I used to work at the California Raptor Center on the UCDavis campus where
we cared for several unreleasable Northern Harriers and also raised and
released NOHAs from eggs collected by the California Waterfowl Association.
I never saw sculls or bones in their pellets--only fur. This was generally
true for all our hawks and was distinct from the owls' pellets which
commonly contained bones. The explanation is that hawks' digestion is more
acidic than owls' and dissolves bone more completely. Relatively large
amounts of bone pieces of an appropriate size are very important in the
nutrition of young raptors. Raptor babies picked up by well meaning people
and raised on something like hamburger die of a rickets-like bone condition.
And quite a few raptors who feed themselves on larger animals switch to
smaller prey (with smaller bones) when they have young chicks to feed.
Is it possible your vole bones are from the pellets of something like the
Short Eared Owl?

Alice Swan
Orcas Island

----- Original Message -----
From: "Rob Sandelin" <floriferous at msn.com>
To: "Tweeters (E-mail)" <TWEETERS at u.washington.edu>
Sent: Friday, May 07, 2004 10:14 AM
Subject: The graveyard of voles


> This week at Bob Heirman park my students found a log with dozens of
skulls
> and bones on it. Since a Northern Harrier is often seen here I assume
these
> are regurgitated pellets from that bird. The log is in a large area of
> grass. I have not seen so many in one place before. Is this common for
> Harriers to have, as one 8th grader so eloquently put it, a puke perch?
>
> Rob Sandelin
> South Snohomish County at the headwaters of Ricci Creek
> Sky Valley Environments <http://www.nonprofitpages.com/nica/SVE.htm>
> Field skills training for student naturalists
> Floriferous at msn.com
>
>