Yolk Testosterone Levels are Not Consistently Higher in the Eggs of Obligate Brood Parasites Than Their Hosts

Cuckoos, cowbirds and hosts: adaptations, trade-offs and constraints

“…This should include further research on the interplay between hormones and begging behaviour. While two studies have shown that brood parasites do not deposit more testosterone into their eggs than their hosts (Hauber & Pilz 2003;Torök et al 2004), Groothuis & Ros (2005) showed that testosterone reduces begging, and so there is still ample scope to test whether hormones play a part in the superior competitive ability of non-evicting brood parasites. It might also be useful to use comparative approaches to generalize how different parasitic species exploit their hosts in terms of begging behaviour.…”

Corticosterone levels in host and parasite nestlings: Is brood parasitism a hormonal stressor?

“…Indeed, numerous studies from many points of view provide us with excellent examples of ongoing coevolution in birds with behavioral (Briskie et al, 1992;Kilner et al, 1999;Madden and Davies, 2006;Soler et al, 1995aSoler et al, , 1995cSoler et al, , 2011, morphological (Brooke and Davies, 1988;Krüger and Davies, 2004;Krüger et al, 2007;Langmore et al, 2011;Lemons and Sedinger, 2011;Spottiswoode, 2010;Welbergen and Davies, 2011), genetic Gibbs et al, 2000;Martín-Gálvez et al, 2006, 200707) and ecological consequences of parasitism (Krüger et al, 2009;Møller et al, 2011;Smith et al, 2002;Ward and Smith, 2000). However, studies about physiological adjustments due to brood parasitism are still scarce and those that exist focus on maternal effects in eggs (Cariello et al, 2006;Hahn et al, 2005;Hargitai et al, 2010;Hauber and Pilz, 2003;Pilz et al, 2005;Schmaltz et al, 2008) or the immune system of the nestlings (Soler et al, 1999a). To the best of our knowledge nothing is known about other physiological indicators like hormones in developing nestlings in response to brood parasitism.…”

Hormones and Regulation of Parental Behavior in Birds

“…One obligate brood parasite, the brown-headed cowbird, displays a seasonal rise in plasma PRL (Dufty, Goldsmith, & Wingfield, 1987). This prediction was tested in the brown-headed cowbird, but yolk T concentrations were not consistently higher than in the hosts' eggs, although cowbird chicks possibly have greater sensitivity to androgens (Hauber & Pilz, 2003). Parasitic chicks of brown-headed cowbirds display more vigorous begging behavior than their nestmates, presumably to induce their adoptive parents to feed them preferentially (Hosoi & Rothstein, 2000).…”