Monday, May 9, 2011
Bullock's Oriole Migration
Posted by Robert Mortensen
I am very excited as this is the time of year when they arrive where I live. I have often wondered where they winter. When they migrate north, what route(s) do they take? Well, eBird (meaning all of you as eBird users!) can help us answer that.
I put together the following animated map which shows Bullock's Oriole range by month. I hope eBird will at a future date allow me to look at the range by week as they tend to move pretty quickly in April and May and I think we can learn a whole lot more by looking at weekly details.
What can we learn from this month-by-month map?
First, Bullock's Oriole appear to winter in Mexico, particularly along the western side of Mexico.
By March, they are all over California and the lower half of Arizona.
In April they began to spread until May when they spread dramatically across the western United States following the continental divide as if it was some invisible wall. Bullock's Orioles even make their way up into parts of British Columbia and Alberta.
June and July show that reports are more localized, but still covering the same range. This makes me think that they are on nesting grounds and not traveling to and fro so much. By September, the southern migration is well underway.
It also appears that the best chance for our friends in the eastern half of the United States to see a Bullock's Oriole is for a winter vagrant...those silly birds that got their instinct wires crossed and head east rather than south.
Bird migration is such an interesting phenomenon and pondering it stirs my soul with wonder and amazement!