﻿372 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  19 
  2 
  9 
  

  

  area, 
  the 
  greater 
  is 
  the 
  competition 
  for 
  territories 
  -with 
  the 
  result 
  that 
  the 
  terri- 
  

   tories 
  are 
  smaller 
  than 
  elsewhere 
  where 
  the 
  cowbirds 
  are 
  fewer. 
  The 
  smaller 
  each 
  

   territory' 
  the 
  less 
  assurance 
  a 
  female 
  has 
  of 
  a 
  requisite 
  number 
  of 
  nests 
  in 
  which 
  to 
  

   Iny, 
  and 
  so 
  what 
  probably 
  happens 
  is 
  this: 
  After 
  utilizing 
  all 
  the 
  available 
  nests 
  in 
  

   the 
  territory 
  of 
  any 
  one 
  male 
  she 
  passes 
  on 
  to 
  that 
  of 
  the 
  next. 
  If 
  that 
  territory 
  is 
  

   already 
  occupied 
  by 
  a 
  female, 
  the 
  nev/comer 
  finds 
  the 
  available 
  nest 
  supply 
  inade- 
  

   quate 
  and 
  passes 
  on 
  still 
  further 
  afield. 
  Often 
  she 
  may* 
  leave 
  an 
  egg 
  or 
  even 
  two 
  in 
  

   a 
  certain 
  territory 
  before 
  passing 
  on. 
  Inasmuch 
  as 
  there 
  are 
  at 
  least 
  50 
  per 
  cent 
  

   more 
  males 
  than 
  females, 
  it 
  means 
  that 
  after 
  each 
  female 
  has 
  exhausted 
  the 
  

   "territory" 
  of 
  her 
  particular 
  male 
  she 
  still 
  has 
  half 
  as 
  much 
  more 
  coming 
  to 
  her 
  in 
  

   other 
  plftces. 
  This 
  arrangement 
  not 
  only 
  gives 
  all 
  the 
  females 
  a 
  fairly 
  equal 
  

   chance 
  to 
  lay 
  the 
  maximum 
  number 
  of 
  eggs 
  but 
  it 
  also 
  brings 
  about 
  a 
  state 
  of 
  

   affairs 
  wherein 
  each 
  male 
  can 
  find 
  siilisfaction 
  in 
  the 
  appeasement 
  of 
  its 
  sexual 
  

   desire. 
  However, 
  this 
  state 
  of 
  affairs 
  can 
  hardly 
  be 
  called 
  polyandry 
  for, 
  although 
  

   in 
  the 
  course 
  of 
  a 
  season 
  each 
  female 
  may 
  have 
  several 
  mates, 
  she 
  has 
  only 
  one 
  at 
  

   a 
  time 
  and 
  only 
  one 
  in 
  a 
  territory. 
  Most 
  monogamous 
  birds 
  change 
  mates 
  with 
  

   each 
  brood 
  and 
  yet 
  no 
  one 
  would 
  call 
  the 
  females 
  polyandrous, 
  the 
  males 
  polyg- 
  

   amous, 
  or 
  the 
  species 
  promiscuous. 
  In 
  the 
  cowbirds, 
  if 
  the 
  birds 
  were 
  originally 
  

   more 
  than 
  one 
  brooded, 
  the 
  broods 
  have 
  been 
  merged 
  in 
  adaptation 
  to 
  the 
  

   parasitic 
  habit. 
  One 
  would 
  be 
  more 
  justified 
  in 
  calling 
  tl>e 
  males 
  polygamous 
  as 
  

   the}" 
  have 
  intercourse 
  with 
  some 
  of 
  the 
  wandering 
  females 
  while 
  still 
  mated 
  

   themselves. 
  Yet 
  the 
  male 
  does 
  not 
  leave 
  his 
  territory 
  to 
  collect 
  a 
  harem 
  but 
  

   takes 
  what 
  comes 
  his 
  way, 
  and 
  not 
  having 
  any 
  concept 
  of 
  parental 
  instinct 
  can 
  

   hardly 
  be 
  accused 
  of 
  polygamy. 
  There 
  is 
  a 
  great 
  difference 
  between 
  this 
  and 
  a 
  

   nonparasitic 
  species 
  wherein 
  the 
  male 
  has 
  a 
  paternal 
  interest 
  in 
  two 
  nests 
  simul- 
  

   taneously. 
  

