Nest-Site Selection by Roseate Terns Breeding on Arlde Island,
Seychelles
JAlME A. RAMOS
lnWc•.uo Politknko de B~an('.a . EKob Supe-rior ~riria. Camf)\n de Santa Apol6nia.
:.SOI-8!1"1 8t';lSPJt('li, P<'lrtug~
bttentcl: jramos@i pb.pt
Ab!ttrut. -Nf'_~ , -s;,e $tlecck),l b)' tf01Jieal Roseate Tetm <St..,, dftutallil) "'a" e~.mlned on .-\rkle bla.nd. St)'-c hcllt'$. (;,;m tin~· \'•ri:1bln rt'(k«"ti ng ('C.)n(C"IIfmcfll u( the; rlt'&l -tilt', ~hdte r, \qCI<ldvn CCI\'\"f'aud h tii'A ~IIJ< nett
cktuit)' ~ · ere .n~ur~ ror nesHii('S nod r.mdom poin~J. Sfo.a.W>nal \".U'i:u:ion In dte initiation or nrsu with O\'erha.nr
;ttld ll ~t•J f'l nfl t•C"I)()I" (.Ill h ~tC"hiug lU((~ ~ oiS .u1d 3<1uh inlr"A ~J IC'<il'k :.gg~lv•l l ~rclll (.hkb "Vit: :t~ exJ~fni n C(I . Rt,.
~te T<rnuel«ttd ndl-lih($dOs.tt to taller vtnbl
ol!;«ts.
and whh a higher percentage of roe b. I • or bra.n<hcsM"rh.;'tngillg IlK" n e:~otth-;w occurred :u •andllm pulnu. N~t--4lt~ ifl ,.,uaJI eo l oni,~difCe • ·ed il\\ll'e from the 3\·.-nable::
hllblt.n th:an did tho~ lu the mal11 <o l o n ~. Ncstl.nK d~:n~ily W".ts ~illw·l y tor r d lt~ "ith Llk amount of rock 00\'t'r
On A•'idc and od1(>r c.olonln. l11 dW! u·oplu Row>.ue Tt'l'll.5 bn!td at h• gl~ot>t ' der~cl eJ than d~ r lemper:ue COllllleJ"'
fMtU .•nd .tp:•clng lktW«U n~ I Khbo n m:.y ~ 11 main f..ctor I" th~ \Ck t llon of neM.Wtc=,, op«l:lll)•for bltd• J\oth •g
;U du: 1)('11.1 I)( du: tue«d•••g k ~W• l. N~~ite- dl:lr.u ! tt'fi:l.tl(~ nvuLblt ~)' '(lt t • ~n~ lt:lod nt) inU1.1e•u:e ( Ill h ~1rhl • •s ,., ....
u·~. U U\> •r~·~:r,thc J>toportion ofcltk ~ th.u cllC'd f••ottt.lduh pt'(kll\~ ""'~• .~oi sn inc. •11 dy &owe• ln ut'1olt 'loith ~cth.u • JCt ,
C'A.tm:ell.lrntru i.s :1 mam f:~o~' t(n vr R~t t: T<nt n(' ~lrtJte .)('h:c:tlun tlnV1.1gl•vm h., l).i('ediug r.mgr, in IM.Itlt t•l:Jpi.,..,d
n.nd u :mpc~t(' atcat.. bot tlk r-acton ~l«lintt for conct:.llmt'rll \C'Cnt lO v.ll'y i11n011ft'l colonial. On Ari« C~JtKC': ll ·
111(111 :.pp t~1('(( I~) l.tt: :WIY.ull:llgi'.'IJ'i.,i in dri'C'Il(ting: lt:MtoriQ, ~ nd !UOlt:C.inft }'~k lllM thM; ~ f1 011' 2U:.t.b 4)(21dll f"-AI"
IHici.,l O\'C"fh:ln5) 4'0\lld be prO'idcd IU t<nh ,mCt' chick .)llr'lh"A1, /~ rit'C d Z6 }If M 11198, «('rf!M' 1) jHl} I ~
Kt)' \1t'Or&. - Ro ~ .u e Tem, Stff'NfJ dlluttJUJ, ''~ -' t ~ t e ~~N:dnn,trop l ~ u:rru. ntoltlng dmuhy. Sq'Chel kil.
The SHady or neu ~ he sclt.( Llon ls
hnpor--UUH on 1heore1ical :and npplicd conlk:rvatlon
RMund.s. llrecfling bird .~ an• confiaurd tn the
neiHiite chu·iug iuc:ub:\lirnl a nd the chic:k·
1>t1:u•Jng pt:riod, and Lhe selcclion of ~ w
:lJ>-proptiale ncat..site ~ hould allow birds to m in· hnize the <td\'e~ effect.< of preda1ion. inclemcnc wemher, or conspecific aggres.
sion, arf'ecdng reproducti\'c fim<.-ss and sur·
"h11l (Paruidgc 1978). NcMing h:tbit~lt ' " ~' Y
be ~udfidaUy manipul:ucd 10 mthancc::
pr<>-duc:ti\ily of eudungered SJ>ccies ,:~ tu .: h
as
lh<' Rostatc Tern (StmJo d()tJgn/U,). Nest-site:se-lection has been quite well studied in tcm.s, including Ro:seatc Terns in temperate ;.\re;u (Burger and Cochl\:ld 1988.•: Cochfeld and Bur·gu 198:8; Ramos and del Ne\'0 1995o). Tropic:tl
Rcueate
Tern populations have re· ceived much less auention (but see Burger and Gochfeld 1988b). This study cx;unin<s nc:.st'l$itese:
le ... <: Lion by Ro..'lc;oue Tcnu on Aride hhuul (Seychelles). \\'here this species nesL~under a tree (J'i.s6nitJ grtmdis) canopy {War-man 1919).
