﻿SOCIAL 
  PARASITISM 
  IN 
  BDIDS 
  FRIEDMANN 
  373 
  

  

  hypotheses. 
  The 
  first 
  to 
  be 
  considered 
  is 
  that 
  the 
  source 
  of 
  the 
  

   parasitic 
  habit 
  is 
  to 
  be 
  sought 
  in 
  the 
  polyandrous 
  condition 
  which 
  all 
  

   parasitic 
  birds 
  were 
  supposed 
  to 
  exhibit. 
  Pycraft 
  (40) 
  and 
  Fulton 
  

   (24) 
  are 
  among 
  the 
  best 
  known 
  exponents 
  of 
  this 
  view. 
  While 
  it 
  is 
  

   possible 
  (though 
  not 
  probable) 
  that 
  some 
  parasitic 
  cuckoos 
  may 
  be 
  

   polyandrous, 
  the 
  cowbirds 
  are 
  certainly 
  more 
  or 
  less 
  monogamous, 
  

   and 
  such 
  promiscuity 
  as 
  occurs 
  is 
  more 
  likely 
  to 
  be 
  a 
  result 
  than 
  a 
  

   cause 
  of 
  the 
  parasitic 
  habit. 
  Vidua 
  macroura, 
  a 
  parasitic 
  African 
  

   weaverbird 
  is 
  also 
  monogamous, 
  and 
  Chance 
  (13) 
  writes 
  of 
  the 
  

   European 
  cuckoo 
  that 
  " 
  * 
  * 
  * 
  whether 
  cuckoos 
  are 
  polygamous, 
  

   polyandrous, 
  or 
  promiscuous 
  is 
  a 
  very 
  open 
  question. 
  I 
  am 
  inclined 
  

   to 
  the 
  belief 
  that 
  they 
  are, 
  at 
  least 
  often, 
  promiscuous. 
  I 
  should 
  not, 
  

   however, 
  lightl}' 
  dismiss 
  the 
  theor}^ 
  that 
  some 
  pair 
  as 
  normal 
  birds 
  

   * 
  * 
  "'." 
  Fulton 
  admits 
  that 
  the 
  question 
  of 
  polyandry 
  and 
  para- 
  

   sitism 
  is 
  all 
  in 
  a 
  circle 
  and 
  that 
  it 
  is 
  hard 
  to 
  say 
  which 
  came 
  first. 
  He 
  

   inclines 
  to 
  the 
  view 
  that 
  polyandr}^ 
  causes 
  parasitism. 
  In 
  the 
  cow- 
  

   birds 
  the 
  circle 
  is 
  still 
  open 
  and 
  there 
  can 
  be 
  no 
  question 
  that 
  parasit- 
  

   ism 
  is 
  not 
  caused 
  by 
  polyandry. 
  

  

  The 
  best 
  theory 
  advanced 
  as 
  yet, 
  and 
  one 
  which 
  my 
  studies 
  tend 
  to 
  

   support 
  in 
  part, 
  at 
  least, 
  is 
  that 
  of 
  Prof. 
  F. 
  H. 
  Herrick. 
  This 
  writer 
  

   studied 
  the 
  cycHcal 
  instincts 
  of 
  birds 
  and 
  found 
  that 
  not 
  infrequently 
  

   the 
  cycle 
  is 
  interrupted 
  by 
  various 
  causes 
  which 
  result 
  in 
  a 
  general 
  

   lack 
  of 
  harmony 
  between 
  its 
  successive 
  parts. 
  He 
  suggested 
  that 
  the 
  

   parasitic 
  habit 
  may 
  have 
  originated 
  from 
  a 
  lack 
  of 
  attunement 
  of 
  the 
  

   egg-laying 
  and 
  the 
  nest-building 
  instincts 
  which 
  resulted 
  in 
  the 
  eggs 
  

   being 
  ready 
  for 
  disposition 
  before 
  a 
  nest 
  was 
  ready 
  for 
  them. 
  His 
  

   theory 
  was 
  based 
  largely 
  on 
  a 
  study 
  of 
  the 
  black-billed 
  cuckoo, 
  

   Coccyzus 
  erythrophthahnus 
  , 
  and 
  a 
  comparison 
  of 
  its 
  life 
  history 
  with 
  

   that 
  of 
  the 
  European 
  cuckoo, 
  Cuculus 
  canorus, 
  which, 
  of 
  course, 
  is 
  

   parasitic, 
  while 
  the 
  former 
  is 
  not. 
  

  

  He 
  found 
  that 
  of 
  all 
  the 
  perturbations 
  which 
  are 
  apt 
  to 
  arise 
  at 
  

   almost 
  any 
  step 
  in 
  the 
  cyclical 
  sequence 
  of 
  instincts 
  the 
  commonest 
  

   was 
  a 
  failure 
  in 
  the 
  "adjustment 
  of 
  nest 
  building 
  to 
  the 
  time 
  of 
  egg 
  

   laying," 
  and 
  it 
  was 
  at 
  this 
  point 
  that 
  he 
  suggested 
  the 
  parasitic 
  habit 
  

   took 
  its 
  rise. 
  

  

  "The 
  door 
  is 
  thus 
  opened 
  wide 
  to 
  parasitism 
  in 
  its 
  initial 
  stage, 
  

   whenever 
  the 
  acceleration 
  of 
  egg 
  laying 
  or 
  the 
  retardation 
  of 
  the 
  

   building 
  instinct 
  becomes 
  common, 
  with 
  or 
  mthout 
  irregularity 
  in 
  

   the 
  egg-laying 
  intervals." 
  He 
  applied 
  this 
  idea 
  to 
  both 
  the 
  cuckoos 
  

   and 
  the 
  cowbirds 
  and 
  probably 
  would 
  haA^e 
  extended 
  it 
  to 
  cover 
  the 
  

   parasitic 
  weavers 
  and 
  honey-guides 
  as 
  well 
  had 
  he 
  known 
  of 
  them 
  at 
  

   the 
  time. 
  He 
  writes 
  that 
  "Parasitism 
  could 
  never 
  succeed 
  as 
  a 
  

   general 
  practice 
  on 
  a 
  large 
  scale, 
  and 
  the 
  face 
  that 
  it 
  is 
  a 
  speciait}^ 
  of 
  

   two 
  families 
  of 
  birds 
  shows 
  that 
  it 
  is 
  probably 
  correlated 
  with 
  a 
  

   peculiarity 
  which 
  they 
  possess 
  in 
  common. 
  This 
  is 
  to 
  be 
  found 
  in 
  a 
  

  

  