Dear Tweeters: I have been monitoring an expanding number of nests for a
few years, and thought you may be interested in what I have found with
respect to nest supports.

Of 100 Osprey nests, 21 are on natural supports such as live trees or snags.
79 are on power line cross arms or platforms erected to attract the birds
away from the power lines. My sample is biased in that most of the nests are
within developed urban or rural corridors. In our area, we have lots of
unsurveyed Osprey nests in the forests surrounding upland lakes where the
only supports available are trees or snags.
So it is important to understand the options available to the birds within
your sample area. It is easy to imagine why, if given a choice, the birds
prefer manmade structures. It is usually easy to get the sticks to stay in
place when starting the nest for one thing. Also, the structures are often
the highest, lonliest and most stable support around, which makes for easy
approaches and good observing when watching for predators. We must remember,
that the birds see these things as nothing more than supportive
configurations of some inanimate object in proximity to a food supply.
Osprey nests and powerlines are not comfortable bedfellows, and BC Hydro
maintains a program of monitoring potential problems and providing
alternative structures to entice birds away from hazardous locations.
I do not work for Hydro, but their data would be interesting.

Alternatively, I have 16 Bald Eagle nests that I have been watching in the
same corridors, and all of them are on natural supports such as snags or
live trees. But of course, the eagles don't mind being a little more hidden
in or near branches.

Cheers


Rick Howie
Kamloops, BC
rick.howie at shaw.ca