Habitat , ... riablc~ :tppan:ntly seler.tcd b}' tempt"ratc Roseate Terns for nesling v:\1)'
C:olonbl \\".\tciblrd$ VI CS): 4 9-~ .; .a. t U~
among co lon1~ . but a common )):mem ls
the s,ek'(t_ion of
ccrruin
ch ar.:IC:ltl'bliC!: forexample, p110ximity to an ele\'llUld lwm sut h
a.•
a rock (u' t:tll ''tgttation, chat pa·o\ffdesUC!§I:Slte conw alcntnt (Bua·ger:u•d Cochf~ld
1988a, 1988b; Gochre!d and Burger 1988: RamO$ and del Nevo 1995). Ndt ~ it .c:s In tropical colonies such as on Culcbr.a. Puerto
Rico. seem to be more open. l11erc. Rosc:uc::
Tc:nl$ nest dosc:r to COilSpec:.itics. f ~ll · tht:r
fro1n vt:getatit)n and wiiJl greate•· "is-ihili'Y in-dices th:ln d(' those ne:uing in t<'mper:ue: a ....
ea.
(Rurgcr and Cochfeld 1988b). 'rbL<pattcl'll lll:ty in rmn be explained l>y the gr·eater a\'ailolbility of operl habitatS in tropi-cal arta.ll, 1\ince RO.<t."':'llt ·1cnu Ol\ Culebm also .selecl concealed .shes: Lheir nescs a.re dose!' to 0\'erha.nging rock! and to rail er ''t:g· ctmion tJ1:-m \\'ouJd be e>:JX:Cted by ch;mce. Conceahncnt may be beneficial aga.inst avian
preda<ors (llurger 0o1d Gochfe ld 1988b) and nest-she competitors (Ramos and del
Nc,·o
1995).
Despite some plasdcit)· in nc.:~ting habiutt b}' RU$C::IIC; Term (Ramos and del Ne"'O 1995), pterlou.s studies sugge.n that primaJ)'
ROSP.ATF ' r'r.RN NEST Sm:.s 439
features of nc:-st..site selection mav be! COO'I·
'
mon
tQ both tcmpc.:tate <tndu·opico'l Ro$Cr.ue
Tern populations. Thc.-rcforc, it i.s imponam
to study nest-site selection iu additional
trop-ical populations to undco.'"tand pattC'nu of
ne.n·site sclcctiorl and their driving facton.
On Alide Island. two lizard>. Wrigbl Skinl<
(MabU)'<I wrighli1) and St:ychcllcs Ski11k
(MabU)'<I S«hdkl,.is). art· the main egg pr<'<l·
ato"' (Ayrton 1994: M>ul 1996; Ramos 1998), taking o11ly \UI~ilh:nded eggs (Ramos W98). Avian predators are rlOt present. 11lert:f'or·c.:. Aride Rose:ue Ttwns .!lhould have
leS$ 11eed to conceal their
nen.;;.
Nc:swite t h::tr:.ctui~ties
or
Roseate ~ ICn ''$on Aride l ~l.and are described in relation to ;w;.ilrthle httbhat., t~ compare nor-5ite setec·
tion becwcerl
tr·opicalarld ternpemu: JlOI)Uia ..
tions :u1d to 5\Jbrgest p4>3-,;jlJ1e 111:\nipulntiorl$
uf the habitat that could enhance br'Ceding
success of
thise••dnnger-cd species (Coch·
ftltii!ISS: Nisb<lti9S!l).The Indian ()cean iJ
•h• world '• slronghold for ohls •fl'ldes
(Cochfeld 1983) , but Wl')l liule I• knmm
nbou1 itS ecology.
Mde l.t:And N *IO'S, " *"O'E), U~ ?$.2 h1• Roy..t $u.
tie')" for Nawrc: ConM"rration f(')Cn<' riMnp; tQ 161 m. h
l:i a drn~)"'~Uted gmnitit: blltnd, qcUted m:Linl)' wilh Plunr~ :.nd has ~
rr: ... •
open , , ~de arr.u. OfM:IIgll<k• '1\'Cl'lr orig.il•:.lty tlomlilj:IU'd by\\ k~'-' (.\tlii"JSS'Ii.'
U,.•td~) bm n:ctntly ha'-r b«n bw.Wtd t, +Ill aonthii• <<:o~» hc.rb (A.tJIAAIW ~p>. whi;;h lonn& ;a dell3oe' m"t or
iolt:Mi (Wllrman atld Totld 19&4). Opt"n rotll,y ~£e'd lte
ti!Mf'W:u-d en the &eouhorc:.
