... • ' ::•.;•.: •:•;,':•*c•': ...... ' ".•.•'•. •:C•..' .':"-•..... * :%" -:. '":'::2":•:'•' *" ':'"'?'•" •;' ':" ....--'*;;•-:s•"'*".-•...' .... ?' ' " . .. .•...
ß•C*:.".:? -,'.' ..:.;...... :,......
.• . •", .
. .':'-':•:.....; .::.:ß . :-:::¾:.'.:':"•¾:.-::::---.::::.g...... :•.•.:• ..• ..
..•..,'•• ...... •:;...... •.• ...... • , ::: .-.::•;•:'-• ;-•.--•...... :•.-•:.•,:?-•. . •.•- ß ...... ß •. ,•-.,.:.:,.;- •: '•...... ,:,-* ,--"'..:: -- -•.,--',Z•. ::.... . -.. ß..... • ...' ..... '•. .:.':--.:.%*'• •--.."...... :½...... •:.- ...... ::." ...,...... ß•½•':•.::7!"• ...... ,.. "•. .,-'•...' -•..•.•.--*.' ..... ¾.;...... --,• -%'--:...... '•-;•. • ,,.-:---,--•:•½-:...r:'..' ,. •. • ...... • ,. '•-' ß/. •-•-----......
• •'.• ' .-:•.....'";- ,. . ß ß .•'.;'. •. •.• - • .. •. ½ . .. :-"...,
_ Plate 4. Cultivated machair on •orth Uist. •ote the strip of fallow machair to the left of the •1ough. High densities of breeding Ringed Plovers occur in many such places on the Uists. 12
.. . :.•'it:,..:• "•
Plate 5. Dampmachair with silted drainage ditch of the type likely to be cleared, Baleshare,North Uisto
•-...... •-•;..,;.t:.....;•...... :..•.:.•.--:•Z?::..?;•-•.• •..-.:-:-•.• • :.•'• ...... •.•½.•..•,....•.:.•.•..•....•...•.•.-•.....•.-••..••:•.•••.•.•••.•.:.•...... ;..... •;;,•.•-;.•,:.'•¾:•
:ß ...... •_._.•.•.•••.•.••••.•••::•;::•; ,:•:,:•:..•,:.:,•..• ,,•.•.;:•.:• ,•?:;...... ½•....• ::?:....•;•.,.•:-•.- -•.•,•/•':::..• - . -,...... :.;;;??.•;,..::. ¾:.:'.:...... -: ... • ...... ,....Z.'... • "•,'½ ' ' ' ' ' .:-.F.-::- :-•"•'• ':• ':"-'::":½•:'* % .- '-'. .'•'• •' • . ..:., ...... ::•.½--,, ,.'-•;'"'"'"' 7'• :';•'•...•7...... '• "' .'.-;i'•' . -- . -- • ..::• ,½.. '?';•'•,.?...... ',•"•. .r'"' ...... •.7'.•: ½¾..:. ' -'-.' - .•... :. ?"'• •.•..*.••:..' •. ' •'•,k;•:,-?...; '" % .L. •,.• '• •' ..
..
•,. ..•½..
.
•* '½• '" Plate 6. Grazedsaltmarsh on Baleshare,North Uist. There are high densities of breedingLapwings, Redsha•s and Dunlins on this site. 13
Plate 7. Fen fringing eutrophic Loch Hallan, South Uist, a typical area for RedshankM and Snipe.
Plate 8. Blackland on Baleshare, North Uist, showing numerous rocky outcrops and small marshes. Snipe, Redshanks, •apwings and Oystercatchers are characteristic breeding waders of this habitat.