Anything but Common: The Hidden Life of the American Crow

Since American crows spend so much time as a family, inbreeding might lessen the amount of healthy breeding partners long term. It might also exacerbate certain negative traits, predispositions of certain illnesses or other diseases. We see similar concerns show up with dogs that are repeatedly interbred with close relatives to create traits which, while desirable to humans, can be detrimental tot he dogs (see, for example, the snout of the pug being too short.) Could more inbreeding lead to shorter beaks, weaker eyesight, or other negative traits in crows? The species as a whole could be weakened as family groups get tighter and tighter genetically.

1.  When it comes to inbreeding, are these unwilling females?   I'm sure some are unknowing inbreeding too. 2. Extra-pair fertilization is not surprising to me in any species of animal.  It can be beneficial to bring in new strong traits but also go the other way and introduce a weakness.   But I can see that it can also lead to unknowing inbreeding.

I have heard about social vs. sexual monogamy as a common issue. Males with often less investment into raising their offsprings will benefit by more effectively spreading their genes.  For females, I can see the potential advantage of having a genetically more diverse groups of offsprings, which may translate into better chances of survival under changing/challenging conditions.

Inbreeding within the crow families and communities can mess with the crow gene pool. Causing them to potentially die earlier from health problems due to incest. This can also make them less genetically different from each other meaning they can become endangered and potentially not have inherited skills to keep them alive in the wild. This is really interesting considering how smart crows are.

1. The level of threat to crows from inbreding is probably relatively low, but may also serve as a polpulation control mechanism. As states in Ms. Townsend's article, inbreeding did lead to increased vulnerability to mortality from disease. 2. Extra pair fertilization is not suprising to me, as I learned about it in my evolution class. This could be beneficial it helps to diversify the genetic pool of the population.

1. Inbreeding could reduce genetic variation making crows more vulnerable to disease and environmental pressures. 2. Yes, this is surprising to me. I always thought that a major distinction in reproduction strategies between mammals and birds, was the need for birds to be monogamous. It could be beneficial to the male, allowing him greater access to mates and securing his genes into the next generation.

The rate of inbreeding among crows definitely surprises me, as crows are so intelligent they should be able to recognize who is related to them. Inbreeding poses the threat of inherited genetic conditions and health problems, shortened lifespans, weakness or failure to thrive.

As Dr. Townsend said in the summary of her research, inbred crows can have shortened lifespans and can be found to have died from disease more than non-inbred birds.  This seems that it could be detrimental to crows and their numbers as a whole, and in some areas, it might be.  But knowing their great numbers and their widespread range and the fact that this a really only a 17% phenomenon, perhaps the flip side of this practice is that it is a tool to help control population in the long-run.  Not that the birds are thinking that way, of course. They want their offspring to be successful.  Just a thought. As for extra-pair fertilization among birds, it doesn't really surprise me.  I used to care for a large flock of wild mallards and mating season was an eye-opener for me.  I often saw a female and a male cooperatively raising the ducklings. Granted, to my uneducated eyes, it seemed that the female was doing most of the work, shepherding, scolding, protecting. But the dedicated male was always behind them, helping to round up the slower babies, keeping an eye out for other ducks who might prey on the young.  But during the breeding season, even though there was obviously a dedicated pair, other groups of males (I assumed they were bachelors)  would often swoop in and mate with a very unwilling female, while the dedicated male protested from the side or tried to chase the invader(s) off.  It's obvious that out of a nest of 14 eggs, some of them had to be fertilized by different fathers.  And if that happens in the duck world, it must happen with other birds, though not as noisily and therefore obviously.

The first thing that comes to mind, as a threat is inherited weakness or illness. Extra pair fertilization probably increases the survival of the family and the entire group.

The problem of exaggerated recessive negative genes  is always a danger, as with most mammals (I think).  Without diversity in the gene pool, they may all become susceptible to the same pathogen or negative survival behaviour. Extra pair fertilization broadens the gene pool, providing better balance against group susceptibilities.