'rr.m pof'l'\lhlli(lns In hrl'nllnx ~~'~ ilrt r~llm~tl'd lit
17't.OO() (or Soo()• Tem (S~n ju.KftM) , 8.600 ((I( f<11iry Tc:m {~ albcs), 110.000 for J~r Nodd}' (.'btOttf
l<"lt•.-lmhU), !t,G()() for Sr<WI!l Noddy (AttOVJ 1t6/Uw), 70
ror 8rid1W 1~rn (Sr'"'" nn~h,.,•nl (lk1tt 1997) n.nl.l 1,119 for Ro~3tc ' lC.m (RamO!I 1993). ' Mk Lnkr Nod-dy and F.UtyTtrn n<"t in u-eesthrou,ghout th~ island. in-o;;hM!ing :above tht Ro:lc:ue Ttrn (Oionia. 11•c Soocy
"l'c:n\ ' '(1.~ in (!potu gbl.l~ :11\d ut)dfN' t.ht! tndl)ttc.l lrrto l~ll<IP)' (P...,.,e et aL J99i} :~I>Ot tl 20.30 m frOtfl tht ft()..~
ate 'IC:rn "'b<:olunks. and dl<' Br.,....,. Noddy n~t' on
boulden and in paJm tree~. 'Then: are llt.rgt nvmben of Writ;ht Sk.inks Mid $q'<hd l ~ Skint:$, ... ·hkb (C("((on
(e--ces. dropptd fish and cggr. of seilbird~ (8rookt" and
HouJ.ton 1?83),
On ru;d~. R~te Tt'tru .re known ro nest in opet\
gladn ;an,t unrltt t.h~ e:anopy of Piltmfa (W.lrm:ul 1979),
l\hhough rht ((l,lll(lr tohiut I~• l)()t !:>.:tit usec.l f.incc
19~ {Aynou 19!).4; Moml 1996). Pri<» tc> 199.3, cht
1:\rget-wkmy HI'!~ l«'fl:c gliKlc:) W'.u ;au open ~('(;~. Thb ~~
... as in,'<ickd b)· AI)ISt.a:sU. and dea.rc:-d in Jgf)j tu t'ncour·
ag-<" Ro~t<' TC"m$ to n!C.$t, but WM itntC'41d colonized by
Sooty Tem) bc"ll.<•u~ A"J$1~ ~~~ inhfbitt Sooty Tettl
noting (fc:arC' d a.t 1{1.)7), The n:m.;,~ining ~ n gl3(1('"
:ut" c'>C'<:Ui•itd b)• So.M)' Tem.i, "''here thdr nndng cknsi·
li(';$ are m udr bi,gh e,. d~.< ~ n u.ndet' the .;.'(IQ(llaud cal'topy (feOLrc ~ aL 19-J?), ..o ic b unlik~;ly ch:u Rox-ate 1Cm$ l!.itl re--neu ln ~ll gbdes.
T l u~ .u udy " ~ .u c~rricd nuc fron1 M3)' 10 July 1997. Thrtt colol'lid Wt"t.:- IOQI«I In 1997: " we&.tt rn ¥o'(l()(i•
lands~ ta main colony and twO .wlx:okmi~). "tloiJ tor-cue", ~ud """ftlern tOOlling tod.s~ . ·n,c first cwo 4)(11c,~ ll it.$ '1\'t"l'e undtr a c1u1opy of f'ijiJIIIitr and tht:' third ~ in gr.L» lllrtd QJk" ~~~ b)' tht' , · ~~~. Su: du~eh~t
"'~r~ round on lht-wcs.~tm too~tln~t R)(k$ bot 11.11 ~>$
..., ·~re abandoned .1o000 afkTlayins. T~ breeding popu-blttln in the nll11l t.(liatl)' of the ... 'C~ t cf'n woOtll.:md~ w;a,_, f:$1hnattd :at l.OSS pairs (Ram~ 1998). The l\11'0 sub<ol·
tmin """ere srn:&ll dltnt'lC gNttpS abolll ~5() 1t1 diJ.t~n•
frorn chc main colony. h,a\ing Mx and H! nau. respco
tn·cJ)·. BoU Wonuc. abo\Jt 700 m fronr the wc~t('rn '1\voc:J...
Unll ('(lkmy, h:\d t.e\'ell n~b:. Apru't from .an1c tt<!c •1t"''• lh~t'e w.u little gniUHd ''t&t'latkln whhl.rl lht!
WOOI:IJillnd (Oionie•: J(lltiC' (~;rn ,,_,u.:ht) :iq!ohthi.J; cJlC
nesting arc.l .lpfM':aftd 1.00 dtrut" for tern' to ..,.";l)k throuah. Tht•r,':OIJ'tt.:r 1 u:fflr tO 1hc bile~' wc~tcr n WOCJd>.
bmb cokln)' a• the m~ln co~ny ltlld 1~ od1('n <1j flllllll
colon in.
Thf~(' -"lud) gtoup.'I ... 'C:t~ dc:tirrc:d: (I) t he: ' ' " all colo
M~"- (2) • ~o qu.adt~~ iu 11\c 1'1\ahl «<ll'u\)'. an tda~
qu;•dnn whh ·19m' 'illld 11 c-t'IHcr q••·•d,1u whh f'W m' , 'AI Id
(3) nn &It'll oflll.lom ISO 1111 lll'OIIIId !I bliud In tht 111oaln
fOIOtt)' (blind ;.re:.). NC'ttlln the bflnd :ue~ we-re ••odl-:d
~l\l u SJ low-fliuurb;tnceuu1!hodt.. All n~u "''t'f~ llllll)pcd
at e h~ rhJUt or t)tjt'lll)II!Jt, (I I till I\ IM':rlr,lU'Ittlt blind. CIC:~ I ·
C'd (,)11 lllll'<"e UUII k .1!)o111 C,lllt\lll t'ltr 111){1V( I he )trc)\llld; and thc (~~oln ol ~, und ct•IC:Iu were numitorctJ daiJ)'.
Th~ 1wo c1ulMitab In the: 111<tlu colony "~re nc~blht~
.,i1h r'11ner fl'llMJI a1ul J llirlj(, 16 d:.)._ ana rht ftn1 cgf(
w,u K'l'fl (I j\11\r.•l , AU llf"b ht 1h41 qu .. tlr-.ui ill'ld ,n,o.fl
colunia were mn•'k<'d whh mrmb(-rt'd JM:j;• 01 wuOOc'' tongu~cptttw:.n. 'l'hc:-twO ()Ua.dr"u. lfl'cre ' 'bUIIlty
lso-b.ttd from tatb (lthtr a.nd from r.hc blind art:t by rocky
b:tn~J'l.: (lnly tliH~ 1n I he one nudy p l01 ph'rl ~ few
ueighbon Mt their n~" during the db.uubat..cc: or
<"i-<h rac._rth ,;~h .
Or1.11llcd Mit•ltc (ha~ctc- l i,tka "~ lllt'.lm~d du 1 ~
tn~ 20-50 mimtw ~ iriu , btcWttn tht' 16th and !lOlh cl;()'
:.nrr tht! fil'$1 tgg ... -a_, k('u, 10 mlr)imiu di)C UfbOnur.
