Hi Peter,
Well a fair question. Yes I can pick them apart, from other than just the
colour differences. I really was referring to flocks. Whether I could always
or mostly identify one alone individual, to species, at that distance, I
really am not entirely sure, but maybe. Yes with binoculars. I don’t think
it overly unreasonable, as I have seen many experts in waders pick between
similar species in mixed flocks at that sort of range or more. And yes it is
a general impression and I probably never did get to measure 80 metres, and
whether with binoculars or the naked eye I really don’t recall. But it was
certainly true at the time (probably without binoculars). It goes back to
1978 when I spent weeks (months?) tracking both species around LaTrobe
University where they both formed flocks (usually mostly separately). I
could certainly pick the flocks apart at that distance. I find the demeanor
of the two as different. Tree Sparrows are smaller and a bit elegant in
overall look. As they are not near where I live (Canberra), I had not had
much opportunity to spend time with them since then, other than regular
trips to Melbourne. However recently I have had the chance to reacquaint
with them when I could watch them again a lot, on my trip to China &
Philippines.
So these are the differences that I think I can use fairly reliably: apart
from the obvious colouration items of the head and white wing bars, that all
the books show.
A flock of Tree Sparrows all look the same. A flock of House Sparrows do
not, because the sexes are different. And you won’t normally find a flock of
only male House Sparrows. That was the basis of my study. This difference
suggests differences in social behaviour. And there are differences in their
behaviour.
Even without a look at the detail, a flock of Tree Sparrows on the ground or
flying away look very distinctly chestnut brown above because that is their
basic colour: reasonably consistent, from the rump, back, wings and head.
The wings are even rather more reddish in colour. Female House Sparrows are
grey-brown with no chestnut colour and male House Sparrows are mixed grey
and brown but notably grey on the top of the head and rump (which are
chestnut on the Tree Sparrow). So the colour impression of a flock, even at
a distance is quite different. In mixed flocks, even in quick views, the
size difference can also be obvious (House Sparrow is bigger).
A flock of Tree Sparrows flying away will typically fly in a far more
cohesive group (than House Sparrows do). All tend to fly off the ground at
the same time. A flock of House Sparrows will fly away in singles or small
subsets. Of course that is a statistical difference with some small overlap
and it depends a bit on the context (number of individuals, how close they
are and what makes them fly).
Tree Sparrows have shorter legs and sit much closer to the ground. I think
they far more visibly crouch before flying.
Tree Sparrows have shorter and rounder wings, that gives them a slightly
different flying style.
The calls are distinctly different. Yes not likely to be loud enough to be
picked at 80 metres.
Philip
