Happy Earth Day! Let’s Talk about Bird Nests!


I have been sitting at my computer writing final exams for my courses (only one week of classes left!). I have been splitting my attention, however, between the physiology of DNA replication and the activities of a pair of robins up in my backyard spruce tree.
The robins are flying in great beak-loads of wet, muddy grass and straw and are building a nest at the end of one of the middle level branches of the spruce. Last year, just below this construction site, a pair of cardinals built a nest that they eventually abandoned after it was raided by blue jays. The branch that the robins have selected seems to me to be too light and too subject to wind stresses and damage. The open location also makes the nest visible to jays (as the cardinal found out last summer). But, it’s their nest and if it fails they will have two or maybe even three more tries to successfully reproduce.
A few days ago (while I was writing African ecology final exam questions) I watched a crow snapping a dry twig off of the dead, lower branches of another spruce that borders my side field. The crow took the twig, trimmed it down to a straight, foot-long piece and then flew off into the dense tree canopy at the lower end of the field. He returned in about 15 minutes and repeated the procedure several times. He was also building his nest. I plan to go down into the lower woods soon to see if I can see his chaotic piles of sticks up in the branches. It is surprising that a crow would try to nest so close to so many houses.
The robin’s nest will be a tight, neat bowl of mud cemented grasses. The crow’s nest will be a broad, random pile of sticks. The killdeer, though, makes an even odder nest.
Killdeers have been screaming at passing humans for several weeks now. A pair (or more) lives up on the flat roofs of Penn State New Kensington’s Science and Engineering Buildings. They stand on the raised parapet at the roof’s edge and watch each of us enter and leave the building. They complain loudly about our movements. The killdeer nest is a flat cup of stones or gravel situated in the open spaces of an old field ecosystem or in the case of our Penn State birds on the flat, graveled roof. Several years ago down at Chincoteague Island Joe, Marian, Deborah and I spent over an hour searching for the ground nest of a killdeer in the front yard of our rental cottage. The quality of the camouflaging of the eggs along with the racket and distraction behaviors of the mother killdeer made it very difficult to locate the nest. A predator would have given up more quickly than vacationing nature lovers!
We have found many interesting nests over the years. We have found thrush nests lined with the shed hair of our horse and our dogs. We have found tiny hummingbird nests seemingly woven out of spider silk. We have had generations of barn swallows grow up in caked mud nests stuck up under the roof edges of our back porch. Each nest is both a functional expression of the biological need to reproduce and also a work of art.
Keep watching the birds and the flowers! The trees are leafing out rapidly (and, they are predicting snow tonight!). It’s always interesting to be in Pennsylvania!
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