1. The usual genetic abnormalities and increased risk of illness/death (just as with humans).  2. This wasn't surprising as I had learned that many other bird species have extra-pair fertilization (I believe most of those who pair up for either many breeding cycles or for life, do this), so why not crows as well. I think it would be beneficial in terms of increasing genetic diversity. Not that the crows probably care about genes, per se, but they likely do care about long-term survival, and increased genetic diversity can improve survival.

1.  I’m no biologist - but i have always believed that inbreeding can not only stunt development/evolution of future generations, but perhaps contribute negative issues.  Do crows suffer from this same issues with inbreeding?  I would imagine that inbreeding may cause possibly some areas where birds may not become disease resistant - or not fully able to genetically consider the impact of global warming through out the entire region?  I wonder, as stated, why such birds who travel far distances remain homebodies with regard to mates.  Why aren’t there more sub-sets of crows due to evolutionary changes that may occur in different regions? 2. I suppose the more invested adults may enlarge the family network of crows?

I was surprised that there was inbreeding among the American Crow population, especially the mother son inbreeding.  The threat to the Crows from the inbreeding could be that there are genetic problems like deformities that could cause early death for some Crows.  I would imagine the "extra-pair" fertilization would be helpful in maintaining the population of Crows, but, again, I have concerns about the above mentioned problems of inbreeding.

Could it be , that crows aren’t thinking about their genetic makeup at ALL (AND ) that males could , since they are dominant, affect an outcome more so, than the other way around? I also think that maybe, just maybe,  genetic science isn’t ‘all there’ yet as many would like us to believe . Do not get me wrong; I believe that the science as we know it probably is right......but 25, 50 a hundred years from now , something new will ‘pop up ‘ and we’ll have a more concise understanding of the data we may be getting .

1.  I'm not sure about the specifics of the genetics of crows, but perhaps it could cause genetic deformities in future generations, especially with the mother-son inbreeding? 2.  Perhaps it's an instinctive survival behavior that helps to increase the species population where disease and enemies may be a factor?

Inbreeding can have same result among crows as with humans. Recessive genes can combine to create deformity or genetic weakness among the group. Apparently, inbreeding was not uncommon among early isolated human groups and even humans today isolated by geography, social or religious structure. I don't find any of this surprising.

If breeding is really all about preserving genes, then I guess inbreeding makes sense. But still, I am disappointed to hear that some crows practice incest.

Good day, I'm very much enjoying the "Anything but Common: The Hidden Life of the American Crow" course. After watching the "Secret Sex Lives" video, I have a question: What is the evolutionary purpose for the female crow to seek additional breeding opportunities outside of her existing pair bond? Would love any feedback, even if speculation, thank you! Gigi Guthrie

Inbreeding, just as with humans, could increase the likelihood of harmful mutations becoming expressed as disabled offspring or death before reaching breeding age. I didn't know birds paired up so much, so extra-pair fertilization is not so surprising to me. It could be beneficial in widening the gene pool.

There was an interesting paper on inbreeding in black robins showing both positive and negative effects.  I can't remember the citation. The "secret sex life" and small amount of this inbreeding behavior might help maintain crow social bonds in some ways that might offset the deleterious genetic problems that might occur.  While it may seem very strange to humans, it might "work" in some ways for crows and other animals.  Extra-pair fertilization is not at all surprising to me in birds, humans and many other so-called monogamous animals, and could definitely add some "genetic diversity" to these close-knit groups.  A risk-benefit analysis played out over the long evolutionary history of such behaviors . . .

1. Inbreeding may cause genetic issues such as weaknesses and shorter life span perhaps. 2. This is not that surprising. It is always nice to think that crows are monogamous but oh well...Yes, I believe it could be beneficial for their genetics especially if the extra male is from a different family.

1. The most obvious problem would be genetics.  As shown in several monarchs, inbreeding has negative hereditary implications. 2.  Not really, it seems like a smart solution to sustaining the species.  

2. Yes, I didn't know that crows had such weird sex lives, but then again so do humans. It depends whether it could be beneficial or not, depending on the relationship

1. Genetic damage and body/mind abnormalities are well known among humans that inbreed, so I suspect crows would suffer the same sort of flaws in the offspring. 2. I have learned that genetic diversity is generally good, minimizing inherited flaws; so I expect that extra pair fertilization would be beneficial.