WhenToBird

Polioptila caerulea · Polioptilidae

When Do Blue-gray Gnatcatchers Arrive in Pennsylvania?

Adult Blue-gray Gnatcatcher
Photo: Laura Clark, CC BY 4.0 via iNaturalist

Blue-gray Gnatcatchers reach Pennsylvania in early April, are common by the second week of April, peak in early May (23% of checklists), and most are gone by early September.

When to look

First arrivalsApr 1-7early April
Common byApr 8-14the second week of April
PeakMay 1-7early May
Most gone bySep 1-7early September

Best: early May. First arrivals early April; most are gone by early September. Peak: on about 23% of Pennsylvania checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprpeak season
  5. Maypeak season
  6. Juncommon
  7. Juluncommon
  8. Auguncommon
  9. Sepuncommon
  10. Octnot usually seen
  11. Novnot usually seen
  12. Decnot usually seen

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

0%10%20%30%Jan 1-7: 0.1% of 47145 checklistsJan 8-14: 0.1% of 35840 checklistsJan 15-21: 0.1% of 35423 checklistsJan 22-31: 0% of 49126 checklistsFeb 1-7: 0% of 36366 checklistsFeb 8-14: 0% of 42248 checklistsFeb 15-21: 0% of 55888 checklistsFeb 22-28: 0.1% of 42050 checklistsMar 1-7: 0% of 42709 checklistsMar 8-14: 0.1% of 43985 checklistsMar 15-21: 0.1% of 44547 checklistsMar 22-31: 0.1% of 66940 checklistsApr 1-7: 1.8% of 51147 checklistsApr 8-14: 7.5% of 54868 checklistsApr 15-21: 17% of 57252 checklistsApr 22-30: 24% of 81727 checklistsMay 1-7: 24% of 76472 checklistsMay 8-14: 21% of 79341 checklistsMay 15-21: 19% of 61724 checklistsMay 22-31: 14% of 70722 checklistsJun 1-7: 12% of 45652 checklistsJun 8-14: 10% of 41810 checklistsJun 15-21: 9.3% of 38973 checklistsJun 22-30: 8.7% of 44255 checklistsJul 1-7: 7.8% of 34822 checklistsJul 8-14: 7.3% of 31104 checklistsJul 15-21: 6.8% of 29262 checklistsJul 22-31: 6.6% of 41436 checklistsAug 1-7: 6.4% of 29189 checklistsAug 8-14: 6.5% of 28840 checklistsAug 15-21: 7.1% of 29948 checklistsAug 22-31: 7.5% of 48235 checklistsSep 1-7: 6.6% of 37175 checklistsSep 8-14: 3.8% of 36527 checklistsSep 15-21: 1.2% of 37261 checklistsSep 22-30: 0.4% of 43583 checklistsOct 1-7: 0.1% of 35352 checklistsOct 8-14: 0.1% of 35560 checklistsOct 15-21: 0.1% of 33119 checklistsOct 22-31: 0.1% of 44654 checklistsNov 1-7: 0.1% of 32965 checklistsNov 8-14: 0.1% of 31305 checklistsNov 15-21: 0.1% of 29471 checklistsNov 22-30: 0.1% of 38642 checklistsDec 1-7: 0.1% of 28779 checklistsDec 8-14: 0.1% of 29486 checklistsDec 15-21: 0.1% of 37465 checklistsDec 22-31: 0.1% of 50651 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 Pennsylvania 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.

Embed this map on your site

Where in Pennsylvania

Best counties

Share of checklists at the peak
  1. Philadelphia CountyBest late April · 4183 checklists that week, 96,503 in all43%
  2. Bucks CountyBest early May · 3120 checklists that week, 95,030 in all35%
  3. Snyder CountyBest late April · 270 checklists that week, 5,676 in all32%
  4. Schuylkill CountyBest early May · 754 checklists that week, 22,261 in all32%
  5. Lancaster CountyBest early May · 2973 checklists that week, 97,892 in all32%
  6. Blair CountyBest early May · 526 checklists that week, 13,387 in all30%

Best spots

Share of checklists at the peak
  1. Pickering Preserve - CharlestownChester County, best late April · 113 checklists that week, 1,023 in all93%
  2. The Willows ParkDelaware County, best late April · 26 checklists that week, 549 in all90%
  3. Ridley Creek State Park (Hunting Hill)Delaware County, best late April · 108 checklists that week, 1,073 in all90%
  4. North Park (Mill Creek)Berks County, best early May · 21 checklists that week, 373 in all90%
  5. Municipal LandDelaware County, best late April · 30 checklists that week, 628 in all90%
  6. Evansburg State ParkMontgomery County, best early May · 67 checklists that week, 1,212 in all89%

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

Best time of day

In Pennsylvania, the Blue-gray Gnatcatcher is most often listed on checklists started between 6 and 8 am (10% of those checklists).

0%5%10%15%12 am: too few checklists (1558) to judge1 am: too few checklists (1136) to judge2 am: too few checklists (839) to judge3 am: too few checklists (842) to judge4 am: too few checklists (2550) to judge5 am: too few checklists (18294) to judge6 am: 14% of 92903 checklists7 am: 9.0% of 241233 checklists8 am: 7.3% of 271994 checklists9 am: 6.1% of 236842 checklists10 am: 5.3% of 199508 checklists11 am: 4.7% of 161893 checklists12 pm: 4.5% of 143945 checklists1 pm: 4.5% of 134352 checklists2 pm: 4.2% of 129692 checklists3 pm: 4.1% of 126132 checklists4 pm: 4.8% of 115055 checklists5 pm: 6.7% of 90719 checklists6 pm: 7.3% of 67534 checklists7 pm: 4.9% of 43004 checklists8 pm: too few checklists (13966) to judge9 pm: too few checklists (3913) to judge10 pm: too few checklists (1989) to judge11 pm: too few checklists (1146) 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
January0.1%0.1%0.1%0%
February0%0%0%0.1%
March0%0.1%0.1%0.1%
April1.8%7.5%17%24%
May24%21%19%14%
June12%10%9.3%8.7%
July7.8%7.3%6.8%6.6%
August6.4%6.5%7.1%7.5%
September6.6%3.8%1.2%0.4%
October0.1%0.1%0.1%0.1%
November0.1%0.1%0.1%0.1%
December0.1%0.1%0.1%0.1%

Neighboring states

  • Maryland: arrives late March, 1 week earlier than Pennsylvania
  • District of Columbia: arrives late March, 1 week earlier than Pennsylvania
  • Delaware: arrives late March, 1 week earlier than Pennsylvania
  • New Jersey: arrives late March, 1 week earlier than Pennsylvania

Common questions

When do Blue-gray Gnatcatchers arrive in Pennsylvania?
Blue-gray Gnatcatchers reach Pennsylvania in early April, are common by the second week of April, peak in early May (23% of checklists), and most are gone by early September.
When do Blue-gray Gnatcatchers leave Pennsylvania?
Most Blue-gray Gnatcatchers have left Pennsylvania by early September, when reports fall below half their usual rate. Stragglers are still reported until mid September.
When is the best time to see a Blue-gray Gnatcatcher in Pennsylvania?
The Blue-gray Gnatcatcher is reported most often in early May, on about 23% of Pennsylvania checklists.
Where in Pennsylvania are Blue-gray Gnatcatchers seen most often?
By county, Philadelphia County, Bucks County, and Snyder County have the highest peak reporting rates for the Blue-gray Gnatcatcher (counties with at least 200 checklists).