Colonial Waterbirds Nesting on the Niagara River,
1976-2011.
Dave Moore1
Francie Cuthbert2
Chip Weseloh1
Linda Wires2
1Canadian
Wildlife Service
2University of Minnesota
Niagara River RAP Implementation Committee Session
10 Apr. 2013
Niagara College, Niagara-on-the-Lake, ON
The Great Lakes Bi-national Decadal Colonial
Waterbird Survey
Objective of surveys:
• To visit all islands on the Great Lakes and
to census all species of colonial waterbirds
that nest there (n=16).
They are conducted at approx. 10 year intervals:
Census 1 = 1976-80
Census 2 = 1989-91
Census 3 = 1997-2000
Census 4 = 2007-09
Page 2
The Great Lakes Bi-national Decadal Colonial
Waterbird Survey
Ring-billed Gull
Great Black-backed Gull
Common Tern
Double-crested
Cormorant
Herring Gull
Forster’s Tern
Caspian Tern
American White Pelican Great Blue
Heron
Great Egret
Page 3
Black-crowned
Night-Heron
Black Tern
• SNEG
• CAEG
• LBHE
• BOGU
• LIGU
Methods
• Census nests late in incubation or brooding
• Count all AONs
Approximate Census Timing:
8-30 May =
Gulls (& scouting for other species)
1-7 June =
Common & Caspian Terns
10-30 June =
Cormorants and Herons
Census Methods:
Preferred Method = Ground count (of individual nests)
Other Methods = - extrapolation from ground counts
- boat estimates
- aerial surveys
- estimates from aerial photographs
Page 4
Niagara River – colony distribution
Lake Ontario
Canada USA
Niagara River
Lake Erie
Page 5
Niagara River – abundance & trends
Double-crested Cormorant
1200
USA
Canada
1000
2
Nests
800
3
600
3
5
400
3
4
200
0
1991
1993
1995
1997
1999
2001
Page 6
2003
2005
2007
2009
2011
Niagara River – abundance & trends
Black-crowned Night Heron
500
Canada
USA
1
3
400
Nests
3
300
1
2
200
100
1
0
1976-80
1989-91
1997-99
Page 7
2007-10
Niagara River – abundance & trends
Great Blue Heron
80
Canada
USA
Nests
60
1
40
1
20
0
0
0
1976-80
1989-91
Page 8
1997-99
2007-10
Niagara River – abundance & trends
Great Egret
30
Canada
USA
5
*
Nests
20
1
*17 nests at 2 sites in Canada in 2012
10
1
0
0
0
1976-80
1989-91
1997-99
Page 9
2007-10
Niagara River – abundance & trends
Common Tern
500
Canada
USA
5
400
Nests
2
1
300
3
200
3
100
4
0
1976-80
1989-91
Page 10
1997-99
2007-10
Niagara River – abundance & trends
Herring Gull
300
USA
Canada
5
2
200
Nests
1
3
13
100
3
2
5
3
0
1976-80
1989-91
Page 11
1997-99
3
2007-10
Niagara River – abundance & trends
Ring-billed Gull
20,000
USA
2
Canada
5
6
15,000
Nests
1
1
2
4
10,000
1
5,000
2
0
1976-80
1989-91
Page 12
1997-99
2007-10
Niagara River – abundance & trends
Species composition
100%
% total nests
80%
60%
40%
20%
0%
Page 13
Niagara River –
staging & over-wintering
• 1st site in NA to receive “Globally significant IBA” designation
• Important over-winter feeding area for 100,000+ gulls (daily)
• 19 species have been recorded (14 spp. on a single day)
• Two species occur in globally significant numbers:
• 100,000 Bonaparte’s Gulls (20% world population) pass through
annually; daily mean =10,000, maximum = 40,000
• Herring Gulls – daily mean = 20,000, maximum = 50,000
Page 14
Niagara River –
staging & overwintering
• Ring-billed Gull -- 18,000-27,000 individuals per day (fall / winter)
• Common Tern – 5,000+ individuals in Niagara Gorge during spring
migration / staging
• Waterfowl –
• daily totals of 20,000 individuals of 20 species
• significant numbers of Canvasback, Common Merganser,
Greater Scaup & Common Goldeneye
Page 15
How important are rivers to
maintaining GLs waterbird diversity?
0.6
Shannon-Wiener Index (H’)
Diversity / Richness
0.4
13
11
0.2
*
9
7
LO
SLR
7
6
5
0
LH
LSC
DR
LE
NR
Water body (upstream
 downstream)
Page 16
How important are rivers to
maintaining GLs waterbird diversity?
100%
% nests on connecting channels
Connecting channels represent ~2% of the
total area downstream of the St. Marys River
80%
60%
40%
20%
0%
FOTE
BLTE GBBG BCNH RBGU COTE GBHE DCCO GREG HERG CAEA CATE
Page 17
LBHE SNEG
Summary
• Most species are more numerous on US side of river; BCNHs the exception
• herons, terns and cormorants have increased since monitoring began; the
two gulls show inverse-U pattern, but consistent with GLs-wide trends
• overall healthy waterbird community on Niagara River; status ‘improving’
overall
• Diversity lower on connecting channels than adjacent lakes
• Lowest on Detroit River, highest on SLR; NR had 2nd highest diversity
• For most species, abundance is disproportionately higher on connecting
channels than predicted by their area; rivers very important for some species
• NR has continental significance as an overwintering / migratory staging area
for some species
Page 18