Back in July I heard though the grapevine that a friend of mine from the Georgia Sea Turtle Center was attempting to rehabilitate a injured bird that washed up on shore that day.  She sent a moderately pixelated picture taken with her cell phone of a gray and white bird with a bill that superficially resembled a gull, and asked what species I thought it was.  On closer inspection, I noticed a slight protrusion at the base of the bill that narrowed it down to a group of birds known as the "tubenoses," and the length of the bill led me to believe it was a type of shearwater.  After consulting my handy-dandy field guide, I came to the conclusion it was most likely a Great Shearwater.

The tubenose group includes not only shearwaters, but also albatrosses and petrels.  All three of these groups are in the order Procellariiformes, which is derived from the Latin word procella, meaning "a strong wind or storm." This is most likely a reference to seeing these birds frequently in storms on the open ocean.  The nerdy name for the tubes are naricorns, and their primary function is a matter of debate.

Some believe the tubes primary function is to help these wandering sea-farers detect their fishy prey, and it is believed that tubenoses scan the sea breezes by zig-zagging upwind toward the source of an odor.  Their extraordinary sense of smell may also help tubenoses find other individuals, breeding areas, and nest sites.  Whereas most birds do not have well-developed olfactory senses because a large schnoz tends to be detrimental to a bird's aerodynamic properties, the tubenoses are one notable exception.

Tubenoses also have large salt gland housed above their bills.  These glands remove salt from the blood of the tubenoses, and excretes them out of the naricorns, enabling tubenoses drink saltwater right out of the ocean without succumbing to dehydration.   The length of the tubes may have evolved as a way to direct this salty liquid away from the bird's eyes.

The function of the tubes is most likely a combination of things, but whatever the case, the ability of the birds to spend almost their entire lives on the open ocean is remarkable.  In fact, the wing shape and proportions allows most tubenoses to simply glide on the updrafts created by waves without having to flap their wings at all.  But what about sleeping?  Many tubenoses can lock their wings in place and snooze in mid-flight.  The only time these birds touch land is during the nesting season where they seek out remote islands and gather in large numbers to build their nests and raise their 1 egg per clutch.

Unfortunately, this bird passed while I was on my way over to see it.  But as far as the population is concerned, Great Shearwater numbers are high, and are listed as a species of least concern according to the IUCN.  However, this does not mean that this species is not experiencing its own set of problems.  Every year, Tristan islanders arrive on Nightingale Island to harvest this species in the thousands, and there has been no study on the sustainability of this practice. Also, feral cats on the Faulkland Islands may pose a threat to this species as well.

Although this individual died, it did inspire me to learn some more about this unique group of birds, and for that, I am thankful.

No comments:

Post a Comment