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Monday, September 12, 2011

Deadly debris

This week we all got a good reminder that no piece of debris is too small to kill or injure wildlife. First we found this Sooty Tern fledgling stumbling around the colonies one evening. Because the poor creature was unable to fly, we captured it easily by hand and it became quickly evident why it was hobbling around. Its left leg was completely non-functional because a small section of monofilament fishing line had become tightly wrapped around the upper part of it. It had been there for quite some time because tissue had actually grown over the line.

Though this bird was still quite lively and, true to Sooty form, still attempted to bite and jab its handler, you can see from the condition of this bird's feathers that its chances of surviving this are not good. With feathers this far gone and its first molt not due for quite some time, our poor, (de)-feathered friend will not be able to leave the island and forage on its own. This is what will ultimately kill the bird. And while we cannot say for sure that the leg injury caused the feather degradation, its easy to imagine how weeks of hobbling around a seabird colony dragging wings through dirt and guano led to the present condition.

Anybody care to guess how long the offending piece of fishing line was?  Make an estimate, then check the answer at the bottom of this post!* 

These poor little Honu were recently found on the island as well. Since they turned up aways inland, the likely scenario is that they hatched out on the beach and somewhere between the ocean and middle of the island got tangled in this section of net. This particular piece of netting measured only 17" long and 3" wide. Typical commercial fishing gillnets like this can be up to several miles long. If a section this small can kill two turtle hatchlings imagine the damage that a mile of this stuff could do. It's an ugly thought.

We make every effort we can to remove the trash that washes ashore or gets blown inland, but even though Tern is a small island, there's still a lot of ground to cover by three people. We also have to carefully weigh the impact of our increased presence in active bird colonies and monk seal habitat with the benefit gained from removing debris immediately. There are no easy answers and we're still figuring out what our best approach should be. One thing is for absolute certain: it's important that the US Fish and Wildlife Service maintains its year-round presence out on Tern Island. If there were no staff and volunteers out here to collect debris and watch out for the turtles, seals, and seabirds that call this place home, there would be far more deadly entanglement incidents like this.

Shameless subject change! On a completely unrelated, but far brighter note, check out this Red-tailed Tropicbird chick. Born and raised right under our front porch, we get to enjoy watching her grow every day! Their eyes aren't actually quite that big, but they have a thick, black eye ring. So when a tropicbird chick looks at you straight on, their eyes look exaggeratedly large, cartoonish, and ridiculously adorable. Really, is it possible to not smile when you see this face???


(*Answer: 13 inches, which is an exponentially tiny fraction of the amount of derelict fishing gear and other debris that's out there in this bird's ocean habitat.)

Wednesday, September 7, 2011

A calm day on Tern

September 6, 2011: For the first time since I arrived to Tern almost 3 months ago, it is still. The Northeast tradewinds, normally a constant presence at the atoll, are almost entirely absent. Without even the slightest breeze, it's oddly quiet today. Not only do we not hear the sound of the wind moving between antennas and solar panels on the roof, but the sound of waves crashing against the shore south of the barracks is absent. The waters outside the lagoon are glass calm and a more subtle shade of blue than we usually see.

The birds have also quieted down substantially and it feels a little eerie out in the colonies. Everybody's laying low because it's HOT out there. Gular sacs are all aflutter (at least among the boobies and frigate birds), the sooty tern flocks are in disarray without a steady wind to orient themselves by, and everybody else has flocked, literally (bad pun fully intended), to any available shade.

With Tern Island's shrub habitat in decline and roughly 30% of the island taken up by a barren expanse of compacted gravel that does not support native plants (and therefore most of our bird species), shade is at quite a premium on Tern Island. Lucky for the birds, most of the chicks are past their most vulnerable stages in their lives when they lack the physical and behavioral adaptations to handle the heat. Here are a few examples of how Tern's seabirds coped with today's high temperatures.

Frigatebirds (ʻIwa) display perhaps the most diverse (and amusing) range of behavioral responses to heat. Here are just a few of them. There's the open wing posture (apparently this reduces water loss somehow). There's gular fluttering (intensity and duration of flutter typically correlates to how heat stressed a bird is), which really requires video footage for one to fully appreciate (stay posted on this one). And then there's what I've decided to call the 'I give up' posture. C'mon, it's not that hot, is it?

Scott has been steadily amassing a pretty sweet driftwood collection for his study plot in our Active Management Revegetation Zone between the runway and the colonies. Birds are attracted to the wood every day for the perching structure it provides, but today saw especially high interest in Scott's installations for the shade they provide.

When there's a steady wind (which is most of the time) all the sooty terns (ʻewaʻewa) in a flock like this will almost invariably be pointing straight into the wind. Seriously, on a windy day these birds are as effective as any windsock in indicating the wind direction. This is another behavioral response that helps them stay cool. I imagine it also keeps the feathers nice and smooth. You'll see from this photo, however, that on a dead calm day like today nobody quite knew where to stand! A minor detail, I know, but when you share a small island with thousands of seabirds, you notice things like this.

This little dome thing here is a recycled fuel barrel being used as a shade structure. We painted it white so it will reflect heat, drilled a few holes in the sides for cross-ventilation, and then anchored it to the ground. We're still in the early stages with these designs and if you look closely, you'll see a little gizmo on the ground that looks like a thumb drive. This is a temperature logger. We are currently measuring the inside temperature of our shade structures and comparing them to the temperatures under our natural shrub habitat. If these perform similarly, we'll make more and place them out in the colonies in time for the next breeding season.

Even a simple concrete block out on the runway surface makes a difference. We're still not quite sure how this tiny brown noddy (noio) chick made it way out there, but it looks like it's been reunited with its parents and managed to find a good spot to wait out the heat!

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