WhenToBird

Empidonax traillii · Tyrannidae

When Do Willow Flycatchers Arrive in Illinois?

Adult Willow Flycatcher
Photo: Steven Smethurst, CC0 1.0 via iNaturalist

Willow Flycatchers reach Illinois in the second week of May, are common by mid May, peak in early June (11% of checklists), and most are gone by early August.

When to look

First arrivalsMay 8-14the second week of May
Common byMay 15-21mid May
PeakJun 1-7early June
Most gone byAug 1-7early August

Best: early June. First arrivals the second week of May; most are gone by early August. Peak: on about 11% of Illinois checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprnot usually seen
  5. Maypeak season
  6. Junpeak season
  7. Julcommon
  8. Auguncommon
  9. Seprare
  10. Octnot usually seen
  11. Novnot usually seen
  12. Decnot usually seen

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

0%5%10%15%Jan 1-7: 0% of 29700 checklistsJan 8-14: 0% of 20189 checklistsJan 15-21: 0% of 19784 checklistsJan 22-31: 0% of 26641 checklistsFeb 1-7: 0% of 20478 checklistsFeb 8-14: 0% of 21967 checklistsFeb 15-21: 0% of 28735 checklistsFeb 22-28: 0% of 24223 checklistsMar 1-7: 0% of 26775 checklistsMar 8-14: 0% of 27579 checklistsMar 15-21: 0% of 27193 checklistsMar 22-31: 0% of 42278 checklistsApr 1-7: 0% of 34579 checklistsApr 8-14: 0% of 38290 checklistsApr 15-21: 0% of 39261 checklistsApr 22-30: 0.1% of 59584 checklistsMay 1-7: 0.3% of 60485 checklistsMay 8-14: 1.8% of 59647 checklistsMay 15-21: 6.1% of 43173 checklistsMay 22-31: 12% of 47913 checklistsJun 1-7: 12% of 31151 checklistsJun 8-14: 10% of 27692 checklistsJun 15-21: 8.6% of 23983 checklistsJun 22-30: 6.0% of 28448 checklistsJul 1-7: 6.0% of 21273 checklistsJul 8-14: 5.4% of 19284 checklistsJul 15-21: 6.3% of 17712 checklistsJul 22-31: 6.1% of 24500 checklistsAug 1-7: 3.6% of 18498 checklistsAug 8-14: 2.2% of 19331 checklistsAug 15-21: 1.4% of 19983 checklistsAug 22-31: 1.1% of 31892 checklistsSep 1-7: 0.9% of 26396 checklistsSep 8-14: 0.4% of 25011 checklistsSep 15-21: 0.1% of 23597 checklistsSep 22-30: 0.1% of 30638 checklistsOct 1-7: 0% of 23949 checklistsOct 8-14: 0% of 24412 checklistsOct 15-21: 0% of 22359 checklistsOct 22-31: 0% of 29794 checklistsNov 1-7: 0% of 21877 checklistsNov 8-14: 0% of 19742 checklistsNov 15-21: 0% of 18989 checklistsNov 22-30: 0% of 23905 checklistsDec 1-7: 0% of 16935 checklistsDec 8-14: 0% of 16687 checklistsDec 15-21: 0% of 20931 checklistsDec 22-31: 0% of 29011 checklistsJanFebMarAprMayJunJulAugSepOctNovDec
Share of complete checklists reporting it, by week (4 per month). Grey bars: fewer than 10 checklists, not counted.

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.

JanFebMarAprMayJunJulAugSepOctNovDec
today
Second week of November

Each county is shaded by the share of complete checklists there that listed the bird, blended with the weeks either side. Darker is more often. It follows where people watch birds, not how many birds there are. How to read it.