'fllh OCC'urred l)bol.lt eigh• tu ll("n tb)~ ahcf' lhe pt"~ k ut
C88" 1 ~)i.ng. but n('.)t-lllitpping rrorn the- blind &110 ... ~
that on I) nlnt> eggs. ~rc ~t befote 20 Jtm~. with OtH!
bring r·elahl. Sin<:e HR nesu v.efe IU:\flped 1n'ior to IS
June:, and a»\mllng au t'IIU:ot1 propon.ion o( egg kt.~ In
tht blind area and quadr.u.s p lus .unall <~oni~ proba·
bly (lnly ~bo~u J . .f~ of ll•<" ue'tS 'I\'~ re kl.\1 in c.hc <tulKI• rui. atltl rhto .!.fflall t'OI41li'.!l prior to neuo6ile (t"" rarct>rl·r.a• lon. 1l1b b a .t.~n."'ll tll'TOT that W'.luld 1'1)1
h~\'C' a.lft'<ted dlt' a:tudy o( n~&li.ng p;.lttcmt.
t·or the $mall c-olonin ;)nd th~ ~"" q u:tdr.,~-t, dat,;t WC'I'e tu11C"e1td !lit :tU 11e•1$ "nd :.t :11 Umil.•r nurnb..-r 1,;1'
r.lndom poinu. In th<' Cl'ftt('r quadr.u. d ue to hjgh ne51
density. nes~~t" :utd n.ndom poinu ~re <har.t<tcr·
Ued only in the: fine 16 mt o( the q uadr.u. Jo'or the edge:
M d rxntcr quadraa
or
the main <o l ont~ the x coordi·tl2te ()(the ~ndom poiJil\were c:uahiWiec.l•~•em:ukl l ·
ly (t\•ety m~t.t.r) and they «W)f~ti1t:ue f'11nd(wnly. using a
1<ihlc of r..n(lom tt taJubc:'tt. t"vr th ~ ' •nail colon!~::~-. rh ..
Dndorn poinu were dett>nnin~ by usl.ng ~ 1abk of r.tn·
0.:1<rlption
04tanoe eo tht nc~rC~ot ~"Cetk';l l Qt!t<:t (n>tk ork>l; nlOfe 1.h.1n <1 <"In high) from the
Wge of ~.M nm to the ba~ or th~ rock or log (cm).
(H))«' hc~h l VtgctaUQn <:<wt!r
Hc:igh1 ol n~r~t c1cv.t~tcd obJ<:~'1 (cm),
V«ti~l obj~t ilround nQ4
O~t oo:erh!lngtrtR Vi~biJil)' (rom ~.bo~'C Ncighbor di.n:u't(e
V('gecadon c«.n'C!'r wilhin 1 m radius o r ne« ($. ,.)iual tstim:uioo).
Vcnie2l objc:c• around the-llc:\.1 wlthlu 30 c:m ( ~ . ,.;~w c:-.ti.nr.-liq n). o~, (1\'('rhangiug: the·~(%, ,WJal «dmation).
~t·~IC' 'i!oibk from above- ( ~. ,i,)ual ~im~livn) ,
L)i~:lif\c:t tc> neM«t nrighbor <cm).
poims. Thi! .\light diff~ r 'tnc~ in W •lpl:ing .,..'a$ "'*d be:·
~t,i$ol'. the ~oud techojque $hOtlld be ntore
appropri-Ate to~: .~o<~.mp l ing "''"'ib.ble habitat in an arc:-a "-'here O<':W
are Jnorc \Clllt.et«<. Seo.·en c .or\ tim.t.~ tl..' \'.lrbbl~ td'k..:t•
ing COIICif':llmtnl of the n<:$tott.it.t,$helccf', ''<1.rttation ro' ~
..,. :md uUr..uj>e<:itlc: nc~t dc: n ~il)• were r-c c <Jrd~ (TAble
1).
Chard<1Criscics of ~tc T~m nC't"'*'it<:s l<>'t:fC
ro!YI-I:ICI!tc:d ~~i1\$ l th ~ o( r:lrliiom poh.tt& for dh.· :~ortl.all oo*'
OOIC'S, d •t- P.dgt .-nd tftt oenttr quadr.\t:s, and <'h:U'<M!tcri$tia uf new. uftl•c main coJony ag.Urut th OK" of th<" $m;1JI colonid. using Krushl\\'alli~ H 1esu.
Hatching: $\ICCtss ~-:u : r4:gi~teicd ror urn A(1.t'\Sh~ and (h2~cer11ti«<Oi rll ):\l'td bet\lllt':tn succt':$,{ul :\nd uniUC>
CQ..-.ftrl n~•:~, wirtg logi5lic rq;rmon.
In rhc b-lhtd : 11 ~:\, th.; q;g·l:tying ~ai()O .,.. . .., di\'idcd into C>A'O periods (I~ Jun~ and afc·et 6 J une}. 1 rlOit'!d
"''hc1hcror not e-ach neM WM plact!d \ 11)&-r \J\'ethlmg1n;g
obj<<·t,s (rod: ,,r klgl). Young chH:b could ~ pc-<'lc.cd by t4o:luh.s ifth q· "'"ndCK'd tfom th(' territory or when kft
ungu:n'tlcd b)• d1cir p::&•'Cnu.. \"oung chk b ... -hkh were
S«n dead or .,..Trkb disa~ared afcet being b:wtly
p«kcd y;fu~n lan obk>:r'\'('(1 were rt~rdcd as h .. 't,hlg dl'tt.l from pt-d.tng. Ovtrhanging obftns p((J\idt' ~
t«tiQn fiorn inclement wt"~lher aad Would
rnjnimizc-thc: cRbcu of :adult :t~cto'Siotl; ttw.-rcrorc, n cst~icet ....;tl,
M'trhanging o~ts may ht-pref~tred (i.e . .sel~cttd b)·
the carlics1 br~dert ). A <'hi,s.clu.arc attJ11)3l.' tdtcd lht'
rtl.llll•ypoth< ~ that nnt1ild iniciau:d ...,;thin each~
b);n,g ~ri.od had .-n cqual frequency ol nest-1'itef ~~oith
0\'Ctlr:mgill!;' o ~ccu. :U\d due O \ 't:rh~ n gt h.'ld ru> inOtt· ence on chkk mortalitr fronl adult ):teckiug.
