Jan
14
7:00 AM07:00
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Jan
15
6:30 PM18:30
2026 COS Annual Meeting
RSVP Required
Join the COS Board of Directors as we celebrate our many accomplishments in 2025, play games, and announce exciting new plans for the new year, and much more!
Jan
17
10:00 AM10:00
Snowy Owl Irruption! at North Park Village
RSVP Required
Join Chicago Ornithological Society for an in person program as we explore and take a deep dive into everything we know about Snowy Owl irruptions!
Jan
24
10:00 AM10:00
Snowy Owl Irruption! at Big Marsh
RSVP Required
Join Chicago Ornithological Society for an in person program as we explore and take a deep dive into everything we know about Snowy Owl irruptions!
Jan
25
8:00 AM08:00
COS in the Suburbs: Crabtree Nature Cente
RSVP Required
Experience birding in January in the northwest suburbs. A diversity of birds can be found throughout the prairie, woodland, and wetland habitats.
Jan
25
10:00 AM10:00
Humboldt Park Sunday Social Bird Walk
RSVP Required
Join us as we explore Humboldt Park in search of winter birds in this incredible oasis in the surrounding urban environment.
Jan
31
8:00 AM08:00
Montrose Point Beginner Bird Walk
RSVP Required
Join COS for a beginner-friendly winter bird walk at Montrose Point, where we’ll learn birding basics while spotting Chicago’s year-round residents and seasonal visitors.
Feb
7
9:00 AM09:00
Starved Rock Scramble
RSVP Required
On this trip, we'll explore the magical winter landscape of the canyons along the Illinois River at Starved Rock- Ottawa, Kaskasia and Illinois.
Feb
7
10:00 AM10:00
LaBagh Woods Stewardship Workday
Join us for a habitat restoration workday at COS’s flagship stewardship site LaBagh Woods, and help bring back critical bird habitat.
Feb
8
8:00 AM08:00
COS in the Suburbs: Crabtree Nature Center
RSVP Required
Experience birding in February in the northwest suburbs. A diversity of birds can be found throughout the prairie, woodland, and wetland habitats.
Feb
10
6:30 PM18:30
Birds & Bytes: Birding Oaxaca
Virtual Program
RSVP Required
Join COS for the latest episode of our virtual program series Birds & Bytes for a conversation with Em De Blas on lessons learned while birding Oaxaca.
Feb
15
10:00 AM10:00
Humboldt Park Sunday Social Bird Walk
RSVP Required
Join us as we explore Humboldt Park in search of winter birds in this incredible oasis in the surrounding urban environment.
Feb
18
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
Mar
14
8:00 AM08:00
Mudhen 5k Trailrun at Big Marsh!
Join Chicago Park District, Friends of Big Marsh, and Chicago Ornithological Society for the return of the Mudhen 5k fun run at Big Marsh Park on Saturday, March 14!
Mar
15
10:00 AM10:00
LaBagh Woods Stewardship Workday
Join us for a habitat restoration workday at COS’s flagship stewardship site LaBagh Woods, and help bring back critical bird habitat.
Mar
18
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
Mar
25
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
Apr
1
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
Apr
8
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
Apr
15
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
Apr
22
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
Apr
24
to Apr 27
City Nature Challenge 2026
COS is excited to once again be a co-organizer of the Chicago area team in this year’s City Nature Challenge!
Apr
29
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
May
6
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
May
13
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
May
20
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
May
27
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
Jun
3
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
Jun
10
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
Jun
17
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
Jan
11
10:00 AM10:00
LaBagh Woods Stewardship Workday
Join us for a habitat restoration workday at COS’s flagship stewardship site LaBagh Woods, and help bring back critical bird habitat.
Jan
10
9:00 AM09:00
Winter Waterfowl Watch at Northerly Island
Chicago Ornithological Society and the Chicago Park District are excited to join forces and host the first ever Winter Waterfowl Watch!
Jan
6
5:30 PM17:30
Family & Adult Owl Prowls at North Park Village
In partnership with the Chicago Park District, come and learn about the raptor of the night- the owl! This interpretive program and guided walk will lead participants through the preserve in search of owls.
Jan
4
8:00 AM08:00
Sloughs of the Palos Area: Cranberry Slough
RSVP Required
Join COS for a hike through Cranberry Slough in search of an array of woodpeckers and other winter residents.
Dec
25
7:00 AM07:00
72nd Lakefront Christmas Bird Count
RSVP Required
Join COS for the annual Lakefront Christmas Bird Count! Every year on Christmas day, birders sally forth to count birds and contribute their sightings to the oldest continuously running citizen science project in the world.
