From the Contact Station March 2018

I saw an eagle; it was so big!

Winter is a great time for seeing the “big birds.”  Many are here to fuel up for the coming nesting season up north.  Some are hunters and are easily seen flying over the refuge in search of prey.  Some are stalking prey on the ground.  Then others are on the open ponds or fields looking for a more vegetarian diet.  Nevertheless, they standout.  There are several ways to assess size of birds; weight, body length when perched or height when standing or wingspan come to mind.    Let’s focus on wingspan for now as most of these birds can be seen flying around us while we drive the River S.

Our commonly seen Red-tailed Hawk has an average wingspan of 49 inches, a bit over 4 feet.  That is a lot of bird. By comparison, the Red-shouldered Hawk has a wingspan of 40 inches.  If a buteo hawk is flying overhead, could you tell which one it is by the wing span size?  Probably not, but if you see the two together circling in a thermal, you can see the difference.   So how does the Bald Eagle compare?  It comes in at a whopping 80 inches.  Just to cover all bases, the Golden Eagle has a 79-inch wingspan.  Goldens, which we rarely see at Ridgefield, beat out the Bald Eagle slightly in weight, but your just not going to be able to distinguish that inch for a bird in flight to know which eagle you have.  What can be so deceptive about wing size is how far away they are when you are observing them.  Lone birds in the sky can always be difficult when thinking only of size. However, it is good to have in mind the differences between wingspans so when you get two birds in proximity to each other, you have another clue to identification. Of course, how they fly and wing shape are better details to find your way to identification.

Let’s look at some other refuge frequent fliers.  At 72 inches, the Great Blue Heron is getting up there with the Bald Eagle.  It wouldn’t be the first time with a quick glance I thought Bald Eagle only to have a Great Blue Heron lumber by.  They hold their wing differently as they fly.  While the Bald Eagle sails through on what some describe as washboard wings (blocky and squared), the Great Blue Heron tends to round its wings with tips down as it floats.  But they both qualify as “big birds.”

Our winter waterfowl and cranes are interesting to compare.  In the middle of this discussion for wing length are the Canada and Cackling Geese.  They range from 43 to 53 inches and if you lined up all the subspecies of these two species, they would look like those cute Russian nesting dolls.  I love to see the swans come in for the first time in the winter.  Our more common Tundra Swan averages a 66-inch wingspan while the larger Trumpeter Swan competes with the Bald Eagle at 80 inches.  That’s a discernable difference, but have you ever seen them flying together?  I haven’t.  They are prone to calling as they fly and that is the best way to tell them apart.  There is another big white bird that we have been seeing more of late.  However, they tend to fly very high, only occasionally landing in a suitable pond and at limited times of the year.  That is the American White Pelican.  A wingspan any bird would envy at 108 inches.  When they land, they look like they are folding in those black tipped, white wings.  They usually circle in large flocks and are so far away, you just don’t get the immediate impact of the wing span.  They are wonderful to watch though.

Our Sandhill Cranes have a wingspan varying from 65 to 90 inches.  Like the Canada/Cackling Geese, there are several subspecies, but interestingly, the wingspan is more a matter of feather wear of the primaries, than variation among subspecies.  Cranes take three to four years to replace these feathers and can therefore have a reduced wingspan over that time due to feather wear.

This information is more an interesting bit of trivia than a scientific approach to identification in flight.  There are so many more useful characteristics for identification.  And, as a caution, I used one field guide source for this information but reports of wingspan vary between publications.  Some variation also exists between the sexes, with raptors having larger females. So, the information is relative.  I invite you to visit with Annette on Saturdays in the Contact Station.  She has put together a visual guide to difference in wingspan among our “big birds.”  It’s just another way to enjoy the wildlife on our River S tour.

-Susan Setterberg, Board President and Contact Station Volunteer

Photos; Eagle- Dennis Davenport 2016 Photo Contest Honorable Mention & Sandhill Cranes- 2nd Place