79 it is stated that Tawny Frogmouths are not cooperative breeders
; this is contradicted by Rae (2014) who describes four such cases.
"Some people have concluded that environmental variability promotes cooperative breeding and other people have concluded that cooperative breeders
tend to occur primarily in environments that are more stable," Carlos Botero, a biologist at Washington University in St.
The evolution of delayed dispersal in cooperative breeders
This mating system does not appear to be common for birds; only 2.4% (220 of 9,000) of avian species have been characterized as cooperative breeders
(Stacey and Koenig, 1990; but see Emlen and Vehrencamp, 1983).
Fairy-wrens are habitual cooperative breeders
. The helpers are generally older silblings or half-siblings of the current nestlings, and their behaviour is likely explained by an instinctive desire to see more of their shared genes entering the gene pool.
For instance, "cooperative breeders
," "allomothers," "eusocial," and "altruism," have specific meanings within subdisciplines and do not translate clearly into other contexts, especially with regard to human behavior.
Craig and Hulley (2004) noted that many species with a coloured iris are cooperative breeders
, and cooperative breeding has been reported in the Brazilian tanager (Sick 1997).
He calls the aphids with temporary soldiers--those that eventually grow up to reproduce--"cooperative breeders
." In contrast, Crespi categorizes aphids with permanently sterile armies, known mostly in Asia, as "truly social," in the group with bees and ants.
"More work could help us understand the key problem of why these wolves are cooperative breeders
, along with about 3 percent of mammals and 3 percent of birds," said Sparkman.
The result paints two different pictures of evolution: Among pair-breeders, sexual selection on males makes the sexes look increasingly different; in cooperative breeders
, competition among females leads to them evolving the same showy traits as males.