Dec
20
7:00 AM07:00
1st Chicago South Christmas Bird Count
RSVP Required
Join COS for the annual Chicago South Christmas Bird Count! Every year on Christmas day, birders sally forth to count birds and contribute their sightings to the oldest continuously running citizen science project in the world.
Dec
17
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
Dec
16
5:30 PM17:30
Family & Adult Owl Prowls at North Park Village
In partnership with the Chicago Park District, come and learn about the raptor of the night- the owl! This interpretive program and guided walk will lead participants through the preserve in search of owls.
Dec
14
10:00 AM10:00
LaBagh Woods Stewardship Workday
Join us for a habitat restoration workday at COS’s flagship stewardship site LaBagh Woods, and help bring back critical bird habitat.
Dec
14
7:00 AM07:00
77th Lisle Christmas Bird Count and Dinner
RSVP Required
Join COS for the 76th Annual Lisle Christmas Bird Count and Dinner! Every year on a wintery Sunday in December, birders sally forth to count birds and contribute their sightings to the oldest continuously running citizen science project in the world.
Dec
11
6:00 PM18:00
Flock Club: Sojourn Cocktail Bar
COS proudly presents Flock Club - a social event by and for birders. Join us as we gather to share our passion for birds in a casual and accessible environment.
Dec
11
6:00 PM18:00
Marian R. Byrnes Natural Area Owl Prowl
RSVP Required
Join COS for an owl prowl at Marian R. Byrnes Natural Area.
Dec
7
1:00 PM13:00
Owls of Chicago at North Park Village
RSVP Required
Join Chicago Ornithological Society at North Park Village Nature Center as we take a deep dive into everything we know about Chicago's many owls!
Dec
7
10:00 AM10:00
Humboldt Park Sunday Social Bird Walk
RSVP Required
Join us as we explore Humboldt Park in search of winter birds in this incredible oasis in the surrounding urban environment.
Nov
27
9:00 AM09:00
Humboldt Park Birdsgiving Stroll
RSVP Required
Join us as we explore Humboldt Park in search of birds on Thanksgiving morning.
Nov
24
9:00 AM09:00
COS in the Suburbs: Crabtree Nature Center
RSVP Required
Experience birding in November in the northwest suburbs. A diversity of birds can be found throughout the prairie, woodland, and wetland habitats.
Nov
22
10:00 AM10:00
Owls of Chicago at Big Marsh
RSVP Required
Join Chicago Ornithological Society at the Ford Calumet Environmental Center as we take a deep dive into everything we know about Chicago's many owls!
Nov
22
10:00 AM10:00
LaBagh Woods Stewardship Workday
Join us for a habitat restoration workday at COS’s flagship stewardship site LaBagh Woods, and help bring back critical bird habitat.
Nov
22
6:00 AM06:00
Park 566 Owl Prowl
Join COS for an owl prowl at Park 566. We will look for owls of all kinds but will focus on finding Short-eared Owls that are seen there frequently!
Nov
19
6:00 PM18:00
Nov
18
5:30 PM17:30
Family & Adult Owl Prowls at North Park Village
In partnership with the Chicago Park District, come and learn about the raptor of the night- the owl! This interpretive program and guided walk will lead participants through the preserve in search of owls.
Nov
18
5:30 PM17:30
Flock Club Book Club: Birding to Change the World
Join COS for Flock Club Book Club to discuss Trish O’Kane’s Birding to Change the World.
Nov
15
10:00 AM10:00
Owls of Chicago at North Park Village
RSVP Required
Join Chicago Ornithological Society at North Park Village Nature Center as we take a deep dive into everything we know about Chicago's many owls!
Nov
12
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
Nov
9
10:00 AM10:00
LaBagh Woods Stewardship Workday
Join us for a habitat restoration workday at COS’s flagship stewardship site LaBagh Woods, and help bring back critical bird habitat.
Nov
8
9:00 AM09:00
Hawkwatch at Northerly Island
Join COS for a morning observing hawks migrating down the lake front. This is a mostly stationary birding experience.
Nov
8
6:00 AM06:00
Park 566 Owl Prowl
Join COS for an owl prowl at Park 566. We will look for owls of all kinds but will focus on finding Short-eared Owls that are seen there frequently!
Nov
5
7:00 AM07:00
North Pond Wednesday Bird Walks
In cooperation with Third Coast Birding and Peggy Notebaert Nature Museum, COS is proud to continue our long tradition of Wednesday morning bird walks at North Pond!
Nov
2
10:00 AM10:00
Humboldt Park Sunday Social Bird Walk
RSVP Required
Join us as we explore Humboldt Park as migratory birds flock to this incredible green oasis in the surrounding urban environment.
Oct
29
7:00 AM07:00