HomeMy WebLinkAboutAuthority #03/18 Double-crested Cormorants 04-20-2018.pdfDouble-crested Cormorant
Management at
Tommy Thompson Park
Karen McDonald – kmcdonald@trca.on.ca
Andrea Chreston – achreston@trca.on.ca
Double-crested Cormorants at
Tommy Thompson Park/ Leslie St. Spit
•Cormorants arrived at
TTP in 1990 with 6 pairs.
•Since then the population
has grown across 3 of
the park’s 4 peninsulas
and is the largest colony
in North America.
•Management of the
colony began in 2008.
Tommy
Thompson Park
Leslie Street Spit
Toronto Islands
Downtown
Toronto Portlands
•Toronto’s only Important Bird Area –globally significant •7 Species of Colonial Nesting Waterbirds. •The largest colony of Double-crested Cormorants in North America •Significant colony of Black-crowned Night-Herons in Canada •Concentration area for migratory bird species. •Significant overwintering area for waterfowl.
Cormorant Impacts on Forest Communities
OBJECTIVES
•Increase public knowledge, awareness, and appreciation of colonial
waterbirds
•Deter cormorant expansion to Peninsula D
•Limit further loss of tree canopy on Peninsulas A, B and C
•Continue research on colonial waterbirds in an urban wilderness
context
GOAL
To achieve a balance between the continued existence of a healthy,
thriving cormorant colony and the other ecological, educational,
scientific and recreational values of Tommy Thompson Park.
CORMORANT MANAGEMENT STRATEGY
Management Approach
Pen
A
Pen
B
Pen
C
Pen
D
Inactive Nest Removal
(prior to breeding season) * *
Enhanced Ground Nesting * *
Pre-Nesting Deterrents * * *
Post-Breeding Deterrents
(as required) * * A
B
C
D
A
B
C
D
Cormorant Population
In 2016 70% of the colony nested on the ground.
Overall population increase is supported solely by ground nesting.
0
2000
4000
6000
8000
10000
12000
14000
Peninsula A tree
Peninsula A ground
Peninsula B tree
Peninsula B ground
Peninsula C tree
Total nests
Management begins
Cormorant Population
0
2000
4000
6000
8000
10000
12000
14000
Peninsula A tree
Peninsula A ground
Peninsula B tree
Peninsula B ground
Peninsula C tree
Total nests
Management begins
In 2017 60% of the colony nested on the ground.
Lake Ontario high water levels complicated management efforts.
Cormorant Nests by Peninsula
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
Pen A tree 101 49 22 39 19 13 5 14 14 4 0
Pen A ground - - - - - - - 10 541 1525 1821
Pen B tree 1072 1050 917 781 1262 982 1310 1316 1184 1007 2474
Pen B ground 1302 1009 1957 3310 4547 5812 6986 7799 7608 8555 5836
Pen C tree 4584 4609 4668 5304 5546 4934 3689 3270 2561 2184 2710
Total 7059 6717 7564 9434 11,374 11,741 11,990 12,409 11,908 13,275 12,841
B. Von Bockenstale
Ground Nesting
Ground-nest Expansion
G.Fraser
2017 Lake Ontario High Water Levels
Authority Board Recommendation
•THAT staff report and present to the Authority biennially regarding
the management of Double-crested Cormorants at Tommy
Thompson Park or more frequently should the management strategy
be significantly changed.
Financial Implications
•Estimated cormorant related management costs $55,000 annually
•Funded through City of Toronto levy, plus Remedial Action Plan
grant
THANK YOU!
G.Fraser