Chick1tn-f,,te<l v,hh llcb (bird' ~!CI"\ '~::11 )t:m<i:ing 1,1n one foot
on!)•) in th-e btind arca, quadrdD-and ~maU coloniC$
WC're n ot((~ Also.
REsUL'!S
Nest~ire characreri$tics on Aride
lo lhe small c.olc>nid, llClit site:- ~ ~ differed from random points "ith r~pect to all char-acteristics measured. while i11 the edge
quad-rat. fh:c.• ofs.c,·cn cha_ract<"ristics differed, and in the c.:entcr quadr..tt only four characrcris-tics were $ignificou;ltly different (1ablc 2). In all plot• ()~ect distance, OQject height and
Object ovcrfl.a.nbring w cr~ rht! main ''ariabiC!' distinguishing nest sites from random points
(l3ble 2). Roseate 1C:t'fl$ klc:<:tcd n~l"$i te$
dosea· to t'lller w;tticaJ obj~ts. and with ;t
higher percentage of rocks. logs or br.tnchcs
o~·erhangi . ng the nt';$t thottJ were present at
the tanrlom points. In smal.l colonie$, Rose· ate ·terns seleued tlf".Sl-sites wiLh a t..1.Jier nca•-est \~n ical o J~c c.t. rnorc vc:gcutdon
cov-er~ more '-"ertiaJ o~jects around the nest and
mote disL'ltH (rom the nearest neighborthatl
were prescm at neu-sites selected in &he
main colon~ ··
The center quadral had 1.2S nests m·2
and the edge quadr.u 0.6~ ne<L< m·1. Aride Roseate Terns kept. on :werage, a minimum distance
or
abom 0.5 m from lhe nearestn~ighbor. Neighbor disuulce wa.'i $igniticant~
ly correlated "i!h object height (r,= 0.27, P < 0.01) and \'crUc.al object around the nest (r,
• 0.22, P < 0.05). Obscl"ations from the
bl.ind showed that Roseate Tcm individuals
built SC.':'\ · ~ral trio:tl nC$t-<:ups wi1hin Lltc tcrrit~
ry.
Among otlu.-r po5-'Siblc \'3:riabks that mayha ... e influc:n<:<.'<llhe exact lc.K".ulon of thl' de~
flnitivc nest-site, the nature or the rubsuate
(it is probably eMicr to make a n~t c-up if the
gtOutld is S()ft) and the aggressi\'Cn<.~ of
neighhor$ (fi\'e pairs were :seen changing
nest-sites after much agg1'es.o;ion from
neigh-hors) sccml·d impottaru. Se\•ei"'J.l suc:h trlal
m:sNiite.s seemed to fx: closer to the nearest neighbor than were rhc C'\'eocuaJ ncst-6ilt"S.
0\•erall, neSLo6ite char.•cteristics had no influence on hatching succes.~ (logistic
··e-gression. X',= 8.08. P = 0.33). Hatchingsuo-cess in the small colonies (H.O%, N = 25)
\~lower 1han in the main colour (blind ~ ~r
ea, 56.7%, N • 171) but the difference ""'
not signifiont (X2
1• 2.21. P > 0.05. Yates
hatch-l
.s
J
..
i
f
---• <H! l!!
..:..eee
~-,.."!'
...:.,.;.,:,.;
C"! ~c~- '='! ·~ C!
---1:'0
••
$!
..
~
~
..
.,
~
••
..
~
:
-
..
~
441
ing success of d1e center quad•-at \Oo'3S
significantly higher than that in the e:dge quadrat (73.8% and 51.1
%.
N • !14 and N •45: x ~,
•
5.7, P < 0.05. Yates corrcc1ion). sug· gesting that factors other rhar\ physical cha,...acteristks of the nl:St·.sire~ oonl.ributed to
hatching success.
In the blind ~rea, thtrt was no rlifl:Crc•·lcc
in lhe rrequenc;y Of HC$t-$ilc;$ ~ith 0\'C::rh<mg
initiated between the periods t..() June and after 6 June (X' , • !tO. P > 0.05. Ya.tC'$ COrT<:<-I.it.n\, 'f<thlc 3). Tiu; presence of overhanging
objt--ctS (I'OCk or ICJ~rs) did not ha,·c any sign iF
i(:anl t!ffC(I Oil halchiug SttCCCSS for both tht·
period.< 1-6 June (X', • 0.68, I'
>
0.05. Yatcs correction) arl(l after 6 June (X' 1• 1.9, P > 0.05. V:uesc:o•·rcc1iOn,
1itb1c S). but it Yt"a s:~ ig · nil1camly a.ssoci::ued with Lhc proporliun or c:hk~ that died from 3duh pecking (rourchicks iu nc.sbsircs wilh ovc.:rhang and 15 in uc.·.:H-shes without O\'Crhang: X"', • 5.26, P
<
0.05. Y:ttes tOri'CCtion). During I hit study vi.-.. tually nil chicks died from st:•r,,.llon. ond I here w::tS txten~ i ve hucrr<'rcmcc from neigh·bors and failed brctders during ehkk feed· h\g (Rnmos lfi98). Some mct.lhmHitt.'<l chic:lu "'r.re ~en hiding in overhang$ or r;,c. lng wu·lie:al rock.' where they ('<mid fwalluw
large
pJ"ey
wilhout btlng robtK:d .Chick:t were nlso heavily in(C"$tCd with ticks (A.,Jil)-.mma /0<11/osum) in July. Of all
marked ne1tS, on1)1 two chicks ncdgcd, from an isolated :nnaU colony whhont tick.1.
