Brood parasites are organisms that rely on others to raise their young. The strategy appears among birds, insects and some fish. The brood parasite manipulates a host, either of the same or of another species, to raise its young as if it were its own, using brood mimicry, for example by having eggs that resemble the host’s (egg mimicry).
Brood parasitism relieves the parasitic parents from the investment of rearing young or building nests for the young, enabling them to spend more time on other activities such as foraging and producing further offspring. Bird parasite species mitigate the risk of egg loss by distributing eggs among a number of different hosts. As this behavior damages the host, it often results in an evolutionary arms race between parasite and host as the pair of species co-evolve.
In many monogamous bird species, there are extra-pair matings resulting in males outside the pair bond siring offspring and used by males to escape from the parental investment in raising their offspring. This form of cuckoldry is taken a step further when females of the goldeneye (Bucephala clangula) often lay their eggs in the nests of other individuals. Intra-specific brood parasitism is seen in a number of duck species, where females often lay their eggs in the nests of others.
Most avian brood parasites have very short egg incubation periods and rapid nestling growth. In many brood parasites, such as cuckoos and honeyguides, this short egg incubation period is due to internal incubation periods up to 24 hours longer in cuckoos than hosts. Some non-parasitic cuckoos also have longer internal incubation periods, suggesting that this longer internal incubation period was not an adaptation following brood parasitism, but predisposed birds to become brood parasites. This is likely facilitated by a heavier yolk in the egg providing more nutrients. Being larger than the hosts at growth is a further adaptation to being a brood parasite.
There is a question as to why the majority of the hosts of brood parasites care for the nestlings of their parasites. Not only do these brood parasites usually differ significantly in size and appearance, but it is also highly probable that they reduce the reproductive success of their hosts. The “mafia hypothesis” evolved through studies in an attempt to answer this question. This hypothesis revolves around host manipulations induced by behaviors of the brood parasite. Upon the detection and rejection of a brood parasite’s egg, the host’s nest is depredated upon, its nest destroyed and nestlings injured or killed. This threatening response indirectly enhances selective pressures favoring aggressive parasite behavior that may result in positive feedback between mafia-like parasites and compliant host behaviors.
DES MOINES – The mother of Mollie Tibbetts, the University of Iowa student whose disappearance and killing attracted national attention, has taken in the son of Mexican immigrants who worked with her daughter’s accused killer, according to a Washington Post report.
In a story published Friday, The Post reported that Laura Calderwood brought Ulises Felix, 17, into her home. Ulises’ parents worked alongside murder suspect Cristhian Bahena Rivera at a dairy farm in Brooklyn, Iowa.
After Bahena Rivera’s arrest, Ulises’ parents fled town for Illinois and left behind their American son, a high school boy, according to the Post. When Tibbetts’ younger brother, Scott, asked Calderwood whether they could take in Ulises, the 55-year-old woman wondered what her daughter would do, Post reporter Terrence McCoy wrote.
Ulises has been living in a spare bedroom in Calderwood’s house. Mollie’s brother, Scott, also lives there.
Mollie Tibbetts was found dead Aug. 21, her body hidden in a cornfield in rural Poweshiek County, Iowa, after a month of searching for her.