There were two fascinating articles in the April 8 issue of "Nature".

The first was a brief review of recent research about bird vision in the
UV spectrum. Birds can see light in the UV range, and apparently use it
in many ways. Kestrels use UV reflection of vole urine scent trails to
home in on their prey. Birds may use UV light to recognize their eggs;
the UV reflectance of some African cuckoos' eggs closely matches that of
the hosts. Birds such as Blue Tits, which look monomorphic to us, may
be dimorphic in the UV range, and females prefer males with the
brightest UV crests. Birds may vary in the amount of UV light reflected
from bare parts, as well. The gapes and skin of the nestlings of some
species, especially those that nest in cavities, also reflect UV light,
and the young with the strongest immune systems may reflect the most.
Parent European Starlings give more food to the brightest, presumably
healthiest, chicks. As the author of the article says, "if you want to
get inside an animal's mind, it helps to see the world through its
eyes".

The second article was about the ability of hummingbirds to flex their
lower bills in two dimensions while catching insect prey. In the three
species of hummingbird studied, when the birds open their bills to catch
a small insect, the bones at the base of the lower mandible flex outward
and the distal half of the lower mandible bends downward. (There are no
joint in the bones of the bill at the points of flexion; the thin bones,
themselves, bend.) This flexion increases the size of the gape, making
it easier for the birds to grab the insect, and is used only during
insect capture. The majority of successful captures by Ruby-throated
Hummingbirds were made at the flared-out base of the bill.

Rachel Lawson
RachelLawson at softhome.net
Seattle