Mike

The number of crows in my area appears diminished but I may be noticing a dispersal due to the winter.  I have not seen any one legged crows but  West Nile Virus is definitely in my area according to our state DNR.  I see that our crows are always competing and fighting for scraps of food.  Pairs may cooperate but not larger groups.  Not much feeding of birds goes on in my neighborhood and we are far enough away from corn fields that more than one family may not be supportable.  

I think that crows have a harder time becoming breeders because they are not as promiscuous as many other bird species who only come together to mate and stay only long enough to defend a nest and raise a brood.  The crow also seems to have a complex social system that relies on longevity and close ties to a family unit unlike more prolific and unattached bird species.  Crows also tend to be more sedentary and not migrate like other birds.  They do not seem to have the same desire to venture very far from their homes and the home may be limited in opportunities to carve out territories that can support expansion.

I don't  think that my rural area is advantageous for large crow roosting.  We have old growth hardwoods but not as many deciduous trees.  The Mississippi River flows through the area and it's a major flight way for mostly migratory water fowl and increasingly the American Bald Eagle.  I see many eagles far inland from the river and I wonder if increasing Eagle numbers are affecting the local crow population.

I was surprised at how in depth the crows are identified, marked and followed during their life cycle.  The longevity of crows was surprising given how tough living in the wild must be.