1908
April 1
Concord, Mass.
  Brilliantly clear with warm sun but chill N.E. wind.
No snow left in woods but some ice in wooded swamps.
  A pair of White-bellied Nuthatches are haunting the elms
about the farm house, as they have done every spring for years.
I saw them there this morning about seven o'clock when my 
attention was especially drawn to them by an odd note
that the male was uttering. He gave it at least fifty times
at intervals of three or four seconds. It was a monosyllabic
call full and rather musical and wholly lacking the nasal
quality which is so characteristic of most of the notes of this
species. It resembled the flight call of the Bluebird for
which, indeed, I at first mistook it. I noted it at
the time as heu or pheu. As nearly as I can remember
I have never heard it before. The bird was in constant
motion all the time he was uttering it and apparently
devoting his attention solely to searching for grubs among
the upper branches of the elm while his mate was
similarly engaged on one of the lower branches. At length
she took wing when the male pursued her in silence for a minute
or more during which both birds doubled and twisted 
through the tops of dozens of trees along the roadside
flying with wonderful speed the male never more than 
two or three feet behind the female and sometimes within
six or eight inches. How the chase ended I did not
see for both birds passed out of sight towards the 
Ritchie place still keeping up their erratic flight 
as long as I had them in view. This behavior
led me to infer that they were amorously inclined
& that the note I heard was a love call. The male
has been calling wot wot wot every morning of late but
I did not hear him utter that cry today.
Odd note of male White-bellied Nuthatch
Love flight of pair of Nuthatches