Central Oregon Migration Arrival Dates

The impetus for these charts was the publication of Phenology Charts in Corvallis Audubon’s The Chat in the 1970s.  In the spring after I moved to Bend in July, 1981, I noticed that migrants on this side of the mountains arrived on a  different schedule than those in the valley. At some point later in the decade when I had a PC and a database  program, I devised a way to calculate these dates for Central Oregon. Most of the early data was taken from the  Fieldnotes Columns in The Eagle Eye while in recent years eBird has made considerably more data available.  This data will be updated in the coming year.

How to use the chart:  The data in the first chart is arranged by the arriving migrants in Central Oregon (Deschutes, Crook & Jefferson Counties except as noted) from the earliest to the latest. The species is listed in the first column.  Any comments about data limitations in the data are in the next column.  The number of years for which we have data is listed next.  Typically the earliest data is from 1982 though there are some species with earlier information. The early date is the earliest day in the year the species was reported during the years of data.  Similarly, the late date is the latest day in the year that the species was first reported during that year.  The Average arrival date is computed by using the Day of the Year value (the sequential day number starting with day 1 on January 1 going through day 365 on December 31) and adding all of those numbers. The earliest and latest dates are removed and the resulting number is divided by the remaining number of years seen.  In the second chart the species are arranged by their phylogenetic order like you would find them in your field guide.