  

  In 
  fact 
  if 
  the 
  females 
  did 
  not 
  wander 
  further 
  afield 
  after 
  exhausting 
  the 
  possibili- 
  

   ties 
  of 
  the 
  territories 
  of 
  tlieir 
  respective 
  mates, 
  at 
  least 
  one-third 
  of 
  the 
  males 
  

   would 
  not 
  b« 
  able 
  to 
  appease 
  their 
  sexual 
  desires 
  without 
  forsaking 
  their 
  territories 
  

   and 
  intruding 
  into 
  those 
  of 
  other 
  males. 
  The 
  loyalty 
  of 
  each 
  male 
  to 
  his 
  territory 
  

   is 
  not 
  to 
  be 
  thought 
  of 
  as 
  "virtuous" 
  in 
  any 
  way 
  [For 
  the 
  biology 
  of 
  "virtue" 
  see 
  

   any 
  of 
  the 
  pseudo-scientific 
  sentimental 
  nature 
  writers], 
  but 
  is 
  due 
  to 
  the 
  fact 
  that 
  

   he 
  would 
  have 
  nothing 
  to 
  gain 
  by 
  wandering. 
  

  

  So 
  then, 
  it 
  seems 
  that 
  the 
  shiny 
  cowbird 
  is 
  monogamous, 
  under 
  normal 
  con- 
  

   ditions, 
  but 
  where 
  artificial 
  conditions 
  have 
  caused 
  a 
  great, 
  unnatural 
  increase 
  of 
  

   the 
  species, 
  the 
  inherent 
  instinct 
  is 
  not 
  strong 
  enough 
  to 
  stand 
  unmodified 
  against 
  

   the 
  increased 
  competition, 
  and 
  frequently 
  is 
  modified 
  so 
  extensively 
  as 
  to 
  belie 
  its 
  

   original 
  status. 
  

  

  The 
  sexual 
  and 
  territorial 
  relations 
  in 
  the 
  North 
  American 
  cowbird 
  

   are 
  practically 
  the 
  same 
  as 
  in 
  the 
  preceding 
  species, 
  except 
  that 
  they 
  

   are 
  usually 
  less 
  violently 
  modified, 
  as 
  the 
  birds 
  are 
  not 
  so 
  crowded. 
  

   In 
  a 
  general 
  way 
  this 
  is 
  also 
  true 
  of 
  the 
  red-eyed 
  cowbird, 
  but 
  in 
  the 
  

   latter 
  species 
  the 
  numbers 
  are 
  usually 
  low 
  enough 
  so 
  that 
  the 
  birds 
  

   have 
  sufficiently 
  large 
  territories 
  to 
  avoid 
  competition, 
  and 
  monogamy 
  

   is 
  more 
  easily 
  observed. 
  It 
  is 
  only 
  fair 
  to 
  sskj 
  that 
  less 
  is 
  known 
  of 
  the 
  

   habits 
  of 
  this 
  species 
  than 
  of 
  any 
  of 
  the 
  others, 
  but 
  for 
  our 
  purposes 
  

   it 
  is 
  relatively 
  unimportant, 
  as 
  it 
  is 
  off 
  the 
  main 
  line 
  of 
  cowbird 
  

   descent. 
  

  

  HOW 
  DID 
  THE 
  PARASITIC 
  HABIT 
  COME 
  ABOUT? 
  

  

  Before 
  utilizing 
  the 
  above 
  data 
  in 
  the 
  formulation 
  of 
  an 
  explanator}" 
  

   theory 
  it 
  may 
  be 
  well 
  to 
  present 
  and 
  comment 
  on 
  the 
  leading 
  current 
  

  

  