March 2017: The Eyes of March

 

The anticipation of the ospreys’ return pulls everyone’s eyes toward the sky. The excitement mounts as Dunrovin pulls the winter bird feeder from the perch, cleans the web camera domes, and everyone begins to wait—watching an empty nest with fingers crossed that our beloved birds will return for another season of breeding. Sometimes during this March waiting period, other uninvited birds think that they will set up shop. Last year we had a great horned owl visit the nest regularly and even knock Harriet from her perch within the first few days of Harriet’s return. This year, we just had a pair of Canadian geese check out the digs. They moved a few sticks, momentarily sat down to try it out, then, luckily, they moved on. This March waiting game can be nerve wracking. Our hearts belong to the ospreys, yet we all know that nature does not always follow our hearts’ desires.

Since the first years of using our web camera, it has become very apparent that identifying individual ospreys that stop at the nest is difficult. All ospreys have similar plumage color patterns. However, the web cameras do allow us to notice differences. Careful inspection and attention to details generally reveal subtle differences in head and face plumage, but when the action is quick, it can be nearly impossible to tell one bird from the other. Some general rules do help. Females are bulkier than males, and they may have more of a “necklace” of dark feathers on their chests. But in the absence of singularly distinguishing characteristics, such as the “wonky” feather displayed by the male osprey, Stanley, from the Hellgate nest, it takes a practiced eye to positively distinguish one bird from the other.

One clear distinguishing feature of our female bird, Harriet, is the large number of black flecks in both of her eyes. We noticed this very early on in our relationship with these birds, and we have since come to rely to some degree on the birds’ eyes as identifiers. Note the differences in Harriet’s eyes versus Hal’s eyes. Hal has very clear, yellow irises with no distinguishing black flecks, whereas Harriet’s eye show large “fields” of black flecks in the lower half of both her eyes. The female osprey at the Hellgate nest got her name Iris from the distinguishing black flecks in her eyes.

 

 

 

Ospreys’ eyes are protected by three eyelids: the upper eyelid resembles that of humans. Their lower lid closes when sleeping. Their third eyelid is really a nictitating (which means “blinking”) membrane that sweeps horizontally across the eye’s cornea from the medial side. This translucent membrane is hinged at the inner side of the eye and serves multiple functions. It keeps the eyes clean and moist, it protects the eyes from wind, bright light, and possible obstructions, and it serves as a set of goggles as the ospreys dive into the water to catch a meal.

 

 

Ospreys’ eyes start out as dark orange or rust colored for the first several years of their lives, then gradually change to the adult bright yellow pigmentation.

 

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1 Comment

  1. Marion Lavery on March 29, 2017 at 11:07 pm

    Thank you Suzanne!