contact with their bills, which
minimizes the time needed to
chase after discovered prey.
Examining the bill morphology of 10 species of ibis in
museum collections, Cunningham and her team did indeed
find that the birds possessed a
bill-tip organ similar to those in
snipe and kiwis. It did not matter
whether the ibis foraged in terrestrial grassland and forest or in
open waters of lakes and lagoons.
Interestingly, the species that
probe for food in aquatic habitats
have more extensive and densely
pitted bill-tip organs than do terrestrial species.
“In the past, it has been
assumed that probe-foraging
ibises detect their prey only when
it touches the bill tips...that pursuit
time between the detection and
capture of prey is therefore almost
non-existent, and that the birds
can assess prey characteristics
only after capture,” wrote Cun-
ningham et al. in the April 2010
issue of The Auk. But if the birds
are instead using remote touch,
this means they are sensing the
prey items before they come into
contact with the bill, and this is
followed by a “pursuit” phase.
As seen in shorebirds such as
sandpipers, the bill-tip organ is
quite sensitive to pressure waves
produced by prey in the substrate.
The birds can actually use this
organ to estimate the size and
shape of organisms they detect
under the surface, sight unseen.
Dan Williams of Signal Mountain, Tennessee, was interested
in my report of a male eastern
towhee feeding some wood
thrush nestlings. Friends of his
had seen a similar situation with
eastern bluebirds and Carolina
chickadees. Apparently a pair of
each of these species was fighting
over the possession of a nesting
box in the couple’s backyard.
Things settled down, and the
couple thought no more about
it—until they noticed that both
species were visiting the nest box!
Peering inside, the couple discovered three bluebird eggs and
four chickadee eggs side by side.
Later, when both species were
seen bringing food to the box, the
couple took a second look and
found three bluebird nestlings
and three chickadee nestlings. A
few days later, all of the young
successfully fledged. Dan wanted
to know whether the two species
alternated in incubating the eggs
and brooding the young or whether they sat on the eggs and young
side by side.