First year male (no red visible)
Probably a 2nd year male (little red visible)
Older, More Dominant Male (larger red stripe)
Female
The red-winged blackbird (
Agelaius pheoniceus) is one of the most studied birds. Many papers have been written showing a correlation between the size of the red epaulets (stripe) and the number of females that are attracted. The size of the epaulets have also been shown to correlate to the size of the territory a bird controls; the larger the red stripe, the more area the bird controls. Sounds a whole lot like stripes in the military. With the exception of the female in the last pic, notice the different size red stripes in these birds. It usually takes at least two years for the red stripe to appear above the cream color stripe. From the second year on, the size of the red stripe will be dependent upon good genes and nutrition. So the next time you see one of these real common birds, take notice of the size of the red stripe.
Females
Rearview of Male
Male (note the beginning of a shoulder patch)
Mixed Group (male in center)
Probably a 2nd year male (little red visible)
Older, More Dominant Male (larger red stripe) 
Female
The red-winged blackbird (Agelaius pheoniceus) is one of the most studied birds. Many papers have been written showing a correlation between the size of the red epaulets (stripe) and the number of females that are attracted. The size of the epaulets have also been shown to correlate to the size of the territory a bird controls; the larger the red stripe, the more area the bird controls. Sounds a whole lot like stripes in the military. With the exception of the female in the last pic, notice the different size red stripes in these birds. It usually takes at least two years for the red stripe to appear above the cream color stripe. From the second year on, the size of the red stripe will be dependent upon good genes and nutrition. So the next time you see one of these real common birds, take notice of the size of the red stripe. 
