[mou] RE: [MnBird] question: owl invasion duration

[Alt, Mark]

Betsy Kerr wrote

"I recall reading a while back on this list someone's suggestion that=20
the northern owls were likely to stay around until spring and even=20
become more visible later in the winter.  Can I have confidence in=20
this prediction?  What do the experts say?"

	I am definitely not an expert, Mark Alt responds, yet it is safe
to say Owls won't head north until the snow melts. As the food supply
diminishes from predatory pressure, they may move further south, and
they may wait to be in poor condition before they do that. This is the
tragic Owl at a feeder in listless condition people allude to
occasionally. It all figures into biological models involving carrying
capacity, food chains, and weather effects.
	Great Grays and Northern Hawk Owls eat the Meadow Vole voles for
their primary prey in the winter, whereas in many parts of their range,
Boreal Owls rely on the Red-backed Vole for their primary food source
year-round. Red-backed Voles do not commonly reproduce in the winter,
unlike Meadow Voles, which are able to reproduce at 2 months of age.
Meadow Voles occur in more open grassy areas that are slightly damp in
warm weather. Red-backed Voles occupy mixed deciduous conifer forests.
Boreals are known for their penchant to hang about woodpiles and sheds
in the winter; this is where Red-backed Voles, White-footed Mice and
Deer Mice can be commonly found.=20
These owls may set up territories and try to attract a mate if they find
prey, roosting and nesting habitat, so it is critical for us to not
prevent them from occupying proper habitat at this time of year. We
should mark their locations and look and listen for them in March to see
if they are staying.=20
	I would applaud anyone who finds a consistent Boreal Owl roost
and doesn't report it to list servers or to me, for the benefit of the
owl. It is important for them or anyone to follow up to see what becomes
of this specific bird. An owl found feeding actively should be very
cautiously observed. I read where a Boreal hunting from a perch scans an
area in a 15 meter radius from its perch.  This means if you are within
50 feet of the bird, you are definitely negatively impacting the hunting
opportunities of the bird, if you are within 65 feet; you are probably
adversely affecting the prey activity in the hunting range of the Owl.
Owls hear the same low frequencies we do, but according to Jim Duncan,
they hear them 9 times as strongly. Car engines can interfere with their
sonic scanning as well as us walking around. My advice is, as long as
you are thinking in terms of you impact on the owl, you will be able to
determine what constitutes appropriate behavior for you as an observer.
As in most stewardship opportunities, apathy and ignorance are the
problem, if we approach these birds and are informed and caring toward
sour impact on them, we will do the right thing.  I am going to jump off
this stump now before I fall and break an ankle.


Mark Alt=20
Brooklyn Center, MN=20
mark.alt@bestbuy.com=20
"Birds and their songs are important to me, they add to my enjoyment of
life"=20