Subject: Re: raptor question
Date: Nov 11 09:11:57 1996
From: Christopher Hill - cehill at u.washington.edu




On Mon, 11 Nov 1996, Tracee Geernaert wrote:

> A duck hunter at work asked me a question I thought I'd forward. He was out
> in the grain fields on the Samish Flats and came across a freshly killed
> Pintail. It was very early in the morning and the duck had a full crop. We
> concluded it was picked off the night before and he wanted to know the
> likely predator. I thought a Great Horned Owl could easily take a duck but
> what about a Short-eared or Snowy? Aren't they both diurnal? I remember Bud
> Anderson telling us that Falcons will hunt at night if they can't hunt
> during the day without getting ripped off by bigger raptors. Any thoughts
> out there in tweeterland?

To add to Mike Patterson's reply, a good clue when trying to
decide "hawk kill or owl kill?" is the extent of plucking. Most hawks
pluck bird prey extensively before eating (unless it has been windy, there
will be LOTS of feathers scattered around a hawk kill). Owls pluck much
less or not at all. Great Horned Owls usually decapitate their prey, at
least up to the size of terns and pigeons. I think that is fairly general
owl characteristic with prey too big to swallow whole - I know Saw-whet
Owls will remove the head from mice and eat it separately. I have heard
that small triangle shaped "nips" out of the breastbone of a partly eaten
prey are a good clue that a falcon, as opposed to a buteo or accipiter,
has been eating it.

OK, enough of the gory stuff. As to Short-eared and Snowy Owls
being diurnal, they're not. Short-ears often hunt in the late afternoon
on cloudy days, but also hunt at night. People seem to have gotten the
idea that Snowies are diurnal because 1) you can see them in the
daylight, and 2) they will fly around and (rarely) hunt in daylight.
However, a study of radio-transmittered Snowies on the Canadian Plains in
winter showed that the owls were much more active at night than in the
day.

I don't think a Short-eared Owl could or would attack a Pintail -
Short ears are rodent specialists, with about 95% of their diet being
voles in most studies. Snowies, on the other hand, readily take waterfowl
up to the size of a black duck, so they are certainly a possibility. I
have seen a Snowy Owl carrying around a mostly-eaten Canada Goose carcass,
and a Snowy at Logan Airport in Boston was seen attacking and killing a
Great Blue Heron. Not much is too big for them.

Yesterday at the Everett Sewage Treatment Ponds and vicinity, I
and three others saw at least three Short-ears hunting in the late
afternoon. At least four Barn Owls emerged from a roost and were flying
around just as it got dark.


Chris Hill
Everett, WA
cehill at u.washington.edu