Hi Tweets,

Nancy Taylor writes:

>As I bicycled home the other evening along the bay trail in Bellingham,
>I caught an unusual shape out of the corner of my eye. (Only unusual
>in that I hadn't seen any for months.) Red-breasted Mergansers on the
>inside of Bellingham Bay, quite near Georgia Pacific. 2 females, 2 j. I
>referred to the bar graph in Wahl and Paulson, and found that fall
>arrival date is in the middle of the month; that date? Sept. 15.
>
>I would like to find more information on arrival and departure dates.
>The reference reading list in Wahl and Paulson refers to journals such
>as _American Birds_ and _Western Birds_, and gives the addresses to
>subscribe. Would either of these journals be appropriate for this info?

Any journal which has local dated first-seen (arrival) and last-seen
(departure) records can give you this data which after tweaking enough of
it, you can turn into useful information about the migrational/seasonal
coming and going of residents and visitors. One drawback to these journals
is that they're hardly representative of the regions's avifauna as the
reports usually cite what's unusual rather than usual: glamorous rarities
rather than humdrum regular migrants.

When they're not partaking of the Great Mind-Humbling Mysteries of
Migration, migrant birds are commuters catching the 4.10 to Windale. Except
for the odd hail-mary vagrant from waaay far away, nearly all species that
show any seasonal variation: northbound, southbound, post-breeding
dispersal, juvenile migration (in shorebirds),winter irruptive, etc., will
show regular patterns of arrival and departure.

What you need to derive a good arrival or departure date is at least ten
years of good records, good coverage and good record-keeping. See over ten
years when the first northbound arrival date for each species is, when it
clears the area headed N, when the southbound adults and/or juvs return,
when the last record--either of last individual or in the case of species
where a few individual typically winter, last flock of significance, the
size dependent on the species--the first arriving 'wintering' birds in
August and September and when the last one is seen in Spring.

When you begin surveying all your area's bird species for possible seasonal
variation, you'll find *lots* of surprising things hidden in the data, and,
guaranteed, will have to revise many home-truths, local wisdom, and opinions
of what's where, when: species whose occurrence you thought were flukey,
random, turn out to have a record-cluster around a certain week in April,
say, or that in some other species, such as Western Sandpiper, southbound
adult females arrive an average two weeks before the adult males with the
juvs showing up an average two weeks after that. There's all kinds of
interesting stuff sitting there in the data: just don't let *anyone* tell
you that it can't or shouldn't be done or should be done only by experts
(I've heard and experienced variations, from patronising to outright
insulting, on all that stuff locally), just go ahead and do it. Enlist the
more experienced if and when you need to, and I hope they'd be as
enthusiastic and helpful as possible, but make your own mind up. Don't be
afraid to diverge from local wisdom, if that's where your data take you:
where the two conflict, traditional authority is *never* an acceptable
substitute for actual knowledge.

The pattern usually emerges roughly (Week 1, Week 2, whatever, of the month)
with about five years of competent record-keeping; is pretty solid at eight
years, and as firm as it will ever get by ten. After that, it will be
showing chaotic year-to-year unpredictability, but in a given year, about
80% of all migrant birds arrive within three days either side of their
average date, while departure doesn't seem to be as regular. A few, like
Vaux's Swift, show great variation, but most are usually predictable to the
week. One thing I'd suggest is make sure that the first arrival sightings
are *visually* confirmed, not heard-only. Birders are nothing if not
competitive, and finding the first arrivals opens the door to 'pushing' an
ID, particularly a voice-only contact.

How do you get an average? Gruntwork. Here's how I do it because I've never
been able to figure out how to get a spreadsheet to do it. Take a piece of
paper and rule it into twelve columns. Not on the top line at upper left but
on the second-top line put down Jan 01 on one side of the column and 01 on
the other, then on the next line Jan 02 and 02, and so on so that Feb 01 is
32, etc. When you come to the beginning of a new month mark which month it
is. Eventually, you'll put down Dec 31--365. Then go back and at the top of
each column write each month(s) included in that column--helps you keep your
place.

