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Re: Re[2]: Bird nests



> > Nesting in trees is not a basal bird adaptation.  Many groups of birds
> > (ratites, megapodes, sea birds, anseriformes, etc.) nest on the ground, and 
> > most of these nests are no more "out of the way" than are those of crocs', 
> > lepidosaurs', or turtles'.
>     
>>Also, I didn't mean just, or even primarily, trees.  Islands are
>>as isolated, so are cliffs. Redwing blackbirds nest in dense stands 
>>of rushes or cattails, always well out from shore, and *over* water 
>>(no land underneath at all).

What may be surprising, and possibly helpful, in this context is the fact
that a goodly number of small passerines which, if not arboreal, at least
spend much of their time off the ground in shrubbery, nest on the ground!
These include a number of wood warblers (Parulidae or Parulinae). For
example, the Red-faced Warbler of the American SW and Middle America forages
in the middle layers of conifers, but nests on the ground (oftenn  concealed
under a log or stone).  I have no idea why this is, but I wonder if it might
possibly be to avoid arboreal nest predators such as some snakes or other
birds - it may be that (following a suggestion in Morse's "American
Warblers") if other species are tree-nesters and that is where nest
predators tend to hunt, it is advantageous to nest in a less obvious place.
The moral may be that we should not always assume that an arboreal species
will do everything in trees.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
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