[Tweeters] Brandt's Cormorants nesting on human-made structures

Kelly McAllister mcallisters4 at comcast.net
Mon Sep 25 18:26:53 PDT 2017


I did a little internet searching, a year or two ago, to try to determine
how often Brandt's Cormorants had been documented using human-made
structures. This was prompted by the realization that Brandt's Cormorants
were nesting on a tower in Grays Harbor, along with Pelagic and
Double-crested Cormorants. I didn't find much, one location in California if
I remember correctly. The note, below, describes Brandt's Cormorants nesting
on the Astoria-Megler bridge. Double-crested Cormorants nesting on the Lewis
and Clark bridge is a relatively new phenomenon. Cormorants are hard on
bridges, contributing to more rapid deterioration and the need for more
frequent painting. Perhaps some non-metal structures built for the
cormorants, in places where endangered salmon stocks are less accessible,
would be worth the investment. Now, what to do about the much maligned
Caspian Terns..



Kelly McAllister




Estuary Cormorants Nesting In Low Numbers; Corps Unsure If Culling Will
Resume Before Season Ends
Posted on Friday, September 22, 2017 (PST)


About 200 double-crested cormorants are nesting on East Sand Island, some or
all with 7- to 10-day old chicks, far fewer of the birds than would be
expected at what Portland Audubon had deemed the largest colony of
double-crested cormorants in the world.



Instead, at this point in September, the several thousand double-crested
cormorants in the lower Columbia River estuary are queueing up for their
migration, according to the U.S. Army Corps of Engineer's cormorant
management team that is overseeing culling operations in the lower river.



"We'll continue monitoring the island to determine the fate of the active
nests and chicks," the management team says.



The Corps is using aerial imagery to get an accurate count of active nests
on East Sand Island and adding ground surveys from a blind in order to
monitor the age of the chicks.



In its last posted management timeline update (
<http://www.nwp.usace.army.mil/environment/cormorants/timeline>
www.nwp.usace.army.mil/environment/cormorants/timeline), September 1, the
Corps said it observed about 7,000 cormorants. Some 4,000 were
double-crested, while the remaining 3,000 were Brandt's cormorants. At that
time, the nest estimates stood at just 30 double-crested nests and about 200
Brandt's nests, but the management team's more recent survey found up to 200
nesting birds. That's because during the September 1 survey the island was
inaccessible due to birds "loafing" on the beach. Follow-up aerial imagery
has been more accurate.



Culling, harassing and egg oiling of the birds and their nests was suspended
by Wildlife Services, the U.S. Army Corps of Engineers' contractor, April 27
and has not resumed because the cormorants have yet to settle down to
significant nesting activity.



In June, the Corps said that as many as 40 eagles harassed the sea birds,
keeping them from nesting on the island and driving them to other areas,
such as local bridges, as well as Willapa Bay and Grays Harbor.



The final survey at the Astoria-Megler Bridge, upstream of East Sand Island,
found the lowest number of cormorants there since April. Many of the birds
observed were juveniles and both double-crested cormorant and Brandt's
cormorant chicks were observed under the main portion of the bridge
supports, according to the management timeline. Morning survey totals were
very similar to totals recorded the previous evening (August 26), with the
lowest number of departing birds this season. About 1,400 double-crested
cormorants roosted on the bridge overnight.



A count August 17 of cormorants at the Lewis and Clark Bridge in Youngs Bay
near Astoria, found 53 nests (there were 147 nests July 20). The management
timeline said that most of the chicks had fledged from nests but some
juveniles remained.



This is the third year of culling for the Corps and the second year in a row
that the birds have been late to nesting, requiring the Corps to suspend its
operations designed to reduce the number of breeding pairs in the lower
river. Cormorants feed on juvenile salmon and steelhead, some of which are
listed under the federal Endangered Species Act.



Last year culling was suspended in mid-May and Wildlife Services didn't
resume until October 3. By mid-July last year some 15,300 cormorants were
seen "loafing" on the island. By August about 23,000 were on the island and
by September many were rebuilding nests and laying eggs. Still, the agency
managed to cull nearly 3,000 of the cormorants in 2016, almost all of those
by the end of October.



This year, however, Wildlife Services has culled just 248 double-crested
cormorants and no nests have been destroyed. At this point, the Corps is
unsure when or if it will resume culling before the season is over.



"We are waiting for further information from our field crew and coordination
with the adaptive management team - including biologists with U.S. Fish and
Wildlife Service - before drawing conclusions about the fate of the colony
and any potential management actions that could occur later this season,"
the management team says. "As detailed in our management plan, we will adapt
our management actions to the best and most current information available to
us and we are monitoring the existing nests and chicks to determine their
fate and status of birds in the estuary."



The Corps was permitted in 2017 by the Service to cull 2,408 double-crested
cormorants and destroy up to 4,058 of the cormorants' nests in order to
"reduce the overall population of the colony to a number that represents an
acceptable level of predation on juvenile salmonids," the management team
says. "We continue to manage within the bounds of what was permitted by
USFWS."



Beyond 2018, the goal is to support a local colony of double-crested
cormorants while minimizing the potential for expansion to levels that would
hurt the chances of survival for salmonids protected under the Endangered
Species Act.



That would mean a cormorant colony at East Sand Island of between 5,380 and
5,939 breeding pairs, while modifying the island so that it would support
the smaller colony.





-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman1.u.washington.edu/pipermail/tweeters/attachments/20170925/263a10e3/attachment.htm


More information about the Tweeters mailing list