Comparbon with Other Colonic."
In term$ of physical features, nest·site
characteristics on Aride ~·ere similar to tha1
in the United States (Burger and Cochfcld 198&~; Cochfcld and Burger 1988), the Azorc• (Ramos <tnd del Nevo 1995) and
wmc: ~olonic-.5 on C\dcbra, Caribbean (Burg ..
er and Gochfdd 1988b) . Vegetation <OI'cr atuurld Lhe nest-.$ite
'"''$
a major di£fcrcnccbe L\\ 1ee •~ tropical Roseate Terns on Aridt: an.d
those on Culebro. The beneficial effect of
ground cover on Culebra v;as replaced by
chc tree canopy on Aridc:. 01l1cr tropical R~
.\eate Tern populations.
sctm
to nes.t in moreopen areas: in the Vitgin l$lands on um-ege>
442 COLO~W.. WATERBIROS
(NortOrl 1988), in Pargvc:ra. Puc:rt<> Rico, on barren COI'all'ubblc: ca)'S (Shealcr· 1995), in
T(U)>!:ania and South Afrita <>n bare cor.il rock or on ntat$ or detriws (Thom<uS and El· liot J 973; R.•ndall and Randall 1981) , and on 1J1c Crcat Roltrier Re~ f. Austt3.lia, on Oat t:a)'S of cordHinc s•md CO\~red v.ith grass-. which Lhe bird~ prefer for ncsrlng (Milton
n
tJL1996). on low \'cgetated cays v.ith Black·
naped Terns (Stnna surMtnma) (Smhh
1991) and on bare s<tnd near Bl;u;:k·naped Terns (Gochfcld, pcrs. comm.),
Mean nc:\rc.sr-ncighbor distance found in this nudy is consistent with those fouad
Cor otJlCI' ttopica1 colonies: 00 cm in Soulh Africa (Randall and Randall 1981 ), 41).70 cm in P:U'g\lcra (Shcalco· 1 99~) and 63-97 on Culebm (Burger and Gochfeld 19ll8b). but much smaller r.h:m th o~ reponed for ttm· penne Roseate Tern populations: 80· 126 cm in the Azores (Ramo> 1990) and 143 cm in
New York (llurgcr """ Cochfeld 1988a) .
Ncst-..'4ite sclccdon by Rrucatc Tt•rns on
Arldc resembled that oftempemrc and some cropic:ll countcrparL~. 1Topltal Roseate Terns seem to se.lecL C011c:ealed uesl-5ites if 1hry al'e nvallablc~. but arc 1\()L coruuained
from nesting in open are:'s (Shealer 1995) .
So.cial racwrs 31'C irnporranL in rhe !I.Ciec-tion of m:switcs since Aridc Roseate Terns nt-srcd, on average, ru: closC' as 0.5 m 10 nc:ighbors., whc:u mar
ay
concealed sitc.-s wen: a\'ailable :.~round the colOn)'. At high llt'-5tdensities. fewer \'<ltia.b1cs differed bctv.•ccn ncshsites and available habitat, suggesting that peak~ncstiug bil'ds were: unable
eo
sdect nest·Sites differing in physio}l featurc.s fron1t.he avail:\b1c habitat, c.lue !C) che proximity or neighbors.
Distance to thC' twarcst ndgh bor ~•'s
pos·
hivelr irtOucnced by lhe amount of rock cov-er in the area. :suggesting that a mg:gedtcmin will accommodate mol'e br(.--cding birds. Tropica1 Roseate Terns are more
ag-grtossh-c than tenlpetare cou nrerpa1, ~ (Butg·
er and Gochfeld 1988<:: Shealer 1995: pen. obscnoatlons). This ha' been viewed as a
l'e-flcction of the more esposed nesting habitat~
in o·opical areas (Shealer 1995), but could simply be a renection of higher nest densities
in tropical areas. Higher nest densities may
al.so make 50Cial :stimulation more importam for Roseate Tenu b•·eeding in 1.he tropics.
Predation a1'1d ii\ICI \$~dlic competition have been invoked 10 explain \'attability in nest-site ~elect i on by ccmper.uc :uld troric::tl Koseate 'ICrns (Burger and Cochfeld
t988a,b; R:uHO!o a11d del Nc\'o 1995). On
Aride nest-site c:harac.tel'i.stics. notably O\'t'!l'-hanb,~· had no influence orl hatching success
and prcdador1 or lnu!'r"!Spccific competition
((t\Jid not explain conc:caJmcru. ThC' hig·hu
h:uching sm:ccss in the c:cnwr qu;tdmt nmy ,., ••pl•inecl by older and more •xperl· cnced birtb prc.+Mtmably uesling in the c:en· tcr of the col Oil)' (Cou l ~;on 19GS: Burger ttol 1996). Eccopnnuicr'! \\ '~ re presC'rU on Al'idc and
rnay
also in(luence IH!St-she selectjon,buL thl\ needs ~ \'3hr:uing .
