and Waxwings in Winter and Summer
observers see American robins and waxwings being very sociable to each
other in winter. They don't look alike or sound alike, yet the two species
are okay hanging out with each other. How
are they alike and different?
Tale of Two Species
American robins and waxwings are both flocking species in winter. That's
because both eat fruit. Flocking is helpful because flocks
have more eyes to discover new sources of fruit. Where they
find fruit, it's abundant. Lots of fruit means flock members don't have
to worry about competing.
are very sociable in winter, though not quite as sociable as waxwings.
are the least territorial of all songbirds. They don't defend a nesting
territory against their own species. Waxwings don't even defend a personal
space. They often sit shoulder to shoulder when feeding on berries
or flower petals. You can sometimes spot them
passing one berry down a line of birds, each bird passing the berry to
its neighbor before one bird suddenly swallows it (more on that below).
Robins never pass food back and forth. Robins usually
don't sit quite as close together; they never sit shoulder to shoulder,
even in trees.
days grow longer and spring turns to summer, waxwings remain sociable.
But robins slowly become more territorial. Some
robins will start squabbling in the feeding flocks. Some robins will sing
now and then. Little
by little the robins' increased squabbling and singing will break up the
robin flocks. In other words, the robins'
to being territorial is what eventually breaks up their flocks.
have a loud song.
Their song helps warn away other robins. This is how they ensure a big
territory for getting enough worms for their babies. Waxwings have a soft
little snore (recordings courtesy Lang Elliot) because they don't
need to warn each other away.
Theory on Waxwings' Berry-Passing Habit
do waxwings pass berries back and forth among themselves? Journey
North robin expert Laura Erickson wondered about this until one
winter when she was caring for an injured Bohemian Waxwing. A huge
flock of Bohemian Waxwings were visiting her yard, feeding on mountain
ash berries. Following their example, Laura fed some of these berries
to her hurt bird. Ten or fifteen minutes later, out they came in
the bird's poop, completely undigested! The waxy coatings of the
berry were apparently too thick for the bird's stomach acids to
dissolve during the short time the berries were in its stomach.
So Laura picked some more berries. This time she rolled them in
her fingers for a few minutes to soften them. Then she fed the softened
berried to the waxwing. Voila! Now the bird could get the
nutrition from the berries.
charming food-passing habit apparently serves two purposes: It helps
to cement the bonds between these sociable flocking birds. It also
helping them digest their food!
This! Journaling Question
are robins and waxwings alike and different? Make a Venn diagram to
sort out the facts you found on this page. How does each type of behavior
benefit the species?
Science Education Standards
- An organism's
behavior patterns are related to the nature of that organism's environment,
including the kinds and number of other organisms present, the availability
of food and resources, and the physical characteristics of the environment.
- An organism's
behavior evolves through adaptation to its environment. How a species
moves, obtains food, reproduces, and responds to danger are based in
the species' evolutionary history.