Roosting habits and Post-breeding dispersal of juvenile Great Egrets in
Ontario.D.V. Chip Weseloh & Dave Moore
Canadian Wildlife Service - Ontario
www.ec.gc.ca
Harbor Herons and Waterbirds of Greater NY/NJ Harbor Working Group
12-13 January 2011Staten Island, NY
With field assistance by Linda McLaren, Tyler Hoar and Dave Andrews
Objectives for 2010
• Confirm seasonal use pattern at major roost site.• Locate other roost sites, track numbers and usage.• Mark YOY egrets with highly visible wing-tags• Make greater efforts at re-sighting tagged egrets
SUMMARY1. Not used in spring, bimodal autumn peak #s2. 30 roost sites;NN= 8, 24 km; Roost size = 2-400+3. 118 egrets tagged at 3 sites 4. 39 individuals reobs., Egrets go to S. Ontario,
Michigan, Ohio and NY- Few birds went north.
LakeHuron
LakeErie
LakeOntarioChantry Island
Nottawasaga Island
Middle Sister IslandEast Sister Island
Middle Island
Toronto Harbour
High Bluff Island
Locations of colonies & nest numbers – 2000sDickerson IslandBergin Island
Motor Island
Decade
Number of
Colonies
Number of Nests
(maximum)
1950s 1 11960s 2 101970s 4 631980s 4 108+1990s 6 1782000s 11 359+
Barrier Island
Luther Marsh
Use of Luther Marsh roost site, by week, 2008-09
Opening day - duck hunting:27 Sep. 200826 Sep. 2009
0
100
200
300
1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1
Apr May Jun Jul Aug Sep Oct
201020092008
20082009
No.
Gre
at E
gret
s at
Roo
st (m
ean/
wee
k)
Date
no egrets present
Use of Luther Marsh roost site, by week, 2008-10
0
100
200
300
1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1
Apr May Jun Jul Aug Sep Oct
201020092008
200820092010
No.
Gre
at E
gret
s at
Roo
st (m
ean/
wee
k)
Date
Opening day - duck hunting:27 Sep. 200826 Sep. 200925 Sep. 2010
no egrets present
= Confirmed Roosts
= Unconfirmed Roosts
= >100 Birds
Locations of Great Egret Roosts in the Lower Great Lakes Region
26.
27.
28.29.
30.
GREG roosts – nearest neighbour distances
0
5
10
15
1-20 km 21-40 km 41-60 km 61-80 km 81-100 km >100 km
Nearest Neighbour Distance
No.
Col
onie
s
mean = 84.6±47.2 km (N = 24)Median = 24 km
Mode = 8 kmrange = 1 – 160 km
Week
Num
ber o
f con
firm
ed &
pro
babl
e ro
ost s
ites
occu
pied
Occupancy of GREG roosts, 2010
0
5
10
15
20
1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1
Jun. Jul. Aug. Sep. Oct. Nov.
0
5
10
15
20
1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1
Jun. Jul. Aug. Sep. Oct. Nov.
probableconfirmed
Size of Great Egret Roosts (n=25)
2
7
6
2
8
0
1
2
3
4
5
6
7
8
9
0-5 6-20 21-50 51-100 >100
Size Category
Num
ber
of R
oost
s
Occupancy of small roosts, 2010
0
1
2
3
4
25-Ju
l
1-Aug
8-Aug
15-A
ug
22-A
ug
29-A
ug5-S
ep12
-Sep
19-S
ep
26-S
ep3-O
ct
10-O
ct
Metcalfethe Coves
Date
No.
of G
REG
s at
roos
t
Applying wing-tags
Applying wing-tags
Tagged egrets in the field
Tagged egrets in the field
Re-sightings of wing-tagged GREGs
MI
OHPE
NY
ON
3
Nottawasaga I.
Chantry I.
Middle Sister I.
2
2
55
MI
OHPE
NY
ON
8
Nottawasaga I.
2
Chantry I.
6
Middle Sister I.
All re-sightings, 2010
www.ec.gc.ca
