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 Island

East 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 1

1960s 2 10

1970s 4 63

1980s 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

2010

2009

2008

2008

2009

No

. G

reat

Eg

rets

at

Ro

ost

(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

2010

2009

2008

2008

2009

2010

No

. G

reat

Eg

rets

at

Ro

ost

(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

. C

olo

nie

s

mean = 84.6±47.2 km (N = 24)Median = 24 km

Mode = 8 kmrange = 1 – 160 km

Week

Nu

mb

er o

f co

nfi

rmed

& p

rob

able

ro

ost

sit

es o

ccu

pie

dOccupancy 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.

probable

confirmed

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

Nu

mb

er o

f R

oo

sts

Occupancy of small roosts, 2010

0

1

2

3

4

25-J

ul

1-Aug

8-Aug

15-A

ug

22-A

ug

29-A

ug

5-Sep

12-S

ep

19-S

ep

26-S

ep

3-Oct

10-O

ct

Metcalfe

the Coves

Date

No

. o

f G

RE

Gs

at r

oo

st

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

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