Characteristics of Procellariiformes
The Procellariiformes is an order of birds ranging
in size from the Least Storm-Petrel (six inches) to the giant
Wandering Albatross (wingspan close to 12 feet). They are distributed
throughout the world, but they tend to be found primarily in southern
waters.Their bills are always hooked, and are divided into plates,
which are separated by grooves. There is a salt gland in the eye
socket that concentrates salt and excretes it in drops that travel
down the grooves, to drip off of the tip of the bill (see inset
below).
The most distinguishing feature of Procellariiformes,
however, is their nostrils, which form raised tubes, as can be
seen in the picture below of the Galapagos Waved Albatross. The
portion of the brain that is associated with smell is enlarged
in Procellariiformes, and it has been suggested that they are
able to smell their prey. It is not known, however, whether their
tube-like nostrils are an aid in olfaction. A second function
of the tubular nostrils may be in the spreading of stomach oil
over the feathers.In addition to the oil formed in the uropygial,
or preen gland at the base of the tail, Procellariiformes form
a foul-smelling oil in their stomachs that are also spread on
their feathers. It may be that the tubular nostrils are the conduit
for the oil. This stomach oil is responsible for the characteristic
musty odor of Procellariiformes, and is squirted by young and
old alike, at intruders.
The order Procellariiformes contains four families,
three of which are found in Galapagos:
|
Diomedeidae
|
Albatrosses
|
| Procellariidae |
Shearwaters and true Petrels
|
|
Hydrobatidae
|
Storm-Petrels
- White-Vented (Elliot's) Storm Petrel
(Oceanites gracilis)
- Band-rumped (Madeiran Storm Petrel (Oceanodroma
castro)
- Wedge-Rumped (Galapagos) Storm Petrel
(Oceanodroma tethys)
|
| Pelecanoididae |
Diving Petrels |
Albatrosses and frigatebirds are the most primitive
members of their orders (Procelariiformes and Pelecaniformes,
respectively), and skeletal similarities suggest that the two
orders are related. Procelariiformes are also closely related
to Sphenisciformes, the penguins.
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