Date: 4/16/25 1:09 pm From: Dominik Mosur via groups.io <dominikmosur...> Subject: [pen-bird] [CALBIRDS] April migration: Late and Slow! , Some annual early questionable reports
A very informative post from Paul Lehman regarding this year's spring
migration and related matters. It's from Southern California but highly
applicable here as well.
Dominik Mosur
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From: <lehman.paul...> via groups.io <lehman.paul=
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Date: Wed, Apr 16, 2025 at 12:06 PM
Subject: [CALBIRDS] April migration: Late and Slow! , Some annual early
questionable reports
To: <calbirds...> <calbirds...>
I think almost everyone in California would agree that the passerine
migration so far this April is notably LATE and SLOW. Down here in parts of
southern California, a number of folks (including myself) have commented on
it being a good migration earlier in the season for Violet-green Swallow,
and since then OK for Western Kingbird and Chipping Sparrow. But almost
everything else.....late and slow! One very common refrain virtually
statewide has been, "Where are all the Hooded Orioles?" Here in San Diego
County, where common and widespread, they were remarkably scarce until just
a little over a week ago. Still below average, but at least they have
filled in a fair bit of their widespread range locally--but this is almost
A FULL MONTH LATE. Bullock's Orioles and Black-headed Grosbeaks have also
finally begun to increase, but still below normal and running 2-3 weeks
late. And where are all the many Ash-throated Flycatchers that normally
start appearing by late March? Anyway, the list goes on and on. So, what's
happening? Major population declines? Inappropriate local weather
conditions locally for migration? Or something odd going on farther to the
south(east), either en route or closer to the wintering grounds? In support
of the latter factor are reports that a fair chunk of southern Arizona had
it driest winter on record, EVER, and--perhaps more important--one friend
of mine reported that parts of Mexico had a cooler or colder than usual
(relatively speaking) winter and early spring--which could well translate
into a lot of stuff running late. We will certainly know a lot more once
the next month plays out!
It's another first half of April, and yet another year of multiple reports
of the following species that are way early and which in most cases likely
reflect misidentifications. (And all of which could really use photo
documentation.) Western Wood-Pewees are not expected to start arriving
until after about 15 April, so any reports before that need to come with
strong documentation, and need to be flagged by eBird filters. (For
example, the all-time early arrival in San Diego County is around 8 April.)
Most such early reports involve either heard-only birds (think vocalizing
starlings or a number of other mimics) or are poorly documented and have no
photos. Often these reports are from observers who do not at all appreciate
how unusually early their bird would be. And a problem that I bet many
birders don't realize is that the first Olive-sided Flycatchers actually
arrive before wood-pewees do--and probably get misidentified. This month,
there were several poorly documented early reports, but also one well
photographed bird in Orange County on 10 April. The next species is
Swainson's Thrush, which already has a bunch of reports in California
during the first half of the month. This species is not reliable until
around late the third week in the month, with a just a few documented
records as early as the 12th-15th. A fair number of the earliest records
are of birds at breeding sites, arriving even earlier than through-migrants
do farther to the SOUTH, but such local breeders need to be heard SINGING.
Unfortunately, almost all of the early reports this month have involved
birds not seen and only heard calling, or heard calling and seen rather
poorly, again mostly by folks who don't appreciate the true status of this
species so early--and who report the bird giving the "wink" or "wheet" call
only, but some other species (e.g., Song Sparrow) can give similar calls.
Last but not least comes Black Swift. There are a small number of legit
records for the last week or perhaps ten days of April in California (some
associated with southern or lowland nesting areas), but of course this
species is a notorious late arriver and typically doesn't show until into
May. The problem here is the usual one of an observer not appreciating the
true status and seasonal timing, and either seeing a White-throated or
Vaux's Swift at a distance or in mediocre light and not properly assessing
size and/or color. And the other recurring problem is misidentifying male
Purple Martins. Heck, some especially early reports of Black Swift, if
indeed of a large all-dark swift, might need to also consider either Common
Swift or White-collared Swift. So far this year, there have already been
one or two Black Swift reports. From previous years, there is an especially
"egregious" report with very limited details coming from Butte County on 30
March 2021 and apparently being validated by eBird.....
Anyway, I'd recommend all county ebird filters be tightened for these and
several other migrants that are notoriously reported "too early" almost
every spring (e.g., add Willow and Dusky Flycatchers to the list), and set
to 0 until these species are truly known to occur REGULARLY in at least
small numbers.
Exceptional arrival and departure dates certainly DO exist. But such
exceptional occurrences need to be appreciated by the observer AT THE TIME
OF THE OBSERVATION and need to be exceptionally well documented.
