Date: 10/11/18 5:55 am
From: Paul Dickson <Paul...>
Subject: [LABIRD-L] staging Ruby-throated
Hummers at my feeders this morning are 4-6 in sight at once which is down from 20+ yesterday. With a bright blue sky emerging and a steady 7 mph north wind I suspect that these will mostly be gone by noon. Checking my notes carefully,
this situation of both an absence of fall fronts reaching Louisiana in September and significant summer drought leading up to September occurred in 2005. Similarly in that year I noted a sustained large number at the feeders until a high pressure system eventually gave them a ride south.
Though I have been able to well document the direct relationship between variation in staging numbers at my feeders and atmospheric pressure in late August and September, these two years, 2005 and 2018 have been my only opportunities to note the what happens when there is no such continental frontal activity at this location. It's one thing to say that hummingbirds use north winds and calm air of high pressure systems to efficiently migrate south but quite another to say that they delay southbound migration until such favorable conditions occur. I am not currently banding and color marking and that would be required to show that the same individuals are staging for long periods of stagnant or tropical influenced fall weather. Though not proof, this fall's observation of swarms at the feeders later than ever before sure indicated that.
Paul Dickson
Caddo Parish, La.
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