fall migration ups and downs, and accurate departure dates for rarities


lehman.paul@verizon.net
 

Both spring and fall migration periods are, of course, not one continuous stream of migrants and rarities, but they are typically punctuated by good periods and slow periods of varying lengths. We had a recent good period for rare birds in the county, starting a week ago on the 3rd and lasting a few days, during which we had the Red-faced Warbler, 3 Prairie Warblers, the Yellow-green Vireo, 2 Eastern Kingbirds, 2 Stilt Sandpipers, several Am. Redstarts, Black-and-white, and Rose-breasted Grosbeak, among others. Then, these birds, after staying a variable number of days, start filtering out and are replaced by not much. So, we await the next arriving pulse!! It should also be said that so far this fall has seen fairly low numbers of most western landbird migrants, even during this recent period of rarity wealth. One regular species in OK numbers seems to be Western Tanager, but most other migrants seem low or very low.

Speaking of departing birds, sometimes it is not easy to determine the definite last date for a rarity because a few reports of such birds continue but are of uncertain validity. A case in point is the Fort Rosecrans Cemetery Yellow-green Vireo, which was definitely present through the 8th, but only a handful of sight reports (no photos) since then, whereas most folks miss the bird (although it was a sneaky individual and easy to miss). BUT, there is also a known Warbling Vireo through today in those same trees. The culprit, or are both birds truly still there?? (Immature western Warbling Vireos in fall can be fairly yellow on the sides, as some of you may have recently seen at Smuggler's Gulch alongside the Red-faced Warbler.)

--Paul Lehman, San Diego