Wednesday, February 29, 2012

Global Warming Causing Infidelity in Birds?

When climate conditions become more variable, birds are more likely to ‘cheat on’ and ‘divorce’ their mates. The hypothesized reason is that birds may be seeking out a greater diversity in genes for their offspring. An unstable climate could be deadly for birds, so breeding with a wider range of mates could increase the likelihood that their offspring are fit for the new environment.

Over 90% of bird species regularly engage in social monogamy. A male and a female will pair off, sharing territory and engaging in social pair behavior for at least one breeding season, although many will remain monogamous for many years. However, researchers have found that some chicks are actually fathered by other birds than the ones who act like their fathers, taking care of the nest. Also, a pair of birds may act monogamous for a few years, and then ‘divorce’, finding other mates in subsequent years. Exposure to a variable climate drastically increases the chances that a bird will engage in extra-pair copulations or will find a new mate for the season.

For example, birds with large beaks are sexually selected for in dry climates, where they are better at eating large seeds; birds with small beaks are sexually selected for in rainy climates, where they are better at eating tiny seeds. It is easy for a female to select her mate in a stable wet or dry climate, but if the climate is variable, she will seek variability. This occurrence is becoming more and more prevalent with recent global warming.

Posted by Erica Fitzpatrick (1)


  1. Could it be that because of global climate change, bird territories are progressively overlapping, and opening new channels of breeding potential for birds which is causing the infidelity; not so much the climate actually affecting their traditional mating rituals? If territories are being crossed with birds that have very different mating rituals, it may simply be a matter of mixed tradition. True to habit, birds will chose mates with the most beneficial phenotypic traits, but that does not necessarily mean that the two mates are of the same species. This may be where the observed "infidelity" occurs.

    - Jeff Keating (2)

  2. I agree with Jeff (above). I think it is more likely that the infidelity of the birds is not a direct result of climate change, but an indirect result. The climate change is causing smaller populations and overlapping territories, as well as changes in migration times that may cause some birds to overlap in areas when they had no before. These new interactions are plausibly more of the cause of the new mating practices observed, rather than the birds realizing that the climate has changed and they should subsequently select another mate. It seems that hypothesis would make their choices deliberate, when mating practice are not deliberate choices but rather instinctual drives.

    Posted by Laura Moro (2)

  3. I would have to agree with the comments above. Because global warming is occurring, environments are negatively effected as a result which creates the issue of fewer resources available for these birds. Therefore, it makes sense that natural selection is occurring as birds with larger beaks survive better in an environment with larger seeds, yet I do not think this is because of climate change. One survives with better resources and in the case of larger seeds, one is better off with a larger beak, which refers to natural selection and mating preference I believe, rather than climate change.

  4. I don't know much about ecology but if there is a correlation between rising temperature in bird infidelity this could be quite alarming. You can't deny the possibility. True it could be due to a overlap of breeding areas, as suggested above, but what if it is actually the climate? One must ask the question.

    posted by Dorian Pillari (C)

  5. Interesting post. When these birds select a new mate is there any underlying theme, or do they just try to mate with as many other birds as possible in these variable times?

    Posted by Michael Thomas

  6. It seems like if climate change is the cause of this, it will just keep occurring more and more. Maybe eventually the birds will be mating so much it results in a population boom and an overcrowding of birds?
    Rhys Ursuliak

  7. I think this is more interesting than alarming. The only reason this would be alarming is if this caused some sort of disturbance in the food web because of an overpopulation of birds. Birds cheating on each other isn't in and of itself a bad thing, it just seems bad to us because it's looked down upon in our culture.

    Mike Selden (C)

  8. I like the theories from the first few comments, I completely understand from their point of view that it's possible that the population ranges are overlapping. It's a possibility that's more than likely. But could it be possible, that it's innately biological more than environmental? could chemical functions in the body of the birds be affected by climate change? This is a wonderful blog that brings up very interesting theories.

    Posted By Andy Zou

  9. This article makes a lot of sense. It seems logical that birds would mate with as many mates as possible if they feel threatened as a species due to a dramatic climate change. However, why wouldn't the birds just migrate to a new location to avoid the drastic climate change? It seems as if they could move and evolve to their new environment and therefore avoid being wiped out as a species.

    Posted by Nicco Ciccolini