On Wed, 24 Apr 1996, Jon. Anderson and Marty Chaney wrote:
> Just got the Spring 1996 issue, Volume 67, No 2, of the Journal of Field
> Ornithology, published by the Association of Field Ornithologists. Hope
> some people get some use from these contents.

> Nest Visitation by Humans does not Increase Predation on
> Chestnut-collared Longspur Eggs and Young. Danielle R O'Grady, Dorothy P
> Hill and Robert MR Barclay. pp 275-280. At Remount Community Pasture,
> Bindloss, Alberta.

Hello tweeters and Dorothy Hill.

(first we should do introductions)

Dorothy - we are a northwestern email forum for birders and
ornithologists. We talk about many topics. In the recent past, we had a
Chestnut-collared Longspur here in Seattle (who was dubbed 'Montlake
Phil'). It was the topic of great discussion. I cc'd this message to you
in the hopes that you would explain some of the aspects of your recent
paper which I address below, and which would probably interest some
tweeters. If you have email addresses of the other two authors, maybe
they'd be willing to address also. I located your email address in _The
Flock_.

Tweeters - Dorothy Hill is the second author on the paper (and the only
one listed in the _The Flock_). I tried to find email addresses of the
other authors, but no luck.

After our 'Montlake Phil', I read this paper with interest. Also because
I was intrigued by the title, which presents this conundrum: How could
they measure nest predation without visiting the nest, and if they visit
the nest to measure nest predation, then how do they get the control group
which hasn't been visited (as stated in the title)? Turns out the title
is rather misleading, what they determined was that the differences in
nest predation levels were statistically insignificant between three
different levels of visitation: every day, every other day, and every four
days. Which is interesting of itself.

They then go on to say in the discussion:

" It is clear from this experiment that nest visitation by humans did not
increase predation on Chestnut-collared Longspur eggs and young in nests".

Hardly clear at all. What is clear is that differing levels of nest
visitation had little impact. But how can you know whether the initial
nest visitation does or doesn't impact nest success? Especially when they
are located using the rope-drag method, which must have some effect on
nests (I've used this method often myself in Alaska). I don't think at
present we have the means of determining this. Short of clairvoyance, or
perhaps the Enterprise's long-range sensors, there is no way at present to
locate and monitor cryptic ground-nesters without visiting the nest (at
least during the initial nest location).

Not to belittle the findings, though, which are interesting. Differing
visitation schedules should expose the nest more often to nest predation,
yet measurements didn't find this. Also interesting was that the authors
found that half of all nest failed. Whether this is a standard rate of
loss for CCLO (or better or worse than average) I don't know.



-------------
Michael R. Smith
Univ. of Washington, Seattle
whimbrel at u.washington.edu
http://salmo.cqs.washington.edu/~wagap/mike.html