Blog 259: Osprey Nest Building

Osprey nests fascinate me. These oversized, sloppy collections of sticks and garbage are tremendously strong, practical, and more sophisticated than they look. Most nest building takes place in the month of April, but the male will continue to provide new sticks and materials throughout the breeding season. One determined male Osprey can collect several hundred sticks in a day. Osprey nests must be built on strong substrates as they weigh an average of 400 lbs. 

Enormous Osprey nest, courtesy of Good Morning Glouster, UK. 

Osprey nests are built primarily with vegetative materials. In southern states, you will  find Osprey nests with palm fronds, twigs, cane fibers, and Spanish moss, whereas in  the north, sticks, twigs, and grass predominate. In Central New York, corn stalks are  often incorporated. The male Osprey brings most of material to the nest, while the  female guards the nest, but both partners arrange the sticks and twigs into place. The male flies by tree tops and breaking dead sticks by off the trees and snatching them  from the ground or water. Females collect finer, softer materials, such as moss, algae,  grass, rushes, conifer sprigs, and sod, to create a soft nest cup for the eggs and  nestlings. 

Finishing touches to the nest can include human debris and trash as treasured  “nestorations”. Ospreys are notorious collectors, satisfying their strong desire to carry items back to the nest by beachcombing and garbage picking all manner of flotsam and jetsam. Be it animal skeletons, plastic bags, candy wrappers, strings, or a broken flip flop, Ospreys search far and wide for additions to their nests. 

Dangerous nets, rope, and fishing line are found in this nest. 

In Ospreys: A Natural and Unnatural History, Alan Poole juxtaposes the oddities found  in osprey nests in the 19th century with those of the 20th century—an interesting  comment on our cultural changes. Rubbish from the earlier era bespeaks of a simpler  way of life with a rag doll, a doormat, a toy sailboat, a feather duster, barrel staves and  hoops, a bootjack, 20 feet of hemp rope, a blacking brush, part of a rainslicker, and  bleached-out animal bones. “Garbage” or “nestorations” from the 20th century reflects  our pervasive use of plastics and petroleum-based products including disposable  diapers, bicycle tires, Hula Hoops, bags, telephone cords, Styrofoam cups, Mylar  balloons, and plastic hamburger containers.  

Enjoy this time-lapse video of a Chesapeake Bay Osprey pair building their nest. True  to form, the pair begins by placing an aluminum strip and a pink plastic boundary ribbon  on the bare platform. As the male Osprey brings sticks and the female tucks them into  place, the sides of the nest build up, following the contours of the nest box with sticks  cutting the corners to make round it. After the outer rim is built sufficiently high to  contain the future nestlings, the center is lined with softer materials to insulate and 

protect the eggs and young nestling. Ophelia and Orpheus will spend hours nipping at  the nest twigs, pulling and pushing them into spaces between the sticks, before adding  another twig. Easily tangled materials like plant fibers, grape vines, fishing line, twine, and plastic ribbons are incorporated into the nest structure and probably help retain the  sticks in place. It seems to be the female’s prerogative whether or not to accept building  materials. If she does not like a particular hard-won stick that the male delivers to the  nest, she will simply discard it and wait for another. 

Plastic bags may make the nest less drafty. 

The shape of an Osprey nest changes during the breeding cycle. The nest is bowl-like  during egg incubation, but flattens after the eggs hatch. The male continues building up  the rim of the nest to protect the inquisitive, yet clumsily nestlings. During the last weeks  of the nestling phase, the nest often becomes completely flat under the weight of 1–4  young Osprey.

Plastic-trash-riddled nest, courtesy of Connie Morgenstern. 

Protect Ospreys and other aquatic birds and mammals by removing trash from beaches  and lakeshores, especially easily tangled plastics, strings, and ropes. When these items  are innocently brought to the nest, the inquisitive and awkward nestlings and adults can  get tangled or strangle. Help Ospreys make safe nests for their broods by limiting your  

use of plastic goods and cleaning up our lakeshores. 

Eyes to the sky! 

Candace 

Candace E. Cornell 

Friends of Salt Point 

Lansing, NY 

cec22@cornell.edu 

Read!  

On Osprey Time 

Ospreys of Salt Point

Explore! 

Cayuga Lake Osprey Trail   

Watch!  

Salt Point Osprey Nest Cam 

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