Colonial Waterbirds Nesting on the Niagara River, 1976-2011.

Dave Moore1

Francie Cuthbert2

Chip Weseloh1

Linda Wires2

Niagara River RAP Implementation Committee Session10 Apr. 2013

Niagara College, Niagara-on-the-Lake, ON

1Canadian Wildlife Service2University of Minnesota

Page 2

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

The Great Lakes Bi-national Decadal Colonial Waterbird Survey

Page 3

Great Black-backed Gull Herring Gull

Ring-billed Gull

Common Tern Caspian Tern

Double-crested Cormorant

Great Blue Heron Great Egret

Black-crowned Night-Heron

The Great Lakes Bi-national Decadal Colonial Waterbird Survey

Forster’s Tern

Black Tern

American White Pelican

• SNEG• CAEG• LBHE• BOGU• LIGU

Page 4

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 5

Niagara River – colony distribution

Lake Ontario

Niagara River

Lake Erie

USACanada

Page 6

Niagara River – abundance & trendsDouble-crested Cormorant

2

3

3

4

Nes

ts

0

200

400

600

800

1000

1200

1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011

USA Canada

3

5

Page 7

Niagara River – abundance & trendsBlack-crowned Night Heron

0

100

200

300

400

500

1976-80 1989-91 1997-99 2007-10

Canada USA

1

3

3

2

1

1

Nes

ts

Page 8

0

20

40

60

80

1976-80 1989-91 1997-99 2007-10

Canada USA

Niagara River – abundance & trendsGreat Blue Heron

0 0

1

1Nes

ts

Page 9

0

10

20

30

1976-80 1989-91 1997-99 2007-10

Canada USA

Niagara River – abundance & trendsGreat Egret

0 0

5

1

Nes

ts

*

*17 nests at 2 sites in Canada in 2012

1

Page 10

0

100

200

300

400

500

1976-80 1989-91 1997-99 2007-10

Canada USA

Niagara River – abundance & trendsCommon Tern

2

3

5

4

Nes

ts

1

3

Page 11

0

100

200

300

1976-80 1989-91 1997-99 2007-10

USA Canada

Niagara River – abundance & trendsHerring Gull

3

25

13

Nes

ts

1

52

3

3 3

Page 12

0

5,000

10,000

15,000

20,000

1976-80 1989-91 1997-99 2007-10

USA Canada

Niagara River – abundance & trendsRing-billed Gull

1

1

52

Nes

ts

1

2

2

4

6

Page 13

Niagara River – abundance & trends

0%

20%

40%

60%

80%

100%%

to

tal

nes

tsSpecies composition

Page 14

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 15

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 16

0

0.2

0.4

0.6

LH LSC DR LE NR LO SLR

How important are rivers to maintaining GLs waterbird diversity?

6

5

77

Water body (upstream downstream)

Diversity / Richness

*

Shan

non-

Wie

ner I

ndex

(H’)

9

1311

Page 17

0%

20%

40%

60%

80%

100%

FOTE BLTE GBBG BCNH RBGU COTE GBHE DCCO GREG HERG CAEA CATE LBHE SNEG

% n

ests

on

conn

ectin

g ch

anne

ls

Connecting channels represent ~2% of the total area downstream of the St. Marys River

How important are rivers to maintaining GLs waterbird diversity?

Page 18

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