Researchers are studying a population of house sparrows on the island of Lundy in the United Kingdom to learn more about the cost of infidelity and how monogamy arrises for the species.
It turns out that males who are partnered with females that cheat during breeding season will provide less food for the offspring. Does it come down to a male with a wounded ego refusing to provide for offspring he isn't sure are his? Maybe not.
Imperial College London reports, "It has long been suspected that males know that not all the chicks in their nest are theirs, and so make a decision to provide less. But an alternative explanation is that cheating females and lazy males tend to pair up naturally."
During a 12-year study, the researchers found that even when chicks of different parentage were placed in the nest of a more faithful couple, the male sparrows fed them just as much as if they were his own. This means that males don't know when they're feeding their offspring, or another's. Instead, it may be that adulterous females and lazy males partner up naturally, or it could be that males become lazy based on the female's behavior during the mating season. If she's off cheating, he will decide to be a deadbeat dad since there's a likelihood that offspring aren't his.
Why do females cheat in the first place, if it leads to a deadbeat partner who risk the survival of the chicks? The researchers are continuing to investigate.
"Being unfaithful may be a costly behaviour for females because they only lay a limited number of eggs, and it may be a hangover from when their ancestors were not monogamous, rather than a useful strategy for getting the strongest offspring."