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Friday, April 5, 2013

Nest Building and Function of Greenery


See the progression of the building of the 2014 nest bowl in this Flickr set by grasshopper! 


BR, Just Plunk The Pine Down Right on Top of Ezra
April 4, 2013, 7:05 AM by elly012912


Nest Building

Posted by ClareEliz in chat on April 2:
  • Nest building usually begins late February or early March.
  • For most of interior North America, first eggs laid mid-late March.
  • Typically, several nests from previous years are visited by both members of the pair. Two or more nests are often repaired, and greenery may be placed on these before a single nest is finally chosen.
  • A nest may be used for ≥1 years by the same pair, vacated for ≥1 years, and used again.
  • Refurbishment of previously built nests includes adding new sticks and twigs to reinforce outside and adding greenery, strips of bark, and other materials to line bowl.
  • Sometimes ≥2 nests are built or refurbished without being used in a particular year.

For more information, see:
http://www.allaboutbirds.org/guide/red-tailed_hawk/lifehistory

and http://www.blm.gov/pgdata/etc/medialib/blm/id/special_areas/birds_of_prey_nca.Par.98205.File.dat/red-tailed%20hawk-web.pdf


    What is the function of the greenery in the nest?

    The nest itself is constructed of sticks and twigs, each of which is usually less than an inch in diameter. Green conifer sprigs are typically placed outside of the nest early in construction. It is speculated that the sprigs may function as a signal, perhaps to other hawks, that this nest is under construction. Alternatively, greenery placed outside and inside the nest may act as a pesticide, killing or discouraging insects or lice.

    The entire nest is typically 25 to 30 inches (63 to 76 centimeters) in diameter. The inner bowl is usually about 5 to 6 inches (13 to 15 centimeters) deep and lined with strips of bark, fresh green twigs from conifer and deciduous trees, and other plant materials. Both members of the pair help with the nest construction, but the female takes primary responsibility for shaping and lining the bowl.

    Source: Preston, Charles R. Wild Bird Guide: Red-Tailed Hawk (Wild Bird Guides). Mechanicsburg, PA: Stackpole Books, 1999. Print.

    Also, see this fascinating article posted by Grandad Rufus about the insect repellent nature of the greenery: