Subject: PINE SISKINS: POPULATION FLUCTUATIONS AND MASS MORTALITY
Date: Nov 30 00:52:07 1999
From: WAYNE WEBER - WAYNE_WEBER at bc.sympatico.ca


Tweeters,

Louise Fountain is absolutely right about Pine Siskins. The
numbers of wintering Pine Siskins in the Northwest fluctuate
dramatically from one winter to the next, by a factor of up to 100. In
some winters they are practically absent. Those same winters, however,
thousands can be found either to the south or east of us somewhere.
I will illustrate using numbers from the Vancouver, B.C. Christmas
Bird Count, which I compiled for almost 20 years. The average count of
Pine Siskins is about 2500. The lowest count ever, 76 birds, was in
1972. The all-time high count of 7527-- 100 times as many-- was the
following year, in 1973. Continuing the trend of wild fluctuations,
the count plummeted to 193 siskins in 1974, then soared to 6183 in
1975. (This is a count with intensive coverage by about 150 observers
every year.)
One subscriber wondered whether pesticides might be responsible
for mortality of siskins. I am not aware of any major mortality caused
by pesticides, but there is at least one instance of mass mortality
caused by Salmonella bacteria, probably associated with backyard bird
feeders. Between November 1992 and January or February 1993, a major
outbreak of salmonellosis occurred in Pine Siskins in southwestern
B.C.
(For details, see "The 1992-1993 Outbreak of Salmonellosis in Pine
Siskins in British Columbia", by Victoria Bowes. British Columbia
Birds, Volume 3, pages 13-14, 1993). Bowes documented a minimum
mortality of 3100 Pine Siskins in southwestern B.C., and estimated
that tens of thousands had succumbed. She also noted that similar
die-offs had been reported at the same time in Washington, Idaho, and
California.
The die-off of Pine Siskins in 1992-1993 was massive, but for some
reason was virtually confined to the one species. Apparently, mass
mortality of Pine Siskins on this scale has not been reported before
or since this epidemic.
So to put it in a nutshell: mass mortality of Pine Siskins is
possible and has occurred at least once. However, the huge
fluctuations in numbers that we normally see from one winter to the
next are just a result of siskins wintering in different parts of the
continent in different years. As with other finches, this is probably
related to changes in the abundance of their favorite seeds from year
to year.

Wayne C. Weber
Kamloops, B.C.
wayne_weber at bc.sympatico.ca


-----Original Message-----
From: Dale B Fountain <dale.fountain at gte.net>
To: godwit at worldnet.att.net <godwit at worldnet.att.net>;
mccomb at olympus.net <mccomb at olympus.net>; tweeters at u.washington.edu
<tweeters at u.washington.edu>
Date: Monday, November 29, 1999 5:18 PM
Subject: Re: Siskins


>Ruth,
>
>I would think that the siskins have just started feeding in a
different
>place this winter and have probably not perished. Several years ago
I had
>large numbers of siskins at my feeders all winter. Then for the last
couple
>of years hardly any. This year I have had up to 52 feeding at the
same
>time. They just travel around and are not as loyal to us as we would
like
>to think they are.
>
>Louise Fountain
>Eatonville
>dale.fountain at gte.net
>-----Original Message-----
>From: Ruth Sullivan <godwit at worldnet.att.net>
>To: mccomb at olympus.net <mccomb at olympus.net>;
tweeters at u.washington.edu
><tweeters at u.washington.edu>
>Date: Saturday, November 27, 1999 9:06 PM
>Subject: Re: Siskins
>
>
>>Hello Jane and Tweeters,
>>I must say there are getting rare on feeders. I used to have so many
on my
>>feeders and there used to be so agressive so little there
where,taken over
>>and scared the other birds away.
>>Now this year i had 4 Pine Siskin sofar and single birds. I have
lot's of
>>House Finches but also miss my Purple finches here all together. It
been
>>mention on tweeters once about finches are declining. I am looking
back of
>>birding this last year and realy think now i did not find to many
flocks in
>>the wild either. What is going on are there some disease as fongus
killing
>>this birds ?As here in my yard never had sick finches as many
reported. We
>>als cleaning our tubfeeders on a regular basis out and use some
bleach
>>water to due so. Also fresh water one a week is verry importend
>>
>>Ruth Sullivan
>>Tacoma
>>godwit at worldnet.att.net
>