- 5 
appr o&okma m aggpeos&v© male at all, but mo& tl » pair ooraea together la 
this way the ohokl r*g ooewa to '•■3© the outcotas of tee same tencbsiioies as la 
a fight. Aa on© sees la my species iww otontial wutoa attack one another, 
’M erean rivals rijot tv? sexual activity In aggswasiv® anoo’uaters, the simplest 
1 ypott -.©ale Is tf at only tee attack aa3 ea;q® drives omS to be active for 
the occurrence of choking 
* 
/, 
Tl^ra remains still a question: why do tr© birds sthm different displays 
| the am drives are active! aynttum suggests that the intensity levs! 
of each activated drive aaogr very mieeeiixlently mil that the Solute level 
af each aa well as the bolsrue 'between tisoie determines the postures. :\y 
applytog eeetwel met* ode one can try to assure the absolute mrf. relative 
strand-tins of the drives concerned, ^nihim has already a careful 
ts ;^f 1 o y-^esaiw displays of the f ©Aid! ; l and It is y\ 
oil cy nark to mmlym the postures of the klttiwa&s la a sindlsr way and to 
co^ara fcl.*e results* 'Che following; obaermtions shoe that there la a differ- 
emc m f & balance of attack aM escape drives in the too posture® 9 asoh-mid- 
* If a contest between an arcb-^l-bew and a oho Mag bird 
2oadtf to a fight* .it is the forcer she will attack first, xf one of ifeu 
e&oagos before it comes to blow, it is as & rule the decking one who retires. 
After a fight tl\® viftnasr often aro3*m&«4oes ar*l she loosr choices. |Vs this 
one cm ooiKjli¥te that* in an a^i-*An£l-bowing bird a^ggre ssivsneso Is higher than 
•am© drive and in a choking bira tee reverse is true 5 . It is core difficult 
to find tim differ©®*® in tl.o absolute intensity level of tee drives in tbs 
ts» msttxmm. 
It Is st first surprising that thef ©males are attracted by aggressive 
behav tour in the males but; it is significant that it is not the moat aggressive 
posture whisk attracts them* The females would probably be too fri#*teaed to 
yA -alight near a male who manifests the htgiost degree of rag®. oynihan found 
^ ,/a gyu ix*king is far aor© aggress 9 than is in tea 
^ i Aka. i'inw a e owbt that the posture Has a osaaon a .in in tie 
ancestral fora. But it appears to have neve loped in different directions bo 
>laaSdhewd®d la tea aggrassive to taa useft betee®? >air. 
tic fact that a posture oaa ga Its ro'tiwtion in the course of evolution 
is a -awtioal Mrteaas, 
>'V 
Mr y ^gb vJ . m - HE - _ J ■ jf i ' nj| - ■ ' 1 • JE B I 
i-Seithsr In tee olasddteaied gull nor in any o-k*,.er gull studied far is 
ol'wk lif: > Jeciom to hssm the function o£ at tract ia^j fecalea. This show that to)© 
■ f '’■* functions of a posture can also olienoe to evolution. It la « 2 Lreidy possible 
'•VC 'f 'f ® ' *° ' :a '® attempt et so aaptesatlcn of wiy the kittiiuke am use i,iio choking 
ismig ■ Idle otoier spooies carnet* Firstly in the yound. nesting gulls the 
ixaloa often pair or ** 3ro*torritories fl she*© the pair does not later neat, 
atsaraaa the kittiwsfee sings €»i its nest. As we will, sec later, tee Choking 
j .3 derived from nest building and it thespefore axt$it b# eapeoted that it occurs 
at potential nests. It may well bo that euah environmental influences have 
played a part in developing; ohoktog as song in the kittlwake . Sec«Kklly 9 in 
the kittiwalse the feioales circle at the sass level as the ledges, in the other 
oiJocioa tloy fly above tlie i^ales. Sda all mm the kittiwakes to oing with the 
_ iir 
1 , 
,yl 
y v fi 
O' 
