Date: 4/16/25 12:06 pm From: <lehman.paul...> via groups.io <lehman.paul...> Subject: [CALBIRDS] April migration: Late and Slow! , Some annual early questionable reports
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.