Ahhough the primar')' feamres of nest· sh<-' selecdon are common to both tl'nlJ)Crnte and tropical Roseate Terns. the reasons be· hind ncSto$ilc selection may wry among col· onics. If not for odacr rc;.t.SOns. r.on tc:almcnl nmy be less stressful for breeding -.dults. 'Ou.-location
or
a ncst•$itc $hould be viewed as ad)namic procedure depe-nding on the ag~
grc:;:!Sh'ellt:S$ of1hc nc.:ighbons. 1hc soreness of rhe l,tround to m.-kc a neat wp. and vcgct<&~
lion alld rock OO\•er, ~ ~ inally, the bendits of
nes-t-site selecrjoo to Rose:ue 'I<:rns may be
Na~ inifi2tcd l<iirbin N11mMrornew; , •• .ith 1\o\'f!lh~iiQ: Hiut.hing 1iu«eu an<tcn-c.rhang (blind a.!'C!1)
% " 'hh o-.~rha n s rh-:tt ~ Wi!h(HII 0\~~iUlg
hatch«! d\at h.accbed
1-Gjlullt 19 34.2 59-~ 7G.9
ROSf.ATE 'l"F.R.N Nf.ST SITTS 44~
dlfficuh to quantify with conventional
ap-proaches like the one used in this study. h
ma-y be nete&'ti.;.U)' tO retord ;;tdult aod t hkk. bdmviorl( and rdatt them to nc :s t ~ itc fea· tu res, lQ deepen our undcrstaoding of nest· site selection.
ln pr.actk;d tenus tJtis study suggests Lho•t
panial O\'Crh;,\ngs m<t>' reduce chick monati-l)' from adult ;;aggrc»io n. Artificial sh elters
incrcaS(..-d the reproducti\o'(' S\KCCS5 of tent·
per.ue Rosca1c
TeniS (Sp<ndclow 1982) andeo~• Id be used i t'l I he tropics.
t\ (1Uo:(}\\1.J11(:.\1t:.'~
I am i.n<kbtW to Dr.J;a.mn UadbUI)' ohh<' R.SNC for
pctl'"i~~n to c:u't}' 0111 rt~c:h work Ol\ Aridt and tOr
lln:lftd:t.l ll"iM;u .c.- 11) tr.m-1 IQ And.:. Th<' Wllfd('l"l'f ol
Alktr, M lk ~ 1\('tb ;md !ktt101.n Ua • "(;~. l •• t rochtec:d me to
th r b l ~uld aud th~lr blrdi! the-ir hC'Ij), fticorwbbiJ) lu\d
""cO<OIIUI 1oafr arc: gr.uefully :P.C.k.nOto•led ged. Thli v.'()fl..
w:lr.\ po~bft whh tlw ~re1u hl"lp o(Panl 8unun \\tKI Mob
Mal!(llu. Thn. pllJWr "' • .._, '"'l"tww:d by the hriJ)fuJ cum• IUt'll lf o r )tll;'h"C'I GuthiChJ. 1\111)' Obttl01M1 omd 0:1\'id 01lffy. t'tn)lly 1 mwt th)nk ffi)' wife l.uC'IA ror hcol' con·
th\1ung-a.uppo11,
At11ol\, v . 1m . 1' h ~ IW•I Rm4:au: ·re!:l'fl bl'«dl•l8 ~;&:·
.OI"'Aridt• b l-'nd. ltc1.n' ' t() dw stO)•al S«it t y ((wl\ ~·
UU'I" Q) J~'f; ,, •; ul ( o n, l.lncoln, (.it(.
6ctu, M. IUIJ7. Aridc b l ~'»d .sclcntlflc r~n 1'116. ~ JIOn to RSNC. R O)~ Sock:\)' (or NAIU«' C'.o n 11 ~·rv.:.·
tic)!\, Uncoln, UK.
Broolw, M. d~ 1,. and D. C. t-hm•ll)n. J983. 11-te biology
~n d i*)ml)l$ ()I th e ~ lt in b ,'lf4b•')Yl ~ AI'i lmdt Md
Mnbw)4J ~~~tftA,ii on Cowin hLlnd, 5<-)"thcUtt
CRqnil-,._ Sdndcb.c:).J O\In\lll ()t'1.001.,_.,, l.ol"ldon 200:
179-19~.
llurgflr.
J ..
m d )1 , ( ~hf,ld . I!)S{b. ~\·~- Jhe K"lt:('llona.nd retnJroral p.1.ttcrm In h iblun use- or Ro.catr and Cc>m rnon Tern~ . J\11) 105>; 433-438..
fiu tsct,J. :and M. Coehfck'l. 19S8b. Ncti:t.Wrc S4lletliM by
R()st">ate Tems In 1\11'() rr()pt(:al Mk)nko1. <m CW.t:bl":',
Puc:nt> Riw. Condor 91): 34!.\-851,
{hll"t(cr,J. an.d M. Gochfdd. 1988c.lk f t' m h~~ggrcos ~i o n
in terns: cff«t or spcdd. d t! n ~il y . and i:,.) l : u.~ o u . A.g·
trri~v•· ~h~vi o\lr 1•1: 1&9-178.
Bt•rg('r, j .. 1. C.
·r.
Nisbct. C. Salina. and M. Coc:hft>ld.1996. Tcmpor.U J,ll.ltcm) ill rcproduc1ivc ~l1(<C'» In
the cnd3.ngcrc<l R OS(" aU ~ Tern (~a tlm.!gtt/lu)
1\Nt-ing<m Lo,g bland. Nt'w\'ork.. and Bird b land, Ma9> sxhusctts. Auk r 13: 13 1· 1-42.
Coulson.j. 1968. OUTertnce in th e qualily of birds u ~ t· i~g in the oc-n cre ~ 1 ld on tht> "'B<:!l of t~. <"Oion y. ~a. tute21 ~ ~784i9.
r eaf"C:,
C.J ..
E. L G£11. P. ~tty , H. £. Carty-a.nd V,j , A~T ·t()J\. I ~. H :a blt~~l u.sr b)• S4:-)'Chdle1 Sooty Tcmll
Slit'-M/VK&oand implia,OOns £01 cokmy mt4n"gem<"nl. Biological Co rt- ~rv"' li o n 81: £"$.76.
C«Jtreld. M. 1 98 ~. T he lt i)Se~ue itm: \Oo"()lk,l (li~ribu •
tion and stJ.tu& of a lhrt'alC'ncd sp«~ 6tologi<:al
Co i \~rv:uio . , 25, 103·125.
