Hi Tweets,

Randy Hill writes:
Are we even through the spring migration for passerines?

Using the terms 'Spring' and 'Fall' to describe migration results in what I
would describe as 'Birders' English', a terminology which has left--and
clearly is still leaving--a wake of confusion and bafflement.

In Vancouver BC, in the years when I was tracking such things, the last of
the locally-breeding migrants--Black Swift and Common Nighthawk--would be
arriving about their then-average arrival dates of May 31 and June 01. the
first 'Fall' migrant was Lesser Yellowlegs, with a then-average arrival date
of June 21. But it could be a day or two early in some years. These very
early migrants were probably First Summer adolescents which had lacked
sufficient hormonal impetus to 1.) go all the way to the breeding sites, and
2.) develop a full Alternate plumage suite; many seemed to still be in
complete Basic--what the guides would call 'Winter'--plumage.

This leads to the situation where the first Winter-plumaged Fall migrants
can arrive in late Spring (that is, before the Summer Solstice) just as the
last Spring migrants are settling down to become Summer residents.
Confusing? especially to beginning birders? You bet it is. Nothing wrong
with the birds' behaviors, just with the terminology used to describe them:
Birders' English at its most absurd and unhelpful.

So, the simplest way to boil out such gorgeously goofy nonsense is to
replace 'Spring' and 'Fall' with 'northbound' and 'southbound'. Voila.
Besides, the seasonal terms were used originally to describe the migrations
in the East, where they're much more seasonally clear-cut than along the
more temperate Pacific Coast.

Further, if you want to understand the workings of annual migration in your
particular location, the key is to compile arrival and departure dates for
every seasonally-various species, including 'fluke' species (whose
extralimital appearances usually turn out to be anything but random), over
at least a ten-year period. As Wayne Weber once pointed out, a decadal
review is now necessary as global warming modifies migration periods. If
possible, include arrivals and departures of birds identifiable by sex and
age, as there are sometimes very clear differences (e.g., some raptors,
gulls and many shorebirds). For birds which are present all year in large
numbers, here such as Golden-crowned Kinglets, the temporary presence of
migrant birds can be masked by the locals, so keeping track of their actual
numbers (or best-guesses, in this instance) will show a strong migrant pulse
in April and a much more protracted one in August-September.

Migration is remarkably simple in concept, but complex in expression. But
keeping track of sighting data will allow observers to see not only the
entire tapestry of general migration but also the myriad threads and
internal patterns from which it is constructed.

Best wishes

Michael Price
Vancouver BC Canada
loblollyboy AT gmail.com

"I feel like a fugitive from th' law of averages!" -- GI Willie