Someone recently wrote of migrant Hairy Woodpeckers. I don’t believe there are
any properlymigrant woodpeckers in N America with the possible exception of the
mostnortherly female Downey Woodpeckers and, of course, Yellow Bellied
Sapsuckers. Western sapsuckers may be altitudinally migrant,moving to lower
elevations in winter.
Woodpeckers are somewhat buffered from winter lowtemperatures in two
dimensions: they roost in cavities and a large part of theirprey—almost all in
some species—are wood-boring insects, themselves shelteredfrom extreme cold.
Apparently tominimize competition, however, Downey Woodpecker sexes practice
resourcepartitioning (and are less dependent on imbedded larvae), females
gleaningon thinner branches and stems than males. Since there isn’t much
difference in size or thermal regulatory capacitybetween male and female
Downey, female migration could be another means ofreducing inter-sex
competition when insects are less available.
While they may not migrate per se, most young woodpeckers do eventually
disperse from the sites where they hatched—CockadedWoodpeckers are an
exception, remaining in family groups indefinitely—insearch of their own
breeding territories. Acorn Woodpeckers create a different kind of exception
living in ‘permanent’colonies around sets of related males and sets of females
also related toeach other but not to the males.
Other woodpeckers, especially those dependent ontree mast and/or swarming
insects, typically wander widely out of the breeding season in search of
patchyfood sources. (Acorn Woodpeckers dealwith patchily available food by
accumulating and storing it enthusiastically.) Lewis’sWoodpeckers are a
classic example of patchy food dependents wandering widely insearch of masting
nuts and swarming ants. At Thanksgiving time, I have seen them as far south as
Baja California Sur, just outside Mulege on the Sea of Cortez. Nathaniel
WanderPortland, OR
Max Planck is supposed to have said: A new scientific truth does not triumph by
convincing its opponents and making them see the light, but rather
because its opponents eventually die and a new generation grows up that
is familiar with it.Andreas Wagner observed of Planck's remark: Science, like
nature, advances one funeral at a time. (Arrival of the Fittest, p.197)