('.c)(hf,eld. M. :11\d
J.
Buf'8t!Y. 1988. Nest ~ite ~ d ccti<.ui:((nnp:.triX»I. ..
or
k()t!t-;tt\' :md O:ltl'lltHJn te-rns (Skrnlf~.flii and S. AinvtM in <' Long b land, New Yott. colo n)'· Bird Bchavior 7: fo&-66.
M:aul, A. M.199{i. Arid•: h b .nd ~lb l r d repou M:.y·AI,.
gust H~); . Rq>Oft tO tbe Ro,"al Sock'ly for N;uure
(:O.t!<Miio•\ , U r~ c:o l n , UK.
Miltoo. D. A .. G.C.Smlth'lltdS.J. M. Bbber: 1996.
Va•+-~ ~ ~ s o ,~m l 11 bretdin& of lite Row.u c Ten\ St.mw
d ~tctWi on th" :O:onhc-m G"':u BWcr.
emu
96;l ~:S.l31.
Nhl>c1, L C. i . 1 ~J . S 1 a1~ :.ncl bio tog,· of the ~ I' U' t h 8snt-m ~u l adon of th " Rtl'lt:at~ Tt•n S~ M.•·
JfiU• ~o A lht'1'aUI!t• n •• "'-'Y~ J\d Ul>ll.ow: 198t-1089. On· publbhtd repon. U. S. Dtpt. of Interior, Fl.sh llnd
Wildlife Strvi<e. Oll'kc- of tnd.ilnscrc:d Spc<ie!l,
Somh l lswllcy, MA.
!1-Vrton. k . L. 1988 ti.Xt\ol•('i(g d utc.:hes ~V •d in t('l~l -'«ifk
c:su;·.(iumlting
.,r
thc- R~;\ 1 (' i('n\ t.Sinnodnt,.um
ln thto Wcu I ndia J.1o1id.a 1-ickt Natumlli4 16:67-70. P\lm'd&'!. L 1978. Hllbhll-1 St>lt"i.dQu, Potgt:' $,51..,,76 i11
Mot. · i~ttrttl ~;. ~~~ t'\'O hr tiu n ~ u y llpprU'ilch (J. lt
Krcbt ltm.l N. JJ., {);nie-l, U..), Simu~;" r AM<Kiltc:•.
S1and.:rl:u'ld, M~ .
fblll4l>t-.J. t\. 1090. C'.olflll)' .al\d ft("jl ..!1co wl«'tlll"'•l by ~~ ·
Jl'lll t' and Chll\tlll}l' Ti•• n,.ln lh t~ AtJJt,..,. "u :hl (:)l· l~ · 01 ltll l ltk•il t l ;~ t e ;tualysh. M. St. th nt.. V n lvt' • ~t)' of O~tthllm,Ourl'lam. UK.
fbn• o~ , J . A, 100M. Ilrt:4:dlng c-co los(y ol' ko.W'.tlt' Te!tn\ o n
Atkle1 toltulCI. St)chdto. I•' J91}7. ~.) ()1' 1 10 ch l1
Ror·
~• Sod~: t y f u•· N;~~h • r•· Ou u :~c'f"\',lllu n , l .. mc::oln, UK.
~ m cn.J . A. ~and A.J . del Ne,-o. 19'J~ . Nnt-.itc -'C:l«tiOt\
by Roseacc Tt'.rru and Common Ttm1 ln thi! Alnre!i.
Auk 1l 2 : t.so.-'!89.
~nd:all . R. M. and B. M. R:.mbtl. 1981. Rou:ate · r ~ m
brct'ding bioloRf, :ul4 fl\clon re!~~ibk' for to .... •
chltt •'H'OodtK'Iion in Abgoa U:1.y. Sout h A!'r'lea..
Oi-trk:h !1:?: l7·2<1.
Shtr:tl•·•· 0 . A. lOOt.. Cc"Jml>·\rarh ... ro,...,:;:lniC I"(QIOJn' ( l f
I"{O>!If";\lt-and S:\ndwk h ·1cm, in l'uf"rtO Rico and iu
1 ~11\ l lo n 10 b t·c: ~!n ~o; ))Crfo nniln«. Ph.O. th6h. RUI· get'£ the Sure U n i~eoity of Ne!w Jetl'itoy, N!'"" Rt utr
swkk. N.J
Smith, C. C. 1991. Ttw R6&t-011e Tt-m Stn'tfa dl•llt<JlM
brt:e:ding on 1hc Nonhem Ctt-u Barrkr R«f.
Qu«n~land . O>fcll:l 1 ~ 3$-~) .
~ t nd t• lt)W,j . A. 19$2. :\n ;~~ n !ltyi.is<of t ('l up o111.1Y'.tri~d0t)
in, :tm:llhe dfc:c-u o l' habititt mod .ifi «~tion o n ,lh~
rco-prodliC li \ ~ :J UC:t~
or
~c:l i ('Tc n u. Colonhl W!t.~tr- b inb5: 19-31.TitfHil:U.. 0. K.. and 11.
r.
1. ElliQt. 197$ Nn.cing ofcheR ~ t t: Tt!fn ($r,...,,o ~lli•) n Qr Oa r~ ~IOLMn . R-ullt!dn oft h e Sri ti~ h OmithQ'og41! Ch•b 00: ~1-'IS. \\'an•1:m, S. R.. 1979. 'rhe R~c-at r: Tcnl Sttnr~ dl.mgt:llil
<arUkotJis on .'\r id ~ lslomd. Seyth t iJM-. Sulktin of
thc-IJ•itbh Om it h ologi~t$ Club. 99: l'l4+12;8.
\\ 'arman.S. R. and D. Todd. 19S-4. A bi~ogiCliS\u "WI)'"O f Aridt Ul<lnd N:uur" Rtserve. Se)dl-cllt"~ 8 i<•IIY.gkal
