Teens and young adults are at increased risk for meningococcal meningitis. What is meningococcal meningitis? The Centers for Disease Control and Prevention (CDC) recommends 2 doses of quadrivalent meningococcal conjugate vaccine for adolescents 11 through 18 years of age.
Physical Differences. Crows and ravens differ physically from one another, their size being the most noticeable. Ravens are larger than crows, making them the largest perching birds. Crows have a smooth texture whereas the raven has a dense and shaggy plumage particularly around the throat. The bill of the raven is also heavier than the crow's bill. During flight, the spreading of the tail can distinguish the crow and raven apart. The tail of the crow spreads into a fan-like structure while the tail of the raven spreads into a wedge shape.
One of the great animal phenomena of the world is the congregation of large numbers of birds into a single group to sleep together. Such communal sleeping groups are known as roosts.. Many species roost in groups; such things as crows, robins, starlings, blackbirds, swallows, and herons. Another idea is that the birds get some protection from predators by being in a large group. 2  This is the wagontrain analogy: safety in numbers. 3  Crows are most afraid of large owls, and sleeping with a bunch of other crows could afford some protection for an individual crow.