ScienceDaily (Dec. 20, 2011) — Mockingbirds rarely remove the ‘alien’ eggs parasitic cowbirds lay in their nests because keeping them dilutes the risk of their own eggs being attacked.
The study, by Oxford University and Argentinean scientists, examined the behaviour of the chalk-browed mockingbird (Mimus saturninus) which is parasitized by the shiny cowbird (Molothrus bonariensis) in Argentina.
Of 347 mockingbird nests studied 89% were parasitized with one or more cowbird eggs, 35% receiving more than three, and 16% more than five (typically, they received around three).
'It might be expected that this high rate of parasitism would encourage a host to evolve more effective anti-parasite defences,' said Ros Gloag from Oxford University's Department of Zoology, an author of the report. 'In fact, the opposite is probably true: the higher the intensity of parasitism, the higher the frequency of puncturing attacks and the greater the importance of diluting this risk. Thus, hosts benefit more by not rejecting parasite eggs when there are more parasites around.'
This is a rather fascinating study, given how counter-intuitive this may seem. However, I would like to see similar studies done with several other species as I don’t think this relationship is universal. Interesting stuff! Click the title to read the entire article.
ScienceDaily (Dec. 19, 2011) — In June 2011, a team of Chinese and Swedish researchers rediscovered the breeding area for the poorly known Blackthroat Luscinia obscura, in the Qinling mountains, Shaanxi province, north central China.