3 March 2015
Capable
of using tools to obtain their food, remembering the faces of humans and
predators, and communicating to others around them, crows are widely believed
to be the most intelligent birds on the planet. Besides this intelligence,
crows have gained an important reputation for being able to survive in many
ecologically diverse habitats such as fields, woodlands, forests, farming
sites, towns, neighborhoods and cities around the world. This and the crow’s ability to travel far
distances, as well as their omnivorously diverse diet, has helped crows to
maintain stable and growing populations, even as human interference and
adversity continues to affect them time and time again.
Current
ecological research has shown that crow populations have slightly increased
from 1966 to 2010 and that the global breeding population is at 27 million. A
fairly recent, and very deadly virus called the West Nile Virus, has been
responsible for many recent crow deaths and has accounted for killing 45% of
American Crows since 1999. Virtually all crows who come in contact with this
virus die within the first week, with very few survivors. Even with these
dangerously high numbers of crow fatalities, the International Union for
Conservation of Nature still lists them as a species of least concern. With
this growing virus epidemic however, it should be of major importance to focus
on protecting these crows before their populations begin to decline and the
virus is too rapidly spreading to stop.
Although
large crow roosts and close contact with one another can be dangerous with the
spread of the West Nile Virus, it is also fundamental in crow’s success and natural social
behavior in order to benefit and enhance their daily lives. These crows usually
spend this time together while roosting in very large “murders” (crow
flocks), which can range from hundreds to thousands and even sometimes to the
hundreds of thousands during the Winter months. Crows take this time to
socialize, to forage for new types of food, and to drive off predators (known
as mobbing). When they're not roosting, crows often stay together in year-round
family groups, which consists of the breeding pair and their offspring from the
past two years. Everyone in these families participate and cooperate in raising
the younger crows.
Probably
the most important phase in the crow’s lifetime is reproduction. In order for these crows
to reproduce, they must build nests in order to accommodate the needs of their
young. Both members of the breeding pair build the nest, which is made largely
by medium-sized twigs with an inner cup lined with pine-needles, weeds, soft
bark, or animal hair. Nest sizes are typically 6 - 19 inches across, with an
inner cup about 6 -14 inches wide and 4 -15 inches deep. Crows will usually
build their nests in trees, however there are many occasions where crows build
their nests in neighborhoods, towns and cities on human made structures such as
buildings, power lines and lamp posts. To build such nests on these structures,
crows use man-made objects to construct these complex designs.
Something
which has fascinated and proven to humans how intelligent crows truly are is
how they are able to recognize human faces from a bird’s eye view and from very far
distances away, and more importantly, communicate these human faces to other
crows. Even more intriguing, these adult crows will later pass this human
facial recognition on to their offspring, so that they also know to avoid these
threats. In addition to knowing these threats, crows also use different forms
of vocalization for different threats.
Over
time, crows have become very ecologically diverse throughout North America and
the rest of the world. This diversity has allowed them to continue traveling
all around North America, even as human civilization and industry expands
rapidly. Some major advances to crow livelihood came from American agriculture
during the 1800’s and
1900’s. Corn
and other grains became a common food choice amongst most crows and this large
abundance of food helped to grow crow populations significantly.
With
such a diverse diet, methods to eating hard to crack foods must be found. Nuts
and small turtles for example, cannot be eaten in their shells, so many crows
have adapted to dropping these foods from high altitudes and then fetching them
as they hit the ground and break. Other, much more modern methods discovered by
crows, involve placing these shelled foods in front of cars on streets and
waiting for the cars to smash them, to which the crow takes great delight in
eating afterwards. These new methods of eating uncommon foods are essentially
important in understanding crow intelligence and how they will continue to find
new solutions to every problem they encounter.
Throughout
this ecological research of crows, I have learned and come to understand many
important and fascinating things about crows who live in many different
ecological habitats and deal with many different ecological factors all the
time. It is important that I can inform others about these crows and also point
out their true importance in the natural world.
About Myself
I am from
Redmond, Washington and am currently attending the University of Washington in
Bothell. As a first year student, I am currently working towards getting my
credits and the necessary prerequisite courses in order to attend the School of
Business here are UWB and to eventually get a degree in Business. I am enjoying
my first year here so far and look forward to continuing my education at UWB.
Photo credits: all by S. Offeman
RESOURCES
The Cornell Lab of Ornithology,
All About Birds, American Crow [Internet]. [Cited March 5, 2015]. Available
from: http://www.allaboutbirds.org/guide/american_crow/lifehistory
KCTS 9, Nature, A Murder of
Crows, Crow Facts [Internet]. c February 21, 2013. [Cited March 5, 2015].
Available from: http://www.pbs.org/wnet/nature/a-murder-of-crows-crow-facts/5965/
Scientific American, Crows Show
Off Their Social Skills [Internet]. c August 8, 2013. [Cited March 5, 2015].
Available from: http://www.scientificamerican.com/article/crows-show-off-social-skills/
Marzluff M John. 2007. In the Company of Crows and Ravens. [Cited
March 5, 2015]. Yale University Press.
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