WhenToBird

Dolichonyx oryzivorus · Icteridae

When Do Bobolinks Arrive in Colorado?

Adult male Bobolink
Photo: Derek Spencer, CC BY 4.0 via iNaturalist

Bobolinks mostly pass through Colorado: they arrive in mid May, peak in early June (1.3% of checklists), and most are gone by early July.

When to look

First arrivalsMay 15-21mid May
Common byMay 15-21mid May
PeakJun 1-7early June
Most gone byJul 1-7early July

Best: early June. First arrivals mid May; most are gone by early July. Peak: on about 1.3% of Colorado 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. Augnot usually seen
  9. Sepnot usually seen
  10. Octnot usually seen
  11. Novnot usually seen
  12. Decnot usually seen

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

0%0.5%1%1.5%Jan 1-7: 0% of 32254 checklistsJan 8-14: 0% of 23278 checklistsJan 15-21: 0% of 22933 checklistsJan 22-31: 0% of 30856 checklistsFeb 1-7: 0% of 21464 checklistsFeb 8-14: 0% of 22910 checklistsFeb 15-21: 0% of 28739 checklistsFeb 22-28: 0% of 21833 checklistsMar 1-7: 0% of 23066 checklistsMar 8-14: 0% of 23783 checklistsMar 15-21: 0% of 24797 checklistsMar 22-31: 0% of 38439 checklistsApr 1-7: 0% of 31676 checklistsApr 8-14: 0% of 35092 checklistsApr 15-21: 0% of 36778 checklistsApr 22-30: 0% of 50885 checklistsMay 1-7: 0.1% of 44186 checklistsMay 8-14: 0.4% of 49011 checklistsMay 15-21: 0.9% of 40784 checklistsMay 22-31: 1.3% of 53073 checklistsJun 1-7: 1.5% of 32432 checklistsJun 8-14: 1.1% of 29978 checklistsJun 15-21: 1.0% of 29457 checklistsJun 22-30: 0.9% of 36072 checklistsJul 1-7: 0.5% of 28857 checklistsJul 8-14: 0.2% of 27224 checklistsJul 15-21: 0.1% of 27629 checklistsJul 22-31: 0.1% of 37318 checklistsAug 1-7: 0.1% of 25893 checklistsAug 8-14: 0.1% of 24870 checklistsAug 15-21: 0.1% of 24035 checklistsAug 22-31: 0.1% of 35691 checklistsSep 1-7: 0.1% of 27068 checklistsSep 8-14: 0.1% of 26709 checklistsSep 15-21: 0.1% of 26098 checklistsSep 22-30: 0.1% of 31550 checklistsOct 1-7: 0% of 24110 checklistsOct 8-14: 0.1% of 23352 checklistsOct 15-21: 0.1% of 21895 checklistsOct 22-31: 0% of 28319 checklistsNov 1-7: 0% of 21698 checklistsNov 8-14: 0% of 21061 checklistsNov 15-21: 0.1% of 19855 checklistsNov 22-30: 0% of 25798 checklistsDec 1-7: 0% of 18626 checklistsDec 8-14: 0% of 19004 checklistsDec 15-21: 0% of 23103 checklistsDec 22-31: 0% of 30802 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 Colorado 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 Colorado

Best counties

Share of checklists at the peak
  1. Boulder CountyBest the second week of June · 3773 checklists that week, 180,634 in all5.1%
  2. Routt CountyBest the second week of June · 341 checklists that week, 10,504 in all4.8%
  3. Fremont CountyBest the second week of June · 336 checklists that week, 15,522 in all2.5%
  4. Larimer CountyBest late May · 6541 checklists that week, 171,224 in all2.3%
  5. Rio Blanco CountyBest early June · 134 checklists that week, 2,806 in all2.1%
  6. Mesa CountyBest early June · 1182 checklists that week, 45,553 in all1.9%

Best spots

Share of checklists at the peak
  1. Carpenter Ranch PreserveRoutt County, best early June · 35 checklists that week, 157 in all94%
  2. Reservoir Ridge Natural AreaLarimer County, best early June · 47 checklists that week, 718 in all87%
  3. Mccall LakeBoulder County, best late May · 21 checklists that week, 218 in all86%
  4. Van Vleet - NorthBoulder County, best late June · 54 checklists that week, 646 in all84%
  5. South Side ReservoirLarimer County, best the second week of June · 31 checklists that week, 684 in all73%
  6. Teller Lake Number 5Boulder County, best mid June · 122 checklists that week, 1,942 in all55%

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

Best time of day

In Colorado, the Bobolink is most often listed on checklists started between 6 and 8 am (0.3% of those checklists).

0%0.5%12 am: too few checklists (512) to judge1 am: too few checklists (468) to judge2 am: too few checklists (513) to judge3 am: too few checklists (656) to judge4 am: too few checklists (1918) to judge5 am: too few checklists (16045) to judge6 am: 0.4% of 71991 checklists7 am: 0.3% of 159189 checklists8 am: 0.2% of 177206 checklists9 am: 0.2% of 165269 checklists10 am: 0.2% of 141029 checklists11 am: 0.2% of 115283 checklists12 pm: 0.2% of 96068 checklists1 pm: 0.2% of 89512 checklists2 pm: 0.1% of 86319 checklists3 pm: 0.1% of 82496 checklists4 pm: 0.1% of 71648 checklists5 pm: 0.2% of 52445 checklists6 pm: 0.3% of 40199 checklists7 pm: too few checklists (24246) to judge8 pm: too few checklists (7986) to judge9 pm: too few checklists (2004) to judge10 pm: too few checklists (888) to judge11 pm: too few checklists (450) 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%
May0.1%0.4%0.9%1.3%
June1.5%1.1%1.0%0.9%
July0.5%0.2%0.1%0.1%
August0.1%0.1%0.1%0.1%
September0.1%0.1%0.1%0.1%
October0%0.1%0.1%0%
November0%0%0.1%0%
December0%0%0%0%

Neighboring states

  • Wyoming: arrives the second week of May, 1 week earlier than Colorado
  • Utah: arrives the second week of May, 1 week earlier than Colorado
  • Nebraska: arrives early May, 2 weeks earlier than Colorado
  • South Dakota: arrives early May, 2 weeks earlier than Colorado

Common questions

When do Bobolinks arrive in Colorado?
Bobolinks mostly pass through Colorado: they arrive in mid May, peak in early June (1.3% of checklists), and most are gone by early July.
When do Bobolinks leave Colorado?
Most Bobolinks have left Colorado by early July, when reports fall below half their usual rate.
When is the best time to see a Bobolink in Colorado?
The Bobolink is reported most often in early June, on about 1.3% of Colorado checklists.
Where in Colorado are Bobolinks seen most often?
By county, Boulder County, Routt County, and Fremont County have the highest peak reporting rates for the Bobolink (counties with at least 200 checklists).