Subject: Common Murre Die-off
Date: Aug 27 14:00:29 1999
From: Jon. Anderson and Marty Chaney - festuca at olywa.net


Jacki Bricker wrote: "This is probably one of *the* most depressing things I've ever read."

Hi Jacki,

While the mortality of wild animals is often a cause for melancholy
reflection to many of us, and while it is likely a great tragedy to the
individual bird, I am not sure that it should be *that* depressing. In
any event, I apologize for assaulting your sensitivities.

I've long since forgotten the 'rule of thumb' that I was taught for the
'average' mortality of birds-of-the-year. It seems that it was in the
80%+ range, or so. Any help out there, Tweets?

With murres, the adults can live for up to 20-30 years. To maintain
the population level, a pair of murres needs to replace itself in the
breeding population - i.e., during the adults' lifetime they need to
produce 2 chicks that survive to breeding age. Maybe the "average
2.2 children per household", to account for additional, accidental
deaths (like bald eagles snatching them off the nesting cliffs, etc.).
Anyway, if that murre pair lays one egg per year and has the
opportunity to have 2 of its chicks recruit to the colonies over their
lifetime, they've replaced themselves.

The other chicks end up being in that group of birds-of-the-year
that we see washing up on the beaches, eaten by predators, etc.

I don't get too worried when I see the annual die-off of murre chicks...

But, considering that the last decade's El Nino/La Nina events have
caused havoc with their prey base some years, eagles have caused
abandonment or disturbances at some nest sites, oil spills, fishing nets
and sport fishing hooks have killed some adults, etc., and there's
been a number of years with poor survival of chicks (and some years
when even the adults were starving...) I would imagine that the current
murre population might be ageing a bit without a lot of chicks entering
the breeding group. It's likely really important to make certain that the
populations remain healthy until the ocean ("Mother Nature") provides
a nesting year that allows a good percentage of chicks to fledge and
make it through a couple of years so they can replace some of their
elders.

It'd be interesting to hear from Roy Lowe down on the Oregon Coast,
or Dr. Julia Parrish at UWash to get a better handle on the murre
population dynamics here on our coast. Hey, B.C. Tweets - what
about the murre colonies to the north of Vancouver Island? How are
they doing?

Jon. Anderson
Olympia, Washington
festuca at olywa.net

----------
From: Jacki Bricker[SMTP:seaotter at eskimo.com]
Sent: Thursday, August 26, 1999 3:57 PM
Subject: RE: Common Murre Die-off

This is probably one of *the* most depressing things I've ever read.

-----Original Message-----

Hi folks,

Regarding the annual die-off of murre chicks is evident to beach walkers, I cannot remember a year of good murre chick production that is not attended by this die-off. El Nino years, La Nina years or any years in-between.
August is often the time that the "Spring/Summer" upwelling begins to shut down, warm water comes near the shore, and the murre's prey species leave, die, or scatter. The fledgling murre follows 'Dad' until, starving and weakened, it washes through the surf to die alone on the beach, and is ultimately scavenged by the Western/Glaucous-winged gulls and *their* fledglings.

Jon. Anderson