When do ospreys leave Illinois?

Most Ospreys have left Illinois by early October, when reports fall below half their usual rate. Stragglers are still reported until the second week of October.

When is the best time to see ospreys in Illinois?

The Osprey is reported most often in the second week of August, on about 4.6% of Illinois checklists.

Osprey · Pandion haliaetus

When Do Ospreys Arrive in Illinois?

Photo: Bill Levine, CC BY 4.0 via iNaturalist

Ospreys arrive in Illinois in late March, peak in the second week of August (4.6% of checklists), and most are gone by early October.

When to look

First arrivalsMar 22-31late March

Common byMar 22-31late March

PeakAug 8-14the second week of August

Most gone byOct 1-7early October

Best: the second week of August. First arrivals late March; most are gone by early October. Peak: on about 4.6% of Illinois checklists.

Jannot usually seen
Febnot usually seen
Maruncommon
Aprcommon
Maycommon
Juncommon
Julpeak season
Augpeak season
Seppeak season
Octcommon
Novrare
Decnot usually seen

Darker months: more checklists report it. Outlined: peak month.

Ospreys in Illinois, species by species

Species	First arrivals	Common by	Peak	Most gone by	Peak %
Osprey	Mar 22-31	Mar 22-31	Aug 8-14	Oct 1-7	4.6%

Osprey

Share of complete checklists reporting each species, by week (4 per month). Gaps: fewer than 10 checklists that week.

Frequency is the share of complete checklists in Illinois that listed the bird, 2016–2025. It is not a head count, and it follows where and when people go birding. How to read it.

Where in Illinois

Best counties for Osprey

Share of checklists at the peak

Richland CountyBest late September · 11 checklists that week, 580 in all44%
Massac CountyBest late July · 50 checklists that week, 1,916 in all42%
Fayette CountyBest late July · 34 checklists that week, 1,050 in all40%
Clinton CountyBest late August · 222 checklists that week, 8,606 in all32%
Moultrie CountyBest the second week of August · 39 checklists that week, 1,367 in all26%
Iroquois CountyBest late August · 60 checklists that week, 2,566 in all23%

Common questions

When do ospreys arrive in Illinois?: Ospreys arrive in Illinois in late March, peak in the second week of August (4.6% of checklists), and most are gone by early October.
When do ospreys leave Illinois?: Most Ospreys have left Illinois by early October, when reports fall below half their usual rate. Stragglers are still reported until the second week of October.
When is the best time to see ospreys in Illinois?: The Osprey is reported most often in the second week of August, on about 4.6% of Illinois checklists.