I downloaded and compiled all the eBird accepted Bohemian Waxwing checklists for the Denver Metro area (Denver, Adams, Arapahoe, Douglas, Jefferson, Broomfield). Hugh Kingery suggested a definition of an irruption to be greater than 4 birds on a checklist and to cover at least a period of 2 weeks. I sorted it into date order for these combined 6 counties. After dropping all checklists with less than 5 birds or an X in the count, I was left with 215 checklists with BOWAs in the Metro area over a 75 year period. Hugh had BOWAs back in 1948 close to the zoo.
eBird was started by Cornell in 2002. Not many birders used it at that time but it is now widely used. Many birders have entered their historical records which is such valuable information. Many thanks to all the reviewers that really make this a trusted source of data. And thanks to all the birders that are now submitting checklists, we really have a great resource of birding data. David Suddjian was the first to see our current amazing irruption on 12/23/2022 in Ken Caryl. He confirmed the 20 flyovers by the "tight formation, size and calls". And it is possible we will continue to see this current irruption even into April. We have to go back *14 years* to get to the closest previous irruption for the metro area. It was in the winter of 2007-2008. It began on 12/14/2007 at Chatfield State Park and the last sighting that winter was at Columbine West on 4/13/2008. The high count that winter was 200 BOWA in Douglas county on 1/15/2008. Going back *2 more years* to the winter of 2004-2005 was a large irruption year as well. It began on 11/24/2004 in Broomfield and finished on 3/21/2005 in Douglas county. The high count for this period was 2000 (a conservative count they said) and was recorded in Adams county at "Federal & 120th by Norm, Ted, Dave and Marilyn" on 11/30/2004. You have to go back another *13 years* to the winter of 1990-1991 to get another irruption for the Denver Metro area. Beginning on 12/12/1990 at Chatfield and continuing to 4/5/1991 at Joe Roller's Yates home in Denver. He had 22 BOWA and commented on their "mean looking facies". There are 5 records for this irruption winter and the average count was around 40 BOWAs. The 1980's had 5 winters with BOWA irruptions. 79-80, 81-82, 84-85, 86-87 and 87-88. The largest count on a checklist for the 1980's was 1000 BOWA on 1/12/1988 in Greenwood Village by Hugh Kingery. He made this comment "Heritage Village, Littleton (6465 S. Niagara).No details. This month saw a lot of BOWAs in metro Denver.". There is only one year in the 1970's and one year in the 1960's that shows irruptions in the eBird historical data in the Metro area. 1976-1977 had a checklist with a high count of 1000 BOWA at Cherry Creek SP on 3/12/1977. And finally in the winter of 1968-1969 there was a report of 2000 BOWA at Bow-Mar on 12/20/1968 reported by Van Remsen with this comment "invasion year; careful estimate". As more historical data is entered and as more birders use eBird, the data will get better. I did download all of the Colorado BOWA data and it contained right at 1000 records. All of Colorado averages an irruption every 3 years. But the Denver Metro area, from 1948-2023, has had 11 irruptions in this 75 year span. So, we average an irruption about every 7 years. Enjoy this one while it lasts. Sure has been fun. Gregg Goodrich Highlands Ranch -- -- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. To post to this group, send email to cobirds@googlegroups.com For more options, visit this group at http://groups.google.com/group/cobirds?hl=en?hl=en * All posts should be signed with the poster's full name and city. Include bird species and location in the subject line when appropriate * Join Colorado Field Ornithologists https://cobirds.org/CFO/Membership/ --- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. To unsubscribe from this group and stop receiving emails from it, send an email to cobirds+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/cobirds/CAG23Tosj6WuR39%2B95K5p_SXegUpYZyN3XiWdaNJgq5tv3h1yeQ%40mail.gmail.com.
