I don't  think that the percentage of inbreeding is high enough to trigger genetic defects that can seriously affect the crow species.  Families too removed from outside breeding opportunities (like being trapped on an island) could find this fatal.  Crows are not Pharaoh's in that they do introduce each enough genetic variability so as not to be a problem.  The advantage of the family cohesive nature might outweigh the downside to inbreeding as the family is more likely to survive intact.  Most genetic mutations are not harmful even if chances increase due to inbreeding.

1.Inbreeding might cause disease, and the crow species might become less diverse due to the tight family(genetically), and could lead to a downfall of the whole species, I wonder if the crows realized this. 2.Extra-pair fertilization might be beneficial, due to the fact that the eggs have a high chance of hatching since their are not in a single nest. The extra-paired males doesn't need to spend that much energy in raising them. The crow population might be more diverse, because traits gets passed around and the young benefits from this.

For individuals, inbreeding could result in genetic defects and greater susceptibility to diseases (overall reduced physical fitness). If the population as a whole has a low level of genetic diversity, the impact of a disease could be more severe, quickly spread throughout the group and lead to the population crashing.

Extra-pair fertilization is a useful strategy for both parties (ie. the breeding female and extra-pair male) to have greater reproductive success, as they aren't putting all of their eggs in one basket, so to speak. The extra-pair male gets to sire extra offspring without spending any energy needing to raise them. The female gets more genetically diverse offspring which should statistically increase their chances of survival - e.g. if the extra offspring have some extra good trait(s) - assuming there is enough food to go around. The only "loser" here is the breeding paired male, who spends time and energy raising young that are not genetically related to him. However, given that crows breed cooperatively, there is still an advantage to this as the extra-pair offspring will help him the future.

I would suppose that inbreeding could be a threat, although the percentage rates of incest and near related are rather high, how many generations has this been happening? If this has been the crow way for eons then maybe there is some sort of genetic advantage. Extra-pair fertilization possibly has some benefit for the health of a flock or family to offset any disadvantage that incest or near related that might occur.

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.