Wayne, Good wok on your thoughts on swallow migration and attempting to
answer the question of early arrivals by testing alternate hypotheses. In
the spirit of answering this question, I offer the following thoughts.

It would be useful to clarify the terminology. By stating "these were birds
were caught up in the "Pineapple Express" (persistent warm, southwesterly
winds)" it suggests that the birds were blown up here unintentionally.
However, you also refer to these barn swallows as "invading" suggesting goal
oriented behavior.

At the core of this question is the decision making process of individual
swallows. Are the following subtle food gradients that inadvertently lead
them north, or are they assessing local cues and gambling that a long
distance northward flight will result in a payoff (food resouces, userpation
of breeding sites, mates etc)?

In contrast, is it possible that these early arriving individuals are
genetically programed for early departures? Perhaps they are simply
experiencing the onset of migratory restlessness (zugunruhe) at a lower
temperature threshold than the rest of the population. Maby they are
inexperienced juveniles and will enjoy low survivorship.

Or as you suggest, are these early arriving barn swallows unintentionally
wisked away in pineapple scented gales? We could probably come up with
dozens of different hypotheses to explane these Hirundo heroics. However,
the key of course, is to develop testable predictions that could
discriminate between the different hypotheses. Ideally, hypotheses could
be answered in the field with a pair of 10 X 50's.

For example, if birds are whisked away unintentionally by strong winds,
perhaps they are in poorer body condition then the rest of population (which
might be possible to assess in the field). Unintentional migrants may also
be more likely to undergo reverse migration (local southward movements).

Any other thoughts on this?

Fred Sharpe
Mats Mats Bay, WA