Now let's say that you're in Vancouver BC tracking Solitary Sandpiper, which
is a rare north- and southbound transient here and you have the following
northbound arrival and departure dates (and I was tempted to omit the
arrival record for 1985 as being too far outside the cluster), which you
then convert to the day-number for that year, average the aggregated number
by the number of years in the sample, and bob's yer uncle--there's the
arrival date:

Year Date Number Aggreg. Average

1982 n.a.
1983 5.09 129 129 5.09
1984 4.26 118 247 5.04
1985 5.18 138 385 5.08
1986 n.a.
1987 4.26 118 503 5.06
1988 5.05 125 628 5.06
1989 5.13 133 761 5.07
1990 5.12 132 893 5.08
1991 5.04 124 1017 5.07
1992 4.25 115 1132 5.06
1993 5.08 128 1260 5.06
1994 4.23 113 1373 5.05
1995 5.11 131 1504 5.05

If you do the same for the last northbound record each year, you will arrive
at the average departure date; the period in between is the northbound
migration window. For Solitary Sandpiper, for example, the entire migration
chronology at Vancouver BC (almost like a tide chart, which it is, sort of,
in a neat way) is:

Northbound
Arr: May 05
Lv: May 11

Southbound
Arr (adult): Jul 17
Arr (juv): Aug 10
Lv: Sep 12

Sometimes the data lets you know that in the southbound window, the
southbound adults clear the area before the juvs arrive, sometimes there's
overlap, but usually the year's last record of a given migrant species is of
a juv/Basic 1 bird. We don't know what the situation is with SOSA because
the number of birders is very small here who age/sex their birds as well as
identify them, and mostly, local records compilers haven't had a field for
that info in any database they're running, god alone knows why.

Any community large enough to have two birders in it can whop up a person
designated to maintain the records for that community or area.

There's also another favorite horse I'm gonna flog for a few minutes here:
in Britain and Europe you'd take a report of a rare bird to a Rarities or a
Rare Birds Committee; here in North America, they're called Bird Records
Committees. Often birders who are not in the top 5%-10% listing/ID
specialist segment but in the other 90% think that because Bird Records
Committees deal only in rarities, that only rarities are important enough to
record, a natural assumption based on this arbitrary usage, an example of
what I'm coming to call 'Birders' English' rather than common usage. It's my
*observation*, not opinion, that the arbitrary meanings of some birding
terminology ('fall migration' that begins in late June being my favorite) in
Birders' English drives many entry- to intermediate-level birders nuts, sure
did me--and, sadly, we think it's *our* fault for not understanding. So if a
birder who is not part of the listing, rarity-junkie elite has a non-rarity
record, where does he or she take it? The usual answer is nowhere. The
record-keeping is skewed and distorted toward the exceptional rather than
the familiar, and the resultant picture is equally malformed. And the
terminology, as terminology does everywhere else, reflects the true intent
and values of the organisation.

Birding organisations seem generically to have more than the usual amount of
resistance to change at the top--love to know why--but this is one change
I'd submit is long overdue. I'd love to see these committees called for what
they really are, Rarities Committees, and see them as an offshoot of the
actual Bird Records Committees which are *actually* concerned with the state
of an area's avifauna rather than what is overwhelmingly the case,
migrational incompetence.

Rant over, let's get back to birds. '-) Having this arrival/departure
information helps--once you have ensured free access to the information,
that is. Sometimes, tragically, that's a problem with that due to internal
politics and 'turf' issues. Grossly stupid, of course, and self-defeating to
boot, but it happens, as too well I know--from any number of directions:
simply knowing this stuff is fun; you can use it in any bird-tourism bumph
for target species for out-of-town, out-of province or state, or
international birders; you can use it for wagering (1st-swallow-back date,
1st Western Sandpiper or whatever species in the shorebird festivals, etc.,
and, boy, I've been really amazed for years that nobody's picked this stuff
up for gambling purposes. You can use it to track the effects that El
Nino/Global Warming is having, i.e. are arrivals trending earlier? There's
lots of patterns implicit--sometimes remarkably close to the surface--to
discover, and there's a really fine feeling when you see something that's
been right there in front of you and the underlying pattern emerges. A
*really* fine feeling.

Michael Price The Sleep of Reason Gives Birth to Monsters
Vancouver BC Canada -Goya
mprice at mindlink.net