13 Apr 2015 — PNW Migration Update

Excellent conditions – clear skies and a bit of a tail wind – lots of birds moving up the Pacific Flyway.

Bank Swallows and Yellow-breasted Chats have made it into the San Diego Area.  Tanagers are up into the Central Valley.  And Hermit Warblers are moving through the Coast Range here in Oregon.

Mike Patterson, who writes the North Coast Diaries blog, has a great piece on phenolongical variation across Oregon’s differing ecoregions.  It’s here  — highly recommended.

It was another night where the large scale impact of weather on migration is clearly on display.  So i threw in a National Radar Composite and a map of the winds at 850 mb heights (roughly 1500 meters).

For commentary on the migration through New England check out Tom Auer’s Blog.  Also, today he has some information on a new radar product coming out of NOAA.  It’s a product they are calling “Bioscatter“.  My guess it is the same algorithm, or a clone, that derives the Hydrometeor Classification images found at the College of DuPage’s weather site, and that i highlight here at times when separating birds from rain.  I have added it to the sidebar under the Weather section.  You’ll have to figure out how to access it by navigating their product menu.

Migrant Phenology for the Northern Willamette Valley

For the general public eBird appears to be coming the “go to” place for information on avian status and distribution.  Data can be readily accessed in a number of visual formats, raw data can be downloaded, and a geographic area of interest can be targeted.  There are limits to what can be visually displayed.  You can only look at the frequency distributions for five species at a time for example.

When spring rolls around here in the northern hemisphere the topic of phenology directly or indirectly always comes up across the birding centric listservs.  Here in the Pacific Northwest the use of the acronym for “First of Season” – FOS – starts in February with the arrival of Turkey Vultures and doesn’t stop until late May or June with the sightings of Common Nighthawks.

The most visited pages on this website are the Willamette Valley Spring Migration Phenology page and the Fall Migration Phenology page.

In an effort to synthesize the availability of data from eBird and the obvious appetite for phenology information i have put together three documents available for download.  They are listed below and will now have their own page in the head banner section – “eBird Frequency Data”.

The data and images found in these documents all come from eBird.  They are all Microsoft Office documents.  Two Excel spreadsheets and one Word document.  The links take you to my public, cloud based, Google Drive. The spreadsheet display from Google is unreadable so you will want to download the file and view it in Excel. They’re actually not too bad viewed in Google Sheets, but not all formatting is supported. The word document is passably displayed, but is better viewed in Word.

What the data represents — the data is from all observations in the eBird data base for 40 selected migrants for only SIX counties in Oregon, all in the northern Willamette Valley.  They are: Columbia, Multnomah, Washington, Clackamas, Yamhill, and Marion.  The migrants are ordered in accordance to the current AOU phylogenetic order, not by arrival date. The data contains all observer errors that got past the review process.  So, that Swainson’s Thrush that shows up in the April 8 time slot — well, i’ll let you decide.

This is just data.  If you want a narrative to go along with it: One of the Pacific Northwest’s birding luminaries, David Irons, has put together an excellent narrative: A Spring Migration Phenology for Western Oregon.
David obviously put a lot of time into this work.  It’s well done and worth the read.

The first is the “Migration Frequency Table.  This document is a spreadsheet that has 40 migrants’ frequency of occurrence shown across 48 time periods.  Each month is broken down into the 1st, the 8th, the 15th and the 22nd.  That’s just how eBird does it.  Each month gets four data points.  There are two worksheets in the document.  One has the species as a column on the left and one has them as a row on the top.  Each specie is designated by a six letter code to save space.  These will be intuitively obvious to any regular field observer.  Not everybody will be able to decipher these codes so here is a link to a generator.  Enter the alpha code and it will show you the name of the species.

What is frequency? As eBird defines it: “Frequency” is the percentage of checklists reporting the species within a specified date range and region. This is the most conservative way of displaying the eBird data. For example, when looking at data from across North America we learn that the Yellow Warbler is reported on roughly 25% of checklists during the week starting 15 May. In contrast, the Cassin’s Sparrow is only reported on .1% of checklists from the same region and date range.

You will also find a row or column depending on which tab you are viewing, labeled “Sample Size”.  For all data shown here this represents the number of records, or checklists, found in the eBird data base for each time period sampled.

The second is the “Phenology Data.  This document is a spreadsheet that has the same 40 migrants, each with their own worksheet. In addition to the “frequency” data i have added: “Average Count” and “High Count”.  eBird defines each of these terms as:

“Average Count” is the average number of birds seen on checklists with a positive observation for the species within a specified date range and region. This calculation differs from “Abundance” in that it only incorporates checklists that reported the species (no zeros), essentially telling us how many of each species we can expect to see where the species [is] encountered. For example, starting on the week of 15 Jan we might expect to see about 29 American Crows in areas where the species occurs. This large number indicates the winter flocking behavior of this species. In contrast, starting on the week of 15 May we might expect to see just 3 American Crows where the species occurs. This smaller number indicates the onset of the breeding season when the large flocks break up and disperse to each pairs’ breeding location.

“High Count” is the highest count of a species submitted on a single checklist within a specified date range and region. For example, a high count of 16 Ospreys during the week of 15 Sep indicates the fall migratory peak for this species. By refining the date range to the month level one can see specific high counts for each day.

The third is the “Northern Willamette Valley Frequency Charts.  This is a Word document that has one page for each of the 40 migrants.  On each page is a screen grab of eBird’s Frequency chart.  It is simply a graphical representation of the Frequency data, and looks like this (click on the image to enlarge the view)

All of this data is readily obtained by anybody that visits eBird.  I have simply put it here, all in one place, all downloadable for anyone’s personal use.

Finally here is a direct link to the cloud based Migration Data directory.