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Where in Illinois

Best counties

Share of checklists at the peak
  1. Boone CountyBest early June · 44 checklists that week, 3,174 in all32%
  2. Clark CountyBest late May · 79 checklists that week, 2,005 in all30%
  3. Grundy CountyBest early June · 93 checklists that week, 5,050 in all27%
  4. Putnam CountyBest the second week of June · 65 checklists that week, 3,333 in all25%
  5. DeKalb CountyBest the second week of June · 101 checklists that week, 8,181 in all25%
  6. McHenry CountyBest early June · 1397 checklists that week, 45,486 in all24%

Best spots

Share of checklists at the peak
  1. Aurora West Forest PreserveKane County, best early June · 28 checklists that week, 401 in all83%
  2. Spring Bluff Forest PreserveLake County, best late May · 41 checklists that week, 783 in all81%
  3. Pleasant Valley 8McHenry County, best early June · 37 checklists that week, 739 in all73%
  4. Veterans of Foreign Wars Little League ParkCook County, best the second week of June · 61 checklists that week, 2,658 in all73%
  5. Lake MendotaLa Salle County, best mid June · 23 checklists that week, 1,574 in all72%
  6. Goose Lake 3McHenry County, best early June · 100 checklists that week, 955 in all72%

Busy spots report more of everything; compare the checklist counts before you drive anywhere.

Best time of day

In Illinois, the Willow Flycatcher is most often listed on checklists started between 6 and 8 am (3.8% of those checklists).

0%2%4%6%12 am: too few checklists (484) to judge1 am: too few checklists (631) to judge2 am: too few checklists (485) to judge3 am: too few checklists (610) to judge4 am: too few checklists (2321) to judge5 am: too few checklists (23536) to judge6 am: 4.8% of 95511 checklists7 am: 3.2% of 164584 checklists8 am: 2.4% of 163654 checklists9 am: 1.9% of 141804 checklists10 am: 1.5% of 122882 checklists11 am: 1.2% of 100640 checklists12 pm: 1.0% of 89894 checklists1 pm: 0.7% of 82729 checklists2 pm: 0.8% of 79801 checklists3 pm: 0.6% of 82169 checklists4 pm: 0.8% of 75124 checklists5 pm: 1.1% of 57708 checklists6 pm: 1.2% of 41843 checklists7 pm: too few checklists (20943) to judge8 pm: too few checklists (6131) to judge9 pm: too few checklists (1677) to judge10 pm: too few checklists (843) to judge11 pm: too few checklists (448) to judge12a3a6a9a12p3p6p9p
Share of checklists started in each local hour that reported it. It reflects when people go birding as well as when birds are active. Grey hours have too few checklists (under 2% of the state’s, or under 200) to judge.
Week-by-week table
MonthDays 1-78-1415-2122-end
January0%0%0%0%
February0%0%0%0%
March0%0%0%0%
April0%0%0%0.1%
May0.3%1.8%6.1%12%
June12%10%8.6%6.0%
July6.0%5.4%6.3%6.1%
August3.6%2.2%1.4%1.1%
September0.9%0.4%0.1%0.1%
October0%0%0%0%
November0%0%0%0%
December0%0%0%0%

Neighboring states

  • Indiana: arrives early May, 1 week earlier than Illinois
  • Wisconsin: arrives the second week of May, in the same week than Illinois
  • Michigan: arrives the second week of May, in the same week than Illinois
  • Iowa: arrives the second week of May, in the same week than Illinois

Common questions

When do Willow Flycatchers arrive in Illinois?
Willow Flycatchers reach Illinois in the second week of May, are common by mid May, peak in early June (11% of checklists), and most are gone by early August.
When do Willow Flycatchers leave Illinois?
Most Willow Flycatchers have left Illinois by early August, when reports fall below half their usual rate. Stragglers are still reported until late August.
When is the best time to see a Willow Flycatcher in Illinois?
The Willow Flycatcher is reported most often in early June, on about 11% of Illinois checklists.
Where in Illinois are Willow Flycatchers seen most often?
By county, Boone County, Clark County, and Grundy County have the highest peak reporting rates for the Willow Flycatcher (counties with at least 200 checklists).